As winters warm and lake ice duration shortens, algal blooms are interfering with water quality in lakes
I鈥檓 motivated because we鈥檙e seeing, in these cold regions of the world, fast rates of change. We鈥檙e losing lake ice cover in Colorado at twice the rates of other temperate lakes in the U.S. There鈥檚 so much we don鈥檛 know about the ecological impacts. Getting a full, year-round picture of ecosystem processes with give us a better idea of what鈥檚 coming听- Isabella Oleksy
Lakes represent some of the most vital natural resources on Earth. While they only hold a small percentage of the planet鈥檚 overall water supply, they provide most of the fresh water people depend on daily. Supported by a new five-year, $2.5 million grant from the National Science Foundation, a group of researchers at five universities will examine how rapidly warming temperatures and shorter winters can influence the growth and toxicity of lake algae. Isabella Oleksy, who studies aquatic ecosystems and recently joined INSTAAR, is leading the Colorado contingent at CU Boulder.
The researchers will use predictive modeling to forecast future outcomes on samples taken from more than 30 lakes across the country to measure the impact of climate change. They will study how year-round algal growth and increasingly warmer winter temperatures could negatively affect lake ecosystems and water quality.
鈥淲e're looking to make future projections of what to expect out of water quality, specifically levels of phytoplankton and the cyanobacteria that are harmful algal blooms, and then potential increases or decreases in toxin concentrations,鈥� said University of Missouri researcher Rebecca North. 鈥淭o do that, we鈥檒l collect data from a whole suite of lakes all the way from alpine lakes in the Rocky Mountains in Colorado and ice-covered lakes up in Vermont and New York State, down to lakes in Missouri and some in Florida. These are the endpoints in terms of what we can expect from a changing climate.鈥�
Researchers will deploy several instruments in the lakes to collect data throughout the year, including during times when lakes are covered in ice. Wildlife cameras and remote sensing imagery will show when ice appears and disappears on the lakes.
Researchers auger a hole through听the ice of the Loch, a subalpine lake in Rocky Mountain National Park, Colorado. 听They used the hole to collect water samples.听This lake will be closely monitored for the first three years of the five-year project.
鈥淚ce duration and ice cover set the stage for all kinds of biological and ecological processes in lakes,鈥� said Oleksy. 鈥淲e鈥檙e seeing winter conditions鈥攕pecifically ice cover duration鈥攃hange very rapidly all over the world, including Colorado. But because we mostly take measurements from lakes in the summer, we have a pretty poor understanding of what this loss of winter means for ecosystem processes in lakes.鈥�
Most of the data the researchers will collect is about lake productivity: broadly defined as a lake鈥檚 ability to support plant and animal life, or as how much carbon the lake is cycling. More is productivity is not necessarily better鈥攋ust different. Different levels of productivity determine the types of insects, fish, and other creatures that can live in the lake. Algae is the foundation layer of productivity.
鈥淎lgae are the base of the lake food web,鈥� said Oleksy. 鈥淢ost organisms rely on algae. But if the species and abundance of algae changes, that changes what insects can thrive there. And that changes what fish can live there. The changes cascade up.鈥�
鈥淲e want a more holistic understanding of what鈥檚 happening,鈥� added Oleksy.
Oleksy鈥檚 field sites include lakes in Rocky Mountain National Park and in the Green Lakes Valley, near the city of Boulder. Her Colorado-based research team documented dramatic changes to productivity of Rocky Mountain lakes. They have found increases in the abundance of filamentous green algae鈥攂asically big mats of algae鈥攐n the margins of lakes, which is unusual for these lakes.
Mountain lakes are usually thought of as having low productivity, with few nutrients. 鈥淏ut we know now that Rocky Mountain lakes have become much more productive since the 1850s, with an accelerating trend in the last few decades,鈥� said Oleksy. Researchers aren鈥檛 sure exactly what is driving the change. Increased temperatures? Nitrogen deposition? Less ice cover? All of the above? Oleksy wants to find what she describes as the 鈥渄ominant lever.鈥�
鈥淚鈥檓 motivated because we鈥檙e seeing, in these cold regions of the world, fast rates of change. We鈥檙e losing lake ice cover in Colorado at twice the rates of other temperate lakes in the U.S. There鈥檚 so much we don鈥檛 know about the ecological impacts. Getting a full, year-round picture of ecosystem processes with give us a better idea of what鈥檚 coming.鈥�
Joining Oleksy and North on the project are Ana Morales at the University of Vermont, Meredith Holgerson at Cornell University, and Dave Richardson at State University of New York at New Paltz. .
Isabella Oleksy takes measurements from a raft on The Loch, a subalpine lake in Rocky Mountain National Park, Colorado. This lake will be closely monitored for the first three years of the five-year project.
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