Standing crop and primary production of benthic microalgae on the tidal flats in Yueqing Bay

The standing stock and primary production of benthic microalgae on tidal flats were measured seasonally at 3 transects (Puqing, Dahengchuang and Puqi) in Yueqing Bay during 2002–2003. The results showed that the integral chlorophyll a (Chl a) concentration in tidal flat mud exhibited a seasonal variation with the order of magnitude: winter (14.0±4.2 mg m⁻²) > spring (13.0±6.3 mg m⁻²) > autumn (7.7±5.9 mg m⁻²) > summer (4.6±3.2 mg m⁻²). The primary production showed an order of magnitude: spring (270.5±224.9 mgC m⁻² d⁻¹)>winter (238.7±225.5 mgC m⁻² d⁻¹)>autumn (214.1±56.2 mgC m⁻² d⁻¹)>summer (71.6±44.6 mgC m⁻² d⁻¹). Both chlorophyll a and primary production showed maximum values in the surface layer of sediment, and decreased rapidly with increasing depth due to sun light limitation. The results of variance analysis indicated that seasonal variation and tidal flat condition affected Chl a greatly, but had no significant effect on primary production. The annual primary production of benthic microalgae on tidal flats in Yueqing Bay was estimated at 16143 tons carbon, which is sufficient to support 1.02×10⁵ tons shellfish production. The environmental factors affecting chlorophyll and primary production on the tidal flats in Yueqing Bay were discussed. By comparing with other bays on China’s coast, it was observed that Yueqing Bay is a region with high benthic microalgae standing crop and primary production, which may be related to the type of its sediment.