New MSU research suggests not all lakes respond the same to climate change

A team of scientists from Michigan State University and the University of Wisconsin analyzed 30 years of data for 365 lakes in the northeastern and Midwestern U.S. to test whether changes in temperature and precipitation affect water clarity.

January 11, 2019 - Author: Ian McCullough

Increasing rainfall and warmer temperatures can cause algae blooms in lakes, which often make water murky, produce unpleasant odors, and cause fish to die. Rain flushes nutrients into lakes that algae use to grow, whereas warmer temperatures cause longer growing seasons and better growing conditions for algae. Keeping excess nutrients out of lakes reduces the risk of algae blooms. Photo: Ian McCullough.
Increasing rainfall and warmer temperatures can cause algae blooms in lakes, which often make water murky, produce unpleasant odors, and cause fish to die. Rain flushes nutrients into lakes that algae use to grow, whereas warmer temperatures cause longer growing seasons and better growing conditions for algae. Keeping excess nutrients out of lakes reduces the risk of algae blooms. Photo: Ian McCullough.

A team of scientists from Michigan State University (MSU) and the University of Wisconsin analyzed 30 years of data for 365 lakes in the northeastern and Midwestern U.S. to test whether changes in temperature and precipitation affect water clarity, which measures the cloudiness of the water. The group’s work is featured in a paper in the journal Ecological Applications

Previous research on a small number of lakes has shown that water clarity responds to climate change, but few studies have looked to see how widespread this is and whether hundreds of lakes across different regions respond the same. 

The team found that water clarity declined in many northeastern states--Maine, Vermont and New York--in response to summer rainfall, but was not affected by temperature. In contrast, many lakes in Midwestern states--Michigan, Minnesota and Wisconsin--responded to summer temperatures rather than precipitation. 

Do these results mean that all lakes in the Midwest are vulnerable to future warming and lakes in the northeast are vulnerable to increasing precipitation? Not exactly. About 33 percent of lakes in both regions were not sensitive to temperature or precipitation, and it was common to find nearby lakes (often within the same county) responding differently to the same climate. These results suggest that lakes don’t follow one general rule when it comes to how they respond to a changing climate. 

“An important conclusion of this study is that we cannot assume that lakes within a given region, or across different regions, will respond similarly to climate change”, said lead author Ian McCullough, a research scientist at MSU. 

For example, clarity in a given lake may decline due to warmer temperatures, but this may not be the case in nearby lakes if those lakes are already rich with algae or nutrients. McCullough added, “It therefore comes as no surprise that lakes are complex, changes in temperature and precipitation may interact, and that local lake characteristics can matter.” 

The team indicates that managers, homeowners and lake associations should remain confident that common strategies to improve or maintain lake water quality, such as reducing nutrient inputs from fertilizers or updating old septic tanks, will likely remain useful in the future. Regional climate change is largely outside of local control, but both local and regional factors influence water clarity. 

McCullough said that large-scale water quality research would not be possible without long-term records from a large number of lakes. Studying responses of lakes to climate requires long-term data simply because climate varies so much year to year. Long-term water clarity records are often collected by volunteer monitoring groups (such as the Michigan Clean Water Corps and Lake Stewards of Maine), and it would be difficult to study lake responses to climate across large areas without the dedicated efforts of these organizations and their members.

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