Temporal variability of intertidal benthic metabolism under emersed conditions in an exposed sandy beach (Wimereux, eastern English Channel, France)

Benthic community metabolism during emersion was measured in a three-year survey by monitoring CO2 fluxes in benthic chambers on an exposed sandy beach of the eastern English Channel (Wimereux, France). The three-year chronology of variations in benthic metabolism was characterised by a high variability around a low value for gross community primary production (GCP: 17.47 ± 40.85 mgC m−2 h−1, mean ± SD) and community respiration (CR: 1.66 ± 1.97 mgC m−2 h−1, mean ± SD). Although benthic metabolism remained low most of the time, some high values of primary production and respiration were occasionally detected. High primary production rates (up to 213.94 mgC m−2 h−1 measured at the end of summer) matched with the development of Euglena sp., together with the occurrence of phytoplanktonic species on the sediment, whereas high community respiration rates were detected at the end of spring on Phaeocystis sp. foam deposits. Community respiration was positively correlated with bacterial abundance, suggesting that CR was mainly supported by microfauna.