Remote sensing the water quality indicators in Manila Bay, Philippines: Spatio-temporal trends of algal and non-algal suspended particulate matter concentrations from reconstructed MODIS satellite data

Wyndel Sañoza

The Manila Bay is a semi-enclosed coastal system that is continuously loaded with anthropogenic influences from the surrounding tributaries. The bay has not been monitored yet using remote sensing satellite data. In this study, the area was investigated using MODIS satellite-derived water quality indicators such as Chl-a, SPM, and turbidity. First, suitable atmospheric correction and cloud masking parameters were applied to retrieve water quality indicators. We found that MODIS-derived indicators showed monthly variation in the area. There was a spatial heterogeneity of the indicators throughout the bay, but the increase was associated to land and river proximity.  In specific, the increase in Chl-a and SPM was associated with wind- and tide-influenced resuspension, rainfall, and river discharge. Chl-a seemed to be dominantly affected by river discharge and bathymetry while SPM looked to be mainly influenced by wind forcing and may be with tides too. Also, the satellite data captured extreme event such as typhoon (associated to stronger winds and rainfall) where it caused an elevated surface Chl-a and SPM in deeper, middle part of the bay. In that, this study demonstrated the potential of MODIS in coastal monitoring of the area and the applicability of the 21-year archived data in management.