Spatio-temporal variations in chlorophyll-a concentration in the Patagonic continental shelf: an example of satellite time series processing with GRASS GIS temporal modules

The planktonic microscopic and photosynthesizing organisms inhabiting oceans, globally called phytoplankton, constitute the basis of all oceanic food webs and play a fundamental role in carbon cycling and biogeochemical cycles. Changes in phytoplankton biomass have significant impacts on all the biological, physical and geochemical processes occurring in the aquatic system. Therefore, there has been a rising interest in studying, monitoring, and understanding these variations and their timing at the regional and global scales. Since algae have photosynthetic pigments, such as chlorophyll-a, that absorb and reflect sun light mainly in the visible part of the electromagnetic spectrum, phytoplankton is capable of changing the optical properties of surrounding water, that is the ocean color. This principle allows to estimate chlorophyll-a concentration (proxy for phytoplankton biomass) through measures of the reflected radiation from the upper ocean layer by means of remote sensing. The objective of this study was to analyze the spatio-temporal variations of satellite chlorophyll-a concentration (chl-a) and phytoplankton blooms in the continental shelf and shelf break of the Argentinian patagonic region using the newly implemented temporal modules of GRASS GIS.