Biological and chemical studies of sea-surface microlayer (SML) in Daya Bay, China IIA. Biological and chemical characteristics of the SML and the correlation among them

Two cruises for multi-discipline investigation were conducted in October and November, 1998 in Daya Bay to collect: (1) samples from five levels including sea-surface microlayer (SML), subsurface (SSL), surface, body (mid-column) and bottom water; and (2) observational data on chlorophyll-a and nutrients, and important factors such as turbidity, BOD, COD, TN, TP and phytoplankton. Results showed that there was no enrichment of chlorophyll-a in the SML, but quite notable enrichment of some organic matter and nutrients. Compared with the findings in earlier researches, PO4−P and SiO3−Si have decreased, and the N/P ratio has increased obviously to even more than 100 in the SML. It is concluded preliminarily that PO4−P and SiO3−Si mainly determine phytoplankton growth in Daya Bay at present.