What Lake Tahoe tells us about a changing climate

A recently published study on how natural and man-made sources of nitrogen are recycled through the Lake Tahoe ecosystem provides new information on how global change may affect the iconic blue lake.
“High-elevation lakes, such as Lake Tahoe, are sentinels of climate change,” said Lihini Aluwihare, associate professor of geosciences at Scripps Institution of Oceanography (SIO) at UC San Diego and co-author of the study. “Small changes in the lake's chemistry can have big impacts on the entire ecosystem.”
Lake Tahoe's nitrogen concentration is one of several factors that helps maintain its crystal clear waters. To keep Tahoe blue in the future, the researchers say it's important to keep a close eye on the nitrogen balance in the ecosystem over time.
“The things we do, as humans, affect change in nature.  We know the Lake's foodweb is changing due to warming and nitrogen inputs. Our marine and aquatic ecosystems across the globe face many of the same environmental stressors. What we've learned about how aquatic foodwebs recycle nitrogen in Lake Tahoe may be applicable to the clear waters near Hawai‘i,” said Stuart Goldberg, lead author of the study and post-doctoral researcher at the Center for Microbial Oceanography: Research and Education at the University of Hawai‘i at Mānoa (Goldberg was a post-doctoral researcher at Scripps Oceanography during this research).
The study, published in Nature Communications, tracked nitrogen, including that produced from the burning of fossil fuels, in the Lake Tahoe ecosystem. Nitrogen can affect both the productivity of lake foodwebs and the composition of the microbes that support nutrition for those food webs.
A main goal of the study was to understand how the nutrient is being cycled through the microbial food web. Goldberg compares the foodweb to a cafeteria that sends out a variety of different dining options that support the community as a whole. Nutrients like nitrogen, phosphorus and carbon come in, and the foodweb changes them into different types of nitrogen, phosphorus and carbon – proteins, sugars, and fats, for example. Some types are easier to eat than others, and are reused or eaten almost instantly. Other types, like the proteins isolated for this study, aren't easily consumed and accumulate in the Lake.