Glyphosate herbicide toxicity to native Hawaiian macroalgal and seagrass species

Differential effects of pollution on adult and recruits of a canopy-forming alga: implications for population viability under low pollutant levels

“…We have shown, in this study, how subtle pollutant concentrations over a period of six months may have no visible effects on adult populations of macroalgae, but can seriously compromise their mid-term and long-term viability by reducing the fertility of the adults and the survival of recruits. A number of studies have already shown that high levels of eutrophication 36,43,82 , heavy metals 44,83 and pesticides 50,64 result in reduction in adult survival, growth and photosynthetic capacity for many species of Fucales, and that this can lead to forests of these species being replaced by simplified systems. However, low to moderate levels of pollution rarely result in an immediate deforestation of fucoid assemblages 43,84 since fucoids seem to be able to resist a certain degree of pollution.…”

“…The scarce studies dealing with the impacts of glyphosate on marine macroalgae are based only on adult stages and show that high concentrations can strongly affect growth, chlorophyll content and photosynthetic yield 50,64,104,105 . However, at lower concentrations of less than 1 µg/L, commonly found in coastal waters 51,64 , glyphosate did not show any impact on the adults 50,104 . Our experiments confirmed this as there were no signs of impairment on adult specimens of C. crinita at glyphosate concentrations of 1 µg/L.…”

“…Research into the specific responses of macroalgae to pollutants currently focuses mainly on their capacity to accumulate heavy metals and their use as bioindicators 44 , 76 – 78 . Moreover, most studies tend to deal with concentrations that are only found in highly polluted sites, such as areas where domestic, agricultural or industrial sewage discharge occur into coastal waters 50 , 64 , 79 – 81 . This meaning that the effects of toxic compounds are only known for very large concentrations, in places where macroalgal forests have already disappeared.…”

“…However, recent works show that moderate levels of glyphosate do exist in marine environments 51 and that its strong capacity to bind with organic matter may help protect it from degradation 103 . The scarce studies dealing with the impacts of glyphosate on marine macroalgae are based only on adult stages and show that high concentrations can strongly affect growth, chlorophyll content and photosynthetic yield 50 , 64 , 104 , 105 . However, at lower concentrations of less than 1 µg/L, commonly found in coastal waters 51 , 64 , glyphosate did not show any impact on the adults 50 , 104 .…”

“…The concentrations of heavy metals used in Cu and Pb treatments were just above the thresholds used by the European Union to categorize a water mass as being of good environmental quality (< 25 µg/L for Cu and < 7.2 µg/L for Pb; Directive 2008/105/ CE). Glyphosate has been detected at concentrations around 1 µg/L in unpolluted coastal waters 51,63,64 .…”