Friday, 13 July 2012

Day 6 - Living in the mud

We know very little about animals living at the abyssal seafloor. However, they are part of important biogeochemical cycles, including the carbon cycle. We need to increase our understanding of their functions and temporal variability to predict not only their fate under climate change but also how they can influence carbon processes at the seafloor.

Claire in the temperature controlled laboratory
I am looking at the macrofauna that are found in the sediment. These tiny animals are measured in micrometres – one millionth of a metre, or one thousandth of a millimetre –  µm. The ones I am looking for measure between 300 to 10 000 µm.

Bivalves, crustaceans and worms are among the inhabitants of the abyssal plain. Marine worms are the dominant fauna of these communities. I am particularly interested in how the marine worm population varies over time – the temporal variation. Do they change from year to year? Is the change in terms of number of individuals or in terms of present species or both? Can we relate the change to environmental factors such as primary production (the amount of plankton) in sea surface water?

Since 1989 cores have been taken at PAP to investigate these questions. Part of the process is done on board. The cores need to be put into a temperature controlled cold room and then sliced at 0-1 cm, 1-3 cm, 3-5 cm, 5-10 cm and 10-15 cm layers and then finally are preserved in formalin. The sieving and sorting of the fauna will take place back to the Natural History Museum and NOC. Processing cores is a long task but we have very motivated teams onboard making it a lot easier, which is good as we should collect more than 120 cores for the marine worm study!

By Claire Laguionie-Marchais, a PhD student at the National Oceanography Centre, Southampton and the Natural History Museum, London.