Mitigating with macrophytes: Submersed plants reduce the toxicity of pesticide‐contaminated water to zooplankton

Abstract

Abstract-In ecotoxicology, appreciation is growing for the influence that ecological interactions have on the toxicity of contaminants, such as insecticides, to sensitive species. Most previous studies, however, have focused on factors that exacerbate insecticide effects on species, while factors that may mitigate these effects have been relatively ignored. In aquatic habitats, a small number of studies have shown that submersed macrophytes can remove some insecticides from the water column via sorption. Although examining sorption dynamics is important for understanding the environmental fate of insecticides, whether and to what extent macrophytes actually mitigate insecticide effects on aquatic species remains unknown. In the present study, the authors examined how much and how quickly several realistic densities of the macrophyte Elodea canadensis decreased the toxicity of the insecticide malathion to Daphnia magna, a keystone aquatic herbivore. To do this, the authors quantified Daphnia survival in outdoor test systems (0.95 L) exposed to a factorial combination of five Elodea densities crossed with five malathion concentrations. The authors discovered that malathion's lethality to Daphnia decreased with increasing Elodea density. Furthermore, the rate at which Elodea reduced malathion's toxicity in the water column increased with macrophyte density. These results provide strong evidence that submersed macrophytes can mitigate the ecological impacts of a popular insecticide and further support that ecological interactions can strongly influence contaminant environmental effects. Environ. Toxicol. Chem. 2013;32:699-706. # 2012 SETAC

Mitigation of malathion's acute toxicity by four submersed macrophyte species

“…Whereas the present study demonstrates strong mitigating effects of submersed macrophytes on zooplankton exposed to insecticides, other studies comparing insecticide toxicity to zooplankton in the presence and absence of macrophytes have found mixed evidence of mitigation. For example, the results from the present study are highly consistent with previous work demonstrating that different densities of E. canadensis can strongly mitigate the effects of malathion on D. magna in a biomass‐dependent manner . Brock et al also found some evidence of insecticide mitigation by macrophytes when they contrasted the effects of 35 µg/L of another organophosphate insecticide, chlorpyrifos, between macrophyte ‐ dominated and phytoplankton‐dominated communities using indoor 850 L experimental units.…”

“…The degree to which macrophytes actually influence the toxic effects of insecticides in aquatic communities is poorly understood. Recently, Brogan and Relyea examined the mitigating influence of submersed macrophytes on malathion's toxicity to the aquatic zooplankter, Daphnia magna . The authors discovered that malathion was up to 9 times less toxic in the presence of realistic densities of the common macrophyte Elodea canadensis than in the absence of macrophytes (median lethal concentration in absence of macrophytes [LC50 no‐macrophytes ] = 2.8 µg/L).…”

“…In fact, at the highest macrophyte densities tested, the toxicity of water that had been dosed with approximately 30 µg/L of malathion to D. magna returned to control levels (nontoxic) within 2 h after the insecticide had been applied. Although the study by Brogan and Relyea demonstrated that E. canadensis can mitigate malathion's effects on sensitive aquatic species, it was not designed to elucidate the mechanism driving this effect. One way to begin narrowing down a mechanism is to test the mitigating effects of other macrophyte species that vary in their influence on the persistence of insecticides in the water column.…”

Modified halloysite as an adsorbent for prometryn from aqueous solutions

“…Attempts have been made of their disposal using different methods: physical -through infiltration (Krutz et al, 2003;Peña et al, 2011), coagulation (Brillas et al, 2003;Hladik et al, 2005), biological -for phytoremediation (Chuluun et al, 2009), culture macrophytes (Beketov and Liess, 2008;Matby et al, 2009;Brogan and Relyea, 2013), and the use of biotechnological methods (Hladik et al, 2005;Kanissery and Sims, 2011;Nawaz et al, 2011). For many years, the studies on the use of adsorbents for the removal of various herbicides from water have been conducted.…”

Pesticides and Herbicides

“…Prorocentrum minimum (dinoflagellate) was reported to be the most affected by the herbicide and most suitable as model organism for ecotoxicity assessments. Mitigation effects of insecticide Malathion caused by macrophyte Elodea canadensis on Daphnia magna were studied by Brogan and Relyea (2013) for potential ecological interactions on environmental contaminants. It was found that increasing densities of Elodea decreased the toxicity of Malathion on Daphnia.…”