Assessment of Estuarine Water Quality at Timucuan Ecological and Historic Preserve: 2023 Data Summary

In July 2023, the Southeast Coast Network assessed water-quality at Timucuan Ecological and Historic Preserve 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 2014). 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 calculated when possible. All measured parameters were rated as good, fair, or poor based on thresholds set by the EPA (2012). • Water clarity was rated good at nine sites (30%), fair at ten sites (33%) and poor at eleven sites (37%). • Chlorophyll a concentrations were rated good at five sites (17%), fair at twenty-two sites (73%) and poor at three sites (10%). • Dissolved inorganic nitrogen concentrations were good at all thirty sites (100%). • Dissolved inorganic phosphorus concentrations were good at four sites (13%), fair at twenty-three sites (77%) and poor at three sites (10%). • Dissolved oxygen concentrations (bottom) were rated good at seventeen sites (57%) and fair at thirteen sites (43%). • A water-quality condition summary index was calculated for each site sampled at Timucuan Ecological and Historic Preserve 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 two sites (7%), fair at twenty-four sites (80%), and poor at four sites (13%). • See supplemental materials to compare the distribution of good, fair, and poor ratings for each parameter across the period of record. • Based on the EPA summary water-quality index rating, overall water-quality conditions at Timucuan Ecological and Historic Preserve during 2023 sampling were fair. • The EPA summary water-quality index rating for overall water-quality conditions at Timucuan Ecological and Historic Preserve is consistent with findings in 2008 and 2013, and an improvement from a poor rating in 2018.

Assessment of Estuarine Water Quality at Timucuan Ecological and Historic Preserve: 2023 Data Summary

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