Spatial and Temporal Variations in Nutrients and Water-Quality Parameters in the Mississippi River-Influenced Breton Sound Estuary

Lundberg, C.J.; Lane, R.R., and Day, J.W., Jr., 2014. Spatial and temporal variations in nutrients and water-quality parameters in the Mississippi River-influenced Breton Sound estuary.The purpose of this study is to investigate the long-term temporal and spatial nutrient patterns in the Breton Sound estuary, an estuarine wetland complex in coastal Louisiana that is highly influenced by the Caernarvon river diversion. A water-quality data set spanning 8 years of monthly sampling was analyzed. Analysis of salinity mixing diagrams indicates the estuary to be a source of ammonium and chlorophyll a, and a sink for nitrate, total nitrogen, and total suspended sediments. The estuary served as either a source or sink for phosphate, total phosphorus, and silicate depending on season. The NOx loading rate ranged from 1.1 g N m−2 y−1 during fall to 4.9 g N m−2 y−1 during spring, with an overall mean of 3.5 g N m−2 y−1. Nitrate removal efficiency varied seasonally, with highest efficiency during the fall (98%), summer (92%), and spring (87%) and lowest during the winter (74%). There was an inverse relationship between nutrient removal efficiency and nutrient loading rate. The results of this study indicate that the estuary is effective in water-quality amelioration through nitrate removal.