Scientists fearful of acid rain's affect on fish

With its exposed tors and open grasslands, Dartmoor is known for its hostile environment. However, it's also a place where wildlife can thrive in the right conditions.

Scientists fear that fish and other aquatic species could be struggling because of years of acid rain.

Take a dip in the Dart and the water couldn't look cleaner. While it's crystal clear, it's not always kind to the fish that find their way there to spawn each winter.

Granite rocks make the water acidic naturally, but the Moor is also struggling to cope with years of acid rain.

What you can't see by simply looking at the river is the chemical balance in the water and what scientists are finding is that when there is heavy rain, the PH or acidity of the water changes dramatically. That can have a detrimental impact on the fish and other wildlife on the river.

The Dart rises on Dartmoor and runs south to the sea. Scientists are finding that when there's heavy rain, the river gets much more acidic. A three year project is underway studying it.

Dr Sean Comber, from the University of Plymouth, said "Today we're seeing the river as we want to see it from an acidity point of view."

"Our problem comes when the rain comes, it washes it out, the acidity, it gets washed out into the river and the PH goes down and the PH goes down to a level that is potentially toxic to the fish, the invertebrates, the creepy crawlies and the algae and diatoms."

The West Country Rivers Trust is working with the University of Plymouth to improve the river.

Bruce Stockley, from the West Country Rivers Trust, said "What we're doing is seeing if we can make small scale changes to the acidity of the river."

Upstream they're adding limestone to make the water less acidic when it rains. Underwater monitors are placed strategically along the river.

Mr Stockley said, "The long term hope is that we find out, can we by adding local limestone to the river, make this a more natural PH?

If that is the case then, we need to look and find out can we apply that? Really this is a scientific study to find out what happens to the ecology when we do this intervention?"

In such a carefully balanced ecosystem, small changes could help make a big difference. Without help, this river could take many years to recover.