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Title:The physiological effects of elevated carbon dioxide, in the context of non-physical fish barriers, on unionid mussels
Author(s):Hannan, Kelly Dillingham
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Carbon Dioxide
Ion Regulation
Abstract:Carbon dioxide (CO2) is predicted to increase in both marine and freshwater environments in the near future. This can be caused by both natural (daily and seasonal fluctuations) and anthropogenic (climate change and more recently non-physical fish barriers) sources. Carbon dioxide has proven very effective at causing avoidance and deterring fish movement. This is promising for its use as a non-physical barrier; however, before these barriers can be implemented, the impacts of elevated carbon dioxide on non-target organisms need to be defined. Freshwater unionid mussels are a non-target taxa that have the potential to be affected by elevated CO2. Unionid mussels are some of the most threatened taxa worldwide, with more than half (71%) of the species in North America listed as threatened, endangered, or already extinct. This, coupled with the fact that there have been many studies documenting a negative impact of elevated CO2 on marine invertebrates, demonstrates a critical knowledge gap that needs to be filled related to potential impacts of elevated carbon dioxide on freshwater mussels. The work presented in this thesis is the first research on the physiological effects of elevated partial pressure of CO2 (pCO2) on freshwater mussels. Freshwater unionid mussels show a number of different mechanisms to buffer acidosis when they are exposed to short, long, and fluctuating elevated pCO2, and there is evidence of recovery should a CO2 stressor be removed. However, there are individual species differences when mussels are exposed to elevated pCO2. General trends observed across most species in response to elevated pCO2 were elevated HCO3-, Ca2+, Na+ and decreased Cl- in hemolymph to regulate acid-base balance. Additionally, unionid mussels also showed evidence of stress in response to long-term and fluctuating exposures to elevated pCO2, as demonstrated by elevated glucose levels and decrease Mg2+ concentrations in the hemolymph. Chapter 1 quantified hemolymph responses of one species of unionid mussel to short-term (6 h) exposure to elevated pCO2 and subsequent recovery (6h), as well as a long term exposure (32 d). To quantify recovery from a long term CO2 exposure, chapter 2 examined long-term responses of two species of unionid mussels to 28 d exposure and 14d recovery. Finally, due to the many different possible mechanisms of future increases in pCO2, as well as CO2 barriers still being in the design stage, chapter 3 looked at yet a different type of exposure that may be more ecologically relevant: the effects of fluctuating exposure to elevated pCO2 on three species of unionid mussels. Together the results of the studies show that, though there are species differences, freshwater unionid mussels exposed to elevated levels of pCO2 have changes in hemolymph that represent acid-base regulation as well as a stress response, and there is evidence for recovery should this stress be removed.
Issue Date:2016-04-22
Rights Information:Copyright 2016 Kelly Hannan
Date Available in IDEALS:2016-07-07
Date Deposited:2016-05

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