Rates and pathways of carbon turnover at the abyssal seafloor: a long-term, in situ experimental study.

Organisms at the deep-sea floor rely on particles sinking from the sea surface for food, which is correspondingly scarce and unpredictable - sometimes half of the annual food supply arrives within a few days. However, despite the enormous extent of this ecosystem (more than 50% of the Earth's surface is sea floor below 3,000 m of water), we know very little about how deep-sea organisms adapt and react to such a pulse. We therefore propose to investigate the fate of a food pulse at the abyssal sea floor in a series of short- and long-term manipulative experiments. With a remotely operated vehicle (ROV), we will sample natural particulate food at the deep-sea floor, label it with a tracer, add it to experimental chambers and plots, and follow its pathway through the community on time scales from days to months. We will focus our study on bacteria because they are more abundant than any other group of organisms in the deep-sea, and on larger organisms living in the sediment because these, through their foraging activities, transport the food into the sediment where also deep-living bacteria can access it. The work will be carried out in collaboration with Prof K Smith at Monterey Bay Aquarium Research Institute (MBARI) during 5 process cruises on MBARI research vessel Western Flyer with the deep-sea ROV Tiburon on board.