Quagga mussels are displacing zebra mussels in lakes

Spreading much farther, they could impact fish

By: Kevin Bunch | Roseville - Eastpointe Eastsider | Published April 12, 2016

 Researcher Ashley Baldridge shows off the tripod and mesh cage used for quagga mussel growth experiments in Lake Michigan.

Researcher Ashley Baldridge shows off the tripod and mesh cage used for quagga mussel growth experiments in Lake Michigan.

Photo provided by Ashley Baldridge

METRO DETROIT — Invasive quagga mussels are pushing out invasive zebra mussels from the Great Lakes, but researchers warn this is not necessarily a cause for celebration.

Ashley Baldridge, a research benthic ecologist with the National Oceanic and Atmospheric Administration said NOAA has been researching the mussel populations in Lake Michigan annually for two decades, and the other Great Lakes on a five-year rotating basis. They use a claw called a PONAR grab to pull up a section of mud from the lake bottom and then count and measure the mussels, she said.

This year, NOAA also has started using cages to measure mussel growth and what impact lake temperature and food conditions have on that rate, Baldridge said; between the two, they have found that zebra mussels invaded the lakes first, but after five to 10 years, their cousins started overtaking them.

“The quagga mussels came in and they have pushed out the zebra mussels,” Baldridge said. “We don’t see zebra mussels out in the lake anymore — they’re only very close to the shore. And now, the quagga mussels are at 10 times higher density than the zebra mussels (have ever been).

“We’ve seen one invasive species overtake another invasive (species),” she added.

The researchers have realized that quagga mussels not only like deeper water than zebra mussels, they have been found as far as 100 meters deep in the lakes. In contrast, Baldridge said, zebra mussels do not go deeper than 50 meters. Since quagga mussels can get more widespread, they can have a more pronounced impact on the water column and the food chain there.

Baldridge said that this time of year there is usually a spring bloom of algae on the lakes, which creates food for zooplankton, which in turn creates food for fish. Since the water column is mixed up in the spring after the winter ice melts, mussels are able to feast on that bloom, leaving less food for other species.

For example, she said, the U.S. Geological Survey, which also surveys the lakes, has seen smaller alewife catches lately, which in turn should have an impact on the salmon that eat those smaller fish.

Mussel population control is still extremely limited, she added. While people have been able to control populations on water intake pipes and other pieces of infrastructure, the broader lakes are so large and deep that there is no effective chemical control or equipment at this time that could help manage them at a sustainable level. And while fish like round goby and whitefish will eat the mussels, it is not at a great enough rate to curtail the population.

Native bivalve species have already been severely depleted or rendered locally extinct due to the invasive zebra and quagga mussels, Baldridge said, and the native species were never as numerous as the invasive species are now.

Quagga and zebra mussels are partially blamed for the toxic algal blooms in Lake Erie, Sonia Joseph Joshi, a communications and outreach specialist with the Cooperative Institute for Limnology and Ecosystems Research with NOAA, told C&G Newspapers in February 2015.

She said their tendency to eat other, benign types of algae leaves a gap in the ecosystem that lets the toxic blue-green algae, known as microcystis, grow unimpeded.

“That’s just allowing for the blue-green algae to grow more prolifically because they have no competitors,” she said at the time.

The mussel growth experiment could help researchers understand how the quagga mussels mature over the course of a year and how quickly. She said the creatures’ growth — particularly in deeper waters — is not as well-studied as zebra mussels, and is virtually unknown in the winter months.

The growth experiments should continue for a year, Baldridge said, at which point she hopes to set up cages in the other lakes to see if there are any differences in growth rates in other lakes.

“I’d be interested in doing these experiments in the other lakes so I can then compare how they’re growing in Lake Huron, Lake Ontario, versus Lake Michigan,” she said. “Every lake has a different personality and conditions, but they all have mussels.”