Metabolismo neto y flujo de nutrientes en la interfase sedimento-agua, en el Golfo de Nicoya, Costa Rica

Abstract

ABSTRACT The seasonal changes in the water characteristics of the Tempisque River determine to a large extent the characteristics of the benthos and its biological activity in the inner Gulf of Nicoya. In the central area of the estuary, primary production in the water column determines the organic matter flux to the sediment, whereas in the inner area, the seasonal changes in the riverine material were more important for the material flux to the sediment. The supply to and content of organic matter in the sediment determined the biological activity in the benthic compartment, which was reflected in the total metabolic activity of the sediment; the magnitude of oxygen fluxes (diffusive and total), as well as, the nutrient content and dynamics. The concentration of the inorganic nutrients quantified in the subtidal sediment was dependent on the sediment organic matter content and chlorophyll a. Nutrient concentrations in the porewater were usually higher than in the water column and thus the sediment was a source of nutrients to the water column, at least in the middle of the estuary. During the rainy season, the nutrient fraction in the interstitial water was the major one, while during dry season the content in the interstitial water decreased, increasing the content of the other two fractions (intracellular and exchangeable). The primary production of microphytobenthos in the intertidal zone was linked to the grain size distribution based on data from two transects sampled from the lower to the upper part of the intertidal muddy flats. Primary production and respiration were higher in the upper part, as well as the abundance of organisms associated with the primary production processes (diatomos and cyanobacteria) and mineralization of organic matter (bacteria). A spatial study of the net primary production, organic matter content and chlorophyll content in the intertidal zone of the Gulf of Nicoya showed difference between the northern area near to the river and and the southern area. The area closest to the river were, in general, more active in term of metabolic activity, showing also the highest contents of organic compounds and nutrient contents.