TR- 546 Texas Coastal Nutrient Input Repository - Task 3 Report Lavaca Bay Water Quality Responses to Nutrient Loading

Authors: Michael Schramm

Links between freshwater inflows, watershed nutrient loads and water quality in Lavaca Bay were explored using generalized additive models. This approach allowed the exploration of nonlinear relationships between upstream inputs and water quality responses while accounting for changes in water quality due to natural variations in precipitation and streamflow. Results show increasing concentrations of inorganic and organic nitrogen at select sites in Lavaca Bay, but no evidence of significant changes in chlorophyll-a or dissolved oxygen concentrations in recent years. Changes in freshwater inflow and, to a smaller extent, changes in watershed nutrient loading explain the variability observed in total phosphorus and nitrite+nitrate concentrations. Limited data and complex responses of chlorophyll-a, Total Kjeldahl Nitrogen, and dissolved oxygen to freshwater inflow and nutrient loadings point to a need for continued data collection and model development. Overall, the study provides a baseline assessment of how management activities in the watershed that are aimed at reducing nonpoint source pollution are linked with water quality in Lavaca Bay to date.