Fertilizers: Feeding the Planet, Endangering our Watersheds

First, Defining Sources of Pollution

Point source pollution is the introduction of toxic pollutants from a single event or location. This event can be as small as an accidental release of chemicals by a water treatment facility outfall, or as large as the Deepwater Horizon oil spill.

Nonpoint source pollution is the introduction of pollutants from many sources that are difficult to tease apart. Runoff from land, precipitation and atmospheric deposition are common sources of this accumulated pollution.

Nutrient Pollution: Eutrophication

Eutrophication — the over-stimulation of microscopic algae as a result of excess nutrients entering a waterway — is a major threat to water quality in watersheds the world over, and Terra Ceia Bay Watershed is no exception. When these marine plants have access to a large amount of nutrients (such as nitrogen or phosphorous), the plants grow and reproduce at such great speed that their accumulation, or bloom, blocks sunlight to those plants growing below. Seagrasses, for example, suffer from being deprived sunlight and therefore energy; the animals that depend on healthy seagrasses are put at risk as well.

When the bloom is over, the microscopic algae die and their bodies decompose in a process that uses oxygen dissolved in the water and in the top layers of sediment. Again, the size of the aggregation of marine plants means lots oxygen is taken out of the water. As a result, animals that cannot move quickly to seek out oxygen become stressed or are killed. Oysters, snails, and larval stages of organisms are among the least mobile and most at risk of death (Morrison and Greening, 2011).

This eutrophication is exacerbated by human activities, particularly the runoff and the creation of fertilizers. Just as fertilizer make more productive plants on land, they also give microscopic algae those same delicious essential nutrients.

Map of gypsum stacks in central Florida. Data from FDEP.

The introduction of nitrogen is not limited to land-based sources. Between 1999 and 2003, more nitrogen was deposited in the Tampa Bay from the atmosphere than from point source pollution (Morrison and Greening, 2011, p. 128). It is estimated that over 35% of that nitrogen to be introduced from atmospheric interactions originated outside the extent of the Tampa Bay Watershed (p.107).

Estimates of annual nitrogen introduced to Tampa Bay over time. Image from Morrison and Greening, 2011.

Although the trend of nitrogen pollution is falling, gypsum stacks full of industrial phosphate production waste remain a threat to our waterways. The risk of one particular point source became very clear to residents of the Tampa Bay region when managers at the closed Piney Point Phosphate Plant detected a leak in the lining of a retention pond.

Piney Point

In March of 2021, a lake containing wastewater at the Piney Point plant sustained a breech in the plastic liner after a heavy rainfall. Managers at the site were concerned that an uncontrolled burst would flood nearby homes and businesses. The response was two-fold: a public communication, in the form of a text, warned nearby residents of the threat and recommended immediate evacuation. In short order, 215 million gallons of wastewater was released into Tampa Bay through Port Manatee. That single event of point source pollution a year’s worth of nutrients (Perkins, 2021).

History of the Piney Point plant and the community that activated to stop it. From FOX 13 Tampa Bay

In the wake of the environmental degradation, lawsuits followed. One such lawsuit was brought against the Florida Department of Environmental Protection (FDEP) and others by a group of organizations including Suncoast Waterkeeper, ManSota-88, and Our Children’s Earth Foundation. The foundation of the suit was negligence on the part of FDEP, who is accused of ignoring US Army Corps of Engineers advice during the permitting process of the site for dredge material disposal (Farrow, 2021). A stay put on the suit was lifted in October, and the claimants will continue to push for justice under the Clean Water Act (Tyrna, 2022).

The state has set up a portal to centralize the information surrounding the Piney Point discharge, including monitoring efforts and the planned response. Updates are also available, including weekly updates to the accumulated rainfall and associated activity to avoid flooding. The summer after the Piney Point release, the Bay experienced one of the most deadly red tide events in recent history. Some experts suspect that the fertilizer industry, including the gypsum stacks around Tampa Bay, exacerbate red tide and other algal blooms (Sampson, 2021).


Bausback, E. (2022, May 24). A Timeline of the Piney Point Wastewater Disaster. Florida Museum. https://www.floridamuseum.ufl.edu/earth-systems/blog/a-timeline-of-the-piney-point-wastewater-disaster/

Farrow, C. (2021). Environmental groups sue Gov. DeSantis over ‘mismanaging’ Piney Point. WTSP. https://www.wtsp.com/article/news/special-reports/wastewater-emergency/gov-ron-desantis-piney-point-lawsuit/67-e39d50c7-428a-4bf2-9bab-1abdb866d180

Morrison, G., and Greening, H. (2011). Water Quality. In Integrating Science and Resource Management in Tampa Bay, Florida. (Yates, K.K., eds). USGS. St Petersburg, FL. https://pubs.usgs.gov/circ/1348/pdf/Chapter%205_105-156.pdf

Perkins, J. (2021). Fishermen and Scientists Probe Phosphate’s Connection to Florida Red Tides. Civil Eats. https://civileats.com/2022/04/26/fishermen-scientists-probe-phosphates-florida-red-tides-pollution-algal-bloom/

Sampson. (2021). Could Tampa Bay’s Red Tide be connected to the Piney Point disaster? Tampa Bay Times. https://www.tampabay.com/news/environment/2021/06/13/could-tampa-bays-red-tide-be-connected-to-piney-point-disaster/

Tyrna, A. (2022). November 2022 Newsletter. Suncoast Waterkeeper. https://www.suncoastwaterkeeper.org/november_2022_newsletter

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