Temporal And Spatial Variation Of Chlorophyll Northwest Of Luzon Island

Phytoplankton are key components of ecosystems,as well as the coupling systems of physical,chemical and biological processes.The spatio-temporal distribution of chlorophyll concentration is closely related to many environmental factors such as light conditions,temperature,nutrients,wind,ocean currents and so on,the variation of chlorophyll has the ability to reflect the ecological response of integrated ecological information and climate change.The phenomena of winter phytoplankton blooms are frequently observed northwest of Luzon Island.The phytoplankton blooms can affect the productivity of the local marine ecosystem in the oligotrophic SCS.In addition,studying the dynamics of this phytoplankton blooms will improve the understanding of the complex biogeochemical processes near the Luzon Strait.In this study,using the multi-satellite merged ocean color remote sensing data from November 1999 to February 2015 in the region northwest of Luzon Island,we studied the spatial and temporal changes of chlorophyll-a(Chl-a)concentration in one longer period.Combined with physical environment parameters such as wind speed(WS),sea surface temperature(SST),sea level anomalies(SLA),and the parameters derived from the above parameters,the relationship between Chl-a and the surrounding environment parameters was then investigated in the study.In addition,the main factors affecting the distribution of Chl-a were discussed by using the partial correlation analysis and multiple stepwise linear regression analysis.The results showed that centers of winter Chl-a blooms northwest of Luzon Island appeared often near the location(119°E,19°N).The concentration of the winter high Chl-a patch was significantly correlated with EPV,ET,WS,SST and SLA(the multiple correlation coefficient: r=0.7850,p<0.05),which indicated that both the wind component parallel to the coastline and the wind stress curls enhanced probably winter upwelling/mixing in the study area,inducing increase of the nutrients into the upper layer and the formation of phytoplankton blooms in the area.What's more,Ekman Transport(ET)and SST played a dominant role in influencing the variation of Chl-a,compared with wind-derived Ekman pumping and other environmental factors.At the same time,the advection effect of the northward background coastal flow was likely to account for the upwelling area being inconsistent with the center of phytoplankton blooms,triggering the centers of phytoplankton blooms shifting northward from the upwelling area in the area.