Tracking Invasive Zebra Mussels In Town Lakes

By Kendra Bobowick

A dive team went hunting for zebra mussels in Lake Zoar last month as part of an ongoing effort in area lakes to detect the invasive species first discovered in 2010. Newtown Underwater Search and Rescue (NUSAR) members searched the water on June 20.

“The hard part is finding where they’re coming from,” said Lake Zoar Authority Chairman Ray Hoesten. He believes the mussels may be moving through Newtown’s waterways via estuaries. Experts such as Candlewood Lake Authority (CLA) Executive Director Larry Marsicano have warned that most often they hitch a ride on vessels as boaters move from one lake to another.

The invasive species has made a new home in Newtown’s and surrounding towns’ water bodies in past years — specifically in Lakes Zoar and Lillinonah. The mussels larval veligers, for which authorities and volunteers are regularly monitoring, have not been found this summer in tested areas of Candlewood Lake, but are showing in Newtown’s lakes.

Regarding the initial invasive discovery in local waters in 2010, Greg Bollard, Friends of The Lake (Lillinonah) (FOTL) executive board member who also heads water quality issues, said, “It was alarming because it was the first major find in Connecticut lakes.” The discovery “sparked regional concern,” he said.

According to the Department of Energy and Environmental Protection (DEEP), zebra mussels were first discovered in Connecticut in 1998 in East and West Twin Lakes in Salisbury. It is uncertain if the mussels found in Lakes Lillinonah and Zoar are the result of downstream migration from upstream sources or the result of a separate introduction.

Managing The Intrusion

Mr Marsicano said that in past years “We researched and developed expertise to sample sites on [Lakes Zoar, Lillinonah, and Candlewood] and upstream to sample water for veligers.” He described the mussel’s early life stage as “planktonic, microscopic, and larval when the adults spawn.” Continued sampling has been successful. “We were finding the veligers in Zoar and Lillinonah,” this summer, he said.

This summer the lake authorities took divers to sites on Zoar and Lillinonah to search areas where adult mussels were spotted several years ago. “The only thing we found with our resources were three large adults in about 15 feet of water [in Zoar],” Mr Marsicano said.

They found that the mussels were “big enough to be several years old.” The dive team found no one-year-old adults.

“If there was a population of mussels in either of those lakes and they were reproducing successfully, we would probably find different age classes,” Mr Marsicano mused. “It makes you wonder where the veligers are coming from. One possibility is they are coming from sources upstream in Housatonic River.” Are there other possibilities? “We just don’t know.” Divers found no adults in sites searched in Lillinonah, he said.

Mr Bollard noted that testing is finding “very few larvae stage in veligers in Lillinonah, but large masses in Lake Zoar.” The detection only confirms presence or absence, not quantity, he explained. Lake Zoar may have larger colonization, “perhaps,” he said.

Further considering the finds, Mr Marsicano said, “If we can confirm that we don’t have a sustaining population in Lillinonah and Zoar then it’s important to find where the veligers are coming from and try to stop that.” He said, “If there is not a sustaining population, then this [invasive species] could go away before it starts.”

Mr Marsicano said the mussels may not reach a critical number where the reproducing adults are successfully fertilizing. He is left wondering, “So, where are veligers coming from?” He would then need to worry about stopping them. “That’s a whole new chapter,” he said.

Mr Marsicano has worked with Dr Kevin Kelly with the federal Department of the Interior Bureau of Reclamation. He described Dr Kelly’s working theory of stopping veligers from moving from one body of water to another by first looking for bottlenecks — smaller volumes of water that are manageable. By introducing carbon dioxide gas, “It’s like a narcotic to [the mussels],” Mr Marsicano said, “They suffocate.” Learn more at www.usbr.gov/mussels/research/current.html.

He is currently working to test Dr Kelly’s theory locally, “to prove if it’s right.”

             Friends Of The Lake

Mr Bollard added his thoughts to the current known zebra mussel population. “The scientific community feels they won’t colonize too much further east,” saying that the water chemistry there “does not support them.”

The mussels “don’t seem to be colonizing as prolifically in Lillinonah as Zoar,” he said. While Zoar is “not infested,” the mussels show “more of a presence there, while Candlewood still shows an absence.” Reasons for these conclusions would be “just speculation,” he said, adding, “The dynamics of each lake is different.”

He said, “Lillinonah is larger than Zoar, so maybe locating them is more of a challenge, and Lillinonah has more frequent water level fluctuation via the power company.”

Like Mr Marsicano, Mr Bollard also wants to know where the mussels are coming from. He looks forward to anticipated DNA testing on mussel samples “to help prove the origins.” Are they coming from Massachusetts, somehow surviving the trip? Collected DNA samples could help researchers pinpoint local mussels’ origins to the twin lakes in Connecticut where the species was first found in this state long before showing up locally. Mussels could be following down from lakes in Massachusetts, “or someplace else,” he said.

Considering the long journey down the Housatonic River into Connecticut, Mr Bollard added, “They are fairly fragile.” An adult could lay one million eggs per season, but in the larvae stage “they can’t take turbulence/various chemistries.” He said the eggs “tend to do well on hard surfaces, but not so well on silty river bottoms.”

Considering what may happen locally in the coming three to five years, Mr Bollard said, “We could have a major colonization because they’re so prolific.”

The mussels could potentially harm the lakes’ environmental health. “Colonization could be devastating and could change the ecobalance and spill over to socioeconomic concerns,” Mr Bollard said.

“The bottom line is, if you are a boat owner or lake user, there is added responsibility that if you’ve been in the water with known mussels, you have to decontaminate before entering another water body. They don’t fly or walk across shore, so they transport on boats.”

He said, “If you frequent Lillinonah today and tomorrow you go to Candlewood, that’s how the zebra mussels can spread.”

Dive teams in Lillinonah and Zoar “have not found where they may be coming in other than boats,” he said.

According to the DEEP website, the zebra mussel is a black and white striped bivalve mollusk, which was introduced into North American waters through the discharge of ship ballast water. Since its discovery in Lake St Clair (between Michigan and Ontario) in 1988, the zebra mussel has spread throughout the Great Lakes, the Mississippi River system and most of New York State.

Zebra mussels were first found in the Housatonic River in 2009 when they were discovered in Laurel Lake in Lee, Mass., and subsequent sampling found them in the lake’s outflow into the mainstem river.