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Warming Proves Bad for Life in Freshwater Lakes and Rivers

In Europe and North America, lakes are warming, which is bad news for water quality and fish
Lake Constance



Flickr/Stefan Munder

London – Austria's alpine lakes are warming, and that's bad news for the region's fish and economy, according to new research in the journal Hydrobiologia.

Martin Dokulil of the Institute for Limnology at the University of Innsbruck studied data from nine lakes larger than 10 square kilometers, or about 2,500 acres. The largest, Bodensee or Lake Constance, touches Austria's border with Germany and Switzerland; on the other side of the country, 800 kilometers (500 miles) to the east, Neusiedler See borders Germany and Hungary.

The maximum depth of the nine lakes ranges from 2 meters to 254 meters (6.5 feet to 833 feet) and they are vital to Austria's tourist industry: They play powerful roles in the Alpine ecosystem in addition to being reservoirs of water.

But the Alpine valleys are warming: From 1980 to 1999 the region warmed three times the global average. By 2050 median temperatures for the region are expected to rise by 3.5°C. The challenge has been to anticipate the impact of global warming on the lakes, researchers say.

"The predicted changes in surface water temperatures will affect the thermal characteristics of the lakes," said Dokulil. "Warmer water temperatures could lead to enhanced nutrient loads and affect water quality by promoting algal blooms and impairing the biological functions of aquatic organisms.

"Significant increases in summer temperatures will affect the carbon cycling in the lakes, with potential consequences on atmospheric carbon dioxide levels and the Earth's climate," he added.

And the fish, too
The Austrian research so far is concerned only with freshwater temperatures. On the other side of the globe, Peter Moyle, a biologist at the University of California, Davis, has been more concerned with the freshwater fish that make their homes in or migrate to California's rivers and lakes.

He and colleagues report in the journal PLOS One – the Public Library of Science – that if current climate trends continue, then 82 per cent of California's native fish could be extinct, and their native homes colonized by invasive species. 

The scientists looked at 121 native species and found that four fifths of them were likely to be driven to extinction or at least to very low numbers. These include prized sporting fish such as the Klamath River summer steelhead and other trout, the Central Valley Chinook salmon, the Central Coast coho salmon and many others that depend on cold water.

"These fish are part of the endemic flora and fauna that makes California such a special place," said Moyle. "As we lose these fishes, we lose their environments and are much poorer for it." 

This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.

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