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Susceptibility of Juvenile Fishes to Environmental Change: Linking Physiological Responses to Behavioral Outcomes.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Susceptibility of Juvenile Fishes to Environmental Change: Linking Physiological Responses to Behavioral Outcomes./
Author:	Davi, Brittany Elizabeth.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
Description:	244 p.
Notes:	Source: Dissertations Abstracts International, Volume: 79-12, Section: B.
Contained By:	Dissertations Abstracts International79-12B.
Subject:	Climate Change. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10747642
ISBN:	9780355967760

Susceptibility of Juvenile Fishes to Environmental Change: Linking Physiological Responses to Behavioral Outcomes.
Davi, Brittany Elizabeth.

Susceptibility of Juvenile Fishes to Environmental Change: Linking Physiological Responses to Behavioral Outcomes. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 244 p.

Source: Dissertations Abstracts International, Volume: 79-12, Section: B.

Thesis (Ph.D.)--University of California, Davis, 2018.

This item is not available from ProQuest Dissertations & Theses.

In chapter one, I investigated the effects of CO2-acidification (i.e. increasing PCO2, decreasing pH) on the physiological performance of juvenile Antarctic rockcod (Trematomus bernacchii). High-latitude oceans are predicted to undergo some of the fastest rates of pH change by year 2100 due to GCC. Since fishes in the Southern Ocean have evolved under stable conditions for millions of years, they have adapted highly specialized mechanisms such as antifreeze proteins, mitochondria proliferation, and homeoviscous adaptions for membrane fluidity to live in these extreme cold environments. Polar specializations may make fishes vulnerable to GCC, particularly juvenile fishes with elevated energy requirements allocated for growth and activity. To evaluate potential energetic costs of elevated PCO 2 on physiology and examine if juvenile rockcod have the capacity to cope with high PCO2, I assessed changes in cardiorespiratory performance, whole-organismal metabolism, and sub-organismal aerobic metabolism via measure of enzyme activity. Ventilation rate, measured as opercular beats, increased with increasing PCO2, whereas heart rate, cardiac stroke volume and output, metabolic rate and cellular citrate synthase activity remained unaffected by elevated PCO 2. These findings demonstrated that juvenile rockcod did not incur additional energetic costs under elevated PCO2 that could not be compensated for, and likely elevated ventilation was a sufficient buffering mechanism to off-gas CO2 from the gill to alleviate any imbalance in blood or tissue pH. Overall our findings indicate juvenile fish T. bernacchii are relatively robust to elevated PCO2 projected to occur by the next century. In chapter two, I examined if juvenile Antarctica rockcod (T. bernacchii) had the capacity to cope with multiple GCC stressors of ocean warming and acidification. Following chapter one's findings, this study tested the hypotheses that the ability of fish to cope with a single stressor may be compromised by a secondary stressor experienced simultaneously. I exposed juvenile rockcod to a matrix of three PCO 2 conditions (ambient [450], moderate [850], and high [1200 μatm PCO2]) by two temperatures (cold/control [-1°C] and warm [+2°C]) and measured physiological parameters such as cardiorespiratory physiology, whole-organismal metabolism and cellular metabolism to assess energetic costs and the ability to compensate over a 4-week period. In addition, I conducted behavior assays after 2-weeks of acclimation to the various treatments to determine if potential trade-offs in physiological and behavior responses occurred. After 14 days, whole-organismal cardiorespiratory performance and metabolic rate increased with warming, but was not affected by elevated PCO2 (showing similar results to Chapter 1). Increased physiological costs under warming correlated with behavioral alterations including increased dark zone preference (i.e. anxiety), reduced swimming activity, as well as reduced escape time (i.e. boldness) suggesting potential trade-offs in energetics for physiological and behavioral responses. After 4-weeks of acclimation, juvenile rockcod demonstrated a degree of temperature compensation as ventilation rate, metabolic rate, and cellular metabolism significantly decreased; however, temperature compensation was only evident in the absence of elevated PCO2. Additionally, ventilation rate and metabolic rate remained elevated after the 4-week exposures to elevated PCO2 indicating additive and synergistic interactions occurred in combination with warming, thereby supporting the initial hypothesis to some degree. Stressor-induced energetic trade-offs in physiology and behavior may be an important mechanism leading to vulnerability of Antarctic fishes to future ocean change. In chapter three, I assessed the effects of multiple GCC stressors of ocean acidification and low dissolved oxygen (DO, hypoxia) on physiology, behavior, and predator-prey interactions of juvenile rockfish (genus Sebastes) in California. Highly productive, mid-latitude coastal systems with seasonal upwelling can exhibit both high PCO 2 and low DO due to expansion of oxygen minimum zones. Recreational and commercially important rockfish in the Northern California Coast recruit to seagrass beds during early life-stages where, in addition to seasonal upwelling, they experience rapid changes in PCO2 and DO levels due to photosynthesis and respiration of the biological community. Rockfish that inhabit seagrass beds may be particularly robust to environmental perturbation with an enhanced ability to compensate for alterations in PCO2 and DO compared to species living in more stable environments; however, studies on fishes in seagrass habitats are often overlooked compared to kelp forests or deep ocean waters when examining the effects of GCC conditions. (Abstract shortened by ProQuest.).

ISBN: 9780355967760Subjects--Topical Terms:

894284
Climate Change.

Susceptibility of Juvenile Fishes to Environmental Change: Linking Physiological Responses to Behavioral Outcomes.
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520 $a In chapter one, I investigated the effects of CO2-acidification (i.e. increasing PCO2, decreasing pH) on the physiological performance of juvenile Antarctic rockcod (Trematomus bernacchii). High-latitude oceans are predicted to undergo some of the fastest rates of pH change by year 2100 due to GCC. Since fishes in the Southern Ocean have evolved under stable conditions for millions of years, they have adapted highly specialized mechanisms such as antifreeze proteins, mitochondria proliferation, and homeoviscous adaptions for membrane fluidity to live in these extreme cold environments. Polar specializations may make fishes vulnerable to GCC, particularly juvenile fishes with elevated energy requirements allocated for growth and activity. To evaluate potential energetic costs of elevated PCO 2 on physiology and examine if juvenile rockcod have the capacity to cope with high PCO2, I assessed changes in cardiorespiratory performance, whole-organismal metabolism, and sub-organismal aerobic metabolism via measure of enzyme activity. Ventilation rate, measured as opercular beats, increased with increasing PCO2, whereas heart rate, cardiac stroke volume and output, metabolic rate and cellular citrate synthase activity remained unaffected by elevated PCO 2. These findings demonstrated that juvenile rockcod did not incur additional energetic costs under elevated PCO2 that could not be compensated for, and likely elevated ventilation was a sufficient buffering mechanism to off-gas CO2 from the gill to alleviate any imbalance in blood or tissue pH. Overall our findings indicate juvenile fish T. bernacchii are relatively robust to elevated PCO2 projected to occur by the next century. In chapter two, I examined if juvenile Antarctica rockcod (T. bernacchii) had the capacity to cope with multiple GCC stressors of ocean warming and acidification. Following chapter one's findings, this study tested the hypotheses that the ability of fish to cope with a single stressor may be compromised by a secondary stressor experienced simultaneously. I exposed juvenile rockcod to a matrix of three PCO 2 conditions (ambient [450], moderate [850], and high [1200 μatm PCO2]) by two temperatures (cold/control [-1°C] and warm [+2°C]) and measured physiological parameters such as cardiorespiratory physiology, whole-organismal metabolism and cellular metabolism to assess energetic costs and the ability to compensate over a 4-week period. In addition, I conducted behavior assays after 2-weeks of acclimation to the various treatments to determine if potential trade-offs in physiological and behavior responses occurred. After 14 days, whole-organismal cardiorespiratory performance and metabolic rate increased with warming, but was not affected by elevated PCO2 (showing similar results to Chapter 1). Increased physiological costs under warming correlated with behavioral alterations including increased dark zone preference (i.e. anxiety), reduced swimming activity, as well as reduced escape time (i.e. boldness) suggesting potential trade-offs in energetics for physiological and behavioral responses. After 4-weeks of acclimation, juvenile rockcod demonstrated a degree of temperature compensation as ventilation rate, metabolic rate, and cellular metabolism significantly decreased; however, temperature compensation was only evident in the absence of elevated PCO2. Additionally, ventilation rate and metabolic rate remained elevated after the 4-week exposures to elevated PCO2 indicating additive and synergistic interactions occurred in combination with warming, thereby supporting the initial hypothesis to some degree. Stressor-induced energetic trade-offs in physiology and behavior may be an important mechanism leading to vulnerability of Antarctic fishes to future ocean change. In chapter three, I assessed the effects of multiple GCC stressors of ocean acidification and low dissolved oxygen (DO, hypoxia) on physiology, behavior, and predator-prey interactions of juvenile rockfish (genus Sebastes) in California. Highly productive, mid-latitude coastal systems with seasonal upwelling can exhibit both high PCO 2 and low DO due to expansion of oxygen minimum zones. Recreational and commercially important rockfish in the Northern California Coast recruit to seagrass beds during early life-stages where, in addition to seasonal upwelling, they experience rapid changes in PCO2 and DO levels due to photosynthesis and respiration of the biological community. Rockfish that inhabit seagrass beds may be particularly robust to environmental perturbation with an enhanced ability to compensate for alterations in PCO2 and DO compared to species living in more stable environments; however, studies on fishes in seagrass habitats are often overlooked compared to kelp forests or deep ocean waters when examining the effects of GCC conditions. (Abstract shortened by ProQuest.).
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