Standing crop and productivity of the benthic microflora living on tidal flats of the Xiangshan Bay

The observations on standing crop and productivity of the benthic microflora living on tidal flats of the Xiangshan Bay, Zhejiang have been carried out in 1992. Four tonal representative transects on the flats, i. e.,(a) Dajiahe(near apex of the bay),(b) Xihugang(in the middle-southern bay),(c) Hutoudu(in the middle-northern bay) and(d) Hengshan(near the bay mouth), were selected in the observations during May and 7une, and the additionally seasonal observations(in February, August and October) at Hutoudu tidal flat transect were also conducted. The results obtained show that there are pronounced spatial and seasonal variations of chlorophyll a concentrations at the surface of the tidal flats, i. e.,the concentrations are higher at near apex than at the middle and near the mouth of the bay, and those are higher in May [(10. 36±8.08)μg/g] than in June [(2.94±1.21)μg/g]. The chlorophyll a concentrations at the surface of the sediments are high, and rapidly decrease with the depth, due to the light limiration, but the concentrations of phaeopigments increase. The average primary productivity of the benthic microflora is(561±385) mg/(m²·d)(C) in May and(535±171 μg) /(m²·d)(C) in 7une, which is higher than the average productivity of phytoplankton in the water column. On the tidal flats of Hutoudu, the highest chlorophyll a concentration occurred in August [(15. 26±19.08)μg/g], the lowest in February(4.24 μg/g), and the primary productivity was the highest in August[(2584±2431)mg/(m²·d)(C)] and the lowest in October [(181±179)mg/(m²·d)(C)].