Benthic oxygen dynamics and implication for the maintenance of chronic hypoxia and ecosystem degradation in the Berre lagoon (France)

Chronic hypoxia and anoxia have strong impacts on coastal ecosystems worldwide. In shallow ecosystems, such situations are essentially driven by high benthic oxygen (O2) demand resulting from organic matter mineralization in surface sediment amplified a low mixing of the water column. However, O2 may greatly vary according to availability, biogeochemical properties, bioturbation macrobenthic fauna. Here we examined how varies response seasonal long-lasting (pluri-decadal) Berre lagoon, ecosystem impacted chronic events since 60 years. Oxygen penetration depth, diffusive total fluxes were measured situ using microelectrode autonomous profiler chamber deployments at three sites quite-permanent (PA), (PI) occasional (PO) August 2016. They seasonally repeated site PI between 2015 Additional physical chemical characteristics also sediment. Sediment profile images macrofauna communities enabled estimate quality ecosystem. The highest was observed after relation important accumulation reduced species Interestingly, both pluri-decadal normoxia produced relatively related higher presence dominated hypoxia, fresher active bioturbating macrofaunal normoxic site. likely resulted degraded state community lower species. occurrence lagoon predicted competition kinetics column reoxygenation induced wind. good agreement hypoxia/anoxia clearly indicates that deoxygenation ecological intensity duration stratification.