In the News

Yuck - Algae in Lake Tahoe
date posted: July 8 2002

There are two major types of algae found in Lake Tahoe. Microscopic Phytoplankton are single-celled or multi-cellular filamentous or colonial “floating” algae that may appear as a greenish cloud suspended in the water. Periphyton is the collective term for the community of “hairy” attached algae, fungi and bacteria that you find on rocks and pier posts.

Throughout the year, field scientists from the Tahoe Research Group collect samples of algae from around Lake Tahoe. There are typical patterns of algae growth during the year with seasonal algae blooms peaking in the spring (February to May) and sometimes again in the late fall when lake mixing provides another influx of nutrients from below for algal growth. Inflow from groundwater, atmospheric deposition and runoff brings in nutrients that feed the algae. In addition, warm and calm weather provides an ideal environment for the algae to grow along the shoreline and in deeper water. Throughout the summer, algae grow in both areas, but become limited by nutrient supply to some extent as the season progresses and snowmelt and stream flow decrease. When the sun is high in the summer sky, the phytoplankton are actually light-limited in two ways. In the surface waters, they are photo-inhibited by too much strong light. Farther down, around 40 feet to 60 feet, they find good light conditions for growth, and below that depth they become light-limited by not having enough light for growth. The numbers and types of algae and their growth rates continually change throughout the year in response to the environmental conditions.