John Meyers: Lake Volunteers Needed

Duluth Tribune:

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The Minnesota Pollution Control Agency is looking for volunteers, nearly 700 of them, to measure water quality across many of the state’s lakes and rivers.

The PCA, which is tasked with both monitoring and protecting the state’s 12,000 lakes and 92,000 miles of streams, this year is asking for volunteers to monitor 676 high priority sites on rivers and lakes, including many in the Northland. Data gathered by volunteers is reported back to the agency and used to track the health of waterways.

Minnehaha Watershed District: Zebra Mussels Improve Water Clarity in Lake Minnetonka

Zebra mussels have caused significant changes in Lake Minnetonka’s water quality, according to findings of a study by Minnehaha Creek Watershed District (MCWD). The District has been monitoring the lake’s zebra mussel population since they were first detected there in 2010. Five years into the study, which was developed in partnership with Blue Water Science, MCWD released its findings on Thursdsay, April 21 at its AIS Spotlight, a gathering of community leaders at Minnetonka Community Center.

The District has discovered the biggest water quality changes are occurring among bays with the highest number of zebra mussels. In Wayzata Bay, which the population topped out at an estimated 200,000 zebra mussels per square meter in 2014, there has been an increase in water clarity and a decrease in algae (Chlorophyll) and Phosphorus. Those changes are not as prevalent in bays with lower zebra mussel populations. In Halsted Bay, which has 28 zebra mussels per square meter, there has been little change in water clarity, Chlorophyll and Phosphorus.

One suspects that some bays with improved water clarity may see an increase in aquatic plant habitat.

NASA: Less Algae, Not Clear Water, Keeps A Lake Blue

Lake Tahoe’s iconic blueness is more strongly related to the lake’s algal concentration than to its clarity, according to research in “Tahoe: State of the Lake Report 2015,” released today by the Tahoe Environmental Research Center (TERC) of the University of California, Davis. The lower the algal concentration, the bluer the lake.

Data from a research buoy in the lake, owned and operated by NASA’s Jet Propulsion Laboratory, Pasadena, California, enabled Shohei Watanabe, a postdoctoral researcher at TERC, to create a Blueness Index that quantified Lake Tahoe’s color for the first time.

The assumption that lake clarity is tied to blueness has driven advocacy and management efforts in the Lake Tahoe Basin for decades. But Watanabe’s research showed that at times of the year when the lake’s clarity increases, its blueness decreases, and vice versa.

Watanabe combined the blueness measurements with data on clarity. Clarity is measured by observing the depth at which a dinner-plate-sized white disk remains visible when lowered into the water. He was surprised to find that blueness and clarity did not correspond. In fact, they varied in opposite directions.

This is due to seasonal interplay among sediment, algae and nutrients in the lake. Clarity is controlled by sediment. Blueness is controlled by algal concentration, which in turn is controlled by the level of nutrients available to the algae.

People Post Pictures of Clear-Water Lakes More Than Turbid Lakes

Roberta Kwok, writing for Conservation Magazine:

Shutterstock

Shutterstock

People were more likely to visit bigger lakes with clearer water, the researchers report in Frontiers in Ecology and the Environment. For every additional meter of water clarity, visitors drove nearly an hour longer to get to and from the lake, spending about $22 more in travel costs. Lakes with boat ramps also were more popular.

The study authors estimate that improving a lake’s clarity by one meter would bump up the average number of visits by 1,389 per year. The overall number of lake visits in a region might not increase, since the number of people travelling to the murkier lakes could drop. But if people opted to visit a lake rather than, say, a pool, the total number of visits could rise.

Recreational demand for clean water: evidence from geotagged photographs by visitors to lakes By Bonnie L Keeler, Spencer A Wood, Stephen Polasky, Catherine Kling, Christopher T Filstrup, and John A Downing