![]() ![]() This is mainly composed of dead plankton and fecal pellets produced by zooplankton, which are exported to the deep seafloor as fine particles of ‘marine snow’. In the absence of sunlight, most animals in the deep ocean (below 200 m) are reliant on detritus from the surface waters as their primary source of food. We postulate that these food-falls are the result of a local concentration of large marine vertebrates, linked to the high surface primary productivity in the study area. Rapid flux of high-quality labile organic carbon in fish carcasses increases the transfer efficiency of the biological pump of carbon from the surface oceans to the deep sea. Using best estimates of carcass mass, we calculate that the carcasses reported here represent an average supply of carbon to the local seafloor of 0.4 mg m −2d −1, equivalent to ∼4% of the normal particulate organic carbon flux. No evidence of whale-fall type communities was observed on or around the carcasses, with the exception of putative sulphide-oxidising bacterial mats that outlined one of the mobulid carcasses. Based on a global dataset of scavenging rates, we estimate that the elasmobranch carcasses provided food for mobile scavengers over extended time periods from weeks to months. The carcasses supported moderate communities of scavenging fish (up to 50 individuals per carcass), mostly from the family Zoarcidae, which appeared to be resident on or around the remains. These observations come from industrial remotely operated vehicle video surveys of the seafloor on the Angola continental margin. Here were report on the first observations of three large ‘fish-falls’ on the deep-sea floor: a whale shark ( Rhincodon typus) and three mobulid rays (genus Mobula). ![]() This model will show how significant the share of scavengers is in overall benthic energy flow, and how sensitive the system may be to changes(climatic, human-induced) in food supply.The carcasses of large pelagic vertebrates that sink to the seafloor represent a bounty of food to the deep-sea benthos, but natural food-falls have been rarely observed. ![]() The results obtained within the project together with qualitative and quantitative information on scavenger associations from the literature will be integrated in a balan ced model of scavenger assemblage trophic links and energy flows. As the metabolic rate is a proxy of overall energy expenditure of an organism, and hence is one possible way of estimating energy flow through the individual organism, scavenger respiration and excretion measurements will be combined with existing informatio n on peracarid energy budgets to etablish a model that can predict daily consumption. The trophic relationships to other taxa will be investigated by analysing the lipid composition and the fatty acid signatures of scavengers and their potential prey taxa. This shelf assemblage will be used as a deep sea-like model.A combination of up-to-date tracers techniques will be used to identify the origin of scavenger alimentation: The trophic level of the different scavenger species wit hin the food web will be determined by carbon and nitrogen stable isotopic ratios. The general objective of this proposal is to evaluate the ecological significance of marine benthic scavenger communities and of the large food fall mediated vertical flux by investigating feeding ecology and physiology of representative species of the Ant arctic shelf scavenger guild. ![]()
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