VOLUME 14 NUMBER 1 (January to June 2021)

Manuel Justin G. Custado*¹ and Carlos Primo C. David²

¹Institute of Environmental Science and Meteorology,
      University of the Philippines Diliman, Quezon City,
      1101 Philippines
²National Institute of Geological Sciences,
      University of the Philippines Diliman, Quezon City,
      1101 Philippines

This study assessed the relationship between runoff and chlorophyll-a in three documented upwelling sites in the Philippines. Linear correlation analysis between remotely sensed chlorophyll-a data and runoff from the Global Runoff Reconstruction (GRUN) dataset determined negative correlations along the coasts of Zamboanga del Norte and the Sulu Ridge and positive correlations off the coast of the Northern Bicol Shelf. The resulting correlations and generated temporal plots revealed the extent of the influence of runoff on productivity seasonally enhanced by upwelling. Generally, runoff had less effect on chlorophyll-a levels than the enhancement driven by upwelling during the northeast monsoon season. Upwelling was demonstrated to be a significant factor to productivity during months of lower runoff rates in Zamboanga del Norte and the Sulu Ridge. The dominance of weaker positive correlations (0.3 < |r| < 0.5, p<0.00001) in the Northern Bicol Shelf suggests the limited influence of runoff on productivity despite the similarity in seasonal patterns within the area. The trends and relationships determined in this study can be used in the management of coastal ecosystems and fisheries within the study sites, particularly in the context of future changes in the global climate.