The Impact of Glyphosate on Waterways, Marine Life, and Agriculture - Moms Across America

The Impact of Glyphosate on Waterways, Marine Life, and Agriculture

By Frank Dean, chemist and biologist


Moms Across America received funding to test water samples in Florida and make an educational video with Frank Dean and Dr. Don Huber about the impact of glyphosate, specifically in Florida, on waterways crops, and health. Citrus farming use is the major focus, but glyphosate herbicides are also used directly in the water, on streets, sidewalks, gardens, parks, and on food crops such as sugar in Florida. Frank generously offered to also write this report on glyphosate and the impact on waterways and agriculture and we hope you will share it with your local farmers, city managers, Parks & Rec Departments, and landscapers.


Herbicides applied to aquatic plants cause algae blooms[i]. Nutrients in aquatic plants are fixed. When the aquatic plants die the nutrients are released into surface waters. When herbicides are used on aquatic plants thousands of tons of fertilizer are recycled into the surface water. Unless, and until, the aquatic plants are removed from the water, the algae blooms will continue to happen.
In 1972 the University of Florida harvested aquatic plants for crop fertilizer[ii]; In many Florida soil types the aquatic plants produced more food per acre than conventional fertilizers[iii] [1] .

Algal blooms of cyanobacteria thrive in the large nutrient load content of aquatic plants killed by herbicides. Besides consuming phosphorus, Blue Green algae thrives on Glyphosate, although high concentrations may inhibit it; Blue Green algae has shown glyphosate resistance as result of pre-selective mutations, and glyphosate serves as a nutrient to these and other microbes that are able to tolerate its effects, while killing those less tolerant.[iv] “Any method of control which does not remove nutrients from the water does not solve the problem. When weeds are killed, they fall to the bottom and decay. During the decaying process they use up a portion of the oxygen in the water and deny that oxygen to the many forms of animal life in the water, thus endangering them or even suffocating them.[v] Harvesting also prevents the inevitable algal blooms which follow destroying weeds by herbicide or cutting weeds and then leaving the plants in the water to rot.” [vi]

Reef loss

The third largest coral reef in the world is dying in Florida[vii]; why? Too much Nitrogen fertilizer in the water is causing the bleaching of the reefs[viii], [ix]. Farm fertilizer runoff is blamed for the changes in water fertilizer concentrations; however, aquatic herbicide sprays can release thousands of tons of fertilizer in a short period of time. Blue Green algae thrive on the released nutrients and can make their own Nitrogen fertilizer from air[x]. The excess nitrogen combined with glyphosate in the water increases reef decline by bleaching of reefs[xi], [xii].
Flora and fauna equilibrium are shifted in the presence of glyphosate. Glyphosate is a biocide and kills all life.

Agricultural issues

Mineral nutrition of the crop

Irrespective of glyphosate applications, concentrations of shoot macro- and micronutrients were found lower in the near-isogenic glyphosate resistant cultivars compared to their respective non-glyphosate resistant parental lines. Shoot and root dry biomass were reduced by glyphosate with all GR cultivars evaluated in both soils. The lower biomass in glyphosate resistant soybeans compared to their isogenic normal lines probably represents additive effects from the decreased photosynthetic parameters as well as lower availability of nutrients in tissues of the glyphosate treated plants[xiii].

Crop Disease

Crops are struggling with maladies that can’t be identified or controlled; crops won’t size or ripen, yields are lower and of poor quality, something just doesn’t look right, and pesticides and fertilizers don’t seem to help. Glyphosate chelates nutrients required to maintain plant health and disease resistance. Glyphosate interferes with amino acid production, and by definition, a metabolic inhibitor. A metabolic disorder is any disorder that involves the alteration in the normal production and consumption of carbohydrates, lipids, proteins, plant hormones, and nucleic acids. Metabolic disorders are evidenced by various syndromes and disease symptoms even if no disease is present. Those changes include the shape, size, color and luster of plant parts.

“Conventional theory is that the Asian citrus psyllid causes Citrus Greening. However, glyphosate causes the yellowing of the citrus trees and the Asian Citrus Psyllid is attracted to the yellow leaves.”- Frank Dean in the “The Impact of Glyphosate in Farming and Waterways” video

Samples Collected

Surface waters were collected through South-Central Florida and sent to Health Research Institute lab for analysis of glyphosate and AMPA (a glyphosate degradation product).

“Glyphosate is not only a very powerful herbicide, itʼs also a very strong biocide. Very selective in the soil, but it stimulates some of our soil borne diseases and it also changes the soil microflora that affects nutrient availability then for the crops.” - Don Huber PhD plant pathologist, on the impact of glyphosate and why farmers would benefit from eliminating its use.

[1] One soil, Arrendondo, pH 6.5, had nearly ideal characteristics for plant growth. The addition of water hyacinth did not increase millet yield in the first crop, but when included in addition to fertilizer there was a positive response over and above the response to fertilizer alone. Fertilizer in terms of N-P-K was added at 0,0,0; 45, 25, 50; and 90, 50, 100 ppm. For the second millet crop in the same pots yields were much less than for the first crop and the residual effect of fertilizer alone was not significant. However there was a residual effect from water hyacinth with or without added fertilizer. Water hyacinth appeared to enhance nutrient uptake through a possible improvement of the root environment in addition to maintaining a source of plant nutrients.

On a less fertile sandy soil, Lakeland, pH 5.0, there was a greater response by the crop both to fertilizer and water hyacinth applications with greater residual effects. The best response was to the lowest rate of water hyacinth application.

The least fertile soil, Leon sand, pH 4.8, gave the biggest responses, with water hyacinth alone giving as good or better yields than fertilizers alone. Second crops were also better, reaching 74% of the first crop yields. In addition to increasing yield, water hyacinth applications increased N–P–K uptake by both crops of millet.

[iii] Parra, J.V. and C.C. Hortenstine, 1974 Plant nutritional content of some Florida water hyacinths and response by pearl millet to incorporation of water hyacinths in three soil types. Hyacinth Control J., 12:85–90
[iv] Evolutionary Ecology July 2007, Volume 21, Issue 4, pp 535-547
[xiii] Zobiole, et al, Plant Soil (2010) 328:57–69

Showing 3 reactions

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  • Steve Cascaddan
    commented 2019-12-01 18:15:09 -0800
    Thank you Michael for your clearer input.
  • Michael Adler
    commented 2019-12-01 17:49:06 -0800
    Harvesting Hyacinth can be a good and useful thing for nutrient removal and improving farm fertility. Please don’t confuse that as a feasible alternative to spraying for habitat management, in most situations for these reasons:
    1) Most landowners still don’t want the stuff dumped on their land, even though it is improves production in annually tilled crops. Transportation costs of for the waste increases project costs exponentially as distance increases.
    2) Harvesting operations are far more expensive, even without considering the disposal costs.
    3) To harvest floating vegetation, and to harvest it efficiently, it must be in open water, not shallows, and it must be fairly dense. This condition is extremely detrimental to submersed aquatic vegetation, and is generally avoided by habitat managers. A goal of lake managers is to prevent conditions from developing, in which harvesting operations would make sense.
    4) Most water bodies are under maintenance spraying programs, where the floating vegetation is treated routinely while there is only a little of it, to keep it from getting out of control. This is far more cost effective than any other control strategy and also avoids the problems of the sudden appearance of large volumes of decaying vegetation in the water. When water bodies are under maintenance programs, the floating vegetation is restricted mostly to the shallows and there is not enough of it to harvest. Harvesters cannot be used to maintain floating vegetation in a small population condition.
  • Steve Cascaddan
    commented 2019-12-01 08:55:11 -0800
    If You Want To This is a very in-depth report on the affects of Glyphosate (certain fertilizer) on Our Waterways, Marine Life & Agriculture.

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