Deep-Sea Food Chains and the Global Carbon Cycle

Carbon dioxide and other `greenhouse' gases are increasing in the atmosphere due to the burning of fossil fuels, the destruction of rain forests, etc., leading to predictions of a gradual global warming which will perturb the global biosphere. An important process which counters this trend toward potential climate change is the removal of carbon dioxide from the surface ocean by photosynthesis. This process packages carbon in phytoplankton which enter the food chain or sink into the deep sea. Their ultimate fate is a `rain' of organic debris out of the surface-mixed layer of the ocean. On a global scale, the mechanisms and overall rate of this process are poorly known. The authors of the 25 papers in this volume present their state-of-the-art approaches to quantifying the mechanisms by which the `rain' of biogenic debris nourishes deep ocean life. Prominent deep sea ecologists, geochemists and modelers address relationships between data and models of carbon fluxes and food chains in the deep ocean. An attempt is made to estimate the fate of carbon in the deep sea on a global scale by summing up the utilization of organic matter among all the populations of the abyssal biosphere. Comparisons are made between these ecological approaches and estimates of geochemical fluxes based on sediment trapping, one-dimensional geochemical models and horizontal (physical) input from continental margins. Planning interdisciplinary enterprises between geochemists and ecologists, including new field programs, are summarized in the final chapter. The summary includes a list of the important gaps in understanding which must be addressed before the role of the deep-sea biota in global-scale processes can be put in perspective.