A study of chlorophyll-a concentration from satellite imagery at coastal area (case study of Merang and Rompin)

Abstract

Chlorophyll-a is the principal biomass indicator of aquatic micro algae that support food webs in the sea. Monitoring the chlorophyll-a contents in the ocean to its conventional state is important to ensure that their concentration is not too low or excessive. A series of Moderate Resolution Imaging Spectroradiometer (MODIS) was used in this study of Merang and Rompin coastal area. There are three objectives from this study which are to determine the chlorophyll-a concentration from ground-truth data and satellite imagery, to determine the correlation of chlorophyll-a concentration from ground-truth data and satellite imagery and to determine the monthly changes of chlorophyll-a concentration at coastal area of East Coast of Peninsular Malaysia. The sampling periods for Merang were done on 20 to 22 June 2011 and for Rompin were done on 30 June to 1 July 2011 and 21 October 2011. The ground-truth data of chlorophyll-a concentration for Merang ranging from 0.1372 to 1.5024 mg/L (surface) and ranges from 0.283 to 1.7369 mg/L (5 meter). While for Rompin shows the range of chlorophyll-a concentration from 0.1697 to 0.7391 mg/L (surface) and range between 0.1 to 0.7882 mg/L (5 meter). However for satellite imagery data, there are some missing data due to cloud cover. The range of chlorophyll-a concentration at Merang was 0.3424 to 0.4972 mg/L for 19 to 21 June 2011. While Rompin the chlorophyll-a concentration range was 0.5214 to 0.9136 mg/L for 30 to 2 July 2011 and range from 0.4708 to 0.725 mg/L for 1 to 3 July 2011. There was a weak arrangement between ground-truth and MODIS chlorophyll-a concentration with R2 = 0.0018 and RMSE= 0.1406. Besides that, the pattern of monthly changes of chlorophylla concentration of east coast of Peninsular Malaysia is due to monsoon period. In nutshell, the monitoring the concentration of chlorophyll-a in in a large water body area by using remote sensing technique is more faster because the level of chlorophyll-a can change in the short time.