Land use effects on nutrient concentrations in a small watershed in northeast Brazil

Abstract

Increases of N and P discharges from inland waters to coastal environments are the by-products of human activities such as agricultural practices. Therefore, the aim of this work is to evaluate the influence of land use change in nutrient concentrations in a small watershed in southern Bahia, Brazil. The study sites were characterized by secondary forest (P1), sand mining (P2), cocoa cultivation (P3), pasture (P4) and mangrove (P5). Dissolved forms of both nitrogen and phosphorus were higher than particulate forms in all sites. The DON concentration was higher than the DIN and the concentration of DON made up 60-73% of the total TDN. Seasonally, high variations between dry and rainy season were not observed in nutrient concentrations in Cururupe River Basin, with the exception of DON, which was higher in the rainy season. DIN, DON and PON export varies over the hydrological year indicating that fluxes were correlated with runoff. Even though the primary vegetation of The Cururupe River Basin was converted to different croplands, mainly cocoa production, the water quality presented low alterations in N and P export from upstream to downstream.