Hypolimnetic Aeration and Zooplankton Distribution: A Possible Limitation to the Restoration of Cold-Water Fish Production

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Author: Taggart, Christopher T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1984
• Subjects: Copepods; Rotifer
• Online Access: http://dx.doi.org/10.1139/f84-020; http://www.nrcresearchpress.com/doi/pdf/10.1139/f84-020

Hypolimnetic aeration of a 1.23-ha eutrophic kettle lake during two consecutive summers increased [O 2 ] to more than 4 mg/L in the hypolimnion for extended periods. This improvement did not lead to the expected development of crustacean populations in the previously anoxic, zooplankton-deficient hypolimnion. The rotifer Filinia longiseta was the only zooplankter present, as isolated populations, in both the epilimnion and hypolimnion during summer. Eighty percent of the summer zooplankton community occurred exclusively in the epilimnion, and this was related to the development of an anoxic and toxic metalimnion that restricted migration from the epilimnion to the hypolimnion. Confinement of the zooplankton to the epilimnion coupled with predation by fathead minnows (Pimephales promelas) appeared to be responsible for the change in the zooplankton community from large cladocerans and copepods to smaller species. This study suggests that hypolimnetic aeration as a means of restoring or enhancing the production of cold-water fish may be thwarted by the development of a stable anoxic and toxic metalimnion that precludes the development of the zooplankton food resource.