Those of you who follow this blog may have read about the settlement panels; squares of plastic that are placed underwater and which allow us to follow how animals settle and grow on the rocks. There are two problems that have to be overcome when deploying anything in the seas around Ascension Island.
Firstly, the panels need to be secured against the affects of the famous Ascension rollers. We came up with several ideas but in the end we decided that no amount of ballast was going to secure the plates against the swell. A colleague of mine at the British Antarctic Survey has tried to use similar panels, held down by ballast, but he lost the lot. We therefore decided that we would strap the plates to objects that had been there for a long, long time.
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Stevie Cartwright attaching plates to an old undersea cable.
Secondly, very little grows on the surface of rocks at Ascension as the black trigger fish will eat almost anything that is exposed. The panels, therefore, need to be fixed to a solid surface that would stop trigger fish getting access to the underside of the plates.
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These plates are attached to the wreck of the Derby, which sank in 1929, and hopefully will stay in place for at least another year!
We chose to position the first of the three plates on one of the cables in Mitchell’s Bay, the second on the wreck of the Derby and the final plates just off Wigan pier. Stevie Cartwright was in charge of fixing the plates using a selection of cable ties and straps. He also cable tied one temperature logger to each of the plates and a tag that lets anyone who finds them know that these are scientific experiments and should not be disturbed.
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Panel in place and waiting for a new community of sealife to move in.
The key to the success of this project is the willingness of local divers Caz, Sam and Nik to visit the panels every 6-8 weeks and take high resolution images of the developing communities. They will post the pictures back to Dr David Barnes in the UK who will identify each of the animals and follow how the panels are colonised through time. This long term project will help us understand the time of year when animals spawn at Ascension and the data loggers also give us one of the first high resolution records of how shallow water sea temperature varies around the Island. These two vital pieces of information can be compared with other parts of the world and will allow us to better manage the Island's marine biodiversity.
We appreciate any of you Ascension divers and snorkellers letting us know if you see any damage to the plates.
- Submitted by Dr Simon Morley