Standing crop and primary production of benthic microalgae on tidal flats in the Sanggou and Jiaozhou Bays,China

The standing crop and primary production of benthic microalgae on tidal flats have season-ally been observed in the Sanggou and Jiaozhou Bays of the northern China coast during 1999 ～ 2000.The results show that the annual primary productions of benthic microalgae on tidal flats in the two baysare 2 532 and 7 542 tons carbon, which would be able to support 3.1 × 103 and 9.2× 103 tons shellfishmeat, respectively. The nature of sediment is essential for governing the biomass and primary productionof benthic microalgae on tidal flats. The biomass and primary production of benthic microalgae on tidalflats with muddy sediments are higher than those with sandy sediments, which resulted from higher nu-trient concentration and lower grazing pressure. That is the reason why in comparison with XiangshanBay the standing crop and production of benthic microalgae on tidal flats of the Sanggou and JiaozhouBays are low. Light was a key factor controlling vertical distribution of biomass and production of benthicmicroalgae on tidal flats of the two bays, resulted in appearance of maximum chlorophyll a and primaryproduction at the surface layer and sharply decreased with depth of sediment.