TY - JOUR
T1 - Differential responses of zooplankton populations (Bosmina longirostris) to fish predation and nutrient-loading in an introduced and a natural sockeye salmon nursery lake on Kodiak Island, Alaska, USA
AU - Sweetman, Jon N.
AU - Finney, Bruce P.
N1 - Funding Information:
We thank David Barto and Irene Gregory-Eaves for assistance in the field. Thanks to the Alaska Department of Fish and Game for providing logistical support and access to limnological data on the study lakes. We benefited greatly from comments made by Irene Gregory-Eaves, Steve Honnold, Nicholas Hughes, and Nick Sagalkin. Thanks to John Glew for drafting Figure 1. This research was funded by the Alaska Sea Grant College Program (Project [R/07-22) and the U.S. Global Ocean Ecosystems Dynamics (GLOBEC) program (contribution no. 366), jointly funded by the National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration (NOAA). Additional support was provided from the Alaska Quaternary Center and the University of Alaska Fairbanks Graduate School.
PY - 2003/8
Y1 - 2003/8
N2 - Stratigraphic changes in the remains of Bosmina longirostris from a lake with an introduced sockeye salmon population and a lake with a natural salmon run on Kodiak Island demonstrated markedly different responses to past fluctuations in salmon populations. In both lakes, there was a positive correlation between the density of Bosmina microfossils and the abundance of sockeye salmon. However, opposite size trends were observed in the two lakes. In Karluk Lake, which has a native sockeye salmon population, Bosmina mean carapace lengths were largest at high salmon densities, and mean mucro and antennule lengths were also large, suggesting strong predation pressure from cyclopoid copepods, and less intense pressure from juvenile sockeye salmon. As salmon-derived nutrients are important in driving primary productivity in this system, changes in zooplankton productivity track salmon escapement, but grazing pressure on Bosmina from juvenile salmon is less important than that from cyclopoid copepods. In Frazer Lake, a lake with an introduced salmon population, Bosmina morphologies were smallest during periods of high sockeye salmon in the lake, suggesting much stronger predation effects from sockeye salmon due to the suppression of Cyclops columbianus. Latent development of compensatory mechanisms and the delayed recovery of copepod populations to salmon introductions has resulted in zooplankton populations that are still recovering from shifts in fish populations that occurred decades earlier. The differential response of Bosmina populations between the natural and manipulated lakes suggests that care must be taken when attempting to extrapolate results from whole-lake manipulations and short-term experiments to natural systems.
AB - Stratigraphic changes in the remains of Bosmina longirostris from a lake with an introduced sockeye salmon population and a lake with a natural salmon run on Kodiak Island demonstrated markedly different responses to past fluctuations in salmon populations. In both lakes, there was a positive correlation between the density of Bosmina microfossils and the abundance of sockeye salmon. However, opposite size trends were observed in the two lakes. In Karluk Lake, which has a native sockeye salmon population, Bosmina mean carapace lengths were largest at high salmon densities, and mean mucro and antennule lengths were also large, suggesting strong predation pressure from cyclopoid copepods, and less intense pressure from juvenile sockeye salmon. As salmon-derived nutrients are important in driving primary productivity in this system, changes in zooplankton productivity track salmon escapement, but grazing pressure on Bosmina from juvenile salmon is less important than that from cyclopoid copepods. In Frazer Lake, a lake with an introduced salmon population, Bosmina morphologies were smallest during periods of high sockeye salmon in the lake, suggesting much stronger predation effects from sockeye salmon due to the suppression of Cyclops columbianus. Latent development of compensatory mechanisms and the delayed recovery of copepod populations to salmon introductions has resulted in zooplankton populations that are still recovering from shifts in fish populations that occurred decades earlier. The differential response of Bosmina populations between the natural and manipulated lakes suggests that care must be taken when attempting to extrapolate results from whole-lake manipulations and short-term experiments to natural systems.
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U2 - 10.1023/A:1025543421436
DO - 10.1023/A:1025543421436
M3 - Article
AN - SCOPUS:0141451884
SN - 0921-2728
VL - 30
SP - 183
EP - 193
JO - Journal of Paleolimnology
JF - Journal of Paleolimnology
IS - 2
ER -