LONG-TERM VARIABILITY AND TRENDS OF SATELLITE-OBSERVED CHLOROPHYLL IN THE PATAGONIAN CONTINENTAL SHELF

DELGADO, ANA LAURA; FONT?MUÑOZ, JOAN; HERNÁNDEZ?CARRASCO, ISMAEL; COMBES, VINCENT; BASTERRETXEA, GOTZON

Simposio; VIII International Symposium on Marine Sciences 2022 (ISMS); 2022

The Patagonian Continental Shelf (PCS), is considered as one of the most productive areas of the world, with high abundance of economically important fish species. The ecological responses of this oceanographically complex region to climate variability are still uncertain. Here, based on 24 years (1998-2021) of ocean color data, we investigate the long-term variability and trends of phytoplankton biomass (using Chl-a, as proxy) in the PCS. Based on Self-Organizing Maps (SOM) analysis in the temporal domain, we first defined 9 topologically ordered biogeographical regions, associated with the oceanographic patterns prevailing in the PCS. Marked differences in chlorophyll patterns were observed, between the highly productive areas, characterized by marine fronts of different origins (e.g. upwelling, estuarine, thermal; 1.4-2.3 ± 0.9-1.7 mg m-3) and the oligotrophic Atlantic oceanic waters, with relatively low Chl-a concentration and variability (0.41 ± 0.18 mg m-3). In 7 of the classified regions significative positive monotonic trends were observed revealing a tendency of increase in the productivity (biomass enhancement) of the PCS. Phytoplankton biomass in the highly productive areas of the northern shelf break outstandingly increase at a rate of 0.42 mg m-3 decade-1. Somewhat lower values, yet significant, were observed in the southern shelf-break (Malvinas Current; 0.16 mg m-3 decade-1), and in the southern Patagonian tidal fronts (0.13 mg m-3 decade-1). In addition to this, also a clear shift in the blooms’ seasonality has been identified, with an increase in the amplitude of the seasonal signal in the northern shelf break and, conversely a weakening of the signal in the oligotrophic Atlantic waters. Our results are consistent with previous descriptions of the response of these waters to climate change and builds the basis of the future scenarios that PCS and beyond will face in a climate changing reality.