Tahoe dive team takes expertise to Minnesota lake

The dive team at Clean Up the Lake (CUTL) has completed two weeks of pilot research beneath the surface of Mille Lacs Lake in Central Minnesota. The primary goal of this project, which was funded by the Clean Water Land and Legacy Amendment, was to gain insight about submerged litter, including its movement in and around the lake. The project also involved documenting aquatic invasive species (AIS).

CUTL is a nonprofit organization well known for performing conservation dives in the Sierra Nevada around Lake Tahoe that focus on submerged litter clean up and AIS surveillance. CUTL strives to protect the environment above and below the water’s surface through scientific research, data sharing, community engagement, media and education. To date, CUTL has performed over 450 clean up dives that have resulted in the collection of more than 77,000 pounds of litter across 127.77 miles of lakebed shoreline.

“We wanted to partner with this organization because they had proven success with large-scale trash remediation in Lake Tahoe — a body of water relatively similar in size to Mille Lacs Lake,” says Ann Brucciani Lyon, Vice Chair of the Mille Lacs Area Community Foundation and Keep It Clean Coalition Member. “It’s been interesting and exciting to work with the CUTL team during their time in Minnesota and to be their first project outside their region. We look forward to their final report and the valuable information and insight it will provide. This information will help inform us on how to focus future clean up initiatives.”

As Minnesota’s second largest lake, Mille Lacs is a premier destination for fishing enthusiasts in the summer and winter, averaging over 2.5 million angler hours every year. The popularity of ice fishing in particular has grown quickly in recent years with better technology, better equipment, and wheelhouses, which make staying on the ice for extended periods more comfortable. With the increased activity comes more pressure on the natural resources including an increase in the amount of garbage and litter left on the ice.

CUTL’s extensive underwater analysis of Mille Lacs Lake included 15 separate sites, including performing 12 surveys with scuba divers and 3 surveys using an underwater remote-operated vehicle (ROV) in some of the most heavily fished areas of the lake. The scuba divers also performed AIS research and removed litter from the lake.

In addition, CUTL held two Litter Sorting events at Isle Public Schools with students, staff, parents, and community volunteers. These educational events involved sorting the aquatic and terrestrial garbage found at Mille Lacs Lake into 83 possible categories and then weighing and documenting it, part of CUTL’s analysis process.

Although every lake is unique, based on CUTL’s previous experience in other lakes and the amount and type of litter found along the Mille Lacs shoreline, CUTL anticipated large litter loads in the rocky reef areas of Mille Lacs. However, they found surprisingly low levels of submerged debris. While CUTL is in the early stages of its analysis, its initial conclusions about what happens to garbage that enters Mille Lacs are:

Heavier items such as chains, metal, wheels, cinderblocks, anchors or glass remain in place submerged for long periods — sometimes decades - the dive team found that almost all the litter removed from Mille Lacs were heavier material types of litter.

Lightweight litter, such as plastics, aluminum cans, fishing lines, and shotgun shells are pushed to shore by wind and wave action because Mille Lacs is extremely shallow. By comparison, in the alpine lakes in the Sierra Nevada litter becomes trapped on steep underwater shelves near shore.
Local Efforts for clean up & stewardship to protect their lake and clean up litter have significantly helped to reduce total litter loads.

Winter ice traps litter and likely carries or pushes it to shore during ice out making shoreline cleanup efforts in the spring essential to reducing the amount of garbage that recirculates around — and degrades in — the lake.

“Our next steps are to analyze all the data we’ve collected and to document those findings in a detailed report that will include future recommendations for litter mitigation for our project partners at Mille Lacs Lake,” said Colin West, CUTL Founder and CEO. “As part of our work to develop a global alliance program, we plan to continue to seek opportunities with our partners at Mille Lacs and with other interested Minnesota lakes and organizations.”