Monitoring chlorophyll a concentration in the Mar Menor coastal lagoon using ocean color sensors

The Mar Menor coastal lagoon has experienced a severe eutrophication process since 2015, with its most visible effect being a series of phytoplankton blooms featured by unprecedentedly high and persistent concentrations of chlorophyll a in the water column. To better quantify and monitor these changes, two suitable chlorophyll concentration algorithms (referred to as BELA, short for BELich Algorithm) for the Mar Menor lagoon are proposed. These algorithms are derived from the analysis of thousands of reflectance spectra obtained from six satellite ocean color sensors, combined with in situ observations performed between 2016 and 2023. Our results demonstrate that the BELA algorithms can accurately estimate chlorophyll a concentration in the shallow waters of the Mar Menor lagoon for values above 2 mg m⁻³, a range consistent with various of the episodes of high productivity observed since 2015. These algorithms perform well for a variety of currently operational ocean color sensors and could be used in future planned missions. This versatility makes them a valuable tool for monitoring and assessing the environmental state of the lagoon.