Variabilidade temporal de clorofila A da zona costeira do nordeste brasileiro

Abstract

Coastal zones are regions of extreme importance for global primary productivity and frequently suffer high levels of human disturbance. Such anthropogenic perturbations directly alter the physical and chemical coastal environment and, consequently, the spatio-temporal distribution and abundance of photosynthetic organisms. Here, we map the spatio-temporal variability of chlorophyll a concentration in a coastal region (Alagoas State) of northeastern Brazil through remote sensing and investigate the influence of environmental factors (i.e. temperature, wind speed and current, discharge of basins and presence of coral reefs) on this variability. Chlorophyll a values varied spatially (0.036- 18.232 mg.m-3) and were strongly correlated with current intensity. The highest mean values for chlorophyll a were observed on the continental shelf up to 50 m deep and latitudinally towards the southern portion of study area. Seasonally, the highest means were between April and June (0.338 mg m-3) and the lowest between October and December (0.184 mg m-3). These values show a similar pattern to the hydrological regimes of eight rivers analyzed. Statistical analysis indicated that the spatio-temporal variability of chlorophyll a values is mainly influenced by the seasonal variation in hydrological regime, and that areas with abundant coral reefs had reduced chlorophyll a levels due to the blocking of nutrients at river mouths.