The trophic biology of the holothurian Molpadia musculus: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon

[摘要] Megafaunal organisms play a key role in ecosystem functioning in thedeep-sea through bioturbation, bioirrigation and organic matter cycling. At3500 m water depth in the Nazaré Canyon, NE Atlantic, very highabundances of the infaunal holothurian Molpadia musculus were observed. To quantify the roleof M. musculus in sediment cycling, sediment samples and holothurians were collectedusing an ROV and in situ experiments were conducted with incubation chambers. Thebiochemical composition of the sediment (in terms of proteins, carbohydratesand lipids), the holothurians' gut contents and holothurians' faecalmaterial were analysed. In the sediments, proteins were the dominant organiccompound, followed by carbohydrates and lipids. In the holothurian's gutcontents, protein concentrations were higher than the other compounds,decreasing significantly as the material passed through the digestive tract.Approximately 33±1% of the proteins were digested by the timesediment reached the mid gut, with a total digestion rate equal to 67±1%.Carbohydrates and lipids were ingested in smaller amounts anddigested with lower efficiencies (23±11% and 50±11%,respectively). As a result, the biopolymeric C digestion rate was on average62±3%. We estimated that the population of M. musculus could removeapproximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m⁻² d⁻¹from the sediments. These results suggest that M. musculus plays akey role in the benthic tropho-dynamics and biogeochemical processes in theNazaré Canyon.

[学科分类] 地球化学与岩石