In the mid-1990s these rivers were suffering sudden surges in acidity, usually after rain. What otherwise appeared to be perfectly healthy streams were sporadically made lifeless by dramatic drops in the pH of their water. Every time life began to recover, another flush of acidity would wipe everything out.
These severe acid events killed invertebrates, fish eggs and even young fish themselves. In fact, the whole ecology of these streams was affected, right down to simple organisms such as the diatoms that were studied as part of Dr Jüttner’s research.
But perhaps the most tangible impact was on the Wye’s salmon population. Historically, these furthermost extremities of the system have been the preferred spawning areas for the river's famously large, multi-sea winter spring salmon. It is no coincidence that the increase in the frequency and intensity of these acid events coincided with the decline in these iconic fish.
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