Littorina obtusata grazing on Fucus macroalgae: Effects of trematode infection and habitat temperature Restricted; Files Only

Abstract

In the rocky intertidal zone, smooth periwinkle (Littorina obtusata) grazing on macroalgae exerts a top-down control on the ecosystem. However, snail herbivory patterns may be affected as sea temperatures rise with anthropogenic climate change. These temperature-driven changes may also intersect with trematode infections, causing snail grazing rates dissimilar to the rates currently observed. In this study, we conducted two pilot experiments and one final laboratory experiment to measure grazing patterns of uninfected and infected L. obtusata on Fucus macroalgae under three temperature conditions (11.95°C, 18.83°C, and 20.03°C). After a 24- hour grazing trial, L. obtusata grazing rates were measured via algal weight loss and feeding-scar area, both representing biomass removed from the algae. Our linear mixed-model analysis revealed no significant effect of temperature, infection status, or snail size – a known influencer of grazing rate – on either grazing metric. These results differ from those of previous studies that suggested that higher habitat temperature minimizes the negative influence of trematode infection on grazing rates for other Littorinid species. The results of this study thus fill a gap in our understanding of L. obtusata biological responses to abnormal temperatures with parasitism as a contributing factor. Additionally, the non-significant results suggest that because snail grazing may not be affected by the interaction of increased temperature and parasitism, gastropod grazing pressures on intertidal macroalgae populations may remain stable under climate change conditions.

Table of Contents

Abstract………………………………………………………………..…………...…..…1

Introduction………………………………………………………..………………...…..2

Methods………………………………………………………………………..………..…5

Results…………………………………………………………………………..……...…11

Discussion…………………………………………………………………...…………..14

References …………………………………………………………………………….…20

About this Honors Thesis

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School	Emory College
Department	Environmental Studies
Degree	B.A.
Submission	Honors Thesis
Language	English
Research Field	Climate Change Environmental Sciences Environmental Studies
Keyword	Snail Parasitism Trematode Mollusc Sea Temperature Marine Ecology Intertidal Ecosystem
Committee Chair / Thesis Advisor	Keogh, Carolyn, Emory University
Committee Members	Martin, Anthony, Emory University Civitello, David, Emory University

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