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

Starkey, Eric; McCay, Daniel

n 2007, the National Park Service (NPS) Southeast Coast Network (SECN) Inventory and Monitoring Program began collecting water-quality data in the estuarine waters near Cape Lookout National Seashore (CALO). Two continuous-monitoring stations have been operational since 2008 at the Shackleford Banks Dock (CALOshak01), and in the Middle Marshes area (CALOmidm02). These stations collect conductivity, dissolved oxygen, pH, salinity, temperature, turbidity, and water level data every 15 minutes. Water-quality technicians make additional water quality measurements, which include monthly measurements of water clarity conditions, nutrient concentrations, and chlorophyll a levels. Staff follow methods 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 Lookout National Seashore fixed-station water-quality monitoring sites are part of the SECN estuarine water-quality monitoring program, which routinely collects data in the vicinity of seven coastal parks 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. Key findings from the 2017–2019 data record are are listed below and summarized in this report. Site CALOshak01 Chlorophyll a concentrations were good for thirty-one samples and fair for one sample. Concentrations ranged from 0.7 µg/L to 6.0 µg/L. Ten samples were tested for dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) during the three-year period of record. All DIN and DIP concentrations fell in the good range. Mean monthly dissolved oxygen concentrations were good throughout the period, ranging from a low of 6.3 mg/L in August 2018 to a high of 9.6 mg/L in January 2018. Individual concentrations ranged from a low of 5.8 mg/L in October 2018 to a high of 10.7 mg/L in January 2018. Mean monthly pH values ranged from 8.1 to 8.2 and exhibited low variability across the period of record. Individual values ranged from a low of 7.7 in September 2017 to a high of 8.4 in February 2017. Monthly mean turbidity values ranged from 2.7 FNUs (formazin nephelometric unit) to 9.0 FNUs. The lowest individual turbidity values for any given month was 0.2 FNUs, and a maximum value of 81.4 FNUs was recorded in September 2019. Water temperatures in 2017–2019 ranged from a minimum monthly mean of 7.6°C (45.7°F) to a maximum monthly mean of 28.9°C (84.0°F). The tidal range at CALOshak01 was 1.9 meters (6.2 feet). Site CALOmidm02 Chlorophyll a concentrations were good at all thirty-two site visits. Concentrations ranged from 0.5 µg/L to 4.1 µg/L. Ten samples were tested for dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) during the three-year period of record. All DIN and DIP concentrations fell in the good range. Mean monthly dissolved oxygen concentrations were good throughout the period, ranging from a low of 6.1 mg/L in August 2019 to a high of 9.9 mg/L in January 2018. Individual concentrations ranged from a low of 4.03 mg/L in August 2019 to a high of 12.9 mg/L in January 2018. Mean monthly pH values ranged from 7.8 to 8.3. Individual values ranged from a low of 7.6 in April 2017 to a high of 8.8 in January 2019. Monthly mean turbidity ranged from 2.1 NTUs (nephelometric turbidity unit) to 11.6 FNUs. Note that the different units (NTU and FNU) are the result of different sensors and are nearly equivalent. The lowest individual turbidity reading for any given month was less than 0.1 FNUs, and a maximum reading of 130.27 FNUs was recorded in September 2019.

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

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