In Hot Water: Aggies Pursue $1.2M, NSF-funded Stream Temperature Study

As scientists observe warming temperatures around the globe, Utah State University researchers are embarking on a National Science Foundation-funded, multi-institution study to explore how temperature increases may be affecting organisms living in the nation’s streams and rivers.

“As ecologists, we continuously wrestle with a simple question without a simple answer and that is, ‘Why do certain species live in certain places?’” says Chuck Hawkins, professor in USU’s Department of Watershed Sciences and the USU Ecology Center. “In aquatic ecology, we need to predict how warming stream temperatures will affect the organisms inhabiting those waters, but we don’t yet have a good enough understanding of the link between temperature, organism physiology and population abundance to make those predictions with high certainty.”

Honing this understanding and making better predictions of how species will respond to climate change is a goal of the three-year, nearly $1.2 million study USU is pursuing with North Carolina State University, Pennsylvania’s Stroud Water Research Center and the University of Arizona. Utah State will receive $237,516 of the award to refine models that describe how spatial variation in stream temperature affects the distributions and viability of different species of stream invertebrates.

Aquatic invertebrates, which include insects, crustaceans, mollusks and worms that live in the water, are critical components of aquatic food webs, says Hawkins, Utah State’s lead investigator on the study.

“We understand that the metabolism of these organisms, and hence their growth and reproduction, varies in response to surrounding temperatures,” he says. “The future viability of these invertebrates will therefore be affected by any future changes in their thermal environments.”

Hawkins says the investigators plan a series of experiments and modeling activities that, in combination, will allow more accurate predictions and interpretation of ecological responses to climate change. The North Carolina and USU groups will conduct laboratory studies to determine how temperature affects oxygen consumption of different species.

“The insects will be placed in small chambers of water with oxygen sensors for 12-hour experiments,” he says. “Water in the chambers will be slowly heated and researchers can measure oxygen consumption, which should correlate with growth and reproduction.”

Researchers at the Stroud Water Research Center will conduct longer-term experiments to determine how differences in temperature affect growth and reproduction of the same species. These experiments will provide information on both the temperatures different species prefer and the maximum temperatures different species can tolerate.

The experimental data will aid USU scientists in refining ecological niche models that predict population viability and species distributions from temperature observations.

“These models are important tools,” Hawkins says. “A challenge with these models is determining if they accurately capture causal relationships. If our model predictions mirror findings from the lab experiments, we’ll have confidence the models are reasonable. If not, we will have to step back and rethink our hypotheses.”

The study will also provide critical information for managers.

“Our findings will help managers set biologically meaningful temperature criteria for streams,” Hawkins says. “For example, power plant or water treatment plant discharges, which often warm water, could be managed so that the temperature of receiving waters does not exceed those temperatures that harm aquatic species.”

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Contact: Charles “Chuck” Hawkins, 435-797-2280, chuck.hawkins@usu.edu

Writer: Mary-Ann Muffoletto, 435-797-3517, maryann.muffoletto@usu.edu