Fixed-station water-quality monitoring at Cumberland Island National Seashore: 2012 data summary

Rinehart, Aaron; Gregory, M.; Wright, Wendy

In 2006, the National Park Service (NPS) Southeast Coast Network (SECN) Inventory and Monitoring Program began collecting water-quality data in the estuarine waters near Cumberland Island National Seashore (CUIS) as part the NPS Vital Signs monitoring program. The CUIS station collected pH, dissolved oxygen, water temperature, salinity, conductivity, turbidity and water-level data. Additional water-quality measurements were made by SECN staff and include monthly measurements of water clarity conditions, nutrients (total dissolved phosphorus [TDP], dissolved inorganic phosphorus [DIP], dissolved inorganic nitrogen [DIN], and total dissolved nitrogen [TDN]), and chlorophyll a levels. Methods used are adapted from the water-quality monitoring program established by the National Estuarine Research Reserve Program. The Cumberland Island National Seashore fixed-station water-quality monitoring site is part of the SECN estuarine water and sediment quality monitoring efforts, which routinely collects data in the vicinity of seven coastal parks located along the southeastern U.S. coast. Information provided by this monitoring program is designed to help managers understand trends and variability related to water-quality conditions in and around park waters. Summary data are presented in annual data reports published by the SECN. Findings for 2012 are as follows: Dissolved inorganic nitrogen and phosphorus were fair in August and November. Chlorophyll a results were good in the second half of the year with June and August reported as fair. Dissolved oxygen readings made at the continuous recording station ranged from 2.5 mg/L in July to 9.1 mg/L in January. Mean monthly dissolved oxygen concentrations ranged from 3.7 in July to 8.0 mg/L in January. Mean daily dissolved oxygen levels commonly fell below 5 mg/L in the vicinity of Sea Camp Dock from late June to early October. A total of 84 days had daily averages below 5.0 mg/L. No daily averages fell below 2.0 mg/L. Water clarity conditions were poor in August, fair in July and good on the remaining sampling dates during 2012. Turbidity readings made at the continuous recording station ranged from 1.4 NTUs in January to 914 NTUs during July. Mean monthly turbidity levels ranged from 12.9 NTUs in January to 90.3 NTUs in August, with high variability throughout the month. The highest daily mean turbidity levels occurred after Tropical Storm Debby. Salinity readings ranged from 14.8 parts per thousand (ppt) in July to 37.6 ppt in August. Mean monthly readings ranged from 24.5 ppt for the month of July to 35.4 ppt during May. Traditionally, higher salinity levels are measured during the summer; however, the 11.64 inches of rain associated with Tropical Storm Debby caused the lowest readings to occur in July. pH values ranged between 7.17 and 8.43 throughout the year with the lowest pH conditions occurring episodically throughout the summer months. Mean monthly pH values ranged from a low of 7.6 in March, July, and September to 8.2 in December. Water temperatures were similar to 2011 with slightly warmer low water temperatures of 11.2 ºC (52.1 ºF) observed in the winter and a monthly average of 14.6 ºC (58.28 ºF) in January. With the highest monthly average of 29.0 ºC (84.2 ºF) as well as the absolute high of 31.4 ºC (88.6 ºF) observed during July. During 2012 approximately 13% of all data collected were excluded from analysis because they were considered anomalous; such data were most commonly associated with problems with pH and turbidity measurements. A suspected tampering event resulted in all parameters being flagged as suspect from July 24 to August 1.

Fixed-station water-quality monitoring at Cumberland Island National Seashore: 2012 data summary

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