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News Article

Groundwater extraction harms food web in streams


Stream habitat lost in Great Plains region

The food web in Great Plains streams could be unraveling, according to a recent study published in the Proceedings of the National Academy of Sciences. Groundwater extraction for agriculture, carried out by pumping from the United States High Plains Aquifer, is causing the loss and fragmentation of stream habitats and affecting fish assemblages. The study by Perkin et al. maps the loss of stream habitat for many small fish in the Great Plains region and attributes it to declining groundwater sources.

"This is one of the first examples that links groundwater depletion to changes in the biotic communities of the river," said Keith Gido, a biologist at Kansas State University and one of the authors of the paper. "We've lost more than 350 miles of stream in the last 65 years because of a reduction in the groundwater, and we expect we will lose another 180 miles of stream by 2060."

According to the research, the reduction of the region's streams is changing the fish community. Several species of fish that were once plentiful in the Great Plains and serve an important role in the food web are no longer found in the area.

"One of our main findings is a transformation of the fish community," Gido said. "We are seeing fish communities change from species that are adapted to large, free-flowing rivers to species that occupy small streams with isolated habitats."

The fish that have already been lost or are most at risk in Kansas streams include the plains minnow and the shoal chub. Even several species such as the red shiner and sand shiner, which were thought to be plentiful, are declining as a result of reduced stream habitat, according to Joshuah Perkin, who was the lead researcher for the study.

"Not only have today's rare fish -- once common in Kansas -- continued to decline, but we also found evidence that the fish that are common today may become rare fish in the future if this problem isn't addressed," Perkin said.

Gido said that even though the fish documented as declining in the study may not have sport fish status like walleye and bass, these smaller fish still have great importance in the diversity and food web of Kansas streams.

"Many of the species that we documented in this paper are not used for recreational purposes but are still an important part of the ecosystem," Gido said. "The larger predators that more humans enjoy for recreational fishing might have some dependency on those smaller species and the consequences of losing those species are very uncertain."

All species of at-risk fish prefer larger, fast-flowing waters and reproduce by spawning above the riverbed so the eggs float downstream. The 2011 and 2012 droughts combined with decreasing groundwater that feeds the streams and many dams have changed the fish habitat and prevent fish from swimming back upstream to start the reproductive cycle over again, Gido said.

Groundwater well data from the 1950s to 2010 were used to track the rate of change in the water table of the High Plains Aquifer. The relationship between the length of stream receiving water from the High Plains Aquifer and the occurrence of fishes characteristic of small and large streams in the western Great Plains was modelled at a regional scale and for six subwatersheds nested within the region. Water development at the regional scale was associated with construction of 154 barriers that fragment stream habitats, increased depth to groundwater and loss of 558 km of stream, and transformation of fish assemblage structure from dominance by large-stream to small-stream fishes.

"When the elevation of the water table is higher than the elevation of the stream, water flows from the water table into the stream and it maintains water in that stream," Gido said. "When the elevation of that water table drops below the elevation of the stream, then the water moves from the stream into the ground. During droughts it's much more likely that streams will dry up completely if the water table also is low."

Projections to 2060 indicate loss of an additional 286 km of stream across the region, as well as continued replacement of large-stream fishes by small-stream fishes where groundwater pumping has increased depth to groundwater.

A small selection of other papers on fish diversity in Great Plains streams, indexed on Environmental Impact, is listed below.

Journal Reference

Joshuah S. Perkin, Keith B. Gido, Jeffrey A. Falke, Kurt D. Fausch, Harry Crockett, Eric R. Johnson, John Sanderson. Groundwater declines are linked to changes in Great Plains stream fish assemblages. Proceedings of the National Academy of Sciences, 2017; 114 (28): 7373  DOI: 10.1073/pnas.1618936114

 

Article details

  • Author(s)
  • David Simpson
  • Date
  • 23 August 2017
  • Source
  • Kansas State University
  • Subject(s)
  • Biodiversity