San Sebastian Water Quality Monitoring

Like many waterways around St. Augustine, the San Sebastian River has a deep and rich history. On its banks sit the Ravenswood neighborhood developed by northern entrepreneur John F. Whitney, grandson of cotton gin inventor Eli Whitney. It contains Spengler Island, where Mary Todd Lincoln visited after her husband had been assassinated.  It was a hub of shrimp boat building in the mid 1900s. But also like many waterways around St. Augustine, the San Sebastian River is suffering from water quality impacts associated with a growing population and new development. Work done by Dr. Matt Brown and his students at Flagler College between 2019 and 2022 indicated that the San Sebastian River was suffering from high levels of fecal bacteria and excess nutrients. These pollutants are among the most common in Florida – often associated with development and land use intensification. This evidence prompted Matanzas Riverkeeper to take a closer look.

Program Director Silas Tanner using a Sechhi disk to determine water clarity in the San Sebastian River

Under the Clean Water Act (CWA), waterbodies across the country like the San Sebastian River are designated for specific uses such as drinking water supply, recreation, or aquatic habitat. These designated uses are associated with water quality standards that must be met to protect public health and the environment. However, when water quality falls below these standards due to pollution or other factors, the water body is classified as impaired. If a waterbody is polluted, verification of the impairment can trigger an array of regulatory processes to help restore the waterway, as well as open up opportunities for grant funding to assist with restoration efforts. However, for an impairment to be verified, sufficient data must be collected according to strict protocols outlined by the Florida Department of Environmental Protection (FDEP).

To this end, Matanzas Riverkeeper has begun conducting water quality monitoring in the San Sebastian River. We will be collecting discrete surface water samples on a bimonthly basis through December 2024 to be analyzed for an array of parameters including alkalinity, turbidity, chloride, color, fluoride, sulfate, total dissolved solids, total suspended solids, chlorophyll, ammonia, total phosphorus, nitrate-nitrite, total Kjeldahl nitrogen, and organic carbon. The primary focus of this effort is to gather more information about the concentration of nutrients in the water.

Water quality results from samples collected on June 10, 2024

Nutrients, namely nitrogen and phosphorus, are critical elements for the health of any ecosystem. However, excess nutrients can have devastating effects on water quality, resulting in harmful algal blooms and low oxygen conditions, which can kill fish and other wildlife. When it rains, stormwater carries runoff from streets, yards, and commercial sites into nearby waterways, which can include nutrient-rich fertilizer. Additionally, aging septic tanks can leach nutrient laden wastewater into the ground, which can then travel to adjacent waterbodies.   

By monitoring these pollutants, Matanzas Riverkeeper hopes to verify the impairment and identify likely sources of pollution so that we can work with local partners to implement effective remediation strategies.