A partial recording of the webinar is available now

Presenters Angelique Dahlberg Ph.D. candidate with University of Minnesota, and Matt Barbour Biologist with the U.S. Geological Survey present on lessons learned from control projects and alternative low-dose copper treatment.

Angelique Dahlberg
University of Minnesota
Title: Lessons learned from open-water dreissenid mussel control projects in North America

Description: Dreissenid mussel control projects have been ongoing since about 2004, yet the methods used and degree of reporting have varied greatly. We conducted a search for and meta-analysis of open-water dreissenid mussel control projects that have occurred in North America, including from published and unpublished reports. In this presentation, I will present information on 33 open-water dreissenid mussel control projects in 23 lakes across North America. In particular, I will share elements of both successful and failed projects, cover knowledge gaps, and highlight suggestions that could contribute to future dreissenid management actions.

Matt Barbour
U.S. Geological Survey
Title: Low-dose copper treatment for dreissenid mussel control as an alternative to traditional management strategy

Description: Copper is a widely used product in aquatic systems largely to control algae and is the active ingredient in the molluscicide EarthTec QZ, one of the few registered products for open water dreissenid mussel control. Many dreissenid mussel control actions have targeted concentrations near the US Environmental Protection Agency’s 1 mg Cu/L limitation with the goal of eradicating a dreissenid population. Treatments at elevated copper concentrations can be highly toxic to nontarget aquatic communities and produce limited success with eradication of invasive mussels. As an alternative to the traditional eradication strategy, we performed two open water, low-dose copper application of EarthTec QZ in 2019 and 2022. Our treatment concentrations, 60-100 µg Cu/L, were an order of magnitude lower than the maximum allowed. The goals of the treatments were twofold 1) to reduce zebra mussel veliger densities and juvenile settlement therefore reduce recruitment into the breeding population in subsequent years and 2) to minimize adverse impacts to nontarget communities. We monitored non-target communities, water chemistry, and zebra mussel settlement before, during, and up to three years after the applications. This presentation summarizes the treatments, assesses them within the functional eradication framework, identifies knowledge gaps for future investigations, and discusses implications for resource managers in applying this strategy.

Presentation summary: 

• The 2019 low-dose copper treatment (~85 µg Cu²⁺/L) administered to a 66.3 ha bay on Lake Minnetonka (Hennepin County, MN) reduced veliger density and settlement through the following year.
• The non-target zooplankton community was affected the year of the treatment, but abundance, diversity, and community structure resembled the pretreatment assessments by the following summer. The non-target benthic community did not show signs of treatment related impacts.
• An additional low-dose copper treatment was administered to a 125.6 ha bay on Lake Minnetonka in 2022. Data for this treatment is being amassed for analysis and monitoring is planned through 2023.
• We are still amassing data from the 2022 field season for the 2022 treatment and for the final year of the 2019 treatment monitoring.