Contribution of Ocean Color Remote Sensing for Monitoring the Response of Coastal Ecosystems to Anthropogenic Impacts: A Case Study on Brazilian Waters

Coastal ecosystems play essential ecological, social, and economic roles at the land-ocean interface and are highly sensitive to environmental changes, whether natural or human-induced. Monitoring these regions is crucial for developing sustainable, ecosystem-based environmental policies (UNESCO-IOC). Brazil, with approximately 8,000 kilometers of tropical and subtropical coastline, hosts diverse coastal and marine ecosystems. However, these areas face significant pressures, including climate change, urban expansion, intensive agriculture, and deforestation. Despite their importance, Brazil, like many coastal regions, lacks extensive, long-term in situ data to assess how these pressures impact biogeochemical quality. Ocean color remote sensing helps fill this data gap by continuously providing key biogeochemical variables—such as phytoplankton biomass, particulate and dissolved matter, and associated organic carbon stocks—for over 25 years. This study demonstrates how optimized ocean color data can offer a comprehensive view of coastal ecosystems' responses to human pressures on both land and ocean. Specifically, MODIS ocean color time series have been analyzed to identify trends in the biogeochemical properties of Brazilian coastal and shelf waters, including estuaries, bays, and major lagoons, over the past two decades (COCOBRAZ ANR FAPESP project). This work illustrates how ocean color data can be a major source of information for supporting the preservation and management of coastal ecosystems.