Nearshore zones

Blue Guill (Lepomis macrochirus)

The integrity of Lake Tahoe’s aquatic ecosystem is threatened by multiple stressors. In particular, the nearshore area is of critical concern since it is influenced by human disturbance and is the primary interface with the general public. Nearshore areas provide the majority of the spawning habitats for native fish and support the production of aquatic plants and periphyton.

Recently, agencies have taken a strong interest in managing the nearshore ecosystem due to increased distribution of non-native plants (e.g., water milfoil, Myriophyllum spicatum, curly leaf pondweed, Potamogeton crispus) and vertebrate species (largemouth bass, Micropterus salmoides and bluegill,  Lepomis macrochirus). Elevated lake water temperature will encourage further spread of these non-native species resulting in potential decline of native fish density, and disruption of their spawning habitats.

In conjunction with native fisheries monitoring, studies are underway to determine the impacts of increased concentrations of on rocks, piers and other hard substrate, and pollution from marinas and accidental spills. Desert Research Institute is currently using sensors in the nearshore area near Incline Village to measure turbidity, light attenuation and relative chlorophyll. A bivalve mollusk, the Asian clam, first observed in 2002, has also established at certain locations in the nearshore areas from Zephyr Cove to El Dorado Beach.

Asian clams excrete elevated levels of nitrogen and phosphorus into the water and bottom sediments. This stimulates algal growth which impacts both water quality and benthic communities. Dense filamentous algal blooms also are associated with the Asian clam beds.These algal blooms were reported by homeowners, residents and visitors, and represent a major new threat to the Lake Tahoe nearshore. Manipulation experiments are currently underway to determine if Asian clams can be removed from Lake Tahoe. Asian clams have both benthic and pelagic life stages enabling it to spread long distances by boats and lake currents.

Two methods of clam removal are currently being utilized. Divers are being deployed with special vacuums to remove the clams and special blankets are used to cover the clams eliminating sunlight and depriving them of oxygen, thus reducing the available food.