Spatial variability of chlorophyll-a in Terengganu Waters from MODIS

Abstract

Application of remote sensing technology for regular monitoring of the near shore and offshore parameters in Terengganu waters is still limited. The objectives of this study are to determine the Chlorophyll-a (Chi-a) distribution in Terengganu coastal and offshore waters using MODIS data and to find the relationship between in-situ and MODIS Chi-a data. The coastal waters was defined as waters < 20 nm from shoreline while offshore waters > 20 nm. Chlorophyll-a in-situ measurements were conducted on the 13-16 May 2009 and 6-9 July 2009. A standard empirical Chi-a OC-3M algorithm were used to analyzed the MODIS Level 2 and Level 3 images. The Chi-a images obtained from NASA and georeferenced to Kuala Terengganu's region using EPOC module. The study reported Chi-a are found to be higher in coastal waters compared to offshore area. The range of in-situ Chi-a concentration in Kuala Terengganu coastal waters is between 0.31 mg IL to 2.07 mg/ L for the month of May while July is 0.25 mg / L and 1.22 mg / L. For offshore area, the Chi-a concentration in May is 0.30mg / L to 2.65 and in July, as 0.14 mg/ L to 0.84 mg/ L. The higher concentration of Chi-a is found to be associated with shallow continental shelf which is near coastal region of Kuala Terengganu, where the ocean depth is about 10 m up to 60 m from the coast towards the deep ocean. The comparison between in-situ and MODIS Chi-a concentration data shows high correlation with R2= 0.898. This high correlation between MODIS and in-situ Chi-a concentration value emphasized that MODIS data can be use to determine and monitoring the near shore and offshore Chi-a in Terengganu waters.