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Some Cyanobacteria Can Ruin the Mood for Invasive Mussels

kevin bunch
Kevin Bunch
Quagga mussels are tested to see what can negatively affect their spawning

 

quagga-mussels
Quagga mussels, pictured here after being exposed to serotonin to induce spawning, can have their spawning efforts stymied by certain kinds of cyanobacteria. Credit: Anna Boegehold

There’s something in the water that can spoil a quagga mussel’s romantic evening, according to a recent research project that found some species of cyanobacteria - known more commonly as toxic blue-green algae - can keep quagga mussels from successfully reproducing.

According to Anna Boegehold, a Ph.D. candidate at Wayne State University in Michigan, quagga mussels typically reproduce using what’s known as the broadcast spawning method, where males and females release sperm and eggs at the same time into the water. When some species of cyanobacteria – like Microcystis or Anabaena, are in the area, these spawning attempts are more likely to be unsuccessful. One specific species, known as Aphanizomenon, seemingly prevents the mussels from attempting to spawn at all – a behavior that could potentially help control the invasive species in the future.

The research project was funded by the US Geological Survey (USGS) and Great Lakes Restoration Initiative and based on the premise that spawning can be induced in marine mussels and sea urchins by feeding them nutritious phytoplankton species. Boegehold and her collaborators were interested in seeing if the opposite was true for freshwater invasive quagga mussels by exposing them to toxic or cyanobacteria with little nutritional value. Between the 2014 and 2016 summer spawning seasons, the team, including Drs. Donna Kashian and Jeffrey Ram at Wayne State University and Dr. Nicholas Johnson at USGS, exposed quagga mussels to 13 different cultures of cyanobacteria largely from the Great Lakes region at concentrations below those found in harmful algal blooms.

In total, seven of those cultures prevented successful fertilization and reproduction to varying degrees compared to a control group of quagga mussels that had no cyanobacteria at all. In some cases, spawning was reduced by 52 percent when exposed to cyanobacteria species and fertilization by 44 percent. The study results were recently submitted for publication. Boegehold  is now testing how cyanobacteria impact veligers - the free-floating larval form of quagga mussels – and is interested in following up on her research to help figure out what Aphanizomenon is doing that keeps quagga mussels from attempting to spawn.

“We want to isolate what specific chemical in that cyanobacteria culture is responsible for preventing the spawning response,” she said. “Clearly, we don’t want to promote toxic cyanobacteria blooms in the lakes, so we want to pick out what chemical is doing that.”

cyanobacteria and quagga mussel samples
Boegehold checks on cyanobacteria and quagga mussel samples in the lab. Credit: Anna Boegehold

Invasive sea lamprey are already controlled in a similar manner by management officials with the US Fish and Wildlife Service, Fisheries and Oceans Canada and the Great Lakes Fisheries Commission, who will periodically use a lampricide to kill the parasitic predators in their larval state. The lampricide breaks down within days and doesn’t bioaccumulate up the food chain, giving it a minimal impact on the environment. Boegehold also highlighted research being done at USGS by Johnson that would help control lamprey with synthetic pheromones that alter their behavior. If a chemical from Aphanizomenon could be isolated, it could potentially be used similarly in water bodies where quagga mussels are found to reduce their numbers, though how it would be distributed and used is unknown at this time. No testing has been done yet to see if how, if at all, the presence of Aphanizomenon impacts the reproduction of invasive zebra mussels and native mussels and invertebrates, though Boegehold hopes to do so if a chemical can be isolated.

Since algal blooms are trending toward taking place earlier in the year, overlapping with the mussel spawning season, and while there haven’t been any determinations on how effective cyanobacteria are at limiting successful quagga mussel reproduction in the wild, that growing gap could reduce any potential effectiveness. Isolating the chemicals found in some of these cyanobacteria could allow water managers to mitigate that trend.

quagga-mussel-eggs
Quagga mussel eggs, pictured here about three hours after being exposed to sperm, have a harder time being fertilized when exposed to cyanobacterial species like Microcystis and Anabaena. Dashed arrows in the photo represent eggs that have not been fertilized. Credit: Anna Boegehold

Quagga mussels and zebra mussels have inflicted massive ecological damage wherever they’ve been found by gobbling up the phytoplankton that make up the bottom of the food web in North American freshwater bodies, leaving less food for other predators, moving nutrients further nearshore and in turn causing a knock-on effect throughout the food web. The mussels also clog water intakes, causing additional costs for water treatment and electricity generation plants. Only a few species, such as the invasive round goby and the rare lake sturgeon, feed on the invasive mussels, but not to the degree that their numbers are being naturally controlled. Since their initial detection in the Great Lakes in the 1980s, they have spread to smaller inland lakes across the region, stretching as far west as Montana and California. While control efforts have been limited to simply trying to keep people from inadvertently moving them between water bodies, a way to prevent them from spawning would be a powerful tool in the fight.

kevin bunch
Kevin Bunch

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

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