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New ways to look at stream health

Study looks at how nutrients in water affect food webs.

In recent years algal blooms in Utah’s waters, particularly in Utah Lake, have highlighted the problem of eutrophication—a high level of nutrients in water that causes a range of ecological problems. But some of the cascading effects of eutrophication aren’t well understood. So Jennifer Follstad Shah, assistant professor of Environmental & Sustainability Studies, and her colleagues combed through scientific studies that documented the effects of nutrients nitrogen and phosphorus—which can enter streams and lakes as pollutants—on food webs.

They found that the effects of the pollution are extensive and not limited to algae growth, with additional population growth in insects that eat algae and fish that eat insects. But nutrients also enhance rates of microbial decomposition of leaves and other organic matter in water. The researchers noted that this decomposition enhancement occurred in streams that were shaded, preventing algae growth. The researchers concluded that if regulators use the amount of chlorophyll in water, a measure of algae growth, as the primary indicator of eutrophication, they might miss significant impacts of nutrient pollution on waterways.

“Having a broader focus than algae for assessing stream health is important because streams and rivers process a large fraction of organic matter derived from terrestrial habitats,” Shah said. “In addition, leaf or cotton strip decomposition assays also are becoming a more common tool resource managers use to assess the health of aquatic ecosystems.”

Read more about this research here.