Clive pollitt

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    Development of Low Budget Survey Equipment and Techniques for Shallow

    Water Ecosystems: A Case Study of the Fal Estuary Seagrass beds

    Clive Pollittt and Claire Eatock

    Authors biographical information

    Mr Clive Pollitt, FdSc Marine Science student. Falmouth Marine School. Falmouth, Cornwall,

    UK. clivepollitt@aol.com.

    Dr Claire Eatock. FdSc Marine Science lecturer. Falmouth Marine School. Falmouth, Cornwall,

    UK. Claire.eatock@falmouthmarineschool.ac.uk

    Claire Eatock is a lecturer and Clive Pollitt a foundation degree student at Falmouth Marine

    school. Clive is an engineer interested in promoting marine biology to the general public.

    Falmouth Marine School

    Killigrew Street

    Falmouth

    Cornwall

    TR11 3QS

    United Kingdom

    Tel: 01326 310 310

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    Abstract

    Seagrass beds are one of the many shallow water benthic habitats that need to be regularly

    monitored. This project used the seagrass beds in the Fal estuary in Cornwall UK as a test case

    to develop inexpensive shallow water habitat surveying equipment that would be suitable for

    colleges and amateur conservationists. It came up with four devices; a simple glass bottomed

    box that could be mounted on the side of a boat; a video camera mounted on a long extending

    pole that could give close-up pictures of the benthos; a photo/video-quadrat made from industrial

    shelving material that could record statistical data for benthic habitats and finally an underwater

    towed video monitoring system that could be used to cover large benthic areas. With these

    pieces of equipment a successful baseline survey of the Fal estuary Seagrass beds was

    completed.

    Keywords

    Benthic, Survey, Seagrass, Volunteer Bio-monitoring.

    Introduction

    Surveying shallow marine benthic environments is important for conservation groups,

    environmental monitoring, water quality control, pollution monitoring and for monitoring global

    warming and ocean acidification. (Rhoads 2004) A large amount of marine life is within the

    shallow photic zone just beyond the shore and in the inter-tidal zone.

    The costs associated with this type of surveying have become prohibitive due the sheer amount

    of area to be covered. This has resulted in large areas being infrequently surveyed, if at all, and

    environmental and planning decisions cannot be easily made with confidence if current coastal

    survey data is not available. An example of this is in the Fal estuary in Cornwall, England where

    a Special Area of Conservation (SAC) was established in 1992 as a result of the European

    Habitats Directive. The local harbor commissioners are one of the organizations who have been

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    made responsible for environmental monitoring of the estuary but have very little current data.

    This is a very typical situation in Britain and Europe at large. The reasons for this situation are

    the costs involved with environmental surveying which are often outside the budget of small

    environmental organizations.

    The Fal estuary was made a SAC largely because of the maerl and seagrass beds that are present

    within it. There is however very little current environmental habitat survey data available, the

    habitat map presently in use being more than 20 years old. (Kevan Cook, Lead Advisor, Marine,

    Truro, Natural England, personal communication, 23 September 2010)

    Volunteer based monitoring programs have been designed and initiated by many organizations

    including Seagrass Watch, (McKenzie 2002) but many have found that these programs are

    difficult to sustain. This is largely due to the fact that most Seagrass is below the water for much

    of the time and qualified volunteer divers are required to do the surveying. (Short 2009)

    Different monitoring options are dependent on the structure and resources available, e.g.

    cumbersome methods are not practical for volunteer-based monitoring networks and also the

    adequacy of different methods for the various species, which requires knowledge of their growth

    rates and basic ecology. (Duarte 2003)

    Many types of equipment have been used to overcome the difficulty of using professionally

    qualified divers. Professional surveying institutions often overcome this by the use of remotely

    deployed video equipment (Potts 1982), which has become a well established tool in many areas

    of marine research. (Holme 1984) Towed video sledge techniques provide a means to visually

    survey large areas of seafloor without the depth or time constraints usually associated with other

    techniques such as scuba diving. (Sisman 1982)

    In the past, techniques such as this have been used to monitor the condition of features in

    candidate Special Areas of Conservation (SAC) (Magorrian 1996) Towed video sledge data can

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    be used to estimate the relative abundance of benthic species using the Visual Fast Count (VFC)

    technique. (Kimmel 1985) The main disadvantage of the towed video sledge system is the

    potential damage it can cause to the fragile seafloor habitat that it is recording. (Grizzle 2008)

    An alternative is to have a Drop Down Video System (DDVS) which is a camera mounted on a

    frame, often associated with a quadrat. (Holt, Sanderson 2001) This is lowered to the seafloor

    where it remains stationary whilst recording the benthos. The position is given by a Global

    Positioning System (GPS) receiver and the equipment is then moved to a new location often on a

    pre-set transect. DDVS recording techniques have been used in a variety of applications and are

    appropriate for the identification of seabed habitats. (Sanderson et al. 1999)

    An underwater Remotely Operated Vehicle (ROV) is a self propelled underwater camera system

    often with artificial lighting capable of descending to depths unreachable by divers and is

    considered suitable for biotype surveying and monitoring. (Arbour 2004) The ROV is usually

    connected to a surface support vessel via a tether cable which controls the ROVs movements

    and passes the underwater video image to the operator for control and recording purposes. Due

    to their maneuverability these systems are able to acquire great detail of the biotype. Together

    with GPS equipment and on-board recorders these systems combine the flexibility of a diver

    together with the advantages of remote control.

    The disadvantage of ROV, towed and drop down video systems is the expense of the equipment

    and of the support vessel, deploying equipment and tethers and the need for highly trained

    personnel. (Epstein 2010) These factors usually place these survey techniques out of the reach of

    small, low budget surveying organizations and volunteer initiatives. (Short 1984)

    The purpose of this project was to develop inexpensive and safe shallow benthic surveying

    equipment using basic skills and the recent development of inexpensive high definition digital

    video cameras and recording equipment. The Seagrass beds in the Fal estuary were chosen as a

    test case.

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    1) Aqua-scope

    The first device developed was built along the lines of a glass bottomed boat. (See figure1) This

    piece of equipment was a large wooden box 75cm high by 75cm long and 40cm wide. The

    bottom of the box had a glass water-proof window installed with handles and boat attachment

    points placed along the sides of the box. The inside was painted matt black and a removable top

    with an observation port were added. It was named the Aqua-scope.

    Deployment

    When the boat had reached the right location to be surveyed the position and depth were taken

    using the boats onboard fish finder and GPS. The Aqua-scope was then placed in position over

    the side of the boat and secured with its fastenings. Viewing of the seafloor was simply done by

    looking into the viewing port. The boat was allowed to drift and the depth, GPS positions and

    benthos were noted as it did so. Still camera and video photography was possible with the

    camera placed at the viewing port or lowered to the glass pane where a very wide field of view

    was possible.

    Results

    General observation underwater to a depth of 4 to 5 meters in bright, calm conditions was

    possible at slack low tide. (See figure 2) The Aqua-scope was successfully used to map the

    position of the major sea-grass beds in the Fal and in particular the St. Mawes Eelgrass meadow

    near the Fal entrance.

    Four surveys were conducted in the summer months of June, July and September and three

    during March using the Aqua-scope. It was also used in conjunction with the other surveying

    equipment developed in the project to help observe the performance and deployment of the

    equipment.

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    Materials and Costs (See table 1)

    Capabilities and limitations

    The data collected by the Aqua-scope could be considered to be equivalent to the data obtained

    from surface snorkeling i.e. a general visual survey of areas of the seafloor where the benthos

    type , coverage and location could be observed and recorded manually.

    The main limitation of the Aqua-scope was the limited depth to which it can be used and the

    inability of the boat to maneuver with it deployed. Any movement by the boat against the tide

    resulted in turbulence and bubbles around the observation glass. The weather conditions had t