Spatio-temporal distribution of chlorophyll-a concentration derived from MODIS satellite remote-sensing and in situ observations in Sanya Bay, China

Shen, Chunyan; Shi, Ping; Zhao, Hui; Zhang, Yanying; Dong, Junde

Spatio-temporal distribution of chlorophyll-a concentration derived from MODIS satellite remote-sensing and in situ observations in Sanya Bay, China

2014

Shen, Chunyan | Shi, Ping | Zhao, Hui | Zhang, Yanying | Dong, Junde

This study examined satellite chlorophyll- a (chl- a) concentration and in situ observations in Sanya Bay (SYB). In situ observation of chl- a was conducted four times per year at 12 sampling stations in SYB from January 2004 to October 2008. Monthly satellite chl- a was derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) during 2000–2012. This study compared satellite chl- a values to in situ measurements in SYB. The two data sets match well in the whole region except for two estuaries. Results show that the average in situ chl- a was 1.49 mg m ⁻³ in SYB. Chl- a was relatively higher (>2 mg m ⁻³) and more variable in coastal areas, with a tendency to decrease offshore (<0.4 mg m ⁻³). The chl- a level in summer displayed obviously vertical stratification, with higher values at the bottom and lower values at the surface. Analysis of monthly mean chl- a showed that the highest level (>2 mg m ⁻³) appeared in December, with the lowest in March (<1 mg m ⁻³). The gradients are ranked winter, autumn, summer and spring. There was higher chl- a in autumn and winter, which may be associated with the stronger wind monsoon then. Annual mean chl- a from 2000 to 2012 varied from 1.17 to 2.05 mg m ⁻³, with the minimum in 2001 and the maximum in 2005. The chl- a level presented a roughly increasing tendency from 2000 to 2012, which may be related to the increasing nutrients associated with the development of tourism and fishery.

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