Kayakers and paddle boarders enjoying Lake Tahoe’s shoreline may see more algae this spring and early summer than in the past several years.

Algae are small microscopic plants that use the sun’s energy and nutrients (nitrogen and phosphorus) in the lake to grow. Algae are found both in the open water of the lake (phytoplankton) and also attached to rocks, piers, boat hulls or other hard surfaces (periphyton) in shallow nearshore areas.

With the many winter storms this year, significant runoff of water, sediments and nutrients to the lake has occurred. The large snowpack also suggests a well above-average spring runoff. The large amount of runoff with associated nutrients will likely contribute to increased algae growth.

---

---

We are already seeing heavy growth of algae on submerged rocks. UC Davis researchers have observed thick, furry growths of white or tan-colored algae at depths below about 2-3 feet in many areas of the lake. The growth of this algae may continue into late spring or early summer in some areas. In addition, a zone of light growth is also being seen in the shallowest waters right below the surface this year. This is likely a consequence of the rapid rise in lake level. The algae in very recently submerged areas have had little time to develop a thick growth.

The type of algae causing the heavier growth (diatoms) grows rapidly in the spring. The diatoms produce a white stalk, which attaches to the rock or becomes entangled with other stalks, eventually coating the rocks in a thick mat. Later in the spring or early summer the diatom growth declines. Pieces of the periphyton mat often detach from the rocks and can be seen floating on the surface. Carried by wind and currents these mats can end up on the shoreline where they decay in the bright sun. Encountering smelly algae along a Tahoe beach stands in stark contrast to the image most visitors have of this clear, pristine mountain lake.

---

---

The heavy growth of periphyton is fueled by inputs of nutrients associated with runoff from tributaries, urban areas, groundwater and lake mixing patterns. Human activities within the watershed can enhance the levels of nutrients in runoff and groundwater potentially contributing to greater amounts of algae growth than would naturally occur. Considerable effort has been made by basin management agencies and local residents to control these contributions of nutrients to Lake Tahoe.

You can help UC Davis scientists track algae growth using the Citizen Science Tahoe app. You can download the app onto your Android or iPhone by visiting http://www.CitizenScienceTahoe.com or from the iTunes store. By taking a few minutes to enter what you see at the beach — everything from algae to wildlife — you are helping the science of Lake Tahoe. Each observation automatically records the user’s location and the date and time. Users can also add photos and their own comments, and earn points for every observation made.

This perceptual data will help lake researchers better understand Lake Tahoe’s fragile nearshore. Scientists will compare this data with their own data from a network of real-time sensors to gain a larger scientific view of the nearshore. As the number of citizen science observations increases, new information and trends will be discovered.

“There are aspects of water and ecological quality that depend solely on the perceptions of individuals,” said Geoff Schladow, director of the UC Davis Tahoe Environmental Research Center. “That is what this app is seeking to measure from everywhere around the lake at all times of year. If you want to contribute to science at Lake Tahoe, simply go to the beach.”

Come discover the UC Davis Tahoe Science Center (http://www.tahoesciencecenter.com). Uncover the Tahoe Basin’s ecological challenges through 3-D movies and interactive exhibits. Family friendly fun for kids ages 8 and older. Drop-in tours are Tuesday through Friday from 1-5 p.m. For school groups, we offer inquiry-based field trips. Check out our monthly lecture series on various scientific topics. To learn more about the Tahoe Science Center and TERC, visit tahoe.ucdavis.edu. The science center is located at 291 Country Club Drive Incline Village, Nevada. Call us at 775-881-7566.