210Po as a Tracer of Variations of Trophic Input to Deep-sea Benthic Ecosystems: A Study of the Deep-sea Amphipod Eurythenes Gryllus from the Tropical Atlantic

Deep-sea amphipods were trapped at different heights above the sea floor (4500 m depth) during two periods (February and September 1991) in the tropical Atlantic Ocean off Mauritania, and were analysed for their 210Po content. In fact, 210Po variations were considered an adequate tracer for reflecting changes in trophic inputs at this location. 210Po and 210Pb concentrations ranged from 23 to 286 Bq.kg-1 dry weight and from 12 to 67 Bq.kg-1 dry weight, respectively, when considering the whole organisms with no clear trend with the height of capture above the sea floor. A comparison with 210Po concentrations in Eurythenes gryllus and other crustaceans from different locations in the Atlantic was carried out. 210Po concentrations in deep-sea amphipods appeared far less important and could be related to their peculiar feeding strategy. A significant inverse correlation was found between 210Po concentrations and weight of the amphipods for the two seasons. Allometric equations for 210Po concentrations revealed similar slopes for the two periods of sampling; however, 210Po concentrations were higher in September compared to February. This difference could be linked to temporal variations both in the mass and organic carbon fluxes into this deep-sea environment. (author)