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 seasonally 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 bays are 2 532 and 7 542 tons carbon, which would be able to support 3.1 x 103 and 9.2 x 103 tons shellfish meat, respectively. The nature of sediment is essential for governing the biomass and primary production of benthic microalgae on tidal flats. The biomass and primary production of benthic microalgae on tidal flats with muddy sediments are higher than those with sandy sediments, which resulted from higher nutrient concentration and lower grazing pressure. That is the reason why in comparison with Xiangshan Bay the standing crop and production of benthic microalgae on tidal flats of the Sanggou and Jiaozhou Bays are low. Light was a key factor controlling vertical distribution of biomass and production of benthic microalgae on tidal flats of the two bays, resulted in appearance of maximum chlorophyll a and primary production at the surface layer and sharply decreased with depth of sediment.

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.

Comparison in diversity of eukaryotic algae in surface sediments from different functional sea areas of Qingdao coast,the Yellow Sea,China:a metabarcoding approach

Surface sediment samples were collected in three different functional sea areas in Qingdao coast,East China,including the inner Jiaozhou Bay,the Laoshan Coast,and the Amphioxus Reserve area.Diversity and community structure of eukaryotic algae especially those of phytoplankton resting stages were assessed by metabarcoding V4 region of the 18S rDNA.Biogenic elements including total organic carbon(TOC),organic matter(OM),total nitrogen(TN),total phosphorus(TP),and biogenic silicon(BSi)were analyzed.A total of 1496 eukaryotic operational taxonomic units(OTUs)were measured,including 207algal OTUs,which contributed to 13.84%of the total OTUs.Ninety-eight species in 8 phyla,24 classes of eukaryotic algae were detected.Among them,47 species have been reported to form resting stages,and 12 species are firstly recorded in Chinese coastal waters.Dinofl agellates dominated in both DNA reads and OTU richness,which contributed to 73.02%and 61.35%of the eukaryotic algal sequences and OTU richness,respectively.DNA reads,OTU richness and alpha diversity indexes of eukaryotic algae were higher in the Laoshan Coast,and lower in Jiaozhou Bay.Eukaryotic algal community differed in the three sea areas,which was dominated by chrysophytes in Jiaozhou Bay,by dinofl agellates in the Laoshan Coast,and co-dominated by dinoflagellates and chrysophytes in the Amphioxus Reserve area.Clustering analysis showed that the Laoshan Coast and the Amphioxus Reserve area are clustered together,while Jiaozhou Bay is clustered separately.Thirty-six harmful algal bloom(HAB)species were detected,and 10 species have been reported to form blooms in Jiaozhou Bay and the Qingdao coast before.Some of these species occurred widely and dominantly in this study,suggesting high potential risk of HABs in the Qingdao coastal area.