Project: Nonconsumptive predator effects in a pelagic community: an integrated laboratory, field and modeling approach

This study will address a fundamental issue about how species interactions influence communities. Classical approaches, including the vast majority of experimental and modeling studies, focus on how species affect the density of other species through predator-prey interactions. This approach ignores a growing body of work that documents how prey modify their phenotype (traits) in response to predators to reduce predation risk, and how this, in turn, can profoundly influence the consequences of species interactions. There is abundant evidence that such nonconsumptive effects (NCEs, also trait-mediated or nonlethal) of predators could be important in pelagic Great Lakes and marine ecosystems. Whereas, the underlying mechanism is well known, there is little understanding of the influence of NCEs, and almost no studies of NCEs in large pelagic ecosystems. The existence of NCEs could strongly affect the qualitative and quantitative nature of species interactions and the properties of communities.

This project will examine the role and operation of NCEs in marine and Great Lake systems. The investigators will examine NCEs caused by an invertebrate predator, the invasive spiny water flea Bythotrephes. The project will attempt to answer the broad questions:
How do Bythotrephes induced effects on prey influence their net effect on Great Lakes communities?
Are NCEs influential in complex field settings?
What is the influence of NCEs of an invertebrate predator on the zooplankton prey assemblages or on the young-of-year fish competitors?
How do factors such as resource level, temperature, and light affect the influence of a predator?s NCE on a prey assemblage (via effects on competition)?

A comprehensive approach based on three objectives will be used that integrates laboratory studies, field surveys and modeling. The investigators will: (1) Determine the phenotypic responses of key zooplankton species to Bythothrephes. This will involve laboratory studies that examine behavioral, morphological and life history responses. Laboratory studies will also quantify Bythotrephes predation rates. Optimization modeling will guide and allow interpretation of these laboratory studies. (2) Develop predictive models of the NCEs of Bythothrephes on zooplankton prey growth rate and competitive outcomes and test predictions with microcosm and mesocosm experiments. This is a key methodological component: If models accurately predict induced trait changes, and their consequences to species interactions in mesocosm experiments, this increases the ability to form predictive models in natural systems. (3) Determine NCEs of Bythotrephese in the field using ecological models based on parameters derived from the aforementioned exercises and field surveys. Field surveys will examine the effect of Bythotrephes on zooplankton prey in the field, and classify abundances and parameters such as young of the year fish density and position and abiotic factors.

Publications related to this project:

Bourdeau, P. E., Pangle, K. L., Peacor, S. D. 2011. The invasive predator Bythotrephes induces changes in the vertical distrobution of native copepods lin Lake Michigan.  Biol Invasions 13:2533-2545.

Pangle, K. L., Peacor, S. D., Johannsson, O. E.  2007. Large nonlethal effects of an invasive invertebrate predator on zooplankton population growth rate.  Ecology, 88(22), pp. 402-412