Fitoplancton en el afloramiento de las Islas Galápagos, durante Agosto 2000

Abstract

Esta investigación es parte del Proyecto Indicadores Biológicos de diferentes ecosistemas marinos del Ecuador, correspondiente a la región Insular de Galápagos durante agosto 2000, con el propósito de comprender la dinámica poblacional del fitoplancton (cuali-cuantitativo) de las diferentes masas de agua que afloran al este y oeste de Galápagos y entre las islas enfocando áreas de mayor fertilidad marina en la época seca.

This study corresponds to the cruise around the Galapagos Islands carried out by the Oceanographic Institute of the Ecuadorian Navy in August 2000. The purpose was to understand, quantitatively and qualitatively, the ecological dynamics of the phytoplankton during the dry season. The chlorophyll "a" data from surface waters registered high concentrations (0.87 - 2.18 mg/m3) southwest off the Galapagos Islands, reflecting upwelling processes. Sub-surface-water values were higher southward, while the lowest values were found to the north. Nuclei of high chlorophyll "a" content were found to the southwest of the Galapagos (10 m), and to the southeast (40-50 m). The cellular biomass was represented by P. delicatissima, species responsible for the high fertility in the center of the upwelling area and to the southwest and south off the Galapagos, Thalassiosira subtilis and Gymnodinium sp. were dominant to the east. The incidence of the Cromwell Current was accented toward 91° and 92°W; toward 89°W different conditions were shown, probably associated to the influence of the Humboldt Current. The biomass in 55µm mesh size fraction was dominated by P. delicatissima (0 m); P. delicatissima, C. compresus and C. curvisetus ( 0 - 50 m). C. tripos and G. polyedra, warm water species dominated to the north off the Galapagos in surface waters, while in sub-surface waters these species dominated to the southeast. This atypical behaviour was observed during the cruise of May 2000, when upwelling conditions were not evident.