Satellite-measured phytoplankton and environmental factors in North-Patagonic gulfs

WILLIAMS, GABRIELA N.; SOLÍS, MIRIAM; ESTEVES, JOSÉ LUIS

Plankton Ecology of the Southwestern Atlantic - From the Subtropical to the Subantarctic realm.

Springer

Año: 2018;

An extensive series of high-resolution satellite images from the Sea-Viewing wide Field-of-view Sensor (SeaWiFS, 2000-2006) was used in the characterization of the phytoplanktonic biomass seasonal cycle of the North Patagonian gulfs (NPG). The NPG system is formed by San Matías, San José and Nuevo gulfs (between 40º47´and 43º00´S and 63º00´ and 65º1.2´W) and is an area of ecological importance and of great significance for marine conservation in the Patagonian Argentinean Shelf. The spatio-temporal variability of phytoplankton biomass in each of these environments was characterized by chlorophyll a data from satellite images (Chla-sat). The observed seasonal variability was explained by factors influencing the growth of phytoplankton: photosynthetically available radiation (PAR from the SeaWiFS sensor) and sea surface temperature (SST from the Advanced Very High-Resolution Radiometer, AVHRR). In situ temperature, nutrient and chlorophyll a concentration data from oceanographic cruises carried out in Nuevo (5 cruises: 1982-1983), San José (4 cruises: 1984-1985) and San Matías (4 cruises: 1986-1994) gulfs were also used to explain the observed patterns.Cycles of phytoplankton and SST over the NPG are typical of temperate waters. However, Chla-sat cycles were different among gulfs. At the same time, Chla-sat cycles over the gulfs were different from that over the adjacent middle continental shelf. SMG was characterized by a bimodal cycle, although in winter mean values were higher than the mean concentration for the whole area. SJG was characterized by a unimodal cycle with relatively high values of chlorophyll a concentration in spring-summer. NG showed a bimodal cycle with maximum values in autumn and spring, and minimum values in winter and summer. Particularities of each gulf are discussed in relation to the seasonal hydrographic characteristics of the water column (temperature and nutrients) and in the context of the Patagonian shelf ecosystem.