Condition and trends of estuarine water quality and seagrass in Fire Island National Seashore: Northeast Coastal and Barrier Network, 2003–2022

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

doi:10.36967/2311455

This report summarizes conditions and trends in routine long-term water quality monitoring and seagrass data collected at Fire Island National Seashore in New York from 2003 through 2022 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 water quality 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. Monitored variables included dissolved oxygen concentration, chlorophyll-a concentration, attenuation of downwelling photosynthetically available radiation (PAR), salinity, temperature, turbidity, and pH. In addition, long-term monitoring of seagrass condition was conducted at permanently established transects. Water quality condition and trends were generally consistent between the spatial station surveys, the trend stations, and continuous logging station. Although the majority of the monitored area was generally classified as being in fair to good condition for most years sampled, there were several years when more than 50% of the park estuary was classified as being in poor condition with respect to chlorophyll-a concentrations and water clarity, as measured by PAR attenuation. Bottom dissolved oxygen concentrations were consistently classified as being in good condition throughout the majority of the estuary. While there was no statistical evidence of significantly increasing water temperature over time, summertime temperatures at the logging station, most trend stations, and in a large percentage of the estuary exceeded 25°C in several years. The formation of the new inlet following Hurricane Sandy in 2012 resulted in significant increases in salinity throughout the system and significant declines in temperature at the trend station closest to the inlet. Trends in seagrass condition in the park’s reference bed varied by species with eelgrass experiencing precipitous declines followed by its complete disappearance and widgeon grass persisting despite significant declines over the monitoring timeframe. 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 and seagrass in Fire Island National Seashore: Northeast Coastal and Barrier Network, 2003–2022

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