Carbonate System Seasonal Behavior along a Southeastern Brazilian Estuarine-Lagoon Complex with Different Degrees of Anthropogenic Impacts on its Sectors

Abstract

This study aimed to understand the behavior of the carbonate system in the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC) to evaluate its potential as a source or sink for atmospheric CO2. This estuarine-lagoon complex is one of the most extensive in Brazil, more than 100 km long and covers protected and sparsely inhabited regions of the state of São Paulo. This system presents, in its southern portion, most preserved areas, and evident anthropogenic impact in the northern portion, where an artificial canal was created in the second half of the 19th century, with the aim of shortening the navigation path link the river to the estuarine system offering a passage to the sea, resulting in several modifications, both from a hydrodynamic and biogeochemical mechanisms. Sampling of salinity (S), temperature (T), total alkalinity (TA), pH, dissolved oxygen (DO), and nutrients (P and Si) were performed along the CIELC in the winter of 2012 and in the summer of 2013. S, TA, pH and nutrients were used to support the understanding the behavior of the species in the carbonate system (CO2 , HCO3 - , CO3 2-) and related variables were used to calculating the partial pressure of CO2 (pCO2 ). The data showed the difference in salinity and carbonate members distinguished the northern and southern areas, the influence of the marine waters entrance by the bars, and the predominance of the system as a source of CO2 , even in the most preserved area. However, the difference in this behavior is most evident under anthropogenic pression offering risk of extreme changes in direction to the southern sector, now observed until the intermediate point of the system. The recommendation is an urgency in monitoring this region to minimizes futures environmental changes, as acidification and the increase as a source of CO2 .