Beyond the clarity: Celebrating unique biology beneath Tahoe’s waters (Opinion)

Sudeep Chandra
Guest column

In the 1800s, prior to big changes from human development, Lake Tahoe’s waters supported a biological community shaped by the lake’s geologic history and deep, nutrient-poor waters.

Lake Lahontan, which flooded much of the western United States approximately 10,000 years ago, left behind many species in Lake Tahoe that are also found in the waters of the Great Basin and Sierra Nevada. As a result, Lake Tahoe supports many native (found in other places) and fewer, but very important, endemic (only found in one place on the globe) organisms.

The clear, cold water of Lake Tahoe hosts many native and endemic organisms. Historically, the lake and its streams supported North America’s largest trout, the Lahontan Cutthroat, which became extirpated (locally extinct) from the basin by the late 1930s. One of the more unique organisms is the wingless Tahoe Stonefly which spends its entire life cycle in the lake, starting with a near live birth.

In comparison, their more common cousins that are typically found in the neighboring streams that fisherman may use to catch fish, emerge from the water and take flight as adults. Other species of note include two blind amphipods, shrimp looking creatures but not true shrimp, which live within the deep plant communities 100 to 300 feet below the surface. Together, these organisms likely play a role in maintaining Tahoe’s clarity.

Since California and Nevada first conducted comprehensive biological surveys of the lake in the 1960s, Tahoe’s native (including endemic) organisms have experienced a population decline of up to 99%. Over that same period, scientists have documented the introduction of nonnative species to the basin as well as an increase in algae growth in the lake, both of which can be attributed to anthropogenic changes. The declining organisms include all seven native fishes and 10 endemic invertebrates, each no larger than the size of a quarter.

In various lake and river studies, biodiversity protection and associated indicators have been used by policy makers as a broader umbrella to conserve important habitats and components of freshwaters. Even though landscape disturbance and nonnative species introductions have reduced Lake Tahoe’s biodiversity, it’s worth noting that the lake still supports almost all the native species that were in the lake 100 years ago.

This is different from other lakes around the globe which have suffered biological losses and species shifts caused by human-induced environmental changes. Native species still reside in our lake, albeit at lower concentrations, presenting us with opportunities for recovering species and reestablishing a healthy ecosystem that contributes to the function and integrity of the lake.

As the Tahoe Science Advisory Council and its partners explore the science-based solutions for restoring Lake Tahoe, we need to integrate the lake’s native and endemic diversity into our planning efforts. Incorporating biodiversity conservation efforts along with the stabilizing lake clarity will be key to maintaining a healthier Lake Tahoe ecosystem.

When you visit the lake and see life along the shoreline, ask yourself whether the species you are observing are native or endemic, and how you might help recover these organisms.

To learn more, check out this Fact Sheet on how Tahoe’s biology has changed. Also – here’s a handy Guide for identifying native and non-native fishes and a photo of the Tahoe Stonefly mother filled with eggs from her abdomen to her head.

Dr. Sudeep Chandra is a professor at the University of Nevada, Reno, Co-chair of the Tahoe Science Advisory Council and director for the Global Water Center, the Institute for Global Studies, and the Castle Lake Environmental Research and Education Program.

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