Effects of coastal lagoon water level on groundwater fluxes of nutrients to the coastal zone of southern Brazil

Abstract

Abstract Groundwater discharge represents a potentially important source of dissolved nutrients to the coastal ocean. The barrier complex along the coast of southern Brazil separates the Patos Lagoon (PL) from the South Atlantic Ocean and supports the formation of the adjacent surficial aquifers which are connected to both water bodies. Due to the high hydraulic head of the PL regarding the ocean, groundwater flows toward the coastal waters. In this study fresh groundwater nutrient fluxes to the coastal ocean were estimated considering high and low PL water level scenarios. The groundwater fluxes were estimated applying Darcy's Law and the result was 0.043 m3 km−1 day−1. Different low and high PL water level scenarios showed a change in the nutrient availability along barrier. In the lowest PL water level scenario, the nutrient flux concentrations became more significant, which may have had an increase of approximately 25%. In the highest PL water level scenario, concentrations had a decrease of up to 78%. In the molar ratio (106C: 16 N: 1P), P resulted as a potentially limiting nutrient, providing a high primary productive potential to the environment (2735 gC m−2 y−1).