Inspections ward off invasive mussels

Watercraft inspection data and scientific reports continue to indicate that Lake Tahoe’s waters remain clear of invasive Quagga and Zebra mussels, which are considered major threats to Lake Tahoe and surrounding waterbodies.

Tahoe Resource Conservation District watercraft inspectors performed 8,000 inspections this boating season, and there were an additional 19,000 launches comprised of watercraft with intact Tahoe-issued inspection seals.

“We’re very happy with the watercraft inspection program thus far,” said Patrick Stone, TRPA’s Senior Wildlife and Fisheries Biologist and lead for early detection monitoring of invasive mussels. “Investigations conducted around Lake Tahoe, Fallen Leaf Lake and Echo Lake confirmed that Quagga and Zebra mussels have not established in our lakes. These results are a credit to the inspection program.”

Concern among local agencies remains high as more Western waterbodies have shown evidence of invasive mussels and other aquatic invaders. Waterbodies in California and Nevada known to be infected with invasive mussels include San Justo Reservoir, Lake Mead, Lake Havasu and the entire Colorado River system. As watercraft continue to arrive from high risk waters, the importance of Lake Tahoe’s watercraft inspection program remains critical. Federal appropriations through the U.S. Fish and Wildlife Service in 2010 enabled the program to implement off-highway inspection stations. This created an opportunity to streamline inspection procedures and increase decontamination capacity.

2010 saw a dramatic increase in watercraft decontaminations, which doubled from approximately 600 in 2009 to 1,208 this year. Improved decontamination capacity at off-highway inspection locations allowed inspectors to be more thorough in treating high-risk watercraft. Additional improvements to inspection protocol allowed inspectors to increase prevention efforts by intercepting watercraft arriving from waters known to be infested with aquatic invasive mussels.

In total, 11 watercraft showing the presence of aquatic invasive species of concern were intercepted and decontaminated.

“It only takes one contaminated boat to introduce aquatic invasive species into Lake Tahoe,” said Tahoe RCD Biological Resources Program Manager Kim Boyd. “We need to remain vigilant and not let our guard down. We hope that by demonstrating the success of the watercraft inspection program for Lake Tahoe, the Tahoe RCD and its partners can create a model for prevention programs by sharing our resources and providing support. The TRPA, our key partner in invasive species prevention, continues to be instrumental in the success and evolution of this program.”

While the addition of convenient off-highway locations enabled boaters to receive their watercraft inspections and decontaminations when entering the Lake Tahoe Basin, marinas and boat launches continued to be the busiest locations for inspections in 2010. Cave Rock saw the most inspections, followed by the Tahoe Keys Marina, Lake Forest Boat Launch, Meyers Inspection Station, Alpine Meadows Inspection Station and Sand Harbor. Off-highway inspection stations accounted for approximately 31 percent of all inspections performed during the 2010 boating season.

This year’s prevention efforts also included a more rigorous non-motorized watercraft inspection process at ramp facilities, U.S. Forest Service kiosks and Fallen Leaf Lake. Tahoe RCD inspectors surveyed more than 1,900 paddlers to assess the risk of transporting aquatic invasive species from previously visited water bodies. Paddlers also were educated about self-inspecting and decontaminating canoes, kayaks and paddleboards.

Current information on the boat inspection program, including hours of operation for boat launches and snow closures, is available at http://TahoeBoatInspections.com or by calling 888-824-6267. For more information on the district, visit www.tahoercd.org.

NASA study finds Earth's lakes are warming

WASHINGTON -- In the first comprehensive global survey of temperature trends in major lakes, NASA researchers determined Earth's largest lakes have warmed during the past 25 years in response to climate change.

Researchers Philipp Schneider and Simon Hook of NASA's Jet Propulsion Laboratory in Pasadena, Calif., used satellite data to measure the surface temperatures of 167 large lakes worldwide.

They reported an average warming rate of 0.81 degrees Fahrenheit per decade, with some lakes warming as much as 1.8 degrees Fahrenheit per decade. The warming trend was global, and the greatest increases were in the mid- to high-latitudes of the Northern Hemisphere.

"Our analysis provides a new, independent data source for assessing the impact of climate change over land around the world," said Schneider, lead author of the study published this week in the journal Geophysical Research Letters. "The results have implications for lake ecosystems, which can be adversely affected by even small water temperature changes."

Small changes in water temperature can result in algal blooms that can make a lake toxic to fish or result in the introduction of non-native species that change the lake's natural ecosystem.

Scientists have long used air temperature measurements taken near Earth's surface to compute warming trends. More recently, scientists have supplemented these measurements with thermal infrared satellite data that can be used to provide a comprehensive, accurate view of how surface temperatures are changing worldwide.

The NASA researchers used thermal infrared imagery from National Oceanic and Atmospheric Administration and European Space Agency satellites. They focused on summer temperatures (July-September in the Northern Hemisphere and January-March in the Southern Hemisphere) because of the difficulty in collecting data in seasons when lakes are ice-covered and/or often hidden by clouds. Only nighttime data were used in the study

The bodies studied were selected from a global database of lakes and wetlands based on size (typically at least 193 square miles or larger) or other unique characteristics of scientific merit. The selected lakes also had to have large surface areas located away from shorelines, so land influences did not interfere with the measurements. Satellite lake data were collected from the point farthest from any shoreline.

The largest and most consistent area of warming was northern Europe. The warming trend was slightly weaker in southeastern Europe, around the Black and Caspian seas and Kazakhstan. The trends increased slightly farther east in Siberia, Mongolia and northern China.

In North America, trends were slightly higher in the southwest United States than in the Great Lakes region. Warming was weaker in the tropics and in the mid-latitudes of the Southern Hemisphere. The results were consistent with the expected changes associated with global warming.

The satellite temperature trends largely agreed with trends measured by nine buoys in the Great Lakes, Earth's largest group of freshwater lakes in terms of total surface area and volume.

The lake temperature trends were also in agreement with independent surface air temperature data from NASA's Goddard Institute for Space Studies in New York. In certain regions, such as the Great Lakes and northern Europe, water bodies appear to be warming more quickly than surrounding air temperature.