Pod skaters are common insects found in British rivers
Heath Macdonald/Science Photo Library
An analysis of Environment Agency monitoring data shows that the diversity of insects and other invertebrates in England’s rivers is better than at any time in the last 30 years. This improvement is likely related to reduced levels of copper and zinc in the water.
Andrew Johnson of the UK Center for Ecohydrology and colleagues analyzed data from 1,515 netted samples across the UK between 1989 and 2018. Each macroinvertebrate (animal without a backbone that can be seen without a microscope) belongs to a family, not a specific species identified by what.
The results show that invertebrate family diversity in British rivers has increased steadily over the past three decades in both urban and rural rivers. “Some would argue that our rivers are our greatest environmental success story since global warming. [second world] It’s war,” Johnson says.
The researchers examined 45 different variables, including chemical levels and physical factors such as temperature, and used models to determine which had the greatest impact on insect diversity. Their preliminary analysis found that declining zinc and copper levels were trends most frequently associated with increased invertebrate diversity.
Metals such as zinc and copper can affect insect growth and inhibit fertility. Presenting the findings at the annual meeting of the European Society for Environmental Toxicology in Dublin, Ireland, on May 1, Johnson said that zinc and zinc were present in wastewater from various sources such as soap, meat and shellfish. He said copper could build up.
Improving zinc and copper levels in rivers, he said, was a result of the privatization of water companies in the UK and the European Union’s decision on wastewater, which requires companies to remove more pollutants before discharging wastewater into rivers. It is consistent with the introduction of regulations.
Copper and zinc levels have also fallen dramatically, according to Johnson, along with the decline in coal burning in the UK. “This also stopped acid rain, which can displace metal and push it into rivers,” he says.
But chemical pollution appears to be a problem in British rivers in general, with data showing declines in some animals such as salmon and eels, Johnson said.
Michelle Jackson of the University of Oxford says a study currently under peer review confirms improvements in invertebrate diversity in London’s Thames basin.
Tom Oliver of the University of Reading, UK, points out that a study he was involved in published last year found that the population of freshwater invertebrates in the UK has increased in recent years. “But there’s a lot of variability from place to place, and different rivers and regions have very different species trends,” he says. “This means that high-resolution monitoring across both space and time is essential for tracking freshwater biodiversity responses.”
Improving water quality is likely the reason for the positive trend, but the rate of improvement has slowed over the past four years, and it’s unclear what impact this is having on invertebrate biodiversity, he said. To tell. “This calls for further investigation into how recent water quality changes are affecting freshwater species.”
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