Fixed-station water-quality monitoring at Cape Hatteras National Seashore: 2017–2019 data summary

Starkey, Eric; McCay, Dainiel

In 2005 the National Park Service (NPS) Southeast Coast Network (SECN) Inventory and Monitoring Program began collecting water-quality data in the estuarine waters near Cape Hatteras National Seashore (CAHA) as part the NPS Vital Signs Monitoring Program. The continuous-monitoring data station is located at a dock at the Ocracoke Village boat ramp. This station collects conductivity, dissolved oxygen, pH, salinity, temperature, turbidity, and water level data every 30 minutes. Southeast Coast Network staff make additional water-quality measurements, which include monthly measurements of water clarity conditions, nutrient concentrations, and chlorophyll a levels. Southeast Coast Network staff follow methods that were adapted from the water-quality monitoring program established by the National Estuarine Research Reserve Program (Wenner and Geist 2001). Data and results are compared to EPA criteria (EPA 2012) which rate conditions as good, fair, or poor. The Cape Hatteras National Seashore fixed-station water-quality monitoring site is part of the SECN estuarine water and sediment quality monitoring effort, which routinely collects data in the vicinity of seven coastal park units located along the southeastern U.S. coast (DeVivo et al. 2008; Gregory et al. 2013). Information collected by this monitoring program will be used to help managers make better-informed decisions by understanding trends and variability related to water-quality conditions in park waters. This data summary report contains data for January 2017 through December in 2019. A gap in data collection occurred April 2017 through October 2017. This data gap should be taken into consideration when reading this summary. Results in this report can be compared with those presented in the 2015–2016 fixed station water-quality data summary report (Hynds and Starkey 2019). Key findings from the 2017–2019 data record are listed below and summarized in this report. Chlorophyll a concentrations were good for seventeen samples and fair for four samples. Values ranged from 0.95 µg/L to 9.48 µg/L. Water clarity was good for seventeen samples, fair for two samples, and poor for one sample (January 2018). Mean monthly dissolved oxygen concentrations were good throughout the period, ranging from a low of 6.2 mg/L in August 2019 to a high of 10.4 mg/L in January and February 2019. All daily means were above the threshold for good (> 5.0 mg/l). Mean monthly pH values ranged from a low of 7.7 in December 2017 to a high of 8.3 in July 2018 and June 2019. The daily mean value ranged from 7.6 to 9.0. Monthly mean turbidity values were highest during August 2019 at 12.6 NTUs (nephelometric turbidity units). The lowest mean daily turbidity reading was 0.3 NTUs in February 2017, and the highest mean daily turbidity of 56.3 NTUs was recorded in August 2019. Water temperatures in 2017–2019 ranged from a minimum monthly mean of 4.1°C (39.4°F) in January 2018 to a maximum monthly mean of 27.9 °C (82.2°F) in August and September 2018. Individual temperatures ranged from a minimum of -1.4 °C (29.5°F) in January 2017 to a maximum of 33.2 °C (91.8°F) in July 2018.

Fixed-station water-quality monitoring at Cape Hatteras National Seashore: 2017–2019 data summary

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