{"id":39102,"date":"2025-07-25T00:01:06","date_gmt":"2025-07-25T04:01:06","guid":{"rendered":"https:\/\/beyondpesticides.org\/dailynewsblog\/?p=39102"},"modified":"2025-07-23T09:22:01","modified_gmt":"2025-07-23T13:22:01","slug":"research-finds-heightened-toxicity-to-aquatic-organisms-from-microplastic-pesticide-interactions","status":"publish","type":"post","link":"https:\/\/beyondpesticides.org\/dailynewsblog\/2025\/07\/research-finds-heightened-toxicity-to-aquatic-organisms-from-microplastic-pesticide-interactions\/","title":{"rendered":"Research Finds Heightened Toxicity to Aquatic Organisms from Microplastic\u2013Pesticide Interactions"},"content":{"rendered":"

(Beyond Pesticides<\/em>, July 25, 2025) The scientific literature shows that microplastics (MPs) and pesticides, both ubiquitous throughout the environment, have synergistic effects<\/a> that threaten aquatic organisms. This means the combined toxicity of the two substances is greater than the sum of two individual exposures. The most recent study to demonstrate this, published in Ecotoxicology<\/em><\/a>, focuses on the impacts of MPs and chlorpyrifos<\/a> (CPF), a widely used organophosphate insecticide, on cladocerans<\/a>, a group of microcrustaceans.<\/p>\n

As Beyond Pesticides has previously reported<\/a>, microplastics are found in all environments and threaten not only human health but all wildlife in both aquatic and terrestrial ecosystems. The universal distribution of plastics means that they cannot be avoided. Humans and other organisms take up plastics in the form of microparticles and nanoparticles by inhalation, ingestion, and skin contact every day. Microplastics are about the width of a human hair<\/a>; nanoplastics are much smaller, about twice the width of a DNA strand. Larger pieces of plastic are ground down to these tiny sizes by weathering, temperature, biological processes, and chemical conditions. (See additional Daily News<\/em> coverage on the health and environmental hazards of plastics here<\/a>, here<\/a>, and here<\/a>.)<\/p>\n

The authors of the current study, in exposing two cladocerans, Ceriodaphnia cornuta<\/em> (daphnids or water fleas<\/a>) and Echinisca triserialis <\/em>(tardigrades or water bears), to MP and CPF both singularly and in combination, are able to assess the short-term (acute) and long-term (chronic) effects for nontarget aquatic organisms<\/a> and the ecological risks they face from environmental contaminants. As a result, no mortality is observed to MP only treatments while MPs preconditioned with CPF (MP^CPF) show acute effects. Chronic exposure also shows reduced survival and reproductive output in both cladoceran species, with C. cornuta<\/em> as more vulnerable than E. triserialis<\/em>.<\/p>\n

The researchers state: \u201cA significant delay in age at first reproduction and shorter generation time were observed in the presence of MP^CPF, suggesting MP-mediated enhanced toxicity of CPF, wherein CPF could have accumulated onto the MP surface, thus, intensifying its toxicity. The enhanced toxicity of organic pollutants by MPs in aquatic environments especially in pelagic [open water] organisms<\/a> is a matter of concern.\u201d<\/p>\n

Background<\/em><\/strong><\/p>\n

Cladocerans play an important role in the aquatic food web<\/a>, helping to transfer carbon and nutrients from lower to higher trophic levels. In documenting impacts to cladoceran species, this represents threats to other aquatic organisms<\/a> and overall biodiversity<\/a>. \u201cIngestion of MP particles or the epiplastic substances by these organisms could be the entry point in the food chain that not only affects the population dynamics of C. cornuta<\/em> and E. triserialis<\/em> but also other aquatic organisms,\u201d the authors warn.<\/p>\n

MP in bodies of water<\/a> come from various sources including wastewater effluents. \u201cStudies have shown that wastewater treatment plants discharge around 160\u2013300 million MP per day into aquatic habitats,\u201d the researchers note. MPs that are smaller than 2 mm can be easily ingested by cladocerans and other zooplankton.<\/p>\n

\u201cVarious aquatic organisms such as zooplankton, corals, fish, and marine mammals have been reported to ingest MP directly and\/or indirectly leading to the transfer of MP across trophic levels,\u201d the authors share. (See research here<\/a> and here<\/a>.) They continue: \u201cThe average size range of MP overlaps with the body size of planktonic organisms, and remains suspended in the water column for a long duration. They are easily mistaken with natural food particles, and hence particulate and filter-feeding zooplankton are more likely to ingest MP-preconditioned with dissolved organic contaminants. Thus, MP have the potential to impact a wide range of aquatic organisms including zooplankton.\u201d (See studies here<\/a>, here<\/a>, and here<\/a>.)<\/p>\n

These MPs, based on their hydrophobicity (tendency to repel water) and higher surface area, can easily adsorb (adhere to the surface) pesticide molecules. The adsorption of pesticides on MP surfaces is extensively covered in scientific literature, such as with the insecticides malathion<\/a> and carbofuran<\/a> and the fungicide carbendazim<\/a>. (See research here<\/a>, here<\/a>, and here<\/a>.)<\/p>\n

For the present study, CPF was chosen as the pesticide to analyze, as it is \u201crepresentative of a highly occurring group of pollutants in the aquatic environment, such as organophosphate pesticides, which have been included in various monitoring programs.\u201d Studies show CPF in surface and ground water, as well as larger bodies of water, that then impacts aquatic community structure and ecosystem processing. (See here<\/a>, here<\/a>, and here<\/a>.) Previous research<\/a> also shows CPF can be sorbed onto plastic surfaces. (See Beyond Pesticides\u2019 Daily News<\/em> coverage on chlorpyrifos here<\/a>.)<\/p>\n

\u201cThus, understanding the combined effects of MP and insecticides on aquatic organisms such as zooplankton is vital for thorough environmental evaluation and effective environmental management of aquatic ecosystems,\u201d the researchers note. They continue, \u201cIn the natural environment, MP co-exists with organic pollutants, and the present study explores the response of the combined effects of MP and insecticide, CPF on pelagic [open water] and littoral [shallow water] cladoceran species.\u201d<\/p>\n

Study Methodology and Results<\/em><\/strong><\/p>\n

The two cladocerans utilized in this study represent species throughout the water column that are important in aquatic food chains. C. cornuta<\/em> prefers open-water habitats while E. triserialis<\/em> is typically found in shallower water and is known for its adaptability to various environmental conditions<\/a>. \u201cFurthermore, these species are the preferred diet of planktivorous fish, playing pivotal roles in transferring carbon through freshwater food webs, and serving as reliable indicators of aquatic ecosystem health,\u201d the authors write.<\/p>\n

To test the effects of exposure to MP and CPF individually and in combination in the two species, polyethylene plastics were crushed and ground, and CPF stock solutions were prepared. Between the control and test groups, the organisms were assessed for mortality and reproductive impacts both acutely (48 hours) and chronically (until the last organism perished).<\/p>\n

As the researchers note: \u201cThe environmentally relevant concentrations of CPF and MP do not incur instant mortality; rather, they are more likely to affect the physiology, behavior, and survival patterns of the exposed organisms. The physiological responses of an organism, which determine survival and ability to contribute to the next generation, are ecologically more relevant parameters.\u201d<\/p>\n

The acute tests for both species reveal concentration-dependent mortality patterns for MPs preconditioned with CPF, but \u201cthe absence of mortality in the MP alone treatment condition, in either species at all the concentrations in acute test, suggests that MP alone does not have any toxic effect on the organisms in the short term.\u201d More importantly, within the chronic tests, increased toxicity is observed when MPs are combined with CPF. Decreases in survivorship and reproduction rates, as well as a delay in reproduction, are noted, with higher sensitivity in C. cornuta<\/em> than E. triserialis<\/em>.<\/p>\n

\u201cThese results indicate the synergistic effect of MP by accumulating CPF on the surface of MP at higher concentrations, suggesting that filter-feeding zooplankton may be more susceptible to the effects of MP^CPF compared to the presence of either MP or the insecticide alone in the aquatic environment,\u201d the authors conclude.<\/p>\n

In explanation of the sensitivity variations between the two species, the researchers say: \u201cThis difference in susceptibility can be attributed to a variety of factors, including their distinct habitat preference, behavior, and respective positions in the food chain. Ceriodaphnia cornuta<\/em>, a pelagic species, may have greater exposure to contaminants in the water column, making them more susceptible to the effects of CPF and MP. The presence of C. cornuta<\/em> in the surface and water column enhances the chances of encounter with floating MP, and their filter-feeding mechanism exposes them to higher quantities of MP and associated CPF, as MP has a larger surface area compared to larger plastic particles.\u201d (See scientific literature here<\/a>, here<\/a>, and here<\/a>.)<\/p>\n

Previous Research<\/em><\/strong><\/p>\n

In Daily News<\/em>, titled Microplastics Interact with Pesticides, Exacerbating Environmental Health Threats, Studies Find<\/a>, Beyond Pesticides shares the findings of a literature review of over 90 scientific articles in Agriculture<\/em><\/a> that document how MPs increase the bioavailability, persistence, and toxicity of pesticides used in agriculture. These interactions between MPs and pesticides enhance the threat of pesticide exposure to nontarget organisms, threaten biodiversity<\/a>, and perpetuate the cycle of toxic chemical use.<\/p>\n

Additional research, cited in the Ecotoxicology<\/em> study, shows:<\/p>\n