Fipronil, a common insecticide, disrupts aquatic communities in the U.S.

October 23, 2020

The presence of insecticides in streams is increasingly a global concern, yet information on safe concentrations for aquatic ecosystems is sometimes sparse. In a new study led by Colorado State University's Janet Miller and researchers at the United States Geological Survey, the team found a common insecticide, fipronil, and related compounds were more toxic to stream communities than previous research has found.

The study, "Common insecticide disrupts aquatic communities: A mesocosm to field ecological risk assessment of fipronil and its degradates in U.S. streams," is published Oct. 23 in Science Advances.

Fipronil is used in the U.S. for insect control on pets, structures, yards and crops. Most of the streams where fipronil compounds were found to exceed toxic levels were in the relatively urbanized Southeast region.

Miller said the insecticide is likely affecting stream insects and impairing aquatic ecosystems across the country at lower levels than previously thought. In addition, fipronil degrades into new compounds, some of which this study found to be more toxic than fipronil itself.

The research team also found delayed or altered timing of when these insects emerged from streams, which has implications for the connections between stream and land-based communities.

"The emerging insects serve as an important food source," Miller explained. "When we see changes, including a drop in emergence rates or delayed emergence, it's worrisome. The effects can reverberate beyond the banks of the stream."

In experimental settings that had a high concentration of fipronil, the researchers also saw a reduced number of insects that scrape or eat algae off the rocks, leading to an increase of algae in those streams.

Mimicking natural habitats

In this study, the research team studied the effects of fipronil compounds on aquatic macroinvertebrates, insects that live on the rocks and sediment of stream bottoms. Examples of these insects include mayflies, stoneflies and caddisflies. These creatures spend the larval life stage in streams as aquatic invertebrates, later emerging from streams as flying insects.

"These macroinvertebrates serve as an important food source for fish and other organisms while also playing an important role in nutrient cycling ," said Miller, an aquatic ecologist with the Colorado Natural Heritage Program, which is part of the Warner College of Natural Resources at Colorado State University.

As one part of the study, the research team built rock trays to mimic the invertebrate's habitat, and placed them in the Cache La Poudre River in northern Colorado. In these habitats, the macroinvertebrates colonized naturally with algae to mimic communities that exist in nature.

Next, the scientists moved the rock trays containing macroinvertebrates into the lab, mimicking a natural environment while also controlling temperature, light and water flow. The team then added a range of concentrations of the insecticide fipronil or one of four associated fipronil degradate compounds - sulfone, sulfide, desulfinyl and amide - and observed the effects on macroinvertebrates.

Scientists found these degradates to be as toxic, if not more so than fipronil. Yet Miller said there is generally a lack of data for the compounds.

Streams in southeast most affected by fipronil

As an additional prong of the research, Miller and the team applied results from the laboratory experiment to data from a large field study conducted by the United States Geological Survey that sampled streams across the U.S. in five major regions.

Miller said fipronil compounds were detected at unsafe concentrations in 16% of streams sampled across the U.S. and were most prevalent in streams of the Southeast region of the country. Scientists found fipronil compounds much less widespread in other regions, suggesting use patterns of the insecticide differ across the country.

"We found that 51% of sampled streams in the southeast revealed the presence of fipronil, while in the Pacific Northwest, we detected only around 9% of streams with the insecticide," she said.

Miller said that while the results are concerning, it's helpful to have this scientific-based evidence to share with the scientific community and regulating agencies.

"We hope our findings provide greater understanding of the prevalence of fipronil compounds across the country and the levels at which these compounds are harmful to stream health," she said.

Colorado State University

Related Aquatic Ecosystems Articles from Brightsurf:

Fipronil, a common insecticide, disrupts aquatic communities in the U.S.
The research team found a common insecticide, fipronil, and related compounds were more toxic to stream communities than previous research has found.

Conservation planning in Amazon should prioritize aquatic biodiversity, study concludes
Simulations using field data suggest focusing on the protection of species that live in rivers and lakes can be more efficient than the approach most used now, which focuses on terrestrial biodiversity.

Aquatic hitchhikers: Using mobile technology to predict invasive species transmission
A new University of Washington study uses passive data from a fishing technology company to model the movement of anglers and predict where aquatic invasive species may be spreading.

Aquatic robots can remove contaminant particles from water
Scientists from WMG at the University of Warwick, led by Eindhoven University of Technology in the Netherlands, developed a 1cm by 1cm wireless artificial aquatic polyp, which can remove contaminants from water.

Wireless aquatic robot could clean water and transport cells
Researchers at Eindhoven University of Technology developed a tiny plastic robot, made of responsive polymers, which moves under the influence of light and magnetism.

Extreme rainfall events cause top-heavy aquatic food webs
In research recently outlined in Nature, scientists across seven different sites throughout Central and South America replicated the extreme rainfall events predicted by climate change science.

Undergraduate student discovers 18 new species of aquatic beetle in South America
Rachel Smith has published a description of 18 new species of aquatic water beetle from the genus Chasmogenus in the peer-reviewed journal ZooKeys.

New study reveals a life aquatic for many spider species
Researchers at the California Academy of Sciences and William Paterson University found that nearly one fifth of all spider families are associated with saltwater or freshwater aquatic habitats.

Working toward protective values for metals in aquatic systems based on the latest science
In a newly published series appearing in Environmental Toxicology and Chemistry, researchers describe the current state of the science, the challenges, and science-based best practices for modeling the influence of water chemistry on the toxicity of metals, which is a critical step in calculating protective metal concentrations in water for the protection of aquatic life.

Aquatic microorganisms offer important window on the history of life
Jeremy Wideman and his colleagues, including Prof. Thomas Richards at the University of Exeter describe a new method for investigating the genomes of eukaryotic flagellate organisms.

Read More: Aquatic Ecosystems News and Aquatic Ecosystems Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to