Marine Science Center of Northeastern University

I investigate the relationships between marine consumers and their prey, and how these interactions shape communities and ecosystems. Specifically, I study the importance of chemical signals to these dynamic interactions using a combination of field and laboratory experiments. My research spans a broad range of taxa (phytoplankton to fishes), organism sizes (microscopic to macroscopic), and habitats (pelagic to benthic). This diverse approach capitalizes on the advantages of working in each system and provides the opportunity to test the generality of my discoveries.

Presently, I am funded by a National Parks Ecological Research Fellowship to examine inducible responses of seaweeds to their consumers. Thus, my field sites now include Acadia National Park and the Boston Harbor Islands in addition to my work in the intertidal surrounding the MSC.

I. Induced responses of algae to herbivores

A. Seaweeds

Terrestrial plants are well-known for their induced responses to herbivores that can strongly affect plant-herbivore interactions and entire plant communities. Despite their prevalence in terrestrial plants and their importance to community structure, induced responses of seaweeds are poorly understood. For example, several previous studies of induced responses in seaweeds used non-standard bioassays, unrealistic damage cues, or limited their scope to studies of one herbivore species interacting with one seaweed species. Standardized studies of seaweed induced responses should lead to a better understanding of seaweed-herbivore interactions and their consequences since seaweeds serve critical roles in marine communities.

B. Marine Phytoplankton

As with seaweeds, our understanding of induced responses of marine phytoplankton is limited. Using Phaeocystis as a model organism, I have examined how grazer cues affect colony formation and the adaptive value of these responses. To our surprise, this simple organism shows surprisingly complex responses including grazer-specificity. These responses may affect the timing of massive blooms of this nuisance alga.

II. Learned aversions in fishes

Under some conditions, innate feeding preferences may be too restrictive for consumers. Learning provides an ecological response to changing prey availability and defenses by allowing consumers to add novel foods to their diets while reducing the risk of consuming noxious foods. Using nudibranchs as a model, chemically defended prey, I study the learned feeding behaviors of fishes to these prey and their chemical defenses. In one study, I found that different fish species learn using different cues and that the sesquiterpene, polygodial, was responsible for creating learned aversions in mummichogs. Understanding how marine consumers respond to new foods is important for predicting changes in food-web dynamics due to the large numbers of introduced species, the frequent range expansions, and the large-scale declines in some common prey species that are occurring in marine systems.

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Jeremy Long

Post-Doctoral Researcher