Advisor(s)

Geoffrey C. Trussell

Contributor(s)

Matthew E.S. Bracken, Salvatore J. Genovese

Date of Award

7-2012

Date Accepted

7-2012

Degree Grantor

Northeastern University

Degree Level

M.S.

Degree Name

Master of Science

Department or Academic Unit

College of Science. Department of Biology.

Keywords

Carcinus maenas, Diversity, Macroinfaunal density and diversity, Nonconsumptive effects, Salt marsh, Top-down vs. bottom-up control

Disciplines

Biology | Marine Biology | Systems Biology

Abstract

Traditional studies of trophic cascades have revealed how predators by limiting abundance of their prey, have positive indirect effects on basal resources. However, recent studies have shown that predators can also indirectly affect such resources without consuming their prey by way of anti-predator foraging adaptive behavior (nonconsumptive effects). For example, on rocky shores, waterborne risk cues from the predatory green crab (Carcinus maenas) cause strong trophic cascades by suppressing the grazing rate of the herbivorous snail, Littorina littorea, on algal resources. L. littorea is also an abundant herbivore in northern New England salt marshes but it is unknown whether C. maenas exerts a similar indirect effect in this system.

Through field experiments conducted in a salt marsh located at the Wells National Estuarine Research Reserve and Scarborough in southern Maine, I examined how nonconsumptive and consumptive effects of C. maenas on L. littorea indirectly influenced benthic macroinfaunal density and diversity, and how these interactions affected marsh primary production and nutrient availability. I hypothesize that predator-induced changes in L. littorea foraging behavior reduced the intensity of foraging competition among macroinfauna for a shared food source (epibenthic diatoms and algae), resulting in an increase in density of macroinfaunal organisms. C. maenas has become increasingly abundant in salt marshes, and it is critical that we examine how nonconsumptive and consumptive effects of this predator on prey populations influence salt marsh community dynamics. Our results suggest that both consumptive and nonconsumptive predator effects influenced macroinfaunal densities and composition. However, the top-down interactions had no influence on primary production nor on nutrient availability. Furthermore, we need a greater understanding of how nonconsumptive predator effects may influence ecosystem level properties such as biodiversity, productivity, stability and energy flow.

Document Type

Master's Thesis

Rights Holder

Genevieve Bernatchez


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