Early detection, vectors and impact of invasive spiny water flea in Wisconsin lakes

Untitled Document
Aquatic Invasive Species (AIS): Spiny water flea (Bythotrephes longimanus)
Project Location: Wisconsin, Dane County, Vilas County, Iron County
Project Start Date: 08/2010
Expected Timeframe/Duration: 2015
Sponsoring Organization: UW Center for Limnology
WI Department of Natural Resources
Web Links:
Primary Contact: Jake Walsh
University of Wisconsin Center for Limnology
jrwalsh2@wisc.edu
608-263-2465

Secondary Contact:
Project Summary:

We study the impact and management of the spiny water flea in the invaded lakes of Wisconsin: four Yahara Chain Lakes (Lakes Mendota, Monona, Waubesa and Kegonsa), two Northern Wisconsin lakes (Stormy Lake and the Gile Flowage) and Lake Gogebic in the Upper Peninsula of Michigan. Working closely with the Wisconsin DNR (Dane, Iron and Vilas County DNR), lake associations (Friends of the Gile Flowage, Stormy Lake Association and Lake Gogebic Improvement Association), and private companies in Northern WI (Whitewater Associates), we hope to better understand the impact of the spiny water flea and improve our strategies for limiting its spread in the area.

Understanding Spiny Water Flea Impact – There are no methods for eradication or control the spiny water flea, so understanding its impact is essential to managing invaded systems. Here we regularly monitor the zooplankton communities and water clarity of invaded WI lakes, as well as the diets of key fish species in Lake Mendota and the Gile Flowage to lend insight into how invaded food webs are changing post-invasion. In Lake Mendota, the spiny water flea has had a large, negative effect on water clarity through predation on the large grazer, Daphnia pulicaria, further worsening the negative effects of the phosphorus loading problem in Mendota’s agricultural watershed. In the less agricultural Northern Wisconsin, is much more likely that the impact of the spiny water flea will be felt elsewhere in lakes’ food webs, where nutrient loading plays a much smaller role in algae growth and water clarity.

Sleeper Cell Population Dynamics - In Lake Mendota, we now know that the spiny water flea invaded the lake prior to 2009, persisting through unfavorable conditions prior to 2009 as a low-density but established “sleeper cell” in the lake. Given a single year of favorable thermal and trophic conditions in 2009, the low-density population “exploded”, leading to the large, negative effects on water clarity observed in Lake Mendota. These adverse impacts highlight the need to understand which systems are most likely to support a “sleeper cell” population of spiny water flea and to better detect these populations at low densities when we are able to mitigate impacts and prevent further spread of the invader.

Improving Early Detection Methods - The spiny water flea is a particularly difficult invader to detect early in newly invaded lakes due to high spatial and seasonal variability in its abundance. To improve our detection methods we’re evaluating the detection probability of currently employed and known zooplankton net haul methods at times of low spiny water flea densities in lakes. Also, we aim to develop a detection method that is effective regardless of seasonal or spatial variability by searching for tail spines and resting eggs in sediment samples.