Top-down effects of an invasive omnivore: detection in long-term monitoring of large-river reservoir chlorophyll-a
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Invasive species are capable of altering ecosystems through the consumption of basal resources. However, quantifying the effects of invasive species in large ecosystems is challenging. Measuring changes in basal resources (i.e., phytoplankton) at an ecosystem scale is an important and potentially translatable response vital to the understanding of how introduced species influence ecosystems. In this study, we analyzed patterns of early summer chlorophyll-a in a large-river reservoir in response to invasion of silver carp (Hypophthalmichthys molitrix). We used 25 years of ecological data from a 30-km reach of Kentucky Lake collected before and after silver carp establishment. We found significant decreases in chlorophyll-a within certain reservoir habitats since establishment of silver carp. Additionally, environmental and biological drivers of phytoplankton production showed no significant differences before and after invasion. These results suggest seasonal, and habitat-specific consumptive effects of invasive silver carp on an important basal food web resource. Further, our results convey the utility of long-term quantitative biological and physiochemical data in understanding ecosystem responses to elements of global change (i.e., species invasions). Importantly, the observed changes in the basal food web resource of Kentucky Lake may apply to other ecosystems facing invasion by silver carp (e.g., Laurentian Great Lakes). Our study offers insight into the mechanisms by which silver carp may influence ecosystems and furthers our understanding of invasive omnivores.
KeywordsPhytoplankton Trophic ecology Invasive species Asian carp Omnivory
We would like to thank D. White for sharing his expertise on the Kentucky Lake ecosystem and helpful comments on earlier manuscript drafts. Additionally, we are very grateful to the numerous other faculty and volunteers of Hancock Biological Station including G. Harris, K. Johnston, A. Hayden, R. Trites, and C. Hendrix for their long dedication and continued contribution to the Kentucky Lake Long-Term Monitoring Program. We thank M. Moore, and C. Mecklin for their statistical advice and consult. We also thank the Whiteman lab, B. Richardson, D. Jent, S. Peterson and A. Gilmore for their helpful dialogue throughout the project. Finally, we are thankful for L. Barmuta and two anonymous reviewers whose comments led to a greatly improved manuscript. Funding for this project was provided by Watershed Studies Institute of Murray State University, U.S. Fish and Wildlife Grant Number (F13AP00999) and the Research Enhancement Award from Kentucky Water Resource Research Institute awarded to B.B. Tumolo.
Author contribution statement
MBF conceived the idea; BBT and MBF developed the experimental design; BBT compiled and organized long-term data into data matrices for analysis; BBT and MBF conducted analyses and discussed results. BBT wrote the original manuscript draft and MBF contributed revisions.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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