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

DOGLIOTTI, ANA; LUTZ, VIVIAN; LUZ CLARA, MOIRA; MAENZA, REINALDO A.; FROUIN, ROBERT

Plymouth

Simposio; TREVOR PLATT SCIENCE FOUNDATION Inaugural Science Symposium; 2023

TREVOR PLATT SCIENCE FOUNDATION

The Southwestern Atlantic (SWA), 30°-50°S and 45°-70°W, is a biological rich area of the ocean both in terms of phytoplankton biomass but also for the great abundance of economically important fish and mollusc species, sea birds and marine mammals. It is a highly dynamic and heterogeneous region characterized by the Brazil-Malvinas Confluence zone, the wide and flat Argentinean shelf, and the presence of several oceanographic fronts which have been associated with enhanced chlorophyll-a (Chl-a) concentration and with intense CO2 uptake from spring through autumn. In this study we evaluate phytoplankton phenology patterns over the SWA area during a 22-year period (January 1998 – December 2019) using satellite ocean colour 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 whole region. And finally, phytoplankton phenological indices and their interannual variability patterns are described for selected sites. The relative importance of different forcing, that may be subject to variations due to climate change (like the incoming solar irradiance and mixed layer depth), in the variability of the phenological indices (like the initiation of the spring bloom) in the different sites of interest are analyzed.