Aquatic Sciences Meeting, Albuquerque 2001

PC12 Trophic Dynamic Studies

Date: Thursday, February 15, 2001

Location: Southwest Hall

Jarnagin, S, T, US EPA EPIC, USGS Nat'l Ctr, MS 555, Reston, VA 20192-0002, USA, jarnagin.taylor@epa.gov

Swan, B, K, Dept of Biology, San Diego State University, San Diego, CA 92182, USA, swan@rohan.sdsu.edu

INTERACTIONS BETWEEN BYTHOTREPHES CEDERSTROEMI AND LEPTODORA KINDTII

Bythotrephes cederstroemi is a non-indigenous predaceous zooplankter invading North American freshwater lakes in the Great Lakes region. We present seasonal population abundance values for both Bythotrephes and Leptodora kindtii from Lake Michigamme, Michigan for the years 1995-1997. We illustrate that Leptodora appears to be inhibited by Bythotrephes. Leptodora populations declined to near zero when Bythotrephes mean whole-depth abundance exceeded 3-5 animals per m3 and late season Leptodora populations consisted only of nauplii. Our population data do not demonstrate the reason for the apparent inhibition of Leptodora by Bythotrephes. Bythotrephes may out-compete Leptodora for a shared food resource or may directly prey upon Leptodora. Our data emphasize the potential for the alteration of food webs due to the introduction of Bythotrephes into freshwater lake ecosystems. Both species rely on resting eggs to overwinter and reestablish populations. The elimination of early season Leptodora adult and juvenile instars and the failure of late season Leptodora nauplii to reach adulthood and produce resting eggs could result in the elimination of Leptodora from lakes where Bythotrephes has invaded.

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Aquatic Sciences Meeting, Albuquerque 2001

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