Under a wave of global change, lakes remain placid

Lake of the Isles, Minneapolis, MN. Photo by John Platek.

Oliver, S. K., Collins, S. M., Soranno, P. A., Wagner, T., Stanley, E. H., Jones, J. R., … & Lottig, N. R. (2017). Unexpected stasis in a changing world: Lake nutrient and chlorophyll trends since 1990. Global Change Biology. DOI: 10.1111/gcb.13810

Swimmers, boaters, and fishing enthusiasts care about keeping our lakes healthy. As climate and patterns of land development change, scientists are diving into the challenge of understanding how these interacting forces impact water quality. In a recently published paper, researchers assembled a database of thousands of lakes across the northeastern United States to address this question. They found that water quality has remained surprisingly stable over the past twenty years.

From citizen science to big data

Local water management groups, including non-profit organizations and municipalities, monitor the health of their lakes by collecting data on nitrogen and phosphorus levels. High levels of these nutrients in lakes can cause algal blooms that harm both aesthetics and fish health. These data on nutrients, algae, and fish are often gathered by citizen science volunteers who want cleaner water in their hometown lakes. However, localized monitoring of individual lakes doesn’t paint the entire picture of lake health.

Processes impacting water quality occur not only within the lake itself, but also on much broader scales. For example, rising temperatures and more extreme precipitation events are affecting lakes across the country. These large-scale patterns interact with local factors such as fertilization rates and impermeable surface coverage to influence nutrient levels in a given lake. To account for this cross-scale interaction, the research tea

m, led by Samantha Oliver at the University of Wisconsin-Madison, compiled water monitoring records from thousands of lakes across the northeastern United States. This way, the team could examine water quality trends both within individual lakes and across the region as a whole. This massive database could not have been created without the help of hundreds of citizen scientists across the region (you can search for citizen-science opportunities online).

What’s new? Not much.

Surprisingly, the researchers found that lake water quality has changed very little since 1990, despite dramatic shifts in the environment and in water management practices. Phosphorus and algae levels have remained constant across the northeastern United States, while nitrogen levels have declined by just 1% per year. Plus, the vast majority of individual lakes—about 80% of them—showed no long-term changes in nitrogen, phosphorus, or algae.

The cause of stability in water quality is still somewhat uncertain. Management practices aimed at cleaning up lakes have grown more common in recent decades. However, these policies may be offset by water quality degradations caused by warming temperatures. Regardless, the steadiness of water quality through time in such a large, rapidly changing region is a remarkable result in itself. This outcome means that we may need more innovative regulations on land use and pollution control to improve lake health.

The continued careful monitoring of local waters by both researchers and citizen scientists will remain vital in detecting future changes to water quality, for better or for worse.

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Daniel Ackerman

I'm completing a PhD in Ecology, Evolution, and Behavior at the University of Minnesota. My research subjects vary quite a bit, from the arctic tundra of Alaska's North Slope to urban lakes near my home in Minneapolis. I study how carbon and nutrient cycles in these natural and built environments are responding to human activity in a rapidly changing world. When I escape fieldwork and labwork, you can catch me canoeing in the Boundary Waters, birdwatching, or reading.

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