Eurytemora affinis, a calanoid copepod, is known to be a versatile, prolific invader of freshwater ecosystems across the globe. It has recently been documented in the Laurentian Great Lakes, including in Little Sturgeon Bay, an embayment of Lake Michigan. One survival mechanism that could make E. affinis a successful invader is diel vertical migration (DVM), a behavior in which animals move to different lakes depths at different times of day in order to avoid predation. Much is known about DVM of E. affinis, but primarily from studies in marine and brackish systems. Our goal was to investigate how E. affinis responds to its new, non-native freshwater environment, and to make inferences about its invasive success. During the summer of 2014, samples were taken at Little Sturgeon Bay twice on four days—once at noon and again at night. Samples were collected at one-meter intervals from one nearshore site and one offshore site. Body size and darkness of different life-stages of E. affinis were evaluated to determine stage-dependent differences in visual predation risk. Abundance of E. affinis was determined at each depth of each site to describe diel patterns of movement through the water column. Results show significant differences among life-stages in both length and visual area, but not our measure of darkness. Magnitude of DVM was greater near shore than in the offshore habitat. This may be a result of greater predation pressure near shore. The magnitude of DVM was also stage-dependent, with adults performing a more drastic migration than copepodites. This stage-dependency could be a result of differing visual predation risk, since copepodites are smaller than adults. The variety of DVM magnitudes exhibited for different life stages and environmental conditions support the notion that E. affinis is highly phenotypically plastic, making it a successful invader.
Level of Honors
magna cum laude
Bart De Stasio
Poli, Alexandra N., "Diel Vertical Migration of an Invasive Calanoid Copepod, Eurytemora affinis, in Little Sturgeon Bay, Wisconsin" (2015). Lawrence University Honors Projects. Paper 78.