When aquatic invasive species (AIS) specialists with the Minnesota Department of Natural Resources confirmed that zebra mussels had been found in Big Detroit Lake in August, many local residents began wondering what changes these invaders might bring.
"Watercraft inspection efforts throughout the Pelican Lake chain, from Floyd to Melissa, will continue and expand in an attempt to contain current invasive species and shield the lakes from other species not currently found in those lakes," says Karl Koenig, water quality and AIS prevention coordinator with the Becker Soil & Water Conservation District, which took over the local AIS inspection program a couple of years ago.
Besides the stepped up inspections and decontamination for boats leaving the lake, and the obvious warning signs placed at public accesses around Detroit Lake, those using the lake won't see a lot of changes to the quality of the water itself.
At a community forum on AIS that was held at M State in Detroit Lakes on Monday, biologist Moriya Rufer of RMB Labs noted that it takes about two years after a lake is declared as infested for the full effect of a zebra mussel invasion to be felt on the ecology of the lake.
Using the example of nearby Pelican Lake, which was first declared as infested in late 2009, Rufer outlined what Detroit Lake residents might expect to see over the next few years.
"When the lake is first infested, they (zebra mussels) are really hard to find," she said.
After the first zebra mussels were found in September 2009, the population "exploded" in 2011, and in 2012, Pelican Lake residents reported that the lake's water clarity had reached a record level, she added.
While clearer water may seem like a good thing, Rufer explained, it can have some negative connotations: Increased clarity means that there is far less algae in the water, and therefore less available food for fish and plankton - because the zebra mussels are eating it all.
Greater clarity also means that sunlight extends farther down into the water, causing many types of fish to seek refuge in the depths - and thus making them harder to catch.
In 5-10 years, some clumps of zebra mussels could begin to wash up on the lake's sand beaches, she said.
"But these can be raked off, like plant fragments," Rufer said, adding that more maintenance may be needed to maintain the quality of both public and private beaches.
It may also be more necessary to wear sandals or water shoes when out on the sandbar between Big and Little Detroit, she pointed out.
Irrigation pipes going into the water will also need to be wiped off more regularly, and it is best to use laser-slotted PVC screens, which are harder for zebra mussels to attach to, she added.
"You can also use copper mesh to cover the outside of the intake," Rufer said.
Once zebra mussels get into a lake, their population will increase exponentially - until the food runs out, she added.
"If they run out of food, there will be a die off," Rufer said, but once the algae in the water starts coming back, unfortunately, so will the zebra mussels.
Monday's forum at M State also focused on the threat of starry stonewort, a particularly nasty form of invasive aquatic plant that has been found as close by as Lake Koronis near Paynesville and most recently, on Turtle Lake near Bemidji.
Nicole Kovar, an AIS specialist with the DNR who was heavily involved in the investigation of the Big Turtle Lake infestation of starry stonewort, gave those in attendance at the forum a crash course on detecting the plant.
Because it resembles some other, non-invasive forms of aquatic life, it can often be hard to identify, she explained - and early detection is key when it comes to keeping starry stonewort from forming the large, thick, dense mats that inhibit boat usage and other recreational water uses.
"Anytime you're suspicious, get a sample and send it to a specialist," said Kovar.
Unfortunately, the fact that it is still so new in Minnesota means "there isn't a lot of research on this plant available," she added.
When asked after the forum how much of a threat he feels starry stonewort could pose for Becker County lakes, Koenig said, "It is difficult to predict exactly how any species may respond to a new habitat, but what I observed on a September visit to Lake Koronis was troubling.
"The starry stonewort infestation at Lake Koronis near Paynesville has affected at least 250 acres of that lake," he continued. "Local residents reported serious impacts to boating and other activities.
"Current treatment options cannot eradicate this species from a lake, so prevention is very important. Starry stonewort infestations can be prevented by carefully inspecting and cleaning boats, trailers and other water-related equipment."
In that regard, Koenig's presentation at the forum focused on the AIS inspection and decontamination of watercraft exiting and entering local lakes, as well as prevention education and enforcement efforts undertaken by SWCD since the agency took over management of the AIS program for the county in 2014.
In 2015, SWCD had 29 inspectors working on 23 lakes in Becker County. During their collective 13,940 hours of work, they did 18,683 total inspections, including 7,768 watercraft exiting area lakes, and 10,879 entering them.
Of those watercraft inspected, a total of 282 -－or about 2.6 percent of the total -arrived at the lake with their drain plugs installed (drain plugs are supposed to be pulled out and the water drained before a boat is moved from one waterbody to another).
A total of 368 inspected watercraft - 3.38 percent of the total - were found to have aquatic plants, water and mud attached (all watercraft are supposed to be thoroughly cleaned before being moved from one lake to another as well).
In 2016, SWCD had 33 inspectors working on 29 lakes in Becker County. During their collective 12,649 hours of work, they did 21,052 total inspections, including 8,112 watercraft exiting area lakes, and 12,920 entering them.
Though there were more inspections done, the number found with their drain plugs still installed actually decreased, to 252, or 1.95 percent of the total. Likewise, the number with plants, water and mud attached also declined, to 238, or 1.84 percent.
In other words, SWCD's efforts to educate the public as part of the inspection process, as well as at presentations to area service clubs, schools, lake associations, and advertising via radio, television and newspaper media outlets, have been quite successful at spreading the word about the need to keep watercraft clean and dry when moving them between lakes.
In the future, Koenig said, he would like to focus more on social media.
"This is a social problem, and we have not been on social media much at all," Koenig said. "I would like to do more with that next year."
Overall, Koenig said afterwards, Monday's community forum did what it was intended to do.
"The purpose of this forum was to raise public awareness surrounding this issue, and based on the feedback I have received, this was accomplished," he said. "I was pleased with the turnout, and was especially thankful to have some of our county, city, and township officials take time to attend this event."