All ETDs from UAB

Advisory Committee Chair

James B McClintock

Advisory Committee Members

Maria Byrne

Charles D Amsler

John M Lawrence

Stephen A Watts

Document Type

Dissertation

Date of Award

2016

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Sea urchins (Class Echinoidea) play important economic and ecological roles in the marine ecosystems they inhabit. However, climate change is causing seawater temperatures to increase and pH and the saturation state of polymorphs of calcium calcite to decrease at unprecedented rates, and these changes may have serious implications for the fitness and survival of sea urchin populations. The purpose of the present dissertation was to determine the effects of ocean warming and acidification on the physiology and behavior of sea urchins. This research was conducted on three sea urchin taxa (Lytechinus variegatus, Heliocidaris erythrogramma, and Sterechinus spp.) representing species that are disproportionately experiencing the effects of climate change, and investigated effects spanning several biological levels of organization, from microbial to ecological. At the microbial level, chronic exposure to elevated seawater temperatures shifted the community structure and function of microbiota associated with Lytechinus variegatus. Changes were also observed at the physiological level. Heliocidaris erythrogramma exposed to near-future warming and acidification exhibited characteristics of a compromised immune system with reduced immune cell counts and a capacity to inhibit a bacterial pathogen linked to disease outbreaks in sea urchins. Additionally, L. variegatus chronically exposed to ocean warming exhibited a reduced feeding rate. On the behavioral level, these results demonstrate that although L. variegatus can maintain righting and covering behaviors under acute exposure to elevated seawater temperatures, these behaviors are compromised under chronic exposure to IPCC predicted near-future temperature. Finally, the echinoid Sterechinus spp. may be increasing covering behavior in response to increased predation pressure from king crabs moving into the Antarctic slope and shelf waters as climate change elevates seawater temperature. Overall, these results demonstrate the wide range of effects that climate change may have on sea urchin populations, as well as the importance of incorporating acclimation time when exposing sea urchins to near-future conditions, in order to most accurately predict the future of sea urchins under rapidly warming and acidifying ocean conditions.

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