All ETDs from UAB

Advisory Committee Chair

James B McClintock

Advisory Committee Members

Charles D Amsler

Robert A Angus

Justin B Ries

Mary A Sewell

Document Type

Dissertation

Date of Award

2015

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Increases in atmospheric carbon dioxide (CO2) concentrations are continuing to increase and have been linked with decreasing seawater pH as well as atmospheric and seawater warming. Warming along the western Antarctic Peninsula is occurring at one of the fastest rates recorded to date and triggering further environmental changes. To date there are few records of the current seawater pH and temperature conditions experienced by benthic organisms in this region or how they will respond to shifts in pH and temperature predicted to occur by 2100 or sooner. The primary aim of this dissertation was to pa-rameterize the current seawater carbonate chemistry and temperature patterns experi-enced by benthic organisms in the vicinity of Palmer Station, Antarctica and then evalu-ate the response of a suite of invertebrate grazers, including the limpet Nacella concinna (Strebel, 1908) and topshell snail Margarella antarctica (Lamy, 1905) and amphipods Gondogeneia antarctica (Chevreux, 1906) and Paradexamine fissicauda (Chevreux, 1906) to predicted changes in seawater pH and temperature. I found that the benthos near Palmer Station seasonally experiences up to a 0.6 unit change in pH and daily changes of as much as 0.13 units, mediated primarily by biological activity. This higher than ex-pected variation in ambient environmental conditions may have contributed to the resili-ence exhibited by N. concinna and M. antarctica. There were multiple interactive effects of temperature and pH on the escape and righting behavior of these two gastropod mol-lusks but little to no impact on their growth, net calcification, shell morphology, or body composition. In contrast, I observed significant changes in the feeding preferences of G. antarctica for chemically deterrent sympatric macroalgae following acute exposure to near-future elevated temperature. A three-month exposure to decreased pH and elevated temperature resulted in a significant decrease in survival of G. antarctica and P. fissicau-da as well as shifts in feeding rates and body composition. Nonetheless, a 30-day meso-cosm experiment revealed that the mobile grazer assemblages associated with the benthic macroalgae of the western Antarctic Peninsula are resistant to decreased pH. The grazers, mollusk and crustacean, investigated here exhibited resilience following exposure to ex-perimental conditions over relatively short exposure periods given the long-lived nature of the species investigated. However, longer-term studies, which include natural diurnal variation in seawater chemistry, are needed to fully assess the resilience of these Antarc-tic invertebrate grazer assemblages.

Share

COinS