Variação Longitudinal da Salinidade do Estuário Hipersalino do Rio Apodi/Mossoró (Rio Grande do Norte, Brasil)

Abstract

In semi-arid and arid regions water discharge in estuaries is often temporary with large flows during rainy season, followed by months (5-10) of insignificant discharge, which may make hypersaline estuaries. This research analyzes the spatial and temporal variability of salinity in the Apodi/Mossoró river estuary. Daily salinity data were collected during periods of high tide (2009-2013) at 7 stations distributed in the main estuarine channel; and data of rainfall. Data set to application of statistical tests and multivariate descriptive analysis was generated. Spatial variations of this parameter were significant (p<0.001), identified by a gradual increase in concentrations toward upstream. This estuary has been classified by eurihalinas zones (1, 2, 3 and 5) and hiperalinas (4, 6 and 7), featuring a horizontal stratification reverse profile of salinity. The hypersalinity had become dominant in the second half year, reaching levels above 70 ‰ (stations 4, 5, 6 and 7). Thus, in this estuarine marine waters exert greater influence over the freshwater, due high evaporation rates and low rainfall, therefore low flows