Primary production processes in the Taiwan Strait——Spatial and temporal variations of phytoplankton biomass and productivity

The abundance,diurnal variation features of phytoplankton biomass and the horizontal distribution patterns of Chl.a and primary productivity in the Taiwan Strait were investigated during a summer and a winter cruise in August 1994 and February 1995,respectively.Results show that the horizontal distribution of phytoplanktat bianass was quite similar to that of productivity.In summer,there was a relatively barren,low productive region in the central location of the northern Taiwan Strait (NTS),and high productive regions were located at the nearshore and to the north of Cape Fugui of Taiwan Island;meanwhile,high productivity regions were only located at coastal waters of the southern Taiwan Strait (STS).In winter,high productive regions of NTS occurred off northwestern coast of Taiwan Island,while that of STS was located along the southern edge of Minnan (South Fujian)-Taiwan Bank.Vertical patterns of the diurnal variation of Chl.a indicated that in non-stratified waters,phytoplankton biornass changed in tidal rhythm;as for the stratified waters,the depth at which the highest variation amplitude located coincided with the depth where the highest variation frequency occurred.The grazing pressure of zooplankton strongly influenced the diumal variation of size-ractionated structure of phytoplankton biomass.As a result of our investigations,we conclude that in the Taiwan Strait,biological pcncesses may be more important at smaller scales where behaviors such as vertical migration and predation may control the phytoplankton production,whereas physical processes may be more important at larger scales in structuring phytoplankton patchness.