ABSTRACT

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.

Significant intellectual contributions will result from this study by addressing a key, but poorly understood, component of species interactions in Great Lakes and marine systems. Societal concern and interest over the influence of invasive species including Bythotrephes in Great Lakes food webs will facilitate educational outreach. In addition, close associations with institutions (e.g., the NOAA Great Lakes Environmental Research Laboratory, GLERL) will develop from the project and there will be strong outreach components that foster educational opportunities. For example, many individuals and groups from high schools and management agencies come to GLERL for education and training. Further, a Great Lakes Sea Grant Network extension educator has agreed to work to bridge the research with educators by helping the PIs engage with the Center for Ocean Sciences and Education Excellence Great Lakes (COSEE) Great Lakes and Sea Grant. The investigators on this project will work with professional educational outreach partners to enhance the broader impacts from the research. COSEE Great Lakes already has a framework in place to reach teachers throughout the region and includes an emphasis on underrepresented groups including tribal educators and COSEE and Sea Grant also are working on a variety of curriculum pieces. This project will contribute to these efforts. Finally, graduate and undergraduate training in research and outreach is part of this activity.