Hundreds of speckled sea trout and redfish have washed up dead in what Capt. Matt Chipperfield, a local fishing guide and environmentalist, called the second fish kill at the preserve in September,News4JAXreported Sept. 25. The exact death toll remains unknown because many carcasses sink, decompose or are eaten by wildlife, though Chipperfield noted observing dead speckled sea trout measuring up to 27 inches.

Runoff sources and pollution levels

Stormwater from Sawgrass flows through storm drains, canals, ponds, golf courses and lawns before reaching a non-tidal lagoon inside the preserve, according to Chipperfield. Accumulated nutrients in the lagoon can fuel harmful algae blooms. A Department of Environmental Protection (DEP) study found harmful stormwater pollutants entering the preserve increased by 600 percent over the past six years.

Multi-agency investigation underway

St. Johns County Commissioner Clay Murphy visited the preserve Sept. 25 and met with DEP and Guana Preserve officials. Murphy toldNews4JAXthat officials found an unusual spike in bacteria at the site, though county officials are not yet narrowing the cause to a single source.

"It's important for us to pinpoint where it's coming from, because it could be a combination of several things … Is it manmade? Is it cattle? Is somebody doing something?" Murphy said.

Weather prevented officials from collecting water samples by airboat on Sept. 25, but Murphy said sampling would take place the week of Sept. 28. Investigators also plan to map every waterway feeding the Guana River system and work with the St. Johns County Sheriff's Office to examine nearby canals.

Proposed solutions and commission timeline

Chipperfield has asked the St. Johns County Commission to adopt a water-quality resolution or a reasonable assurance plan. Environmentalists working with the DEP are expected to submit a water restoration proposal to commissioners in October or November. The Board of County Commissioners meets the first and third Tuesday of each month at 9 a.m.