Benthos

Deep-sea benthic organisms receive a slow nonseasonal rain of fecal pellets and dead organisms. Recent studies in the North Atlantic show that additional large pulses of organic particles arrive at the bottom within weeks to months following the spring phytoplankton bloom, probably accelerated by formation of marine snow particles. A complementary study in the same general area indicated that benthic organisms grow faster than previously believed, with maximum growth rates following the annual deposition of phytoplankton detritus from the spring bloom (Lampitt, 1990). An open question is the extent to which benthic organisms rely on these episodes of rich input. Certain large animals may metabolically cache food resources.

Ocean Margins

The role of coastal areas in global ocean carbon and nutrient cycles is controversial. Several issues remain, such as the percentage of seasonal and annual coastal production that is exported to the deep sea, the percentage of global productivity that takes place in the coastal ocean, and the extent to which the coastal ocean functions as a net carbon sink because of the massive inputs of nutrients. Interdisciplinary studies will be required to resolve the controversies regarding lateral exchanges between estuaries and the coastal ocean, and between coastal and deeper waters. This point is developed further in ''Directions for Coastal Ocean Processes."

Biology of Hydrothermal Vent and Hydrocarbon Seep Habitats

Most oceanic food webs are based on photosynthetic productivity occurring in the upper regions of the ocean. A little more than a decade ago, it was discovered that dense bacterial and animal communities, which rely largely on in situ chemosynthetic activity, thrive at deep-sea hydrothermal vents and at hydrocarbon seep zones. Carbon fixation in these habitats is driven by highly reduced substances, such as hydrogen sulfide, that are exploited by both free-living bacteria and bacteria living within animal tissues.

The role of deep-sea hydrothermal vent systems in generating and dispersing fixed carbon is an area of active study. Although it is unlikely that carbon fixation at the hydrothermal vents is a



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