NRRI researcher Euan Reavie and research fellow Amy Kireta collecting algae in Lake Superior.
Following the algal trail
By June Kallestad
From eNews, September 29, 2005
They're just a fraction of a millimeter long, slimy and sensitive--but what a story algae have to tell.
Algae are one of the indicators ecologists use to understand what's going on in the waters we live near and play in. Algae are the organisms that make rocks and docks slippery in the water. These microscopic species play an important role in the global ecosystem, taking in carbon dioxide and producing oxygen. But even more importantly, their sensitive nature allows them to respond quickly to any disturbances in water quality, and this makes them an excellent warning system for ecological problems.
Which is why Ely, Minnesota, on the border of the lake-laden Boundary Waters Canoe Area, is the University of Minnesota Natural Resources Research Institute's center for algal research. Housed in Vermilion Community College, the laboratory focuses on aquatic studies, including assessments of aquatic ecosystem health and paleoecology (the study of sedimentary records).
Algae thrive in all aquatic habitats, with each of the more than 20,000 species having an affinity for different environmental conditions. And it's that affinity that gives scientists clues about water conditions.
Great Lakes Environmental Indicators
Algae were sampled at more than 200 sites for the study to develop a set of tools for understanding the Great Lakes coastal water quality. The researchers were able to forecast the effects of trends like increased nutrient loads and other impact on the watersheds with the algae.
By studying the paleoecology of two streams that feed into the bay, the researchers are able to evaluate the effect of the resorts and agriculture that hug its shores. A rehabilitation plan will follow.
The Sportsmen Club of Lake Vermilion initiated a study to see if the taconite tailings basins in Mountain Iron are having an effect on the lake's water quality. Reavie found elevated levels of iron, magnesium, lead, and sodium, but thinks the increases are likely the result of air pollution and local activities. The research also found that the level of phosphorous--the number one contributor to algae growth in Minnesota lakes--has nearly tripled since European settlement of the area. Tests also indicated that mercury levels in the sediments are far below some other known contaminated lakes in the region.
"Most algae live a very short life, usually less than a week," explains Euan Reavie, lead scientist at the Ely station. "If something happens in their environment--the pH balance changes or the nutrients increase--a new algal community that is tolerant of the disturbance will quickly replace them."
Although their life is short, algae leave clues behind that scientists can read later--even thousands of years later. Diatom algae have intricate "glass house" cell walls made of biogenic silica, and each species' cell wall exhibits a unique architecture. Long after the diatom algae die, those resilient cell walls accumulate in the sediments, preserving a sedimentary archive of past ecological conditions.
Following the algal trail, Reavie and research fellow Amy Kireta can piece together the history of a lake to prehistoric times, noting when changes occurred and the likely causes of any disturbances. Reavie has used this method many times to reveal human impacts in lakes and define pre-impact conditions to help determine appropriate rehabilitation measures. Sometimes, what is assumed to be a human-related disturbance is simply a lake's natural condition.
"We can save folks a lot of money and headache trying to fix something they believe is human impact when that's not the problem at all," says Reavie.
Often, however, the algae tell them that detergents (especially phosphate-based soaps of the 1960s and '70s), acid rain, mine drainage, or septic system leaks are the cause of water quality problems. In such cases, changes need to be made.