Evaluation of Multi- and Hyper- Spectral Chl-A Algorithms in the RÍo De La Plata Turbid Waters During a Cyanobacteria Bloom.

The Río de la Plata estuary, located in the eastern coast of South America, has large social, ecological and economical importance for Argentina and Uruguay, in which margins their capital cities (Buenos Aires and Montevideo) and a number of harbours, resorts and industrial centres are located. Being the estuary the main source of drinking water for the millions of inhabitants in the region and a recreational area, the increasing occurrence of cyanobacteria blooms, consistently composed of Microcystis and Dolichospermum complex, is worrying and the need for a monitoring tool like remote sensing is highly desirable. In the present study we evaluated existing multi- and hyper-spectral red/NIR chlorophyll-a (chl- $a$ ) algorithms using radiometric and bio-optical field measurements. Empirically derived multi-spectral algorithms showed poor results, while hyper-spectral algorithms showed better and promising results. S3B/OLCI and CHRIS-PROBA chl-a maps were generated using fitted models derived using the existing in situ dataset.