Taking an Ecosystem Snapshot

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Lake Superior’s Health in a Changing World


The circle of water bottles is called the CTD Rosette sampler and collects water at specified depths. The sampler is attached to a cable and lowered into the lake, generating real-time data collection of physical, chemical, and biological conditions. Elizabeth Minor takes a water sample from the Rosette sampler.


The Large Lakes Observatory (LLO) is undertaking research that has never been attempted before. A team has been assembled to simultaneously study aquatic ecology, phytoplankton abundance, nutrient distributions, biochemistry, carbon cycling, zooplankton ecology, fish ecology, and biological productivity on Lake Superior. The operative word is "simultaneously." Using LLO's Research Vessel Blue Heron, scientists, each with expertise in one or more of these areas, will gather data, all at the same time. They will take eight voyages, four in 2014 which have been completed, and four in 2015. They stop at 12 sites each time. The goal is to examine the complex interactions between the sets of data.

Elizabeth Minor, professor in the Department of Chemistry and Biochemistry at the University of Minnesota Duluth (UMD) is coordinating the effort. "It will be a powerful study because of the interplay we get to observe," she said. "To look at Lake Superior's ecology in a concurrent study is very rare." The project seeks to understand the lake’s complex responses to stresses, such as changing thermal structure and arrival of invasive species, and to use that knowledge to aid in refining management strategies. No prior large lake study has included the breadth of measurements, the geographic range, and the span of seasons that this project offers.

"How the lake behaves this year is already proving to be interesting," said Minor. The study began in June 2014, following one of the coldest winter's on record. "We are especially paying attention to if and how the lake's warm and cool water form stratification layers."

Taking these snapshots of the lake ecosystem's health requires an unprecedented amount of equipment and personnel. Loading all of the equipment on board follows a systematic plan that takes hours to execute. Sleeping in shifts, working 24/7, the team takes shipboard samplings at the 12 lake locations, almost all far from shore. The volume of information they gather is massive: nutrients, pH, carbon, oxygen, temperature, particle abundances and composition, activity of photosynthetic and other pigments. They will also measure primary productivity, carbon and nutrient cycling using sediment traps and abundances species of algae, zooplankton, and fish. Ship-based observations will be complemented with year round data obtained using LLO's autonomous underwater glider and moored profiling instruments. The measurements from the 2014 and 2015 voyages will be supplemented with fall 2013 and spring 2016 observations. The $600,000 dollar project is funded by the Minnesota Environment and Natural Resources Trust Fund.

The instrument used for measuring the light in the lake is retrieved
 A net tow for zooplankton is being recovered. The CTD rosette for water sampling is on the right, in the foreground.

The team includes LLO staff: Elizabeth Minor (project management, biochemistry, carbon cycling, aquatic ecology, data integration, phytoplankton abundance, nutrient distributions); Robert Sterner (biological productivity; data management, aquatic ecology, data integration, phytoplankton abundance, nutrient distributions); Erik Brown (carbon & nutrient cycling); Jay Austin (physical processes, moored and autonomous instruments); and Richard Ricketts (ship operations; logistics). Joining the group are UMD Minnesota SeaGrant's Jeff Gunderson and Sharon Moen (public outreach) as well as UMD Department of Biology's Donn Branstrator (zooplankton ecology) and Tom Hrabik (fish ecology). Don Schreiner from the Minnesota Department of Natural Resources will provide fish population dynamics.

Lake Superior is undergoing dramatic changes—less ice, warmer summers, more invasive species. The project will evaluate how these changes impact the lake.

Lake Superior seems timeless, but recently it has been changing dramatically. For example:
Surface summer water temperatures have increased by 5°F over the past 30 years, some of the most rapid change observed on the planet;
Average ice cover on the lake over the past 15 years is 2-fold lower than the long-term average;
The lake’s nutrient content is changing markedly, with nitrate increasing 5-fold since 1900;
The lake is increasingly affected by invasive species (spiny water flea, zebra mussels; etc);
The lake’s biological productivity is decreasing, providing less food for fish;
While lake trout and herring have recovered from mid-20th-Century decimation, lake herring populations rise and fall dramatically from year to year.

LLO has taken on a gargantuan effort, to comprehensively and systematically measure the health of Lake Superior's ecosystem. It promises to be the most significant study of any of the world's large lakes.

By Cheryl Reitan, October 2014.

UMD News Articles | News Releases
Cheryl Reitan, creitan@d.umn.edu

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