APPLICATION OF THE GCOM-C ALGORITHM FOR ESTIMATION OF CHLOROPHYLL CONCENTRATION ON THE BEACHES OF THE NORTH OF FLORIANÓPOLIS ISLAND

Abstract

The bathing water quality of beaches in major coastal cities has been a persistent challenge in Brazil and worldwide. Monitoring and analyzing the environmental variables that influence water quality involves slow, costly, and logistically complex processes. This study aimed to estimate Chlorophyll-a concentrations at nine points along the northern beaches of Florianópolis Island between 2018 and 2025, using chlorophyll dissolved in water as an indicator of bathing water quality. The algorithms GCOM-C/L3/OCEAN/CHLA/V2 and GCOM-C/L3/OCEAN/CHLA/V2V3, based on satellite sensor data, were applied through the Google Earth Engine (GEE) platform using data from the Global Change Observation Mission – Climate (GCOM-C). Results indicate that chlorophyll peaks coincide with periods of higher population density and with viral outbreak events recorded in the northern region of Santa Catarina Island. The findings highlight the deficiencies in sewage and urban drainage systems, as well as the sensitivity of local water bodies, which often reflect the irregular discharge of domestic sewage into drainage channels and rivers. These factors are critical for municipal management to address in maintaining safe bathing conditions. Over the past two years, a reduction in chlorophyll peaks was observed at Ingleses, Santinho, and Canasvieiras beaches, where sewage treatment systems were expanded and domestic networks were regularized. Although the satellite product showed limitations in spatial resolution, the approach proved to be a viable medium- and long-term tool for monitoring bathing areas on a regional and even national scale.