Impact of macrofaunal activities on the biogeochemical cycling in anthropogenically disturbed sediment

Marine coastal areas are important for the ecosystem functioning because they provide a wealth of goods and services. Hence, it is a major challenge nowadays to understand and predict how human activities will affect marine sediment communities, benthic biogeochemical cycling and the link between them. It is known that bioturbation activities affect the ecosystem functioning. In this study, we are going one step further by studying biogeochemical cycling in a range of natural sediment and disturbed sediment, and by assessing the contribution of macrofaunal activities (bioturbation and bio-irrigation) to the ecosystem cycling. We conducted closed-core incubations of sediment sampled along a gradient from fine to coarse sediments, including sediments subjected to fining. Nutrients and oxygen concentration were followed by sampling the overlying water every 2 hours. Bio- and physical irrigation has been quantified by adding a bromide tracer to the overlying water and following the decreasing concentration over time. At the end of the incubation, the sediment was sieved and the organisms retrieved to calculate the bioturbation potential of the community (BPc). With those data, we will estimate the total flux of degradable organic carbon deposited at the sediment surface, its degradation rate and transformation, and the nitrification/denitrification rates. The aim is to assess the effect of fining and the effect of bioturbation and bio irrigation on benthic ecosystem functioning. The research plan and the preliminary results will be reported.

Abstract of an Oral Presentation or a Poster