LWTF’s Zooplankton Farm:

Re-establishing a Native Cyanobacteria Predator

In 2016, with the guidance of one of LWTF’s consultant limnologist Bob Kortmann, LWTF converted the no longer used Frost Hypolimnetic Aeration system to a Zooplankton Farm. The purpose of the Zooplankton Farm is to re-establish a large-bodied, native in-lake zooplankton population.

In the 1960’s, CT DEEP stocked Lake Waramaug with a small fish called the alewife, whose population flourished, and depleted its primary food source – zooplankton. This large decrease in zooplankton allowed for the cyanobacteria population, a food source for zooplankton, to bloom. This was a main factor that caused the extensive and toxic cyanobacteria blooms in the lake in the 1970’s and 1980’s. While LWTF has worked for decades to decrease these blooms, the zooplankton population has never recovered, leaving the Lake vulnerable. The Zooplankton Farm was created to return the native population to their natural population pre-introduction of the alewife in order to armor and protect the Lake against toxic cyanobacteria blooms.

Located at the tip of arrow point on LWTF property, the zooplankton in the farm are feed twice a week with a specific amount of yeast, flour and sugar. Zooplankton are released on a weekly basis by draining the farm a specific amount – monitored by staff gauge on the side of the basin. A pump with a timer is then used to fill the basin to the proper level, which also has to be monitored and maintained. Additionally, the farm is not run year-round. The farm is run from April to October, the duration of the field season.

While a Zooplankton Farm may not be right for all lakes, this novel project may be helpful to other lakes who have had alewife introductions. LWTF created this project using a large data set to inform our decisions, and LWTF continues to monitor both the Farm and the Lake’s zooplankton population, chemistry and more.