|
Island mass effect, which is accompanied by higher bio-productivity and closely associated with fishing activities, was observed in many island (reefs) areas. Recently, we found the Chl-a enrichment (the annual mean≥0.14 mg/m3) in the surrounding of the reefs and atolls in the Xisha Archipelago, based on the daily MODISA Level-2 data during the years of 2003 to 2017. The DINEOF algorithm was used to filling missing values in the MODISA data. The analysis results show that: 1) Generally, the Chl-a concentrations became larger in winter (November to January) and smaller in summer (May to July) in the XA; The seasonal variation of Chl-a is strongly related to the Mixed Layer Depth, which is larger in winter and smaller in summer. 2) In the XA, higher Chl-a were observed in the lagoons of the atolls, where is shallow and nutritious. Hovmoller diagrams of daily MODIS Chl-a along the transect of several atolls show that higher Chl-a also appeared in the downstream side. It seems that the lagoons are the sources of the Chl-a, and the turbulent currents transfer and maintain the higher Chl-a in the downstream wakes.
|
