A new study shows the potential impacts of the “browning” trend on lake nutrients levels, with consequences for lake water quality. Credit: Corman et al., 2018, Figure 1a
Source: Geophysical Research Letters

Thoreau described the golden brown color characteristic of many lakes as “meadow tea.” Meadow tea is brewed by steeping vegetation in rain and snow. These “juices of the meadow” (also called dissolved organic matter, DOM) flow from streams to lakes where they affect water quality in many ways. Northern lakes across the US and Europe have been receiving a stronger brew of meadow tea, characterized as increased brown color in the lakes over the past 30 years. Causes and consequences of this lake “browning” trend remain hotly debated (see Creed et al., 2018).

A major question is: Does lake browning alter the nutrient status, and in turn, primary or secondary production in lakes? Corman et al. [2018] address this potentially critical consequence of browning on lake water quality by quantifying the nitrogen and phosphorus that accompany the increasingly stronger brew of meadow tea received by lakes. They show that the nitrogen and phosphorus accompanying the DOM could account for the nutrient levels in seepage lakes in northern Wisconsin that have browned over time.

This is an important step in quantifying the impacts of browning on nutrient levels in lakes, and it points the way forward for future work including the role of sunlight in releasing the nutrients from the DOM in these tea-colored lakes.

Citation: Corman, J. R., Bertolet, B. L., Casson, N. J., Sebestyen, S. D., Kolka, R. K., & Stanley, E. H. [2018]. Nitrogen and phosphorus loads to temperate seepage lakes associated with allochthonous dissolved organic carbon loads. Geophysical Research Letters, 45.

—Rose Cory, Editor, GRL

Text © 2018. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.