Comportamento geoquímico do carbono dissolvido sob diferentes condições de maré no estuário do Rio Jaguaribe

Abstract

Dissolved carbon transport from rivers to ocean is a key step in the global carbon cycle, since this C species has a strong effect on aquatic ecosystems dynamics. Before reaching the ocean, dissolved carbon can suffer biogeochemical transformations under the influence of the estuarine environment, which respond to seasonal and tidal changes. This study shows the spatial and temporal variability of total dissolved carbon (TDC), dissolved inorganic carbon (DIC) dissolved organic carbon (DOC) and the hydrochemistry of the Jaguaribe river estuary, under different tidal conditions (ebb/flood) during the rainy season and spring tide. DOC concentrations varied from 0.14 to 14.73 mg/L, whereas DIC from 22.3 to 44.26 mg/L and TDC from 28.11 to 57.59 mg/L. all dissolved carbon species presented a non-conservative behavior along the estuary, both during ebb and flood tide. The spatial distribution of DOC along the estuary suggests exportation during ebb tide and accumulation within the estuary during flood tide. The relatively high DOC concentrations found in the Jaguaribe estuary can be associated with leaching of mangrove sediments, anthropogenic emissions and phytoplankton activity. The high DIC observed are due to the large influence of seawater intrusion under the dominant semiarid conditions of the region. Retention of DIC was observed between the Fortim and Ilha do Mel stations during ebb tide and a seaward decrease during flood period. TDC behavior was similar to that of DIC, although some exportation of TDC occurred during the ebb tide. Diurnal variability of all dissolved carbon species was non-conservative, varying according to insolation, probably resulting from phytoplankton activity.