Ground breaking research by an international team of scientists has resulted in greater understanding of the effects pesticides have on aquatic invertebrates. Researchers used novel imaging techniques - developed for mice and rats – to examine what effects different pesticides have inside the bodies of shrimp and snails.

This has shed new light on how different species are affected differently by pollution. The findings suggest that current risk assessments over-simplify the impacts of pesticide pollution on aquatic lifeforms.

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A team of scientists from the UK, Switzerland and Finland measured the sensitivity of three species of aquatic invertebrates (two freshwater shrimp species and a pond snail) to various pesticides. These species are commonly found in European freshwaters and play an important role in breaking down organic material in the water, as well as providing a source of food for creatures higher up the food chain.

However, almost 7,000 species living in European waters are currently facing a major challenge due to exposure to a variety of pesticides entering surface waters as a result of spray drift, leaching and run-off from fields.

UK-based scientists behind the new work, from the University of York, said previous research has shown that aquatic invertebrate species do not all respond to pollution in the same way. Between species and individuals there is a wide variation in sensitivity to toxic elements.

Improving understanding of pesticides' effects

In the recent study, carried out at two Swiss scientific institutes, scientists looked at the way toxic material spreads and transforms as a means of assessing its eventual impacts.

Principal Investigator Dr Roman Ashauer, from York's Environment Department, said, "We produced images of the pesticide distribution within the shrimps and snails to better understand which organs are at risk. It turns out that for some pesticides the distribution in the body matters a lot, whereas for other pesticides… the organism [has the] ability to detoxify."

The research team looked at the effects of three pesticides – diazinon (an organophosphate insecticide), imidacloprid (a neonicotinoid, recently subject to tight restrictions by the EU Commission due to links with health effects on bees) and propiconazole (a triazole fungicide) - on the three species of invertebrate.

Dr Anna-Maija Nyman, a co-author at the University of Eastern Finland, added, "When we think about pesticides and how to kill the pests without harming other organisms, we have to start with mechanisms of toxic action. Diazinon and imidacloprid, for example, are neurotoxic insecticides, which are designed to kill pest insects. Toxicity of these neurotoxicants does vary a lot among species – in our study, the shrimps turned out to be much more sensitive than the pond snail."

Pesticides build up in aquatic creatures' bodies

She said that, whereas earlier studies looked at species' sensitivity to pesticides by assessing chemical concentrations to which they are exposed, looking at how chemicals build up in tissues of different species could actually give a more accurate picture of how they are affected by pollution.

Dr Ashauer continued, "Our study introduces a systematic way of understanding the differences between species' reactions to pesticides. As there are so many species in our waters we need a systematic understanding. We need to better understand species' differences, because we want to kill the pests, but not all the other species in our environment."

Professor Kristin Schirmer, from Eawag and the Swiss Technical Universities in Lausanne and Zürich, said: "I am fascinated about the possibility of using imaging methods developed for mice and rats to see what is going on inside a shrimp or a snail. I am convinced that imaging the chemical distribution inside aquatic species in general holds great promise to better understand their sensitivity to pesticides and other chemicals."

The research was undertaken for the EU-Marie Curie Foundation funded CREAM programme, which aims to improve risk assessments for chemicals (primarily pesticides). The findings suggest that risk assessments will need to be developed further if regulators hope to offer adequate protection to these key wildlife species.