Bonefish & Tarpon Trust Logo
Close this search box.
Close this search box.

Win Back Our Water Campaign Tackles Contaminants, Nutrients and Altered Water Flows

Bonefish & Tarpon Trust’s Win Back Our Water campaign is all about improving the most important habitat of all for our fisheries. Win Back Our Water is a multi-pronged campaign that is centered on multiple issues that must be addressed to bring our water back to a healthy status—contaminants, nutrients, and water flows. In the campaign, BTT is calling for continued support and expedited completion of Everglades restoration projects and for comprehensive water quality reforms on wastewater, septic and stormwater infrastructure, pharmaceutical contaminant removal, and reductions in glyphosate use.

Wastewater Infrastructure

Improving wastewater infrastructure will be a big challenge—but it’s a challenge we must take on. Florida’s outdated wastewater infrastructure is contributing to harmful algal blooms that are causing seagrass die-offs and widespread fish kills. This is because not enough nutrients—the fuel for algal blooms—are removed during the wastewater treatment process. The State of Florida’s commitment to this issue is encouraging, including the recent $100 million allocation to address wastewater infrastructure in the Indian River Lagoon. BTT supports similar investment in other locations statewide. Watch this video to learn more about the need to update Florida’s wastewater infrastructure.

Wastewater contaminants

Nutrients aren’t the only thing of concern passing through our wastewater infrastructure. Contaminants, like pharmaceuticals, which have negative effects on fish, are also not being removed. Recent research projects sponsored by BTT spotlight the scale of this problem. Every bonefish sampled in the Florida Keys, from Biscayne Bay to Key West, and most of the redfish sampled, from the Panhandle to Jacksonville, were found to have pharmaceuticals in their tissue—a total of 58 medications including heart drugs, antidepressants, and opioids, among others. These findings raise questions about impacts to growth rates, spawning, predator avoidance, and other issues tied to behavior and fish health. Click the links to can read about the bonefish and redfish studies. Watch this video to learn more about pharmaceutical pollution.

Aquatic Weed Control

BTT’s commitment to reducing toxicity in our waterways is raising new questions about aquatic weed control methods, including the effects of glyphosate and other herbicides on fish and other aquatic animals. It has long been assumed that glyphosate has a relatively short lifespan in the environment before breaking down (up to a month or so), which is one of the factors that has made it a popular tool to control invasive plants. But glyphosate is frequently being found in samples of water and aquatic organisms. This suggests that either:

  1. the lifespan of glyphosate can be longer than previously reported and lingering in the environment; or
  2. glyphosate is being used so broadly and frequently that it is constantly entering aquatic systems.

This is reflected in recent data from the Indian River Lagoon, where 99% of all fish sampled had glyphosate detected in their tissue. (Watch this video to learn more.) New research is also showing numerous sublethal effects of glyphosate on fish and other aquatic organisms.

Sub-lethal effects

Recent research has examined the sublethal effects of glyphosate, with some concerning results. These include the effects of glyphosate (and other herbicides) on fish behavior and physiological processes, like reproduction or kidney function. This line of research is similar to the work being conducted on the effects of pharmaceuticals on fishes and other organisms (many negative effects from pharmaceuticals have been found). In instances where sublethal effects are found, the impacts aren’t immediately obvious. In short, fish don’t float up dead. Instead, the effects can be manifest by things such as lower growth rates, higher incidences of being preyed upon by predators, and reduced reproductive success.

The types of sub-lethal effects are wide ranging and impact all life stages. A recent article that reviewed 24 scientific studies found a long list of sub-lethal effects, including:

  • Embryos: premature hatching time of embryos and a decrease in the number that hatch;
  • Larvae: changes in larval behavior, such as Increased larval mobility, increased time spent in areas of risk, reduce distance traveled, suppressed response to aversive stimuli;
  • Juveniles: erratic swimming, drastic decrease in food intake, loss of balance, hyperactivity and restlessness, reduced growth rate;
  • Adults: anxiety, decreased sexual activity, decreased distance travelled, memory impairment, disrupted brain processes.

A sampling of other studies on the sub-lethal effects of glyphosate on fishes:

  • A study of chronic exposure on largemouth bass at a concentration that is estimated to occur in water during a contamination event or direct application or spills, and at a concentration that is below the U.S EPA maximum contaminant limit permitted for drinking water, found numerous effects.
  • A study on the effects of a single exposure of glyphosate at a concentration previously detected in the environment showed slower growth rates for juvenile tilapia.
  • A study on the effects of glyphosate and chlorpyrifos, another common herbicide, found effects on brain processes in carp. Interestingly, the fish exposed to both glyphosate and chlorpyrifos had greater effects.

In addition, a recent research article reviewed 73 scientific journal publications, and based on the results recommended the revision of many countries’ regulations for glyphosate concentration in freshwater. This study reported that the United States has the second highest allowable concentrations in freshwater of the 19 countries listed.

The sublethal effects of contaminants, including glyphosate, on fishes has not received the attention that it deserves, and should be included as part of an analysis of tradeoffs. The sublethal effects should be considered, and if data are insufficient for some species research should be conducted, so that tradeoffs are appropriately balanced. And other methods, such as mechanical removal, should receive renewed attention.


Another concern about the use of glyphosate and other herbicides for aquatic weed control is that this approach exacerbates the issue of too many nutrients in the system. When aquatic plants are sprayed and die on site they decompose, and their nutrients are released right back into the water body that is already overburdened with nutrients. In a state such as Florida, where excess nutrients are having negative impacts on habitats and fisheries, this is just more fuel on the fire—and a self-inflicted wound in the larger cause of reducing nutrient loads.

The Isaak Walton League recently completed a study on the effectiveness of mechanical removal, in which they made the cuttings into a slurry that was applied as fertilizer to fields. Thus, the nutrients contained within the aquatic plants were removed from the waterbody, and when the terrestrial plants that received the slurry were harvested the nutrients were removed entirely from the system. Others are also investing in mechanical removal. This and other alternative approaches should be considered as a useful tool, which at present is not occurring. It may be that there are places and situations for which a chemical solution is deemed unavoidable, but other scenarios would be treatable with a different approach.

It’s also important that as part of a comprehensive management strategy that the numerous causes of the high levels of nutrients are also addressed. We shouldn’t be giving a drug to a patient without also addressing the cause of the disease. This is why the Win Back Our Water campaign is multi-pronged.




Kidd, KA, T Backhaus, T Brodin, PA Inostroza, ES McCallum. 2023. Environmental Risks of Pharmaceutical Mixtures in Aquatic Ecosystems: Reflections on a Decade of Research. Environmental Toxicology and Chemistry. https://doi.org/10.1002/etc.5726

Kidd, KA, PJ Blanchfield, KH Mills, RW Flick, 2007. Collapse of a fish population after exposure to a synthetic estrogen. PNAS. 104 (21) 8897-8901. https://doi.org/10.1073/pnas.0609568104

Lagesson, A, J Fahlman, T Brodin, J Fick, M Jonsson, P Byström, J Klaminder. 2016. Bioaccumulation of five pharmaceuticals at multiple trophic levels in an aquatic food web – Insights from a field experiment. Science of The Total Environment. 568:208-215. https://doi.org/10.1016/j.scitotenv.2016.05.206.


Wingen, NM, GK Cubas, GT Oliveira. 2023. Impact of 2,4-D and glyphosate-based herbicides on morphofunctional and biochemical markers in Scinax squalirostris tadpoles (Anura, Hylidae). Chemosphere. 340: 139918. https://doi.org/10.1016/j.chemosphere.2023.139918.

De Maria, M., K. J. Kroll, F. Yu, M. Z. Nouri, C. Silva-Sanchez, J. G. Perez, and N. D. Denslow. 2022. Endocrine, immune and renal toxicity in male largemouth bass after chronic exposure to glyphosate and Rodeo®. Aquatic Toxicology. 246:106142. https://doi.org/10.1016/j.aquatox.2022.106142.

Varela, ACC, SM Soares, M Fortuna, VC Costa, ÍP Barletto, MT Mozatto, L Siqueira, HH Barcellos, RE Barreto, LJG Barcellos. 2023. A single exposure to sub-lethal concentrations of a glyphosate-based herbicide or fluoxetine-based agent on growth performance in Nile tilapia, Journal of Toxicology and Environmental Health, Part A, 86:15, 534-542. https://doi.org/10.1080/15287394.2023.2224380

Zhang, D.; Ding, W.; Liu, W.; Li, L.; Zhu, G.; Ma, J. Single and Combined Effects of Chlorpyrifos  and Glyphosate on the Brain of Common Carp: Based on Biochemical and Molecular Perspective. Int. J. Mol. Sci. 2023, 24, 12934. https://doi.org/10.3390/ijms241612934

Lopes, A.R., Moraes, J.S., Martins, C.M.G., 2022. Effects of the herbicide glyphosate on fish from embryos to adults: a review addressing behavior patterns and mechanisms behind them. Aquat. Toxicol. 25, 106281 https://doi.org/10.1016/j. aquatox.2022.106281

Brovini, E.M., Cardoso, S.J., Quadra, G.R. et al. Glyphosate concentrations in global freshwaters: are aquatic organisms at risk?. Environ Sci Pollut Res 28, 60635–60648 (2021). https://doi.org/10.1007/s11356-021-14609-8


Yearly archive

Stay Informed!
Sign up for our newsletter