Date of Award

Fall 12-2017

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Ocean Science and Technology

Committee Chair

Chester F. Rakocinski

Committee Chair Department

Ocean Science and Technology

Committee Member 2

Robert J. Griffitt

Committee Member 2 Department

Ocean Science and Technology

Committee Member 3

Kelly M. Dorgan

Abstract

Elevated surface temperatures exacerbate the threat of hypoxia within coastal ecosystems. These two primary stressors likely interact as they elicit opposing physiological responses from marine organisms. Metabolic depression is typically associated with hypoxia, while metabolic rates increase with temperature. Moreover, physiological effects of combined stressors may not be additive. In light of increasing pressures from hypoxia, elevated ocean temperatures, and other stressors within coastal regions, studies need to examine effects of multiple stressors on physiology of coastal organisms.

Mass-specific aerobic respiration (VO2) was characterized as a proxy for metabolic cost of Streblospio gynobranchiata, at combined levels of dissolved oxygen and temperature relative to body size. Also, changes in VO2 during acclimation to hypoxia and respiratory recovery following hypoxia exposure were examined. Overall, oxyregulatory abilities were maintained with decreasing dissolved oxygen levels and increasing temperatures except at the highest temperature treatment, indicating the critical temperature was reached within the treatment range. Over a 12 hour period of hypoxia exposure, this species showed an initial acclimation period, followed by a decreased VO2 for the remainder of the exposure. After returning to aerated conditions following acclimation to hypoxia, VO2 appeared to increase and decrease in two cycles over a 12 hour period, possibly reflecting energy cycling in terms of ATP usage. VO2 peaked at 10 hours, overshooting reference normoxia readings, perhaps indicating an oxygen debt. Streblospio gynobranchiata exhibited a high tolerance to these combined stressors, however, further challenges by decreasing oxygen and increasing temperatures may surpass this species’ ability to meet energy demands.

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