Annual budget of benthic production in Mont Saint-Michel Bay considering cloudiness,microphytobenthos migration,and variability of respiration rates with tidal conditions

In order to provide an accurate annual rate of net benthic community production, community photosynthetic response to incident irradiance and respiration were measured at different times of the year, at mid-tide level on the muddiest part of the Mont Saint-Michel Bay. As the water turbidity prevented any photosynthesis by the microphytobenthos during immersion periods, primary production was measured only during emersion periods. In contrast respiration was expected to vary according to the tidal cycle and was measured during both emersion and immersion periods. Primary production and respiration rates under emersion were assessed using in situ infra-red gas analysis of CO₂ exchange measured in a benthic chamber. Respiration rates under immersion were assessed through total CO₂ concentration variations in incubated cores.