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Kent State ecologist part of global collaboration to answer global change questions

January 11, 2019

Kent State Ecologist Part of Global Collaboration to Answer Pressing Questions About Global Change

The work of 153 ecological researchers from 40 countries, including Kent State University Assistant Professor Dave Costello, Ph.D., from the Department of Biological Sciences in the College of Arts and Sciences, has revealed new findings on the effect of climatic factors on river-based ecosystems. The findings are published in the latest issue of the journal Science Advances.

"This is the largest such study, with respect to spatial coverage, and allows us to study carbon cycling in streams at unprecedented global scales," said Dr. Costello, who serves as second author on this paper. "We are able to show how different biomes - large naturally occurring communities of flora and fauna occupying a major habitat, like forests, deserts and tundras - decompose organic material into carbon dioxide and draw conclusions about the susceptibility of these ecosystems to rising global temperatures."

The study found that climatic factors, such as temperature and moisture, influenced carbon-cycling rates of river-based ecosystems. Carbon cycling is critical for the functioning of systems across a range of spatial scales, from local food webs to the global climate.

"River ecosystems play significant roles in the global carbon cycle by regulating rates of decomposition and transporting organic matter to the oceans, but we have only a rudimentary understanding of how decomposition rates vary from river to river," said Scott Tiegs, Ph.D., associate professor of biology at Oakland University in Michigan who led the study.

Unlike most previous studies on carbon cycling in streams and rivers, the methodology in this study was identical across all field sites. The study made use of a standardized, easy-to-use bioassay, which enabled a large number of researchers to participate in the study.

"As a result, we were able to quantify decomposition rates in over 500 rivers across the globe, including every continent," Dr. Tiegs said.

The paper noted that the climatic factors that govern decomposition rates are increasingly impacted by human activities. These findings will help researchers establish baselines to quantify environmental impacts to the functioning of ecosystems on a global scale.

"In addition to providing fundamental information on how river ecosystems function, our results provide baseline data that will enable future researchers to evaluate large-scale ecological responses to warming and other dimensions of global climate change," Dr. Tiegs said.

"There are drastic changes expected at the poles," Dr. Costello said. "Our data show that cold temperatures are greatly restricting carbon loss from northern streams, but as the climate warms, the carbon stored in those streams has the potential to be lost to the atmosphere much more rapidly. The expected loss of carbon from thawing permafrost gets a lot of attention, but our study shows that warming streams in these areas may also amplify the loss of carbon from northern biomes."

The research was sponsored by the Ecuadorian Science Foundation. The article, titled "Global Patterns and Drivers of Ecosystem Functioning in Rivers and Riparian Zones," is posted online at

The Role of Dr. Costello's Lab in the Study

Dr. Costello's lab group at Kent State, which is broadly focused on ecosystem ecology, had four sites in Northeast Ohio that are included among the 500 study sites where they deployed the cotton strips. The sites were Stebbins Gulch at the Holden Arboretum, Triple Springs at West Branch State Park, the Mahoning River at Jennings Woods and Breakneck Creek at the Kent State South Slates property.

"At a given river, the cotton was placed just a few meters apart, yet that boundary between the river and land made a big difference in how quickly the carbon returned to the atmosphere," Dr. Costello said. "In some cases, we predict that leaves falling on land would stay on the soil 10 times longer than leaves falling in the river."

Dr. Costello's biggest role in this paper's manuscript was in the data analysis.

"Scott Tiegs and I designed the statistical analyses we wanted to do, and I implemented all of them to uncover the patterns in these 500 study sites," Dr. Costello said.

His lab is still generating data from the cotton strips to understand what other factors besides temperature and moisture influence decomposition rates. They are studying the role of nutrients (nitrogen, phosphorus and trace metals) on how quickly this carbon decomposes. Early results are showing that the amount of nitrogen trapped by the microbes breaking down the cotton indicates how quickly the carbon decomposes.
For more information about the Costello Biogeochemistry Lab at Kent State, visit

For more information about Kent State's Center for Ecology and Natural Resource Sustainability, visit

For more information about Kent State's Department of Biological Sciences, visit

Photo Caption:

Dave Costello, Ph.D., (left), assistant professor in Kent State University's Department of Biological Sciences in the College of Arts and Sciences, and Devan Mathie (right), an undergraduate honors student working in Dr. Costello's lab, stand in Wahoo Ditch, a tributary to Breakneck Creek in Ravenna, Ohio.

Media Contacts:

Dave Costello

Jim Maxwell

Emily Vincent

Kent State University

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