Assessing Phytoplankton Bloom Phenology in the Southwest Atlantic Using Ocean Colour Remote Sensing

DOGLIOTTI, A.I.; LUTZ, V.; LUZ CLARA, M; MAENZA, R.; FROUIN, R.

Simposio; Trends, Reflections, Evolution, and Visions in Ocean Research: A celebration of the scientific life of Trevor Platt Symposium; 2023

TheSouthwestern Atlantic (SWA), 30°-50°S and 45°-70°W, is a biological rich areaof the ocean both in terms of phytoplankton biomass but also for the greatabundance of economically important fish and mollusc species, sea birds andmarine mammals. It is a highly dynamic and heterogeneous region characterizedby the Brazil-Malvinas Confluence zone, the wide and flat Argentinean shelf, andthe presence of several oceanographic fronts which have been associated withenhanced chlorophyll-a (Chl-a) concentration and with intense CO2 uptakefrom spring through autumn. Inthis study we evaluate phytoplankton phenology patterns over the SWA areaduring a 22-year period (January 1998 – December 2019) using satellite oceancolour data. First, two datasets, CCI-OC(v6) and GlobColour (v4.2.1), are evaluated using in situ Chl-a measurements available in this region. Then,different phenological indices of the spring bloom are estimated for the wholeregion. And finally, phytoplanktonphenological indices and their interannual variability patterns aredescribed for selected sites. The relative importance of different forcing,that may be subject to variations due to climatechange (like the incoming solar irradiance and mixedlayer depth), in the variability of the phenological indices (like theinitiation of the spring bloom) in the different sites of interest areanalyzed.