All ETDs from UAB

Advisory Committee Chair

James B McClintock

Advisory Committee Members

Charles Amsler

John Lawrence

John Valentine

Stephen A Watts

Document Type

Dissertation

Date of Award

2013

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Increases in CO2 concentrations, whether from accumulation of metabolic waste under intensive culturing conditions or from increases in atmospheric levels, lead to decreases in seawater pH and carbonate saturation states. Lytechinus variegatus survive chronic exposure to hypercapnic conditions (pH 7.4 -7.8, partial pressure of CO2 (pCO2) 1738-4290 μatm) in synthetic seawater, yet aspects of growth and development are affected. Rates of embryonic and larval development were delayed and larval size and arm length reduced under high pCO2 conditions. Fecal production rates were higher and ash absorption efficiency (%) was lower in individuals exposed to hypercapnic conditions, suggesting that the ability to process or retain dietary carbonates was affected. Sea urc-hins exposed to hypercapnic conditions displayed reduced total dry matter production, contributed primarily by reduced test dry matter production. Increases in neutral lipid storage in the gut were observed under hypercapnic conditions and gonads exhibited in-creased soluble protein storage. Conversely, organic production and energy allocation increased in the lantern in individuals exposed to hypercapnic conditions. Righting response and covering behavior were not affected by hypercapnic conditions. Carbonate system parameters (i.e., pH, pCO2, and carbonate polymorph saturation states) of a sea-grass-dominated ecosystem where individuals were collected (Eagle Harbor, Saint Joseph Bay, FL) exhibited extensive diurnal and seasonal variability. Monthly values of pH and pCO2 ranged from 7.36 - 8.28 and 194.63 - 2536.80 μatm over one year, with mean diurnal ranges of 0.27 pH units and 517 μatm. L. variegatus are currently experiencing periodic hypercapnic conditions similar to experimental values employed (pH 7.8). There-fore, the experimental results in this dissertation may be more indicative of current in situ growth and physiology. Field conditions may facilitate acclimatization of L. variegatus to predicted increased hypercapnic conditions. Longer term ocean acidification studies (OA) that incorporate the natural diurnal variation in seawater chemistry into both control and experimental treatments are needed to determine the resilience of L. variegatus to near-future OA conditions.

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