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Studying light’s affect on Lake Huron food web

July 16, 2012
Jessica Nikolich - Assistant News Editor , The Alpena News

ALPENA - Mussels were scraped off the side of the Laurentian, an 80-foot white research vessel, in the shipyard Monday afternoon. Biologist Joann Cavaletto claims it will be faster without them attached - it was going 8 knots, and now it might hit 10. With the amount of work she and other NOAA Great Lakes Environmental Research Laboratory scientists hope to accomplish over the next week in Thunder Bay, a little extra speed couldn't hurt.

This is the year of Lake Huron, or what Cavaletto refers to as the "understudy Great Lake." GLERL is partnering with federal, state and provincial agencies in the 2012 Lake Huron Cooperative Science and Monitoring Initiative, which according to a press release, is a joint U.S.-Canadian program led by the U.S. Environmental Protection Agency Great Lakes National Program Office and Environment Canada. One Great Lake is focused on each year, so Lake Huron's environmental trends have not been studied since 2007.

This particular week of research is bouncing off from a similar mission in April, and will be continued even further in September. This way, Cavaletto said the seasonal changes can be examined.

Quagga mussels seem to be the tricky invasive species marine research teams are after this year, and the NOAA group is no different. A bottom-dwelling organism similar to zebra mussels, the quagga mussels filter the bottom of the lake, which in turn, increases the amount of light able to pass through the water. This occurs both near the shore and offshore, and Cavaletto said quagga mussels actually adapt to cooler temperatures, more so than zebra mussels, and are then able to live in deeper waters. Where the warmer temperatures on the surface and the colder temperatures on the bottom come together, more zooplankton and algae form, she said.

Henry Vanderploeg, lead researcher on the Laurentian, refers to this area as the "zone of change," where certain fish and plankton adapt well, and others prefer the colder or warmer areas of the lake. Cavaletto said typically, fish species will hide in darker waters during the day and rise to the surface for plankton feeding at night. According to Vanderploeg, the mussel's filtering may be linked to this increase in algae, which has a negative affect on fisheries and ultimately throws off the food web.

"We're trying to describe the spatial structure of the food web, from viruses to fish. Organisms are very sensitive to light. They come to the surface at night so they can't be seen by predators. The water is clearer now, so everyone is hiding," Vanderploeg said.

"The water is clearer than in the past, and with that clarity, light goes deeper, and fish have less places to hide," Cavaletto said.

She said it's unusual for research teams to conduct both day and night sampling, but throughout the week, the six scientists and four crew members provide enough manpower to achieve a 24-hour rotating system. Right after dark, she and Vanderploeg will be focusing on zooplankton, followed by fish acoustics and genetic population studies.

"We want to capture complete day and complete night; the brightest sun midday to the dark of night," Vanderploeg said.

The team will collect samples and test at sites ranging from 18 to 82 meters deep, and about 26 nautical miles offshore, Vanderploeg said.

University of Michigan lab researchers also are joining the week's mission, led by Ann McCarthy, who will be working to establish microbial communities, or microorganisms, in Lake Huron. McCarthy said a lot has been done to define water changes on the macro level, but the microbial community has not been identified very closely.

"A lot is unknown," she said.

McCarthy and her lab assistants will be measuring at two depths with filtration units that separate microbes by size. Like Cavaletto and Vanderploeg, her research will be done during the day and also at night to profile how bacteria, viruses and animals measuring less than three microns change with sunlight.

"We're trying to cover as much as we can, trying to make the most of the ship time and learn as much as we can about the food web," Cavaletto said.

Vanderploeg was hoping to leave the dock by 6 p.m. Monday to arrive offshore at the 82-meter mark by 10:30 p.m. The team will return Friday, and plans to set off on another cruise Monday. Results from this week's research cruise will be sent to Ann Arbor for further evaluation.

Jessica Nikolich can be reached via e-mail at or by phone at 354-3111 ext. 343.



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