On top of the evidence of neonicotinoid pollution of rivers this survey report illustrates a worrying trend with impact for river life.
Modest levels of pollution found in many English rivers are having a devastating impact on mayflies, new research suggests, killing about 80% of all eggs. Clouds of emerging mayflies were once a regular sight on English summer evenings and they are a key part of the food chain that supports fish, birds and mammals. The finding that even pollution well below guidelines can cause serious harm adds to concerns about plummeting insect numbers.
In October, a study found that the abundance of flying insects has plunged by 75% in 25 years, prompting warnings that the world is “on course for ecological Armageddon”, with profound impacts on human society. Paul Knight, chief executive of Salmon and Trout Conservation (STC), which is conducting an in-depth three-year survey of rivers, said: “The results of this ground breaking new study are irrefutable. We believe this is just the tip of the iceberg. Lose your invertebrates and other species will follow.”
The new research looked at the blue-winged olive, a common mayfly present across the British Isles and most of continental Europe. Its numbers have fallen significantly in recent decades and it has almost vanished from some English rivers. The prime suspects for this decline are fine sediment and phosphate pollution in rivers, which are washed off farmed fields and also result from untreated sewage. Some research has been done on how the larval and adult stages of mayflies are affected by pollution, but not on their eggs.