The results are in. Throughout the last two years, Port St. Lucie Public Works has undertaken a study to determine the extent to which bacterial and nutrient components have impacted the North Fork of the St. Lucie River. This microbial tracking study was performed in collaboration with Fort Pierce’s Harbor Branch Oceanographic Institute, St. Lucie County Health Department and the Florida Department of Environmental Protection. On May 21, representatives from Harbor Branch, who provided analytic services for the project, met publicly with the Port St. Lucie City Council to explain the data.
It is just as the council may have suspected: There is an overall bacterial problem throughout the river, there seems to be a widespread impact of wastewater on the river, and excess of herbicides and pesticides throughout the system indicate an issue with run-off.
Rachel Brewton, a research coordinator with Harbor Branch who specializes in water quality and ecology, says that since 2014, there seems to have been a spike in “poor exceedances” of enterococci and fecal coliform in the river, which might suggest conditions are worsening. The new report should help provide a “roadmap,” pointing to specific areas of concern and possible solutions.
Brewton provided context for the study, saying “every developed area near a waterway has to deal with water-quality issues as they grow. They’re really complicated issues and ever-evolving, as we discover new contaminants. Unfortunately, there is no single solution for maintaining good water quality in an urban area, so it’s something that has to be revisited over and over again.”
The recent study was undertaken throughout the wet seasons of 2016 and 2017, the dry season of 2017, and during a rain event in 2017. It not only monitored bacterial concentration along the North Fork, but also tested the waters for nutrient load to determine possible sources of water contamination.
Molecular and chemical markers were tested at two tributary sites, seven sites along the main stem of the North Fork, and 10 canals that fed into the river. The molecular markers are able to distinguish between human and fowl waste, and the chemical markers are able to detect compounds such as sucralose and acetaminophen, which don’t exist in nature but are ingested by humans, pointing to wastewater impact. Bacterial concentration and reactive nutrients were also monitored.
Two particular sites along the river seem troubled by fecal coliform and waste water – an upstream site at White City Park and a site at the opposite end of the fork, in the estuary just south of Club Med.
In addition, the river’s tributaries seem to be contributing to high concentrations of E. Coli in the river, and numerous canal sites sent up multiple red flags: Stagamore, Hogpen Slough, Veterans Memorial, Elkcam, Monterrey and A-22 are all heavily laden with bacteria and nutrients, where they flow into the river. Also, moderate levels of herbicides and pesticides throughout the whole system would indicate surficial run-off issues.
There is a seasonal correlation, says Brewton. During the rainy season, more nutrients and bacteria were discovered than during the dry season. Unfortunately, the study seems merely to illustrate the extent of the problem, but does not identify specific sources. Much of the wastewater in the river was found in areas with septic, though Brewton pointed out that it also appears in areas largely dominated by sewer. Pet and agricultural waste, as well as fertilizers, may also be causing the high levels of pollution.
However, Dr. Brian Lapointe, a nutrient expert also at the meeting, said that, as of yet, there’s no hard evidence for fertilizer run-off being a major contributor to the river’s nutrient load, and that further tests are needed before any conclusion can be reached.
Another possibility Brewton mentions is that chemical treatment of aquatic plants that would normally help clean the river could be affecting the river’s health.
Brewton recommended a few long-term solutions to the council. The city can undertake a coupled groundwater/surface water study, she says, to better isolate the interaction points between the river and the city’s septic system. Using stable isotopes of water lettuce, sediments and phytoplankton can also hone in on the nutrient sources, as well as investigation of recycled water and Class A biosolids in the system.
At the meeting, Mayor Gregory Oravec expressed his interest in future testing for ruminant tracers, molecular markers that could establish horse or cow waste, and would point more specifically to agricultural sources. He also expressed concern that tributary sites upstream of the city showed high counts of reactive nutrients like ammonium that are generally associated with wastewater – a puzzling discovery, since there are less residents and more farms in that area.
At the council’s July retreat, city staff will present a detailed cost-effective plan for furthering the microbial study and adopting possible solutions. Staff was directed to focus especially on where septic and identified hotspots intersect, as well as develop plans on possible wetland construction that might mitigate nutrient load. City staff will also work with Lapointe and other local scientists to establish the most effective framework for water improvement.
In recent years, the City of Port St. Lucie has singled itself out with a highly successful septic-to-sewer program, and an extensive stormwater treatment program with projects such as the Veterans Memorial Retrofit and the McCarty Ranch extension. At the end of the presentation, Oravec summed up the general feeling of the council by saying, “We are the city of Port St. Lucie. That is the St. Lucie River. It is the heart of the city … if we continue to take care of it, foster it and improve it, then it will continue to be the community gathering place, and we will be reunited with our history, and with something that makes this city very special.”
Article by: Adam Laten Willson, correspondent
