Aerial photography and mapping

Marine Bio-images are pleased to announce that we are now able to offer aerial photography and mapping using Unmanned Aerial Vehicles (UAVs) as part of our overall package of environmental services.

Marine Bio-images services, aerial mapping. www.marine-bio-images.com Hexacopter equipped with stills camera in operation. www.marine-bio-images.com

Hexacopter equipped with stills camera in operation

It is now possible to carry out photographic surveying very cost effectively using remote controlled multi-rotor UAVs as camera platforms. A 6-rotor UAV (Hexacopter) is shown above.

Typically, a surveying ‘mission’ would be flown autonomously, the UAV being pre-programmed with a series of waypoints at each of which a digital photograph would be taken. At the end of the mission the digital images would be downloaded and processed according to the particular project needs.

Examples of the type of survey conducted.

A recent survey was carried out on a a river estuary mussel bed, encompassing about 3 Hectares at an altitude of 65 Meters.  The actual data collection was completed in a flying time of about 5 minutes.  This yielded images with a ground resolution of 1 cm. A sample enhanced colour image fraction is shown here and shows a narrow diagonal strip of mussels on exposed sand with water to the top and right with a couple of seagulls in attendance

UAV hexacopter surveys. A small crop of a photographic still collected during a recent survey, showing mussel distribution along a small spit of sand. www.marine-bio-images.com

A small crop of a photographic still collected during a recent survey, showing mussel distribution along a small spit of sand.

If you would like to know more about our remote and unmanned camera systems, or discuss your survey requirements, please email marine bio-images or call +44 (0)7926478199+44 (0)7926478199.

Marine Bio-images are based in Exeter, Devon, UK. We are available to undertake marine environmental surveys locally and world-wide; recent contracts have included marine environmental surveys in Devon, Cornwall, Dorset and Hampshire, and further afield in Scotland, Italy, Black Sea Bulgaria, UAE and Libya.

 

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Marine Environmental Impact Assessment

The relevant legislation for Environmental Impact Assessment (EIA) in the marine environment can be tricky to keep up with.  Within UK waters, licensing is now generally controlled by the Marine Management Organisation (MMO).

A Marine Bio-images scientific diver videos along a survey transect line as part of a no-take-zone monitoring programme. West Scotland. Colin Munro. Marine Bio-images

A Marine Bio-images scientific diver videos along a survey transect line as part of a no-take-zone monitoring programme. West Scotland.

The requirements for Marine licensing and Environmental Impact Assessment are set within the Marine Works (Environmental Impact Assessment) Regulations under Part 4 of the Marine and Coastal Access Act 2009, and the 2011 amendment.  Essentially what this means is that, before a license can be issued for a given development or activity, the MMO will determine whether an EIA is required; this assessment is based on the type, scale, location and potential environmental impacts of the proposal.  There is a three stage process to the license application:

  1. screening
  2. scoping
  3. environmental review and submission

Up to two hours of advice is given free by the MMO during the initial screening process.  During this process the MMO will determine whether an EIA is likely to be required.

If it is determined that an EIA is required, then the scoping process will identify the sensitivities and issues that will need to be addressed in the impact assessment, and the type of information that will need to be included in the Environmental Statement.  The scoping process is likely to require advice from other statutory bodies, such as Natural England (NE), in particular where there is likely to be a requirement for a Habitat Regulation Assessment or where the proposal may potentially impact on European Protected Species.  The Environmental Statement should include all aspects of the EIA, including a detailed description of the development, an assessment of the information required to properly assess the effects of the development and any proposed mitigation or alternative proposals.

Marine Bio-images is able to assist in all aspects the marine EIA and Environmental Statement production. This includes liaising with statutory bodies, guidance on likely impacts, conducting surveys and data collection and Environmental Statement production.

For more information please email Marine Bio-images or telephone us on +44(0) 7926478199+44(0) 7926478199.

 

 

 

 

 

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Remote Camera Surveys

Remote camera surveys – drop down video, towed video and combined video and stills drop-down or towed systems – have been a major component of our underwater survey work for over a decade.  Remote camera surveys can often be used to identify and map underwater species and features.  They are much faster and generally less expensive than diver surveys (although in some situations diver surveys are required).  They can also be combined with spot dives: towed or drop camera transects providing rapid, wide coverage then targeted spot dives adding detail.

Marine Bio-images drop stills camera and video system being deployed from a RIB as part of our monitoring of Lamlash Bay no-take zone

Marine Bio-images drop video and stills camera system being deployed from our rigid inflatable boat as part of our monitoring of Lamlash Bay no-take zone

At Marine Bio-images we operate lightweight systems that are ideal for deployment from small vessels.  Our drop camera system has proved very successful for mapping seagrass beds (we have used this at many locations in UK waters, off the Mediterranean coast of Southern Europe and North Africa).  The system can be configured as video only or as a combined video and high resolution stills system. Key advantages are the lightwieght, compact size and modular construction.

Diagram illustrating Marine Bio-images' drop/towed camera system in operation.

Diagram illustrating Marine Bio-images’ drop/towed camera system in operation.

This allows the system to be taken as personal baggage on flights, removing the delay of waiting for freight.  The system is also entirely self-contained and can operate without external power with a fully waterproof surface unit.  This makes it idea for operation from small open vessels such as inflatables and RIBs.

Still from our drop camera system taken during a seagrass (Zostera marina) survey

Still from our drop camera system taken during a seagrass (Zostera marina) survey

Our towed camera sled is ideally suited for extensive surveys over sedimentary seabeds.  Like our drop down system this can be configured with both video and high resolution stills.  This has proved particularly successful in pipeline corridor surveys; we have used it in depths of 80-100 metres in the Persian Gulf and Black Sea as a tool to help map benthic species and biotopes within proposed pipeline corridor routes.

Marine Bio-images' towed video sled being deployed along a pipeline corridor off Iran, Persian Gulf.

Marine Bio-images’ towed video sled being deployed along a pipeline corridor off Iran, Persian Gulf.

If you would like to know more about our remote camera systems, or discuss your survey requirements, please email marine bio-images or call +44 (0)7926478199+44 (0)7926478199.

Marine Bio-images are based in Exeter, Devon, UK.  We are available to undertake marine environmental surveys locally and world-wide; recent contracts have included marine environmental surveys in Devon, Cornwall, Dorset and Hampshire, and further afield in Scotland, Italy, Black Sea Bulgaria, UAE and Libya.

 

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How to buy bad science.

Summary

Lyme Bay Closed Area was a first for British waters.  The very first statutory closed area established for conservation reason, protecting fragile reefs and associated species from the effects of bottom-fishing trawls and scallop dredges.  It was a long process to get there, 16 years of surveys, reports and campaigning.  That it was established is an unqualified success.

Since it was established, annual surveys have been conducted and reports produced by Plymouth University’s Marine Institute describing the phenomenal re-growth that has occurred since the protection was introduced. I was directly involved in these studies, running a specific component (diving surveys 2008-2010).  The study was a DEFRA Science and Research project:

DEFRA Science and Research Projects. Lyme Bay – A Case-study: Measuring the effects of benthic species and assessing potential – MB0101.

The findings reported here suggest that the Closed Area has benefited the marine species living on the rocky reefs to a far greater degree than anyone could have possibly hoped. It seems too good to be true.

What if it is too good to be true?  What if much of the data is not real?

Increasingly concerned about aspects of the study, and after much deliberation, I wrote to the key scientists within Plymouth University’s Marine Biology and Ecology Research Centre and requested that my name as an author on the Lyme Bay study be removed from the final scientific report submitted to DEFRA. This was the first time in 25 years as a marine biologist I have felt it necessary to take such actions.

There are, in my view, three fundamental problems with the study:

  • the study design is such that the comparative areas outside the Closed Area are in no way comparable; they were never likely to support similar species assemblages;
  • the methodology used is highly unlikely to be capable of detecting the type of changes expected within the study timescale, or capable of detecting many of the species claimed to have been detected, indeed it is highly unlikely that some of the species reported as being recorded actually exist in the locations surveyed;
  • the key changes highlighted simply could not have happened; they fly in the face of everything we know about the species and taxonomic groups involved.

I wrote to the key researchers and suggested the report be withdrawn until these points were addressed.  This was rejected.  Aspects of our own study have been incorporated into the final report.  The interpretation of our data is not one I or others working on the diving was involved in, nor one I would concur with.  Our own study was to be published by Natural England as a separate report.  Days before this was due to happen the process was halted.  When querying this I was informed that this was because they were too busy.  More than two years later it has still not been published by Natural England.  It is fair to say that our findings and recommendations do not all concur with those of Plymouth University’s marine biologists.

These issues are troubling. Of greater concern is the opacity of the underlying data on which these findings are based and the apparent lack of interest in both Natural England and DEFRA over very obvious flaws in the study.  This is best illustrated by examples; although this was an imaging based study (species counts through analysis of images collected by remote camera) almost no stills images have been made available, even as part of the study reviews.  Although never made clear, the photographs of species and habitats used in the study reports were not obtained by the camera system employed, nor collected as part of the study and some are clearly not from Lyme Bay.  Attempts to seek confirmation on issues such as the resolution of the camera system employed (which appears to be less than one megapixel) and clarification as to how claimed data extraction could have occurred given turbidity and low camera resolution problems have not been successful.  Comparative data sets between the camera system used by Plymouth University and divers have never been seen nor the results published. Statements made and comparative images depicting the findings of the study, shown on the Plymouth University website research page dedicated to this study are, at best, highly misleading.  Species reported as being recorded by the remote camera system on subtidal (approximately 20-27 metres depth) reef systems in the study area include species normally associated with rockpools and intertidal waters, small species normally requiring microscopic identification never previously recorded in Lyme Bay and small species normally found underneath rocks, yet many common species were not recorded.  It appears that further years funding was awarded to the study without any of these questions being addressed or any raw data ever being seen despite regular meetings with Natural England and DEFRA and interim reports produced.

Why does this matter?

From a scientific viewpoint a unique opportunity was lost.  The significant changes within species assemblages on the reefs within Lyme Bay are very unlikely to have occurred within the first 2-3 years; they will mostly likely occur during the 5-15+ years following cessation of mobile bottom fishing.  If we cannot trust the data collected in the first few years we have no benchmark against which we can measure change.  Currently there is no raw data available to provide this benchmark and even were the raw data made available we cannot be sure what is accurate and what is not.

This was a four year study, costing the best part of half a million pounds. Despite all meetings and interim reporting, it appears that there was a lack of critical analysis.  There is a danger that similar studies may be inclined to reach conclusions preferred by the client rather than one that reflect reality.   A number of marine protected areas (MPAs) have been designated recently in UK waters, with (hopefully) more to come.  These will require monitoring and initial consultations are already taking place.  It is stating the obvious to say that we need accurate and transparent data if we really want to understand the changes that occur in these protected marine habitats.

1. Tread carefully

DEFRA Science and Research Projects. Lyme Bay – A Case-study: Measuring the effects of benthic species and assessing potential – MB0101.

A cobble reef in Lyme Bay, approximately 22 metres depth.  This illustrates typical visibility (~4-5 metres) in the central part of the bay.  Note the survey diver (holding a white monitoring quadrat) only just visible, approximately 4 metres away from the camera. (c) Colin Munro, Marine Bio-images

A cobble reef in Lyme Bay, approximately 22 metres depth. This was one of the diver monitoring stations. This illustrates typical visibility (~4-5 metres) in the central part of the bay. Note the survey diver (holding a white monitoring quadrat) only just visible, approximately 4 metres away from the camera.

For those of us working primarily on the conservation side of marine environmental monitoring and impact assessment, it is important that the work we do, and the data we present, is as robust, evidence-based and open to scrutiny as we expect that of developers, oil and gas industries and fishery industries to be. If not, how can we hold them to account should they fail to meet such standards?  As scientists, it is important that we bear in mind at all times that we are being paid to tell clients what they need to know, and that is not necessarily the same as what they want to hear.  Yet public criticism of the work of other scientists is not an action that should be undertaken lightly, and only after other avenues have been exhausted. One needs to carefully consider both the likely consequences of such actions and one’s own motives for doing so.   For those reasons I have deliberated for over a year before publishing this article.  I suspect I am unlikely to be offered another contract by Natural England in the near future.  That is a pity, but if contracts continue to be administered in this manner it is probably mutually beneficial if I am not.  I should also point out that, before deciding to publish this article, I consulted quite widely with marine biologist colleagues including independent scientists and others working within conservation organisations.

Study of the ecology of Lyme Bay has occupied a fair amount of my professional life. I have been diving and conducting surveys in Lyme Bay since the early 1990s; I ran the first studies investigating the impacts of scallop dredging on the reefs in the Bay and have run or participated in a great many since. So no-one was more pleased than I when statutory protection for the reefs in Lyme Bay was introduced in 2008 through a 60 square nautical mile exclusion zone for mobile bottom fishing.

To determine how well and how quickly the reefs would recover following cessation of disturbance by mobile fishing gear a three year study was commissioned by DEFRA (Department of Environment, Food and Rural Affairs) with the science being overseen by Natural England (NE) Marine Monitoring specialists.  The protection had been introduced due to the concern over (and evidence of) the destruction and decline in the more fragile and slow-growing species that occurred on these reefs, in particular the erect branching sponges, the octocorals Eunicella verrucosa (pink seafans) and Alcyionium digitatum (dead man’s fingers).

Once the statutory protection had been established, it was important to monitor the changes that occurred on the reefs.  There was little doubt that change would occur once such a major disturbance ceased, but how would it happen?  The important questions were how quickly would it occur, which species would re-establish first and how long would it take for species that were typical of undisturbed reefs (the erect sponges, seafans and dead mens’s fingers) to start to recolonise?

Between 2008 and 2011 I collaborated on a DEFRA /Natural England funded study to determine the changes that occurred on the deeper water reef communities within Lyme Bay Closed Area. Specifically I ran a study looking at changes occurring on boulder reef communities lying between 20 and 22 metres depth (chart datum). This work was conducted by a small team of highly experienced marine biologists/divers. The study was a sub-contract, conducted as a discrete, but ideally complimentary, study within the main contract investigating these changes. The main contract had been awarded to the University of Plymouth who were primarily using remote (towed) video (a camera system towed above the seabed, termed the ‘flying array’) to investigate these changes. Our work ran concurrently and was, at the start of the contract, to be published as one final report.

During the course of the study my colleagues and I became increasingly concerned about the reliability of the main towed video study.  So much so that, in late 2011 during the preparation of the final report, we requested our report be published separately as a stand-alone report. We also requested that we conduct our own data analysis rather than providing Plymouth University with our data, to be analysed by them. Our feelings concerning this were so strong that we conducted all analysis and write up on a unpaid basis.  In November 2012, after much deliberation, I wrote to the scientists within Plymouth University’s Marine Biology and Ecology Research Centre who had run the university’s three year study, and requested that my name as an author be removed from the final scientific report submitted to DEFRA. This was the first time in 25 years as a marine biologist I have felt it necessary to take such actions. Our own, separate, report was completed, reviewed, and then, after considerable pressure to modify certain conclusions (which I declined to do) accepted for publication.  It was never published by Natural England or DEFRA.

There were also other discrete components of the over-arching project, in particular a socio-economic study.  My comments here apply only to the benthos study, specifically the ‘flying’ towed video study which formed by far the largest part of the project. I have no knowledge of the socio-economic component or expertise in this area and have no reason to believe it is anything other than excellent.  Nor do I intended these comments as any criticism of Plymouth University’s science in general, which again I have no reason to assume is other than first rate.  I also stress that, before writing this, I wrote several times to the scientists involved in the Flying towed video study, explaining these problems in considerably more detail than below. I asked that any misunderstandings in my interpretation be corrected. After some delay I received a very brief response explaining that I ‘clearly did not like our study‘ and that they could not help me further.

2. Key problems

From Plymouth University website:

As soon as the SI was enforced in 2008 the team undertook the first baseline survey and have monitored the bay annually since then. At first the reefs were slow to respond but in 2010 the results were impressive (see videos from 2008 and 2011 below)

Presenting all the problems of this multi-year study cannot be done concisely, nor can the key problems, without first explaining a little about the ecology of Lyme Bay, the legislation introduced and the study design. However, a snap-shot of the study is presented on Plymouth University’s Marine Biology and Ecology Research Centre’s website, where a page is dedicated to the study. This provides an indication of the sorts of concerns I had. The page is titled Marine Protected Areas: monitoring the Lyme Bay exclusion zone and can be accessed here.

Plymouth University Marine Biology and Ecology Research Centre's Marine Protected Areas web page.

Plymouth University Marine Biology and Ecology Research Centre’s Marine Protected Areas web page.

The page summarises the importance of Lyme Bay, the aims of the study, the methods used and the findings of the three year study. Here is the study description from the web page:

The team developed a non-destructive, cost-effective and time-effective technique for monitoring vast areas of the sea bed in Lyme bay. The technique involves flying a towed HD camera above the seabed to capture video footage of the reef communities that can be analysed back in the laboratory. As soon as the SI was enforced in 2008 the team undertook the first baseline survey and have monitored the bay annually since then. At first the reefs were slow to respond but in 2010 the results were impressive (see videos from 2008 and 2011 below)

(The underlining of the last sentence describing the changes recorded are mine, not from the web page.)

Immediately below this text are two video clips, one entitled ‘Video footage of Lyme Bay reef taken in 2008’ the other ‘Video footage of Lyme Bay reef taken in 2011’. The differences between the two clips are indeed impressive; the 2008 clip (10 seconds) shows a rather barren area of rocky reef with little attached marine life; the 2011 (28 seconds) shows rocky reef supporting a range of larger marine species, the most obvious of which are numbers of large pink seafans (Eunicella verrucosa), a large yellow boring sponge (Cliona celata) and a large ross coral (Pentapora fascialis). Below are two, fairly representative, frame grabs I have taken from each clip, illustrating the differences between them.

Frame grab from video clip entitled 'Video footage of Lyme Bay reef taken in 2008'

Frame grab from video clip entitled ‘Video footage of Lyme Bay reef taken in 2008’

 

Frame grab from video clip entitled 'Video footage of Lyme Bay reef taken in 2011'
Frame grab from video clip entitled ‘Video footage of Lyme Bay reef taken in 2011’

The differences between the 2008 and 2011 clips are indeed striking, and if this is the change that has occurred on that area of reef between 2008 and 2011 it is quite spectacular. However, what you think you are seeing is not necessarily what you really are seeing. Reading the web page, one might assume that we are looking at the same area of reef at two different points in time. We are not. We are looking at two different reef areas. Nor are we looking at two areas representative of the change that occurred in this three-year time period; the large pink seafans visible in the 2011 clip are all at least 15 years old, most probably between 15 and 30 years old. We know this because of their size and ramification (degree of branching) and from what we already know about pink seafan growth rates from earlier studies conducted in Lyme Bay and elsewhere. Pink seafans grow slowly; estimates put this between one and three centimetres per year (e.g. Munro and Munro, 2003, Sartoretto and Francour, 2012). It is also highly unlikely that the Ross coral (Pentapora fascialis) and yellow boring sponge (Cliona celata) colonies visible in the 2011 frame grab could have grown to such size in three years.

Change at anything approaching the rate implied by the two video clips simply does not happen.  This is way beyond the growth rates for any known gorgonion species. To make a terrestrial comparison, this is akin to the 2008 video showing an area of barren wasteland following a major construction programme, with the 2011 video showing ‘the same’ area populated by 10 metre tall birch trees that have sprung up in the intervening three years. Unfortunately this is simply a rather graphic example of much within presentations given and the technical reports published on the DEFRA website.

The statutory closure of such a large area of seabed for conservation purposes was a first for England. It was high profile and highly contentious. It was also likely to be a trial, a test bed to see how well such areas worked in terms of facilitating regeneration and how quickly it could occur. This was a four year study, costing the best part of half a million pounds, easily the most expensive study conducted on the ecology of the reefs in Lyme Bay and probably costing significantly more than all the other studies in the previous sixteen years combined. It was also the most intensively scrutinised study; overseen by Natural England marine monitoring specialists, where annual interim progress reports were produced and quarterly meetings involving DEFRA, Natural England, Plymouth University and myself (as Marine Bio-images consultancy) were held with presentations on study progress given and questions asked. There are two obvious questions here.  Firstly, how did this happen, and secondly, could something so obviously wrong escape notice? Is it possible that no-one was aware these findings could not possibly be correct?

Fundamental problems

There were, I believe, three fundamental problems with the study.

1. The study design the study design is such that the comparative areas outside the Closed Area are in no way comparable; they were never likely to support similar species assemblages; thus differences between the still-fished and now protected areas could not be attributed to the differences in fishing pressure. Indeed it seems clear that this is not the most significant factor in differences between the treatments.

2. The image resolution of the the towed camera system employed is too low to accurately detect recently settled colonies of the species of interest on the reef, and the sled design exacerbates this problem. If this cannot be done then change and ‘recovery’ cannot be recorded.

3. Key changes highlighted simply could not have happened; they fly in the face of everything we know about the species and taxonomic groups involved, yet there has been no attempt to address this.

All studies have problems. The important thing is that they are identified and addressed. Thus the real issues here are not what the problems were but how they were, or were not dealt with. However before that can be properly discussed a little more detail on the nature of the problems is necessary. I am not going to attempt to describe all issues with the study; rather I will select one problem, image resolution, as the issues with this are simpler to explain in non-technical terms and it is fairly representative of how they were dealt with.  I will then briefly describe some of the study design issues.

Image resolution.

The prime means of data collection was by towed high definition (HD) video camera (as described on the University’s web page, image 2, above). The analysis is summarised in the biodiversity final report (Attrill et al, 2012)

Analysis of the video transects was conducted in two stages (Sheehan et al., 2010). Firstly, species counts were made from each entire video transect for infrequent organisms (all mobile taxa) and conspicuous sessile fauna. Secondly, frame grabs were extracted from the video to quantify the encrusting, sessile species, some abundant, free-living fauna and metrics of infaunal density and bioturbation such as burrow densities.

Thus pretty much all new growth and newly settled colonies’ data were gained from frame grabs from the video footage. However, there is a problem here. Video frame grabs are not a good way to produce stills. The maximum possible resolution of the frame grab stills extracted from the video is less than one megapixel (0.92 megapixels to be precise; the video format used was 720 Progressive scan, i.e. each frame was 1280 x 720 pixels, equalling 921,600 pixels). To put this in to context, this is only a fifth of the resolution of the cheapest smartphone camera one can buy and around a 1/20th of the resolution of a good quality digital SLR. In fact this is lower resolution than any consumer digital stills camera one can buy (or has ever been made; the first commercially produced DSLR, the Kodak DCS 100, released in 1991, had a resolution of 1.3 megapixels).  The system was adapted from one used in the clear and well-lit waters of the Great Barrier Reef where, for mapping corals such systems work quite well. The much darker and more turbid waters of Lyme Bay are a quite different scenario. One must also remember the task was not to map or count the presence large colonies, the aim of the study was recording colonisation and early growth of sponges, seafans, dead men’s fingers soft corals and ross coral bryozoans. These are all long-lived, slow growing species (the first three in particular) thus in the first 2-3 years one is recording colonies that are likely to be only millimetres tall. The problem was actually worse than the camera resolution alone would suggest. The camera system was designed to ‘fly’ above the reef. This again may work well in very clear bright waters; in the relatively turbid conditions such as those that prevail in Lyme Bay; the image resolution is further degraded by the considerable distance between the subject and the camera system, far greater than we would normally consider acceptable when collecting similar data using a high resolution camera. The camera to subject distance is around twice what would normally be considered the maximum one would try to extract such data from a much higher resolution stills camera.

Correlating the actual camera resolution with that required to record settlement and growth of small colonies would appear to be impossible; I have seen no coherent explanation as to how it was achieved. There is a bigger problem however when using such a flying towed camera system in Lyme Bay. Lyme Bay waters are far from gin clear; the seabed here is largely sedimentary with significant levels of suspended particles. It is also prone to strong plankton blooms which can reduce underwater visibility to less than one metre. However, and this is the important point, the level of turbidity is not constant. It changes constantly from hour to hour as tidal streams vary in strength, day to day and week to week as gales pass through and plankton blooms come and go. These changes in turbidity dramatically affect the amount that can be seen (and recorded). This is a problem for anyone working in this environment; the only solution being to avoid really bad conditions and to get close as possible to the seabed and the species of interest, thus reducing the amount of water (and suspended particles) between the viewer and subject. Ideally this distance should be no more than 0.25- 0.3metre (as is the case for diver surveys or most towed camera sleds).

The camera to subject distance of the ‘flying’ towed video used is around a metre or more from the subject (taking into account the angular distance as the camera is not looking straight down) these changes in turbidity will create enormous differences in what can be seen on the seabed. Individual organisms that will be clearly identifiable on some occasions will become completely invisible to the camera following relatively minor changes in turbidity. These changes in what is visible will almost certainly be of far greater magnitude than any actual changes occurring in species abundances. This means that improvements and changes in abundances that are not real will appear to occur. It also means that improvements and increases in abundance that are real may not be recorded and even if they are, there will be no reliable way to separate them from apparent, non-real changes.

Positional accuracy

This is not a resolution issue, but is a further confounding factor for image interpretation. The flying towed video’s position cannot be precisely controlled and is never accurately known.  Towed behind a slow moving boat (0.5kt) pushed by wind and tide, repeat surveys of the same transect will never cover exactly the same area of seabed, often being 10-20 metres off the previous year’s track.  The distribution of rocky reefs and associated life is very patchy in Lyme Bay and varies markedly over distances of only a few metres, thus two parallel track lines 10 metres apart (e.g. the same transect recorded at two sampling intervals) will most likely record quite different numbers of target species without any real change in numbers occurring. This is not a big problem for descriptive surveys, but is a huge problem for time-series monitoring.

Examples of image resolution

The problems associated with image resolution are probably best understood by showing examples. As mentioned earlier, recently settled seafans are extremely small, on average no more than 90mm tall three years after settlement. How difficult this would make recording recently settled seafans is clearly illustrated in the images below.  The image immediately below shows a full frame grab (1280 x 720 pixels) taken from one of the Plymouth Universities video tows (this is a typical image; I extracted several for comparison) reduced slightly in size to fit here. The white rectangle shows the area of 900 x 600 pixels on the full 1280 x 720 pixel image.

A 1280 x 720 (full resolution of the camera) frame grab from Plymouth University's towed video, reduced to 900 x506 pixels for display purposes.  The white box shows the area of 900 x 600 pixels at full resolution.

A 1280 x 720 (full resolution of the camera) frame grab from Plymouth University’s towed video, reduced to 900 x506 pixels for display purposes. The white box shows the area of 900 x 600 pixels at full resolution.

The next image (below) shows a fairly low resolution digital SLR camera image (a 6 megapixel camera; modern equivalents are 12-24 megapixel). Again, for the purposes of direct comparison, the white rectangle here also shows the area covered by 900 x 600 pixels on the full resolution image.

A still from an older, 6 megapixel, Digital SLR camera, reduced to 900 x 602 pixels for display purposes. The white box shows the area of 900 x 600 pixels at full resolution.  Note also the differences in contrast, colour saturation and image sharpness with the previous image.

A still from an older, 6 megapixel, Digital SLR camera, reduced to 900 x 602 pixels for display purposes. The white box shows the area of 900 x 600 pixels at full resolution. Note also the differences in contrast, colour saturation and image sharpness with the previous image.

The next image shows shows the 900 x 600 (white rectangle) area from towed video sled image, displayed at full resolution.  As can be seen this is fine for recording larger conspicuous species such as common starfish (Asterias rubens), large seafan and deadmen’s fingers colonies.

A 900 x 600 crop from the above towed video still (white box) displayed at 100%.  This illustrates typical resolution obtained from such a towed video system camera.

A 900 x 600 crop from the above towed video still (white box) displayed at 100%. This illustrates typical resolution obtained from such a towed video system camera.

The next image is the 900 x 600 crop (white rectangle) taken from the 6 megapixel digital SLR image, also displayed at 100% so allowing direct comparison. Note the recently settled pink seafan near the bottom right of the image. This is likely to be that year or the previous year’s recruitment; I estimate it is 10-20mm tall. It would therefore seem unlikely that many such recently settled seafans would be recorded using the towed camera system, let alone reliable counts made.

900 x 600 pixel crop from the 6 megapixel DSLR image from Lyme Bay, displayed at full resolution.  Note the recently settled (1st year) pink seafan in the bottom right of the image.

900 x 600 pixel crop from the 6 megapixel DSLR image from Lyme Bay, displayed at full resolution. Note the recently settled (1st year) pink seafan in the bottom right of the image.

What happened when people became aware of this problem.

The camera resolution was not immediately obvious.  It was not mentioned in the paper describing the system, not in any of the technical reports.  No extracted stills from the towed video were ever shown at any of the quarterly meetings, nor were any used in any of the interim or final reports.  In fact images from other studies (including our own) were used to illustrate their reports, including some images that clearly did not originate in Lyme Bay.  I estimate that around 1000 or more stills were analysed.  This leaves one asking; given so much was made of the capabilities of this system why were none of the images captured by it ever shown?

I personally queried DEFRA, Natural England and the lead author of Plymouth University’s study, pointing out the resolution of the camera.  DEFRA made no direct response; Natural England’s response was that they didn’t know whether this was true (about the camera resolution).  Given that the study was totally dependent on the resolution of the images being good enough to reliably detect new growth amongst key species then Natural England and DEFRA’s indifference to this seems more than a little surprising, particularly so given that funding for the study was to be extended by another year shortly after. It would have taken around 30 seconds to confirm the resolution on Google, or they could simply have asked Plymouth’s team. I emailed the lead author at Plymouth University, including comparative images and my interpretation of the maximum resolution of the still’s extracted from the towed video, asking how they achieved detection of newly settled colonies. This was forwarded to more junior personnel within the team, and I received a reply that neither confirmed or denied my calculation of the camera’s resolution; instead I was informed that special ‘professional’ software was used. Unfortunately this software was not named, nor what it did explained. No examples of improved or enhanced stills were provided.  I am aware of no software in existence capable of enhancing electronic images to anything like the degree that would be necessary. To the best of my knowledge there has never been any clarification of the camera’s resolution, nor have Natural England or DEFRA asked to see any stills images .

How does the data stack up?

So how does the above assessment of the camera’s resolution square with the actual data recorded?  Evaluating the collected data is not straightforward; no raw data has been provided (fundamental rule of any monitoring study, you must provide raw data; only by comparing raw data can we understand what is going on when we find anomalies, without raw data apparent change can simply be subtle changes in analysis or interpretation when different workers are involved).  Reading the final reports we find that the frame grabs from the towed video produce some inexplicable identifications; e.g. rare encrusting sponges never before confirmed in Lyme Bay before and normally only identified after microscopic examination by specialists; small spider crabs that are normally extremely well camouflaged and difficult to identify at much higher resolutions; small crab species that normally live hidden under rocks and fish and starfish species that are normally found in intertidal rockpools rather 20-30 metre deep reefs. Many small, well-hidden species were identified by frame grabs that were never recorded by our dive team (a table listing a few of the anomalous records is provide at the end of this article.)  It is well beyond the bounds of probability that these species really were recorded during the study by flying towed video

How did the video data compare with that collected by our diver monitoring study?

Direct comparison is not possible.  Our study design and survey stations were different.  However, we were commissioned to undertake a a week’s diving survey work on small sections of a subset of of the flying towed video transects.  The purpose of this was to compare the species counts by divers with that obtained by towed video in order to calibrate the video.  So what were the findings of this comparison?  That is a good question.  We provided our data, and the comparison was never seen; the data simply disappeared.  When I queried this in meetings I received no answer.

How did the key, long-lived, slow growing species data look?

This is probably the most important consideration as this was what the study was all about.  If the flying towed video was accurately recording change then what we would expect to see is that the numbers of larger sponges, dead man’s fingers and seafans would remain largely unchanged (given their slow growth and longevity) in both the newly protected area and also in the older established voluntary protected areas lying within it.  We might possibly start to detect increasing numbers of small, recently settled  colonies as colonisation occurred on previously disturbed areas.  However, if the system was simply recording spatial heterogeneity in mature colony distribution (resulting from the fact the camera transects were never in exactly the same place from year to year) and variations in the number of large colonies detected (due to the system’s limited resolution and variable underwater visibility) then we might expect to detect very few small colonies and unexplained large random variations in the numbers of large, mature colonies recorded.  So what was found?

Interpreting the data is a little tricky, as no raw numbers have been provided. However, if one looks at the processed data provided in the final reports owe then essentially we find large, random variations in the numbers of these key species.  This include apparent dramatic increases and crashes between years in species we would expect to be extremely stable (e.g. dead man’s fingers in the longer-established protected areas) and dramatic fluctuations in the numbers of large (i.e. more than 10 years old) seafans within the protected areas.  How are these crashes and fluctuations explained? Well mostly they are simply not.  Increases that support the notion of rapid and dramatic improvements are described and identified as possible signs of recovery; population crashes (sometime larger in magnitude) are generally not explained.  For example, looking at the Alcyonium digitatum (dead man’s fingers) relative abundance data the most striking change is an apparent crash in numbers within the longer, established voluntary protected areas (2009-2010) with a simultaneous large increase in numbers within the new protected area. This was followed in 2010-2011 by the opposite, a rise in numbers within the older voluntary protected areas coupled with a fall in numbers in the newly protected area.  These findings are, at best, highly unlikely (especially when one considers that the longer established voluntary areas lie scattered within the newly protected area, see diagram below) and should prompt closer inspection of the data, particularly given that older voluntary areas all lie within the newly protected area, evenly scattered across it.

Diagram showing the location of the three different 'treatments', 1. the New Statutory Closure, 2. the Pre-existing Voluntary Closures and 3. the still-fished Nearby Sites.

Diagram showing the location of the three different ‘treatments’, 1. the New Statutory Closure, 2. the Pre-existing Voluntary Closures and 3. the still-fished Nearby Sites.

If we turn to pink sea fans we see that the most pronounced change in numbers were in the pre-existing voluntary closures where between 2009 and 2009 the relative abundance dropped by about 2/3; at the same time the relative abundance appeared to be rising within the newly protected area. This was followed by an even larger change, a four-fold increase in relative abundance between 2009 and 2010 within the older voluntary protected areas.  At this stage someone should be asking serious questions about the data.  If we look at size class data it appears that the number of large seafans (<18cm or roughly <10 years old) increased by about 1/3 between 2008-2009, then decreased by about 1/3 between 2010-2011 in the newly protected area.   It would also appear that only tiny numbers of small seafans have been recorded (again, as we would expect given the resolution of the system); Frequency graphs are produced at very small scale so difficult to read accurately, but it appears that less than 20 seafans smaller than 60mm tall was recorded in every treatment in every year; with less than 5 recorded in most years in all treatments. Given that 60mm tall seafans are likely to be around 2-3 years old, this is an extremely small data-set and, even if accurate, little could be read in to it in terms of interpreting the changes that are occurring within the Bay.

Study design

I will briefly touch on the study design. The study was designed to test the following hypothesis.

Over time, species assemblages within sites in the new statutory closure but outside the pre-existing voluntary closures would change to more closely resemble those in the pre-existing voluntary closures but similar change would not occur within nearby sites where fishing by towed bottom gear was still permitted.

This means that the rocky seabed habitats within the new protected area would start out resembling the areas just outside, then gradually change to resemble the rocky seabed areas within the longer established voluntary protected areas.  This could not happen. The  seabed habitats and environmental immediately outside of the new statutory closure were very different from that within the new statutory closure.  That is the very reason that the boundary to the closure was originally set.  The light levels, current regimes, turbidity, amount of rocky habitat, structure of rocky habitats, amount of river water flowing in and the species present were all very different.  In short the areas outside of the protected area did not support the same species assemblages as the reef area within the protected area and never would irrespective of whether they were fished or not. As an example, the ‘still-fished’ control area to the west of the protected area has much weaker tides, has the River Exe and Otter flowing in (no major rivers flow in within the protected area) the water is markedly more turbid, the seabed much more sedimentary and composed of finer material, the rocks present are mostly low-lying sandstone as opposed the harder and more rugged-relief limestone within the protected area.  There are no seabed areas within the still-fished area to the west that remotely resemble the rugged and extensive reefs within the voluntary protected areas.  As a result of these differences the still-fished area to the west support very few sponges and dead-men’s fingers and almost no seafans.  This was explained to all,  in detail, several times at meetings.  I went as far as preparing Powerpoint presentations with graphics depicting current regimes, river inflows and seabed sedimentology, with supporting photographs of reefs from different locations.  Not a single question was asked or comment made at the end of the presentation.

What did the two 2008-2010 monitoring studies find?

As expected, our study found that there were possible, very early, indicators of recovery but that only future monitoring would identify whether these were real. We also (as predicted) found that the areas outside of the protected areas were fundamentally different from protected area itself  in all years, i.e. they started out very different and remained very  different thus these differences could not be attributed to the cessation of trawling and scallop dredging within the protected area (note, this is different from saying that changes within protected were not due to cessation of trawling and dredging, some almost certainly were, it is simply pointing out the irrelevance of making comparisons with non-comparable areas) .  The flying towed video study reported more positive indications of recovery.  Their frequency graphs for most key species indicated that the ‘still-fished’ controls were very different from the protected areas, in all years, however this was not noted in the report text and comparisons were made between both treatments that would suggest these were essentially similar treatments apart from one being fished and one not.  In our report we noted that the still-fished were not similar to the protected area and therefore could not be considered comparative controls.  I was repeatedly asked to remove this from the executive summary of our report. I declined as I considered that to do otherwise would fundamentally misrepresent the findings of the study.

Is it possible that these problems were simply not noticed?

For that to be possible we would have to accept that NE and DEFRA never noticed that, for three years they had seen no data and no extracted frame grabs from an imaging-based study.  One would also have to accept that, when NE and DEFRA were shown video clips of ‘new growth’ , growth that NE specialists recognised was at least a decade old, they assumed this was not somehow not relevant.  If one accepts that these lapses in critical analysis then I will simply state that all of these problems were explained clearly, verbally and in writing, and even in Powerpoint presentations to all relevant personnel.  I have little doubt that everyone was under great pressure from above and that may, in part, explain the reluctance to question the work in more detail.

Why did it happen?

This may be the most important question.  A number of factors combined here.  Firstly there was a lack of experience of working in these sort of conditions coupled with the use of equipment designed for a different purpose and quite different conditions. Secondly, there was an almost complete focus on statistics and statistical design, to the point that basic ecology was completely ignored.  Thirdly, the most obvious questions were never asked and key data, indeed almost all data, was withheld.  There was also very pronounced pressure for the studies to produce the ‘right’ answer.  Recall that there was no interest in whether the towed video camera system was even capable of detecting colonisation.  The findings of our own study differed significantly from that of Plymouth University and it was decided that this needed to be resolved before publication.  Now one might think that looking at both sets of data might be useful here; I proposed it several times however the data was never provided.  Instead it decided that our statistical analysis would be reviewed.  At the start of the meeting I was informed that Plymouth University’s report had already been approved and so was not open to discussion.  Thus in order to resolve the differences between the two studies review and changes to one study (ours) was permitted.

 Why does any of this matter?

Apart from the obvious,  that we should always aim for the best science, why does this matter?  One could argue that the changes described are almost certainly going to happen anyway, not in the time scale of this study and maybe not as neatly as the study suggests, but in 10 to 15 years it is perfectly possible that areas of recently protected reef will look as described in this study.  So what’s the harm?

From a scientific viewpoint a unique opportunity was lost.  The significant changes did not occur in the first 2-3 years; they will mostly likely occur during the 5-15+ years following cessation of mobile bottom fishing.  We do not know how exactly how the reefs will look then; nor do we have a benchmark against which we can measure change.  There is no raw data available to provide this benchmark and even were the raw data made available we cannot be sure what is accurate and what is not.

Talking in generalities for a moment, I think most scientists and environmentalists would agree that a client disinclined to question study findings provided the findings conform to a preferred agenda, and a contractor inclined to mold findings to suit the preferred agenda, is a toxic mix that is lethal to good science and to the development of policy that actually changes conditions in the real World.  Suppose for a moment that, once the closed area had been established, the eventuality of positive change  in the benthic environment of Lyme Bay was not quite the certainty that we believe it to be.  Would that have changed the findings of this study?  Given that the findings appear to be decoupled from what was actually happening on the protected reefs then the answer is ‘probably not’.  Suppose the client was a developer rather than a conservation agency, and that their preferred findings were for their development to have minimal impact and require minimal mitigation measures. This could be contentious, highly politicised issues (as was Lyme Bay Closed Area) for example dredging a shipping channel and removing live maerl beds in the process. If ever the central aim becomes to please the client by providing the ‘right’ answers rather than accurate answers then we are on a very slippery slope indeed.

It also matters in as much as this is being pushed, all flaws airbrushed out of the  presented material, as a shining example of how to monitor Marine Protected Areas in conferences, DEFRA reports and published articles.

Specifically addressing the Lyme Bay Closed Area, this was an experiment on a grand scale, the like of which we have not seen in UK waters before. It was a phenomenal opportunity to record how species colonise disturbed areas of seabed once this disturbance ceases. Data like this simply does not exist. Lyme Bay was in many ways the ideal candidate; it was easily accessible, all within diving depths, and had been well studied for nearly two decades so we already knew a great deal about the species that existed there, the habitats and locations where they were found and which ones had declined in number. Relatively rare within reef habitats, much of it was fairly level seabed, so the establishment of fixed monitoring stations was far easier than would be the case in many other areas. Unfortunately this opportunity has been lost.

There is also the question of what else has been missed. As mentioned earlier, we were commissioned to undertake a series of dives on a subset of Plymouth University’s towed video transect stations in order to provide comparative data (never seen). This was simply a snap-shot, one off visit where we looked at short sections of a few of the flying towed video transects.  However, at some of these stations we found significant damage, tracks several metres wide swept bare of life and almost certainly due to recent mobile fishing gear operating there. These were photographed and the images presented at meetings with DEFRA, NE, Plymouth University.  Perhaps surprisingly no-one asked why this was not being picked up by the towed video system. This would seem to be a fairly important question, as if it is not picking up fairly major signs of habitat degradation then how can it be detecting more subtle signs of improvement.

It is possible that Lyme Bay Closed Area monitoring was an anomaly, possibly due to the high profile and the level of political expectation as regards the outcome. The evidence suggests otherwise. The last Natural England contract I was invited to tender for, some 18 months back, was an extremely challenging survey requiring 3 dimensional mapping, counting and monitoring of very small animals (e.g. individual coral polyps only millimetres in diameter) living within submerged sea caves along an exposed stretch of coast where underwater visibility was normally very low. Moreover, the study was to be conducted in mid-winter, when storms were most frequent, underwater visibility at its lowest and darkness falling at 4 or 5pm. After carefully reading the tender and calling NE staff to discuss this with them I emailed informing them I would not be tendering and why. My reasons were that, in order to do the job properly (by that I mean to have any chance of generating data that was remotely meaningful) was simply far too dangerous at the time of year they required the fieldwork to be conducted and I would not consider risking the lives of survey team members in this way. Secondly, the weighting given to evaluation if different aspects of each bid was helpfully provided: 50% of overall weighting was given to cost; 5% was given to the expertise and experience of the team with regard to the work to be undertaken.  To put this in as polite terms as possible, this is madness. The message this sends out is pretty clear; you can have no experience whatsoever in this field, nor any expertise within the team relevant to the fieldwork, but provided you are cheap enough the contract is yours. This was hammered home further by a maximum of 15% weighting being given to the estimation of the survey actually being successful, so a starting assumption of ‘little chance of success’ even within the very loose adopted definitions of ‘successful outcomes’ is no barrier to being a successful bidder.  This is not only a pointless squandering of money, producing meaningless reports solely to meet targets, it is also dangerous and may lead to fatalities if this approach continues.

Perhaps the most important reason it matters is that a number of marine protected areas (MPAs) have been designated recently in UK waters, with (hopefully) more to come.  These will require monitoring and initial consultations are already taking place.  The worst possible scenario is that we continue along the path of devaluing expertise and placing ever more weight on low cost.  This is actually worse than doing nothing at all, as it inevitably generates bad data, and bad data we think is accurate is worse than knowing we have no data. This could also be a wonderful opportunity to not only monitor the condition of these MPAs; systems could be established whereby comparative data collected from locations around the UK could provide information about changes on a larger scale.  I am aware that there are many dedicated biologists within Natural England who would love to see contract survey and monitoring work conducted to the highest standard and generating real, useful and pertinent data.  I am also aware that front line staff are under enormous pressure from above and that many of these decisions are no longer within their power to make.

An alternative approach

A network of permanently marked fixed monitoring stations could have been established across the newly protected site and monitored annually for a fraction of the cost of the towed video study. High quality photographs from precisely the same position can be taken year after year. These fixed stations can also be used as structures from which to ‘hang’ physical data loggers (temperature, ambient light etc.) allowing correlation of change in the physical environment with biological change.

 It is true that data from permanently fixed stations are not amenable to testing by the most powerful statistical tests, but for working in the marine environment they have one overwhelming advantage, year on year data is directly comparable. Rocky seabeds in UK waters are simply too heterogeneous, in terms of spatial distribution of species, for random sampling. Moreover this spatial variability is evident over distances of tenths of a metres or less. We simply do not have the technology yet to relocate stations to this level of accuracy within realistic budgets unless we physically mark them. We actually do have a small number of marked stations within Lyme Bay closed area (created and surveyed for our diver-based boulder reef study). These are now abandoned and the data gathering dust. These stations could, with a little effort, be relocated regularly and comparative data collected in five, ten and twenty years time. The principle could also be expanded over a much wider geographical area. With a little imagination in the appropriate bodies a network of low-cost subtidal monitoring stations could be established. These could not only be used to collect data on the condition of marine protected areas but could also be collecting data time-series data that would inform us of local and regional changes in species and habitats.

Table 1. Some of the more unlikely species identified from video frame grabs

Species Taxonomic group Comments Recorded by
Grantia compressa Sponge A small flattened purse sponge generally found attached to other species or under overhangs Video frame grab
Sycon ciliatum Sponge A small purse sponge up to 50mm tall generally attached to other species Video frame grab
Actinothoe sphyrodeta Anthozoan A small anemone found on rock faces identified by dark patches at the base of tentacles Video frame grab
Ebalia granulosa Crustacean A small crab (around 10mm across) found on gravel seabeds Video frame grab
Porcellana platycheles Crustacean A small flattened crab (around 15mm across) generally found on rocky shores underneath boulders Video frame grab
Asterina gibbosa Echinoderm A small starfish (up to 50mm across) normally found in rock pools and shallow rock – never found on any dive surveys in Lyme Bay we are aware of Video frame grab
Ocnus planci Echinoderm A rare sea cucumber – small (up to 80mm) difficult to identify without detailed inspection Video frame grab
Aplidium elegans (?) Tunicate Assume this is meant to be Sidnyum elegans – a small (about 50mm) red colonial tunicate requiring detailed inspection to identify Video frame grab
Diademnum coriaceum Tunicate An encrusting colonial sea squirt – very difficult to identify from appearance alone (not previously known in Lyme Bay) Video frame grab
Lissoclinum perforatum Tunicate An encrusting colonial sea squirt – tricky to identify positively (similar to other Didemnid sea squirts) Video frame grab
Molgula manhattensis Tunicate A small (up to 30mm) solitary sea squirt often encrusted with sand and shells- very tricky to spot and identify with certainty Video frame grab
Lipophrys pholis Fish Shanny – a fish normally found in intertidal rockpools Video frame grab

REFERENCES

Munro C.D., Munro L. 2003. Eunicella verrucosa: investigating growth and reproduction from a population ecology perspective. PHMS Newsletter 13: 29-31.

Sartoretto S. and Francour P. 2012. Bathymetric distribution and growth rates of Eunicella verrucosa (Cnidaria: Gorgoniidae) populationsalong the Marseilles coast (France). Scientia Marina, vol. 76(2): 349-355.

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Benthic survey versus monitoring, a comparison of aims and methodologies

The terms survey and monitoring are often used interchangeably when collecting data on the marine environment. More worryingly there is sometimes a blurring of the differences between the aims and methods required for descriptive surveys and data collection as part of a time-series monitoring programme.

In general, the approach to benthic survey differs from that taken to monitoring in a couple of important aspects. In descriptive survey, more emphasis is put on identifying what organisms and habitats are present rather than precisely how many of them are there. Conversely, monitoring often does not give full descriptions of sites, it may only look at a sub-set of organisms, but requires greater precision in recording the number of individuals or colonies or colonies present, or more precise measurement of the condition of the organisms present. The reasons are fairly obvious; with monitoring you are concerned about recording change in numbers, so your numbers need to be pretty accurate and you need to be pretty confident about the identities of what you are recording. This means that we have to be fairly careful when designing or selecting the format in which data is collected. For example, the UK’s Joint Nature Conservation Committee’s Marine Nature Conservation Review’s recording forms are based of the SACFOR Abundance Scales (apologies for all the acronyms). These SACFOR* scales are widely used for marine survey work around the UK today. They have the advantage that they are well known, widely accepted and can be applied to all marine habitats and all marine marcoflora and fauna. They are very useful for descriptive surveys; they give a good feel for the composition of species assemblages and with experience broad comparisons can be made between different sites. Unfortunately they are also sometimes used for time-series monitoring, something for which they are pretty useless. As they use a logarithmic scale each abundance category is an order of magnitude up or down from the next, thus you need in the region of a ten-fold change in abundance to register as change on the scale. For most species change is abundance will be very obvious long before a ten-fold change in abundance occurs, thus recording only SACFOR abundance values will mean that quite large impacts (e.g. a 50% reduction in a key species abundance, or the doubling in numbers of an invasive species) may go un-noticed. This scenario happens all to easily, especially where one organisation is contracted to undertake repeat monitoring and compare data with that collected by a different organisation (something I have often had to do) or when different staff undertake monitoring on different years.

A corollary of this is that you also need a good idea of what your margin of error is and what are your sources of error. These sources of error are particularly important to know if they are variable or intermittent. Again the reasons are fairly self-evident. If you have sources of error that affect the data they need to be identified and recorded if erroneous records of change or false conclusions are to be avoided. A good example of this in diver or remote camera recording is underwater visibility. The waters off Southern England are prone to strong plankton blooms during the summer months. These blooms vary in timing and duration. Sometimes they arrive in late April and linger for months; sometimes the do not arrive until mid-May and disappear after a few weeks. They also vary in intensity and distribution. When the plankton is thick visibility can be 0.5 of a metre or less, often the plankton occurs in patches, so that visibility is less than a metre at one location but several metres only a few miles away. This patchiness can vary from day to day and from hour to hour as the tides sweep in water from upstream locations. Similarly storms and string tides can lift sediment in to the water column, similarly reducing near seabed visibility to a fraction of what it was days before. This can make visual comparisons between different points in time extra-ordinarily difficult. This is particularly true of comparisons between photographs taken as part of a time series. When the visibility is reduced through plankton blooms, strong tides or following poor weather this can dramatically reduce the number of individuals counted within a fixed area when no change in numbers has actually occurred. Thus it is vitally important for monitoring studies that the raw data (i.e. photographs or log sheets with condition records) and not simply numerical count data is available to those tasked with interpretation of the data.

Because we need greater precision and numerical accuracy for monitoring there are differences in the appropriate methods. Video, either diver operated or remote, can be really useful for broad-scale survey as it collects a lot of spatial data quickly and cheaply and can be very useful for identifying habitats and some conspicuous species or flora/fauna types (e.g. for identifying biotopes as hydroid/bryozoan turf or red algal turf or kelp forest). It can also useful for counting larger, conspicuous and widely spaced individuals (e.g. estimating densities of mature seafan colonies), though stills photography sampling or mosaics are normally a much a better option. Video is rarely suitable for monitoring smaller faunal turf species (such as sponges, soft corals, anemones, hydroids, tunicates etc.) as, although quality is steadily improving, video still does not have the image resolution for accurate identification and accurate counts. This is not to say it will never see some of them; rather it may possibly see some but exactly how many in relation to how many are actually there will vary considerably so the data generated will be unreliable.

Suspended sediment and plankton will dramaticallly reduce visibility. Sediment settling out after a storm may also temporarily coat rock surfaces making smaller species difficult to see.

Suspended sediment and plankton will dramaticallly reduce visibility. Sediment settling out after a storm may also temporarily coat rock surfaces making smaller species difficult to see.

 

A Marine Bio-images scientific diver videos along a survey transect line as part of a no-take-zone monitoring programme. West Scotland. Colin Munro. Marine Bio-images

A Marine Bio-images scientific diver videos along a survey transect line as part of a no-take-zone monitoring programme. West Scotland. Visibility here will vary between less than 2m to more than 10m (as in this picture).

 

 

Species for monitoring.

For any given study we will select target species for monitoring based on a criteria such as known or expected sensitivity to the variable (e.g benthic filter feeding organisms may have a know or presumed sensitivity to increased suspended particulates and sedimentation rates due to nearby dredging or spoil dumping). However, there are some fundamental criteria that apply to nearly all monitoring studies.

  1. We must be able to find the species using the selected methodology (e.g. if using remote towed or drop cameras, species that tend to live of hide in crevices or under rock overhangs are generally unsuitable because they are only likely to be recorded by chance and so numbers are likely to be unreliable)
  2. We must be able to accurately identify the selected species using the selected methodology;
  3. The species must be evenly distributed across the habitats in question (e.g rare species confined to a small area within the total study area are unlikely to yield useful data, especially where a study involves treatment and control areas).
  4. The species must occur in numbers sufficient to generate statistically usable data;
  5. The methodology employed must be able to accurately count the selected species otherwise error or bias will occur.
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Lyme Bay, Lane’s Ground Reef: sponge species recovery and opportunities lost

As part of a small study looking in to gear impacts on seabed species, we recently conducted a few dives attempting to record HD video of bottom trawls and crab pots working on the seabed. Unfortunately we picked a period of one of the thickest plankton blooms this year (either very late or very early for thick plankton, but this has been rather a strange summer, weather-wise). Hanging on to a moving trawl net holding a bulking camera in 0-2 metres visibility certainly keeps you alert! However, it’s not really conducive to great images, so we’ll be trying again once the waters clear.

One very useful aspect of this however was a checkout dive on Lane’s Ground Reef. As described in previous blogs (Lyme Bay, what makes it special, Lyme Bay Closed Area Pts 1 and 2)., Lane’s Ground Reef previously supported rich and diverse sponge assemblages, which largely disappeared as scallop dredging intensified within Lyme Bay. Co-incidentally we dived on an area of lane’s Ground Reef that I had surveyed 17 years ago, before scallop dredgers and other mobile fishing gear had significantly degraded the reef, and again in 2007, immediately prior to the implementation of statutory protection from bottom fishing mobile fishing gear within the Lyme Bay Closed Area (within which Lane’s Ground Reef lies). In 2007 the condition of the reef appeared very poor. Although not a detailed survey (as was the 1995 study) the visual appearance was of far fewer sponge species and much lower densities of sponges and ascidians (sea squirts), with many other attached species appearing to have dramatically declined. (See blog: Scallop dredging: why is it so damaging to reefs for more info on effects)

Lane's Ground Reef, a circalittoral boulder reef rich in sponges and ascidians, within Lyme Bay Closed Area, Lyme Bay, southwest England. Colin Munro Photography

Lane’s Ground Reef, an undisturbed patch of reef rich in sponges and ascidians.

Our three year monitoring, funded by Natural England as part of the study to look at whether the reef habitats recovered following cessation of scallop dredging, centred around Lane’s Ground Reef (Report here as PDF). One reason being it was one of the hardest hit of all vulnerable reefs within Lyme Bay but was also one where the basic reef structure (small boulders on mixed sand and gravel) remained intact, thus the potential for recovery was there. Another reason was that Lane’s Ground Reef, of all the reefs in Lyme Bay, was the one reef highlighted as previously supporting particularly rich sponges assemblages and that these rich sponge assemblages were, probably more than any other feature, what made the reefs of such high conservation importance, with many unusual or rare species and others not yet fully identified. We knew that sponges, being soft-bodied filter feeding organisms, were particularly vulnerable to physical impact (i.e. the passing of a scallop dredge would completely destroy them). The available evidence from other monitoring studies (e.g. Lundy Island Marine Nature Reserve and Skomer Marine Nature Reserve) also indicated that many of these sponge species reproduced and grew very slowly indeed (some colonies being decades old and with little or no recruitment over many years). Thus recording and measuring recovery in the sponge assemblages within Lane’s Ground Reef would seem one of the top priorities for assessing recovery of the reefs species assemblages in Lyme Bay Closed Area after scallop dredging and bottom trawling has stopped. It would also provide invaluable information of rates of recruitment and growth of these species during recovery following prolonged disturbance. At the end of our three years of monitoring (summer 2010) we believed we were just starting to detect such a recovery in sponges on Lane’s Ground. The change was small, and not (at least then) statistically significant, but given the expected slow recovery of sponges this was hardly surprising. That we might, after three year just be starting to see a recovery was therefore extremely encouraging. Unfortunately Natural England decided not to fund further years work. In my view this was a serious error of judgement; in essence they have paid for all the set up and groundwork, then said ‘Ok, let’s stop there and not bother getting the meaningful data’. The closure of 60 square nautical miles of Lyme Bay to mobile bottom fishing gear for conservation purposes is unprecedented in U.K. waters and provided a unique opportunity to study the changes that occurred following the removal of these impacts. The uniqueness of this opportunity also lay in the fact that so there was so much existing diver-collected survey and monitoring data for Lane’s Ground; including accurately positioned data going back to the early 1990s. Thus, probably more than just about anywhere else one could think of in Southwest British waters, we knew what they area had been like prior to intensive scallop dredge and trawling; not just anecdotal diver observations but detailed survey reports and quantitative species counts by experienced marine biologists.

Three years monitoring would, at best, only lay the foundations for detecting recovery by providing a baseline against which recovery of the most impacted, slower growing species could be measured. Real change is far more likely to be observed over a 5-10 year period. We hope to start limited monitoring again in 2013, on a self-funded basis, because we believe that understanding the changes that occur on these boulder reefs is crucial to our understanding of how the reef species assemblages are recovering. As the prime reason that for establishing the Closed Area was to protect these reef assemblages and allow their recovery, and was also the driver behind a 16 year campaign (notably by the Devon wildlife Trust) to achieve this, then it seems to me a little absurd not to measure whether this is actually achieving the desired effect. Currently there is no study running that is capable of detecting these subtle changes in species such as sponges, ascidian and other small turf-forming species that create the richness and diversity of species for which these reefs were previously known.

I bring this up now because, during our brief dives on Lane’s Ground last week, our observations did suggest that quite significant recovery, especially within the sponge assemblages, was indeed now occurring. Unfortunately these dives were not on any of our 2008-2010 monitoring stations as this was not practical, so direct comparison is not possible.

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Lyme Bay Reefs

As I’ve been writing a fair amount about Lyme Bay and the Lyme Bay Closed Area protection and its effects recently, I thought I’d post a small selection of images to illustrate why the reefs of Lyme Bay are so important.

Sunset corals,Leptopsammia pruvoti, growing on the Saw-tooth Ledges Reef, Lyme Bay, Southwest England. Colin Munro Photography. www.colinmunrophotography.com

Sunset corals,Leptopsammia pruvoti, growing on the Saw-tooth Ledges Reef, Lyme Bay, Southwest England.

Sunset corals are one of the very few species of true corals (i.e. stony, or scleractinian, corals, the sort that are responsible for spectacular reefs in tropical waters). It is a solitary coral, where each polyp attaches to the underlying rock and grows seperately, so does not form colonies or reefs. They do however grow in quite dense clusters and are quite beautiful. Sunset corals are rare in UK waters, known to occur at only a handful of locations. The saw-tooth ledges reefs in Lyme Bay support one of the densest populations found around the UK and also the easternmost population known in UK waters.

 Lane's Ground Reef, a circalittoral boulder reef rich in sponges and and ascidians, within Lyme Bay Closed Area, Lyme Bay, southwest England. Colin Munro Photography. www.colinmunrophotography.com

Lane’s Ground Reef, a circalittoral boulder reef rich in sponges and and ascidians, within Lyme Bay Closed Area, Lyme Bay

Lane’s Ground Reef is a boulder reef known for its rich assemblage of sponge species. In recent years these appear to have undergone a significant decline, attributed to bottom trawling and scallop dredging, however since the establishment of the Closed Area, from which trawlers and scallop dredgers are banned, there are now signs of a recovery.

Cliona celata is one of the most distinctive sponges found in UK waters. Colin Munro Photography. www.colinmunrophotography.com

Cliona celata is one of the most distinctive sponges found in UK waters

The boring sponge, Cliona celata, is one of the most distinctive sponges in UK waters, with its brilliant sulphur yellow colouring and large size. In fact much of the sponge is hidden as, through a process still not fully understood, it bores in to limestone and sandstone. Apart from this ‘massive’ form shown here, the sponge also occurs in a purely boring form where only the circular yellow oscules can be seen protruding from the rock surface. It is believed that the sponges ability to bore into hard limestone is due to chemicals released, possibily acids.

Large, mature pink seafans, Eunicella verrucosa, growing on the East Tennants Reef, Lyme Bay, SW England.  Colin Munro Photography. www.colinmunrophotography.com

Large, mature pink seafans, Eunicella verrucosa, growing on the crest of a rock slab, East Tennants Reef, Lyme Bay.

Pink seafans, Eunicella verrucosa, are the only seafan (gorgonion) species known to occur in English waters. The East Tennants Reef supports one of densest and most extensive populations of seafans in the English Channel. The seafans found here are notable for their large size in addition to the high density found here.

A perfectly camouflaged Tritonia nisodnheri nudibranch feeding on a seafan (Eunicella verrucosa) polyp. Colin Munro Photography. www.colinmunrophotography.com

A perfectly camouflaged Tritonia nisodnheri nudibranch feeding on a seafan (Eunicella verrucosa) polyp

The nudibranch (seaslug) Tritonia nilsodnheri feeds exclusively (as far as we know) on the polyps of of gorgonions and soft corals. The processes on its back strongly resemble seafan polyps and so it is almost perfectly camouflaged on its host. It has been proposed that its pink coloration comes from feeding on pink E. verrucosa seafans. Like E. verrucosa it comes in two colour morphs, pink and white. In English waters where seafans are mostly pink (a small percentage are white) so most Tritonia are also pink. In this picture the Tritonia can be seen sucking the soft polyp tissue out from within the harder calyx that surrounds each polyp.

For more information about Lyme Bay Closed Area and the work we have been doing there to understand the changes occurring following establishment of statutory protection in 2008, read the blogs on my Marine Bio-images website.

Lyme Bay Closed Area Monitoring

Lyme Bay Closed Area Monitoring: what we have learned so far

For more background on Lyme Bay reefs. Lyme Bay: what makes it special?

And finally, for a clearer understanding of why scallop dredging is so damaging. Scallop dredging, whay is it considered so damaging to reefs?

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Marine habitat mapping

One of Marine Bio-images’ areas of expertise is Marine Habitat Mapping. We have undertaken a great many mapping studies in the past 20 years, these include biotope mapping of the isle of Scilly sublittoral soft sediments, biotope mapping of the littoral and sublittoral habitats of the Dornoch Firth, biotope mapping of Plymouth Sound soft sediment and reef areas, habitat mapping within Lyme Bay, and habitat mapping of the sublittoral within Lamlash Bay No-take Zone (Isle of Arran).  We use a variety of techniques, depending on depth, turbidity and the size and scale of the features to be mapped.  We have particular expertise in combining drop-down and towed camera systems with diver spot surveys.  This technique is highly cost-effective, providing a wide coverage (using camera systems) along with very detailed data collected by divers.

Dense bed of brittlestars (Ophiothrix fragilis), Lyme Bay, Southwest England, UK. Dense aggregations of brittlestars are a distinctive feature of Lyme Bay.

Dense bed of brittlestars (Ophiothrix fragilis), Lyme Bay, Southwest England, UK. Dense aggregations of brittlestars are a distinctive feature of lyme Bay.

We also use acoustic techniques, including side scan sonar, to provide detail on the seabed releif and likley sediment type.  For soft sediment areas we will ground truth this by grab sampling.

Habitats are subsequently mapped using GIS to produce detailed geo-referenced habitat maps for the features of interest.

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Lyme Bay Closed Area Monitoring: what we have learned so far.

After almost 18 years of research, campaigning and negotiation, statutory protection for the most vuulnerable reefs in Lyme Bay became a reality in 2008.  This was deemed necessary as, despite voluntary agreements, it was apparent the damage to the reefs was still occurring.  The questions that needed to be addressed then became:

  • how will the species on the reefs respond?
  • How long will full recovery take?
  • Will the species that appear to have been hardest hit, the sponges, the seafans, the soft corals, the larger sea squirts, re-establish themselves in a few years or will other species colonise the reefs first?

Between summer 2008 and summer 2010 we undertook a monitoring programmme looking at the species present and how there numbers were changing.  In that time we have just started to get the first tantalising glimpse of the changes occurring.

We have now been able to publish our report on the monitoring work we undertook looking at the changes that occurred on boulder reef communities. The full report (as a PDF) can be downloaded Here: Lyme_Bay_Closed_Area_Monitoring_2008-2010_MBI.

However, as this is a fairly lengthy document it seemed a good idea to summarise what we’ve found so far in a fairly non-technical way, so here goes.

Before describing our findings it’s worth going over a description of Lyme Bay and a bit of background regarding the concerns about bottom fishing towed gear and earlier attempts at achieving a degree of protection.  This helps explain some of our reasoning in survey design and interpretation of the data. (If you only want to read the outcomes then skip down to What we have found so far? near the bottom)

Lyme Bay is a large, open, south-facing bay in Southwest England, opening into the English Channel (see study layout map, below).  The West of the Bay is predominantly fine sediment seabeds, fine sands or mud.  The waters in the west also tend to be more turbid.  This is in part due to the tides are being weaker in the western part of the Bay (allowing fine sediments to settle out of the water column) and also because much of the rock here is soft, rapidly eroding sandstone.  But mostly it is because of the two major rivers, the Teign and the Exe, which flow in to the western side of Lyme Bay carrying large sediment loads which are then deposited in the Bay.

Tidal streams are markedly stronger and no rivers flow into the eastern part of Lyme Bay.  The seabed here is much rockier and sediment tends to be much coarser.  The greater amounts of exposed bedrock, in particular the high rocky ledges, and stronger currents, generally results in richer assemblages of filter feeding animals such as larger erect sponges, gorgonians, soft corals.

Map depicting the Closed Area (yellow); pre-existing Voluntary exclusion areas (Closed Controls: light green) and our monitoring station locations (red polygons).  The pre-existing voluntary exclusion areas were agreed between local fishermen and the Devon Wildlife Trust between 2001 and 2006.  They were partially successful but not all vessels appeared to abide by the agreement and damage to the reef habitats continued, hence the statutory closed area was created.

Map depicting the Closed Area (yellow); pre-existing Voluntary exclusion areas (Closed Controls: light green) and our monitoring station locations (red polygons). The pre-existing voluntary exclusion areas were agreed between local fishermen and the Devon Wildlife Trust between 2001 and 2006. They were partially successful but not all vessels appeared to abide by the agreement and damage to the reef habitats continued, hence the statutory closed area was created.

The reefs of greatest concern in relation to damage from scallop dredges and trawlers were located a little to the east of the centre of the Lyme Bay.  They lie in a band between (roughly) 20 and 24 metres below chart datum (approximately 22 – 29 metres actual depth depending on the state of the tide).  Back in 1992 the Devon Wildlife Trust began getting reports of damage to reefs caused by rockhopper trawls and in particular scallop dredges.  We then conducted a series of diving surveys, documenting the damage occurring here for the first time.  After many years of negotiation, Devon Wildlife Trust and local fishermen reached an agreement whereby bottom towed fishing gear would not operate within two vulnerable reef areas, known as Lane’s Ground and Saw-tooth Ledges.  This agreement came in to effect in 2001.   Two other reef areas, known as Beer Home Ground and the East Tennants Reef, were subsequently added in 2006.  This was a considerable achievement by both Devon Wildlife Trust and local fishermen, and the agreement was largely adhered to.  The problem was it wasn’t adhered to by everyone, and one or two scallop dredgers passing through such an area will cause damage that will linger for years.  So, in July 2008 a larger area of 60 square miles within Lyme Bay was closed to all towed bottom gear fishing by Statutory Instrument. This area enclosed the four existing voluntary areas.

At this point the need to begin monitoring of how the newly protected area responded to this protection was recognised.  The question was, how to design the monitoring?  Ideally monitoring would have commenced several years before the statutory protection came in to place, allowing a time series of before and after comparisons . However that had not happened and nothing could be done about that now.  Comparison of change in reef habitats inside and outside of the protected area is another approach, but the problem here is that (as described above) conditions and habitat vary markedly across the bay to the east and west and it was very unlikely that similar habitats existed to the east or west of the closed area box, or that species would reproduce, settle, grow and interact in similar ways east or west of the Closed Area box as they would inside the box.  South (offshore) of the box conditions were very different; the water was deeper and the seabed mostly sedimentary, thus it could not be used for comparison either.  There are also the four existing voluntary protected areas to consider.   One possibility is to compare existing voluntary protected areas with areas in the new Closed Area.  If this approach is taken two important factors must be taken in to account.  The first consideration is that each of the voluntary protected areas was very different to the others, in terms of habitat and the species assemblage they support.  By way of example, if one considers Lane’s Ground Reef and East Tennant’s Reef (See map above).

An isolated seafan (Eunicella verruucosa) on Lane's Ground Reef.  This is a very large seafan for Lane's Ground, most are typically around half this size. Marine Bio-images.

An isolated seafan (Eunicella verruucosa) on Lane’s Ground Reef. This is a very large seafan for Lane’s Ground, most are typically around half this size. note that there are no other seafans in sight; this is typical of their sparse distribution on Lane’s Ground. Note also the small boulders that form the reef. The relative instability in stormy seas are probably factors that limit the size of seafans here.

East Tennants Reef is slightly deeper, exposed to slightly stronger currents and is composed of large slabs of limestone, whereas Lane’s Ground is composed of small boulders on patches of sand, gravel and stones.  Lane’s Ground supports relatively few seafans, somewhere in the order of 1-10 per 100mm2.  No large seafans are found on Lane’s Ground Reef, presumably due to a combination of greater exposure to wave action (as shallower), reduced feeding currents and reduced stability of the smaller boulders.

Dense cluster of large seafans (Eunicella verrucosa) typical of East Tennants Reef.  Marine Bio-images.

Dense cluster of large seafans (Eunicella verrucosa) typical of East Tennants Reef. note also the large, stable limestone slabs to which they are attached, and also the numberous (white, background) soft corals Alcyonium digitatum which are also much larger and more numerous here than at Lane’s Ground Reef. This helps illustrate the uniqueness of each reef in Lyme Bay and why treating either the entire Closed Area or all voluntary closuures (Closed Controls) as a single treatmment or entity would not work.

East Tennant’s Reef, in contrast, supports very high densities of large seafans, averaging several hundred per  100mm2, mature colonies being 4-5 times the size of those on Lane’s Ground.  Thus the biomass and reproductive capacity of seafans on East Tennant’s Reef will be many times greater than that on Lane’s Ground and, as conditions are clearly much more favourable to seafans here, it would be unsurprising if settlement, early survivorship and growth rates were higher here also.  So we can see that it is not possible to treat all pre-existing voluntary areas as one condition or ‘treatment’ to compare with newly protected areas outside.  The second factor to consider is that the differences between the existing voluntary protected areas and the newly protected Closed Area beyond their borders were subtle.  Remember the statutory protection was established because the voluntary protected areas were not being fully complied with.  Thus they will not be uniformly ‘better’ than the areas outside; rather they are a patchwork of relatively pristine and recovering areas (the degree of recovery depending on how long ago they were established, 2002 or 2006) and of damaged areas due to recent incursions.

The hypothesis we were required to test under the funding from Natural England was that:
Over time, species assemblages within sites in the new statutory closure but outside the pre-existing voluntary closures would change to more closely resemble those in the pre-existing voluntary closures and become less similar to sites where fishing by towed bottom gear was still permitted.

From what we already know about the Bay and about the voluntary closures we  can Immediately see problems here:  both in comparing what’s happening inside the Statutory Closure to what’s happening outside and in comparing the voluntary closures to the areas of the new statutory closure outside the voluntary closures.

Lane's Ground Reef is a linear reef, running east-west, composed of a matrix of boulder reef patches interspersed with sand and gravel patches. marine Bio-images

Lane’s Ground Reef is a linear reef, running east-west, composed of a matrix of boulder reef patches interspersed with sand and gravel patches.

Like all the reefs in Lyme Bay, Lane's Ground Reef is not one continuous area of similar habitat, rather it is a complex matrix of ribbons of boulder reef interspersed with patches of coarse sand and gravel.  This is further complicated by the fact that trawlers and scallop dredgers have fished across the reef, creating wide swathes of degraded reef.  In order to ensure meaningful comparisons our monitoring stations needed to be located on areas of boulder reef that did not appear degraded.  It can be seen that these formed only small areas within the Lane's Ground voluntary closure and so careful pre-selection of suitable areas was required before haphazardly dropping our station markers within those areas. arine Bio-images

Like all the reefs in Lyme Bay, Lane’s Ground Reef is not one continuous area of similar habitat, rather it is a complex matrix of ribbons of boulder reef interspersed with patches of coarse sand and gravel. This is further complicated by the fact that trawlers and scallop dredgers have fished across the reef, creating wide swathes of degraded reef. In order to ensure meaningful comparisons our monitoring stations needed to be located on areas of boulder reef that did not appear degraded. It can be seen that these formed only small areas within the Lane’s Ground voluntary closure and so careful pre-selection of suitable areas was required before haphazardly dropping our station markers within those areas.

This is the approach we took.

  1. We elected to work with one Voluntary Closed area only, Lane’s ground reef, as (as described above) the differences between the different voluntary closed areas was far greater than any likely change in species’ abundances due to cessation of fishing  in the three years of the study.  To mix habitats through treating multiple voluntary closures as single treatments would simply create vast amounts of ‘noise’  and introduce many other factors than may be responsible for differences in response, other than cessation of fishing, and so making it impossible to interpret the data. This also meant we could very tightly define the habitat we were studying, in terms of seabed composition, relief, depth, tidal streams and wave exposure, all factors we were aware would markedly modify the species assemblage and so potentially compromise our interpretation.  There were a couple of other factors in our selection process.  Being relatively level with only small boulders present, Lane’s Ground Reef was relatively easy for trawlers and scallop dredgers to work; there were no ledges or large rocky outcrops on which to come fast or damage gear.  The fact that it was level also made it much easier to extract reliable data; it is hard to get good quatitative data from reefs with ledges, overhangs, steep slopes etc simply because of the logistics of laying and counting withing transects and quadrats.  We also had very good historical data on Lane’s Ground Reef.  Numerous surveys (many by ourselves) had been conducted there over the previous 18 years, thus we had a very good handle on the habitat, the species we were likely to find and their distribution.  This hugely aided our survey design.   A final, but very important consideration was that Lane’s Ground Reef had been identified previouusly as especially important for its sponge assemblages.  Now we knew that sponges amongst the most vulnerable to mobile fishing gear and there was a lot of anecdotal evidence and comparative video suggesting that sponges had declined markedly on Lane’s Grouund over the past decade.  But the boulder reef habitat was still largely intact, so this seemed an ideal testing ground to find out whether they would recover once physical disturbance cesed.
  2. The aim, within the hypothesis to be tested, was to compare relatively pristine sites (the voluntary closures) with the newly protected sites within the Closed Area and also with the unprotected areas outside the Closed Area.  But we knew the voluntary closures were not pristine and contained many areas similarly damaged to those within the new closure.  Clearly, simply randomly assigning areas within the voluntary closure would not achieve this, so instead we elected to conduct a pre-survey of Lane’s Ground voluntary closure to identify relatively pristine areas, from within in which our ‘pristine’ comparisons would be haphazardly located (i.e. a random stratified approach).  This proved to be more important than we had expected; significant tracts of Lane’s Ground voluntary closure appeared markedly degraded (i.e. showing clear signs of physical damage or markedly reduced numbers of epifaunal species compared to historical surveys of the reef), with relatively pristine areas appearing no more than small ‘islands’ dotted across the reef.
  3. Comparing with areas outside the statutory Closed Area, as the contract required, proved most problematic.  In the end we elected to compare with areas running along the same depth contour as Lane’s Ground Reef, where similar boulder reef habitat occurred immediately outside the Closed Area.  This was a difficult choice.  Selecting areas immediately outside left our study open to criticisms of ‘edge effects’ such as ‘fishing the line’ (where fishermen tend to work along the edges of a protected area more so than further afield).  Yet as we knew, conditions varied markedly as one travelled east, west or south of the Closed Area, and that similar habitat was very difficult to find outside the Closed Area, thus rendering data from further afield unsuitable for comparison.

The layout of the study is shown here.  Four monitoring stations were located within Lane’s Ground Reef (what had been the old voluntary closure and was now referred to, conforming with the terminology defined by Plymouth University, as the Closed Control), three within the new Closed Area, but outside of the voluntary closure (termed the New Closure) and three just outside of the new Closed Area, termed the Open Controls.  So, testing the hypothesis

What have we found so far?
So, what we found was the hypothesis (comparing station outside the Closed Area to those within) didn’t work – essentially because the underlying assumptions were incorrect, namely that the conditions outside of the Closed Area were similar to those inside.  Even when carefully selecting habitat type the results demonstrate that environmental conditions outside of the Closed Area are too dissimilar for meaningful comparisons (in terms of change likely to be due to bottom fishing effects) to be made.  Given what we already knew about the Bay this was no great surprise.  The data also suggested that the New Closure and the Closed Controls were also different when one looked at all the species studied, but with a fair degree of overlap when individual species were studied.  Again this was not terribly surprising.  What we, however, did see was a certain amount of change in both New Closed and Closed Controls.  Now three years (essentially three data points on our time series) is a very short timescale for the species we are looking at, but what it does suggest is that both new closures and existing voluntary closed areas may be responding to the cessation of trawling and dredging.  Again this is not hugely surprising. We know that the existing voluntary closure had suffered from incursions and so was not pristine at the start of the study;  areas not impacted by direct disturbance (i.e. trawls or dredges passing directly over) are likely to have suffered indirectly from the effects of increased sediment plumes as gear passed nearby and mobilised seabed sediments.  As most of the species of concern (sponges, hydroids, soft corals, gorgonians, sea squirts) are filter feeding organisms it is quite likely this had a deleterious effect on them.   Thus even areas that we had pre-selected as relatively pristine may have deteriorated due to the proximity of mobile fishing gear.  This may seem like a bit of a failure, but it is useful as there is often considerable pressure to design studies that are statistically elegant but do not take in to account the complexities and variability of the real environment.

Signs of recovery?
Perhaps the most exciting of all is the possible early signs of sponge assemblage recovery.

Sponges, in particular erect branching sponges, are possibly the most vulnerable of the prominent species found in Lyme Bay.  They are soft bodied and easily destroyed by physical contact.  They are also filter feeders and so likely to suffer from significant increases in sedimentation.  Many are believed to be very slow growing, studies at Skomer and Lundy Island Marine Nature reserves indicate that axinellid sponges (a significant group of erect branching sponges) suggest they are very long lived.  Sponge assemblages have also previously been identified at one of the most notable features of the reefs in Lyme Bay, with Lane’s Ground Reef highlighted as previously supporting particularly rich sponges assemblages and that these rich sponge assemblages were, probably more than any other feature, what made the reefs of such high conservation importance, with many unusual or rare species and others not yet fully identified.   Thus determining whether sponge assemblages recover, and over what timescale, is fundamental to identifying whether the protection afforded to Lyme Bay is a success.

Lyme Bay Closed Area Monitoring.  Change in erect branching sponges 2008 - 2010 within diver transects.

Change in erect branching sponges 2008 – 2010 recorded within diver transects at Open Controls (outside closed Area), New Closures (within Closed Area but outside old voluntary closures) and Closed Control (within Lane’s Ground pre-exisiting voluntary closure). Note the marked jump in mean numbers between 2008 (the start of our study and the first year of the statutory closure) and 2009. Although there is some drop back in 2010 numbers are still notably higher than 2008.

We believe this work is extremely important.  The opportunity to conduct such a study as Lyme Bay affords us comes only very rarely.  Lyme Bay Closed Area is the first such closed area established for conservation purposes in England’s waters.  Furthermore, there are few areas of coastal seabed as well studied as Lyme Bay, thus although we don’t have the ideal pre and post closure monitoring we do possess a wealth of data on what these reefs used to be like almost 20 years ago.  Given the uniqueness of this opportunity and the very encouraging signs in the data from the first three years it would seem essential that the monitoring is continued.  Currently, although the signs are both encouraging and more or less exactly what we would expect given what we already know about Lyme Bay they are, with only three years data, simply an indication of where change might be heading and no more.  Consequently we are now actively seeking funding to restart monitoring in 2013.

[Rockhopper trawls: bottom trawls fitted with extra large rubber discs on the footrope, allowing them to bounce or roll over boulders and small rock outcrops and so work rocky seabeds that other trawls could not]

 

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Diver surveys and Scientific diving services

A Marine Bio-images diver conducts species counts within random quadrats on the seabed in Lyme bay, Southwest England.

A Marine Bio-images diver conducts species counts within random quadrats on the seabed in Lyme bay, Southwest England.

Much seabed data can be collected remotely nowadays, but sometimes, when detailed biological data, high quality images or detailed inspection is required, the only practical solution is to use professional scientific divers.  Marine Bio-images can provide HSE qualified dive teams comprising highly experienced diving marine biologists. Our divers are both very experienced SCUBA divers and biologists with many years experience in underwater data collection, survey and sampling.  To discuss a diving project call +44(0)7926478199 or email marine bio-images here.

Marine Bio-images diving biologist collecting sediment core samples for infauna analysis, particle size analysis and analysis for carbon content.   Colin Munro

Marine Bio-images diving biologist collecting sediment core samples for infauna analysis, particle size analysis and analysis for carbon content.

A Marine Bio-images scientific diver videos along a survey transect line as part of a no-take-zone monitoring programme.  West Scotland. Colin Munro.  Marine Bio-images

A Marine Bio-images scientific diver videos along a survey transect line as part of a no-take-zone monitoring programme. West Scotland.

Marine Bio-images diver Colin Munro preparing to dive with Sony EX1 HD video camera to recoding impacts of trawl gear on the seabed.

Marine Bio-images diver Colin Munro preparing to dive with Sony EX1 HD video camera to recoding impacts of trawl gear on the seabed. image (C) Holly Latham

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