Waters surrounding Sanibel, Captiva classified as ‘impaired’
The Florida Department of Environmental Protection’s 2020-22 Biennial Assessment Draft classifies the waters in the Pine Island Sound, San Carlos Bay and J.N. “Ding” Darling National Wildlife Refuge as “verified impaired” because they exceed nitrogen and chlorophyll a standards designed to support a healthy ecosystem, according to the Sanibel-Captiva Conservation Foundation.
The DEP evaluates water quality data collected for waterbodies within 29 watershed basins throughout the state. If there is enough data to meet the state’s requirements, the DEP will determine if the waterbody meets water quality criteria consistent with the federal Clean Water Act. The criteria are meant to protect the health of fish and wildlife and ensure that waterbodies are swimmable and fishable and, in some cases, meet standards for shellfish harvesting and drinking water.
In 2020, the DEP analyzed data — including new data provided by the SCCF — that indicates that the waters immediately surrounding Sanibel and Captiva do not meet water quality standards. When waterbodies are identified as impaired, the DEP will develop a plan for reducing the pollutant of concern. In this case, the plan will focus on reducing the amount of nitrogen entering the waterbodies from the adjacent land uses.
In addition to nitrogen and phosphorus, the DEP considers concentrations of chlorophyll a in the water. It is an indicator of how much algae growth is occurring. High levels of chlorophyll a indicate waters are enriched with nitrogen and phosphorus (eutrophic) and the ecosystem can become over-productive, leading to oxygen depletion, fish kills, harmful algae blooms and other ecological problems.
“The sad reality is that most waterbodies throughout Florida are currently impaired, with a large majority of them being impaired for nutrient pollution. Despite all the work that our communities on Sanibel and Captiva have done to preserve natural areas and reduce nutrient runoff from the landscape, the quality of our coastal waters continues to decline,” SCCF Environmental Policy Director James Evans said. “This is in part due to the influence of freshwater discharges from the Caloosahatchee and Peace rivers, but local nutrient sources also continue to impact water quality.”
The waters on the Gulf of Mexico side of the islands are not classified as impaired because the DEP still does not have enough data to determine their status. However, since 2018, the SCCF Marine Laboratory has been systematically collecting water quality data during quarterly sampling cruises. The data is entered into the DEP’s database and will eventually be used to assess the status of those waters.
“What we have discovered so far in the Gulf of Mexico has surprised us a bit,” Marine Laboratory research associate Mark Thompson said. “Even though the Gulf has much more water to dilute pollutants entering from adjacent sources, levels of nitrogen and chlorophyll a near the islands often exceed criteria established for (the) Pine Island Sound.”
The SCCF will work with the DEP to evaluate water quality in the nearshore Gulf waters.
“Our marine lab will continue to document and track nutrient loads entering local waterbodies to assist in identifying solutions to reduce nutrient sources and improve water quality,” Thompson said.
The DEP is accepting public comment on the assessment until Nov. 10.
For more information, visit https://floridadep.gov/dear/watershed-assessment-section.