Global warming threatens freshwater mussels

Freshwater mussels through a microscope.

Freshwater mussels through a microscope. Photo via USGS.

Slight increases in water temperatures may push some mussels into oblivion

By Summit Voice

FRISCO — Global warming may push many native freshwater mussel species to the brink of extinction, according to a new U.S. Geological Survey report. In a laboratory setting, the researchers found that warmer water temperatures impair mussel growth.

Many aquatic biologists see mussels as bellwether species of for climate change impacts.  Freshwater mussels are also good indicators of good water and sediment quality in U.S. rivers. They are also also important in the aquatic food web, filter large amounts of water and suspended particles, and serve as food for other organisms.

The new study is published in the December issue of the journal Freshwater Science.

“Native freshwater mussels may be especially sensitive to climate change because of their patchy distribution, limited mobility, and dependence on host fish for their larval stage, as well as fragmentation of their ranges by habitat alteration,” said Teresa Newton, USGS scientist and an author of the report. “Many species are currently in danger of extinction.”

The scientists studied the effects of high water temperatures, ranging from 20-35 degrees Celsius (68-95 degrees Fahrenheit), on three species of two-month-old freshwater mussels: pink mucket, fat mucket and washboard. Temperatures at which at least 50 percent of the populations died after 28 days ranged from 25.3-30.3 degrees Celsius (about 78-87 degrees Fahrenheit). Heart rates in the pink mucket and washboard mussels declined significantly with increasing water temperature.

The observed effects may ultimately decrease biodiversity and cause a shift to more temperature-tolerant mussel species.

“Freshwater mussels are the most endangered group of organisms in the U.S. and in the world,” Newton said. “More estimates of the upper thermal limits in native mussels are urgently needed to assess the potential effects of global climate change on native mussel populations.”

Over 70 percent of North America’s 302 mussel species are imperiled or extinct. Declines in the abundance and diversity of these mussels have been attributed to a wide array of human activities that cause pollution, water-quality degradation and habitat destruction.

The USGS report is in collaboration with the University of Wisconsin-La Crosse River Studies Center, and is available online. This research was supported by the USGS National Climate Change and Wildlife Science Center which provides scientific information to help land managers effectively respond to climate change. 

Additional information on native freshwater mussels in the midwestern U.S. is available at the USGS Upper Midwest Environmental Sciences Center website.

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