Multi- and Hyperspectral Remote Sensing applications in Highly Turbid Coastal Waters: Challenges and Opportunities

DOGLIOTTI, A. I.

Workshop; 9th EARSeL Workshop on Remote Sensing of Coastal Zone; 2021

Aquaticecosystems are vital components of the global biosphere, but they arevulnerable to natural and man-induced environmental changes, including climatechange. In particular, coastal areas are among the most important and valuableregions in the world from both an ecological and socio-economic perspective.Population growth together with industrialization, intensification of land use and climate change, highlight the urgent need for a sustainable management ofthese systems. Remote sensing have proven to be a very useful and alternativetool to the generally expensive field studies that make it possible to analyzethe spatial and temporal variability of water quality indicators and the stateof the ecosystem on a local and global scale. However, deriving bio-geophysicalvariables of interest in coastal waters from remotesensing is challenging, especially in the presence of highly reflectivesuspended mineral particles and high concentrations of particulate organicmatter (phytoplankton, detritus) which can hinder the atmospheric correctionprocedure and also interfere in the performance of bio-optical algorithms.  The highly turbid waters of the Río de laPlata, located in the eastern coast of South America at approximately 34°S, isan ideal study area where different applications of ocean color remote sensinghave been developed to study natural variability of variables of interest, suchas turbidity, as well as human-induced changes such as intense dredging activities.Innovative atmospheric correction algorithms have been specially developed forthese extreme turbid waters where the existing algorithms have shown poorresults. Given the high amount of sediments the availability of light issignificantly reduced, being not the ideal condition for phytoplankton to growth,however blooms have been recently detected in the Argentine coast of theestuary, like the intense Microcystis sp.bloom that occurred in November 2020-February 2021 along the coast of Buenos Aires. Even thoughretrieving chlorophyll-a (Chl-a)concentration in very turbid waters is highly challenging, blooming conditions(high Chl-a) can be detected and theidentification of cyanobacteria dominated-waters using hyperspectral data hasbeen analyzed and preliminary results are promising. Another application hasbeen developed after a large amount of floating aquatic Hyacinths (Eichhornia crassipes) invaded the coastof Buenos Aires city at the beginning of 2016 which could be observed bydifferent ocean colour sensors and for which a floating vegetation indexadapted for turbid waters has been developed and applied to detect and quantifythem. This presentation resumes the main results and recent advances inalgorithm development and applications in these extreme and optically complexwaters.