Quantifying Annual Nitrogen Loads to Virginia’s Coastal Lagoons: Sources and Water Quality Response

摘要

Coastal lagoons of the Delmarva Peninsula receive varying annual nitrogen loads because of differing land uses. Extensive development and agriculture contribute to elevated nutrient loads in Maryland and Delaware. Agriculture and forests dominate Virginia’s landscape, suggesting these systems receive lower loads. We used a watershed model to achieve three objectives: (1) quantify loads to Virginia lagoons; (2) determine the sources of the loads; and (3) project changes in annual loads under different development scenarios. Model simulations indicated that some Virginia lagoons receive relatively high annual nutrient loads (kg N year−1) due to intensive agriculture and a high watershed/lagoon areal ratio. Model projections also suggested that increased agricultural and residential development in Virginia could lead to annual loads (kg N year−1) typical of impacted Maryland systems. A comparison of Maryland and Virginia water quality responses to nutrient loading suggested that Virginia’s lagoons exhibit a different response to nutrient loading, though the exact mechanism for this difference is unclear.