Estudios ecológicos en el Golfo San Jorge y adyacencias (Atlántico sudoccidental). Distribución, abundancia y variación estacional del fitoplancton en relación a factores físico-químicos y la dinámica hidrológica.
This study was based on four seasonal cruises during 1984 and 1985. It revealed a thermo-haline frontal system formed by the advection of the Coastal Water mass flowing in two branches, one running towards the coast and the other mid-shelf directed. The thermocline developed between late spring and autumn results in a low inorganic nutrient concentration in the upper layer. Nonetheless in winter, a vertical homogeneity and high nutrient concentration were observed. Phytoplankton development presented a typical temperate-seas annual cycle. In winter, reduced populations were dominated by diatoms. The highest biomass concentration in the cycle coincided with the spring blooming, to which Thalassio sira anguste-lineata,Alexandrium tamarense, Heterocapsa triquetra and Prorocentrum micans were associated. Summer concentration decreased sharply with dinoflagellates being dominant, and a minor increase followed in autumn owing to diatom populations. Usually diatom growth was linked to the frontal region. The quali-quantitative flora composition denote this gulf as a southern transitional area with a dominance of temperate-cold communities. A high dinoflagellate cysts richeness and encystment were detected in spring. Trophic relations in the microplankton community were identified, and a spatial coupling of predator-dinoflagellates and photosynthetic prey-dinoflagellates was noted. Consumption and grazing and prey selectivity indexes were also estimated.