Condition and trends of estuarine water quality in George Washington Birthplace National Monument: Northeast Coastal and Barrier Network, 2009-2021

Nagel, Jessica; Paisted, Holly; Peck, Christopher; Duffy, Paul

doi:10.36967/2311158

This report summarizes conditions and trends in routine long-term water quality monitoring data collected at George Washington Birthplace National Monument in Virginia from 2009 through 2021 as part of the NPS NCBN Vital Signs Estuarine Nutrient Enrichment monitoring program. This comprehensive program incorporates spatial surveys, repeated monitoring at trend stations, and continuous monitoring at a fixed logging station in an effort to establish overall condition of the estuary as well as to identify potential trends or changes in condition over time. All monitoring was conducted during a four-week summer index period, biennially. Monitored variables included dissolved oxygen concentration, chlorophyll-a concentration, attenuation of downwelling photosynthetically available radiation (PAR), salinity, temperature, turbidity, and pH. Condition and trends were generally consistent between the spatial station surveys, the trend stations, and continuous logging station. In every year sampled, the entirety of the estuary was classified as having poor water clarity, as measured by PAR attenuation (> 1.61 m-1). Although significant declines in chlorophyll-a concentrations were observed over time, more than 75% of the estuary was classified as being in poor condition, and the area-weighted mean consistently indicated poor condition overall (> 20 µg/L). Bottom dissolved oxygen concentrations increased over time with the majority of the estuary typically classified as being in good condition. Salinity within the estuary was variable and turbidity declined slightly over time. While there was no statistical evidence of significantly increasing water temperature over time, temperatures in the majority of the estuary exceeded 28°C for most years. The identification of status and trends may help managers to make better informed decisions, develop effective mitigation measures, reduce management costs, and provide a means of measuring progress towards goals.

Condition and trends of estuarine water quality in George Washington Birthplace National Monument: Northeast Coastal and Barrier Network, 2009-2021

Series