by SC Publisher Shannen Hayes
photos, video by SC Associate Publisher Chuck Larsen
The Jordan Marsh Water Quality Treatment Park is removing nitrogen and phosphorus from the Sanibel Slough and has met many of the design expectations during the first year of operation, according to a report by the Sanibel Captiva Conservation Foundation Marine Lab.
Located off Casa Ybel Road, adjacent to SCCF’s Bob Wigley Preserve, the 3.2-acre marsh is in the eastern basin of the Sanibel Slough. In 2017, the Florida Department of Environmental Protection designated the slough as “impaired” and mandated reductions of 54 percent for nitrogen and 74 percent for phosphorus for the eastern section.
SCCF Marine Lab Research Associate Mark Thompson gave a first-year report, from March 2019 to March 2020, to the Sanibel City Council Tuesday, Feb. 2. It showed 34 percent of nitrogen and 55 percent of phosphorus were removed from the Sanibel Slough.
Thompson reported that while there was not a statistically significant improvement on nitrogen or an overall impact on water quality in the east basin in the first year, there was improvement in removing phosphorus. And phosphorus is the most important nutrient to remove.
“We are seeing a downward trend and heading in the right direction,” Thompsan said. He added that increasing the flow rate of water will aid in removing more nutrients.
The marsh acts like a filter with 20,000 littoral plants of more than 15 different species helping to take up nitrogen and phosphorus as water runs through three stages before returning to the Sanibel River. Thompson explained that “plants remove nutrients. They need nutrients. They use nutrients. The whole idea of a treatment marsh is to have shallow water plants.”
Thompson also explained most of the nitrogen and phosphorus removal is happening in the first stage and no or little removal in the third stage, which is too deep for some plants. He suggested adding floating plants such as duckweed or floating islands to the third stage.
Director of Natural Resources Holly Milbrandt said some of the secondary goals of the Jordan Marsh project were to enhance existing wildlife habitat, provide recreational opportunities and educate park visitors on the various best management practices used to improve water quality.
The Jordan Marsh Park, 790 Casa Ybel Rd., is accessible to pedestrians and bicyclists but there is no onsite parking. Thompson told council members people are enjoying the park and suggested adding an observation tower to better see how the marsh is designed to work and further help educate visitors.
Milbrandt reported the $165,000 engineering cost and $475,000 construction cost of the project were funded through the South Florida Water Management District’s Cooperative Funding Program, the Lee County community park funding program and budgeted city funds.