Nitrogen Pollution is a Significant Threat to Healthy Waters on the Suncoast


Too much nitrogen

Excess nutrient pollution, nitrogen in particular, impacts native plants and animals by harming or even eliminating suitable habitats that should be present in our local waterbodies. Critical bay habitats such as seagrass meadows are impacted by nitrogen pollution. Nitrogen fuels algal production, which smother seagrasses and/or block light essential for seagrass growth. Nitrogen is also fuel for harmful Red Tides.


Where is the nitrogen pollution coming from?

Beginning in August 2021, surface water grab samples were collected at areas identified by partners and scientific advisors at locations that may be receiving high levels of nitrogen pollution from the surrounding land. Samples were collected every two weeks for one year. Some sites are no longer monitored due to their initial low concentrations and Suncoast Waterkeeper's limited resources. New sites were selected in September 2022. Currently, 12 sites are monitored monthly for all types of nitrogen (ammonia, nitrite-nitrate, and organic nitrogen). These combined types are reported as total nitrogen in milligrams per liter (mg/L). All samples were analyzed at Benchmark EnviroAnalytical, a National Environmental Laboratory Accreditation Program (NELAP)-certified lab in Palmetto, Florida.

A healthy total nitrogen concentration threshold of 1.65 mg/L was adopted for our report card because it is the state's numeric nutrient criteria threshold for streams in West-Central Florida. Additionally, an average total nitrogen concentration of 1.65 mg/L represents the 88th percentile for total nitrogen samples collected at sites (n = 65) across the Sarasota Bay watershed from 2005 - 2021. This means only 12 percent of the 65 locations monitored over 16 years had average total nitrogen concentrations that exceeded this threshold. Sites with total nitrogen concentrations exceeding 1.65 mg/L indicate that total nitrogen levels are far above the average and what would be considered background nitrogen pollution levels. Furthermore, the state's numeric nutrient criteria were established with the understanding that concentrations above the threshold would cause problems for aquatic systems. Finally, it is essential to note that some of the sites monitored are canals that are not classified as "waters of State" and, therefore, are not required to meet this healthy threshold. However, regardless of a waterbody's classification status, as explained above, the threshold set by the state of Florida helps us understand where nitrogen pollution may be coming from and where solutions are needed to enhance water quality in all waterbodies across the Suncoast.

Nitrogen Report Card

Suncoast Waterkeeper rated the total nitrogen concentrations for 20 locations across the Suncoast using the standard grading scale. Grades were based on the number of samples with total nitrogen concentrations exceeding what is considered healthy for regulated waters. All monitored locations with less than 10% of samples exceeding the healthy threshold received an A, more than 10% but less than 20% received a B, more than 20% but less than 30% a C, more than 30% but less than 40% a D, and more than 40% an F.

Seven locations had less than 12 samples analyzed for nitrogen concentrations during the 2021 - 2023 sampling period. These locations were included in the report card, but their grades are expected to change as we continue to monitor these new locations.  


Suncoast Waterkeeper has communicated these results with local governments in charge of meeting the state's water quality criteria. We will continue to monitor and report on nitrogen pollution throughout the Suncoast.  


Suncoast Waterkeeper is grateful for funding from: