Assessment of estuarine water and sediment quality at Cape Hatteras National Seashore and Cape Lookout National Seashore: 2021 data summary.

Starkey, Eric; McCay, Daniel; Cooper, Christopher; Hynds, Mark

doi:10.36967/2294854

In July 2021 the Southeast Coast Network conducted an assessment of water quality in the vicinity of Cape Hatteras and Cape Lookout National Seashores as part of the National Park Service Vital Signs Monitoring Program. Monitoring was conducted following methods developed by the Environmental Protection Agency (EPA) as part of the National Coastal Assessment Program (EPA 2010). Laboratory analysis measured chlorophyll a and total and dissolved concentrations of nitrogen and phosphorous. Field measurements included water temperature, pH, dissolved oxygen, and salinity. Water clarity, which requires a Secchi depth measurement, was obtained when possible. All measured parameters were rated as good, fair, or poor based on thresholds set by the EPA (2012). All measured parameters were rated as good, fair, or poor based on thresholds set by the EPA (2012). Water clarity was not calculated at all sites due to the shallow depth of the water in the sound. Of the sites where water clarity could be assessed (5 sites), four measured good and one fair. Sites that were too shallow to measure water clarity had water column conditions that did not preclude light from penetrating to the bottom of the water body so no ecological effects would be expected.Turbidity measurements ranged from 1.0 to 8.0 FNU (Formazin Nephelometric Units) and are good (i.e. < 25 NTU [Nephelometric Turbidity Units]) according to North Carolina Standards (NC Administrative Code 2019). Note that turbidity units of FNU and NTU are roughly equivalent. Chlorophyll a concentration was rated good at 29 sites (97%), and fair at one site (3%). Dissolved inorganic nitrogen (DIN) concentration was good at all 30 sites (100%). Dissolved inorganic phosphorus (DIP) concentration was good at all 30 sites (100%). Dissolved oxygen concentration (bottom) was rated good at all 30 sites (100%). A water-quality condition summary index was calculated for each site sampled at Cape Hatteras and Cape Lookout National Seashores based on the categorical assessments of chlorophyll a, DIN and DIP concentrations, dissolved oxygen, and water clarity. This summary index indicated good water-quality conditions at all thirty sites (100%). Based on the summary water-quality index rating, overall water-quality conditions at Cape Hatteras and Cape Lookout National Seashores during sampling in 2021 were good. For sediment, ecological condition was ranked as good at 30 sites (100%). As a result, no adverse impacts to benthic organisms due to sediment contamination are anticipated at any of the sampled sites. This ranking was assigned according to the 2010 Environmental Protection Agency, National Coastal Condition Assessment (NCCA) thresholds for sediment chemistry.

Assessment of estuarine water and sediment quality at Cape Hatteras National Seashore and Cape Lookout National Seashore: 2021 data summary.

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