71 Environment metaphyton problem—free-floating, nuisance algae that forms mats above the bottom of the lake. Dependent on currents and wave patterns, the algae can wash onshore, where it rots. “We’ve discovered that metaphyton is heavily linked to the Asian clam, which are about the size of a quarter when mature, and microscopic as juveniles,” Berry said. These filter feeders take in water and excrete nutrients that cause big blooms of algae. Lake Tahoe is so large that it visibly dips toward the center due to the curvature of the earth. With drones, Berry captures imagery to record the clarity of the lake and the presence of algae around its 72-mile shoreline. After flying test plots that ring the lake, he dives in to scoop and sample sand to count the number of clams. Data is processed and analyzed with GIS to communicate conditions and collaborate with other scientists to gain an overall understanding of the lake. This data records changing conditions and informs testing of management techniques to address the problem. “Tahoe is a popular lake, and the majority of people interact with it right along the shoreline,” Berry said. “When there’s rotting algae on beaches, it causes concern. Right now, aesthetics is one of the main concerns.” Sensing to Inform Science TERC is an offshoot of the University of California, Davis. It was established in 1968 to monitor Lake Tahoe to support state agencies in both California and Nevada, which have jurisdiction for different parts of the lake. For more than 50 years, TERC has recorded warming water temperatures and earlier peak snowmelt. Monitoring has shown changes to the food chain in response to the changing climate. TERC observes this complex ecosystem with a combination of sensors and systems, including a network of water sensors that provides real-time reads on quality. Researchers then go out with data capture tools to verify changes. They analyze that data in the office using GIS and other tools to determine the causes of changing conditions. When Berry began the drone program, it was uncertain if it would work to see through water and quantify algae volumes. It has proven effective, but there were lessons. For instance, drone flights take place in early morning now, when winds are calm (reducing obscuring ripples) and the sun doesn’t glint off the water. Berry considers many factors to optimize the quality of the data he collects. He avoids strong winds to ensure safe takeoffs and landings. It’s the trickiest part of each flight, A band of metaphyton (unattached algae) appears offshore in this drone image taken at a site in South Lake Tahoe. Photo by Scott Hackley, courtesy of Tahoe Environmental Research Center.
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