Seasonal variations of community production,respiration and biomass of different primary producers in an intertidal <Emphasis Type="Italic">Zostera noltii</Emphasis> bed (Western English Channel,France)

Gross primary production (GPP) and respiration (R) in an intertidal Zostera noltii (Hornemann, 1832) community were estimated each month from in situ CO₂ flux measurements during the emersion period in the Bay of Morlaix (France). Simultaneously, the Chlorophyll a biomass of Z. noltii leaves, associated epiphytes and sediment within the benthic chambers were also monitored. The significant positive exponential relationship established between R and the maximum daily temperature emphasized that temperature was a good predictor of seasonal variation in the community R in Z. noltii bed. In contrast, the amplitude of the fitted curve on GPP was low and represented <25% of the annual mean value (90.9 ± 15.2 mgC m⁻² h⁻¹). The Chlorophyll a biomass of sediment was high (133.70 ± 22.96 mg m⁻²) but it was likely constituted by detritus which did not contribute much to the community GPP. The Chlorophyll a biomass of associated epiphytes was higher in winter and varied over the year inversely with Z. noltii. Therefore, the asynchronous dynamic of primary producers could support a constant rate of production at community scale over the year.