Particle flux and food supply to a seamount cold-water coral community (Galicia Bank, NW Spain)
| Autor: | E.M. Berghuis, Gerard C.A. Duineveld, Marc S. S. Lavaleye |
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| Rok vydání: | 2004 |
| Předmět: | |
| Zdroj: | Marine Ecology Progress Series. 277:13-23 |
| ISSN: | 1616-1599 0171-8630 |
| DOI: | 10.3354/meps277013 |
| Popis: | In a European effort (Atlantic Coral Ecosystem Study (ACES project)) to determine the key conditions for the occurrence of cold-water corals on the NW Atlantic margin, a coral community on a seamount off NW Spain (Galicia Bank) was studied. Cold-water corals (Lophelia pertusa, Madrepora oculata) grow at a depth of ~800 m as isolated patches amidst small ripples and larger waves of foraminiferal sand. A 17 mo deployment of a near-bottom sediment trap revealed a large seasonal and annual variability in the flux of phytodetritus and carbon. The daily carbon flux in the first 5 mo of 2000 was on average 37 mgC m -2 , and in the first 5 mo of 2001 17 mgC m -2 . Quantities of faecal pellets and swimmers (copepods, amphipods) were also highly variable. A comparison between the daily carbon flux and the sediment carbon oxidation rate calculated from in situ com- munity oxygen consumption (SCOC), i.e. 17 versus 7 mgC m -2 d -1 respectively, indicated that a sur- plus of carbon is not oxidised by the sediment community. We argue that the strong tidal currents (max. 30 cm s -1 ) and the mobile sediment lead to winnowing of the sediment and to near-bed trans- port of the organic material. The low biomass of the benthic community and the domination of filter- feeders support our arguments. By means of analyses of stable isotopes (δ 15 N, δ 13 C) we attempted to find potential food items of the cold-water corals among the particles collected in the sediment trap. The difference between the δ 15 N signatures of coral tissue (9.5‰) and phytodetritus (2.2‰) was >1 trophic level, indicating that sinking algae are not the sole food source. The δ 15 N signatures of swimmers caught in the trap, ~10‰, were on the other hand in the same range as those of the corals. A mixed diet of animals and algae could be one explanation for the observed δ 15 N of corals. The δ 13 C value of the coral tissue, -20.55‰, excludes a food source consisting of bacteria supported by methane seepage, as suggested by earlier studies. |
| Databáze: | OpenAIRE |
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