Effects of thermal and hypoxic stress on respiratory patterns of three unionid species: implications for management and conservation
Mussels are at particular risk from thermal stress and hypoxia due to limited range and mobility. Of interest to managers is whether sensitivity is uniform or varies among species and subpopulations. We used respirometry to investigate effects of temperature on energy demand and hypoxia tolerance of two narrowly distributed species (Cyclonaias petrina, Colorado River; C. necki, Guadalupe River), and two subpopulations of a widely distributed species (C. pustulosa: Colorado and Navasota rivers) in central Texas. We observed zero mortality during acclimation and respirometry runs even when mussels were exposed to hypoxic conditions for several hours at 36 °C. However, type and magnitude of sublethal effects varied across species and subpopulations as temperatures increased. C. pustulosa (Colorado River) exhibited the greatest increase in energy demand, C. petrina exhibited a decreasing ability to regulate oxygen consumption and an increase in critical dissolved oxygen concentration, C. pustulosa (Navasota River) exhibited metabolic depression, and both C. petrina and C. necki exhibited increasing frequency of valve closure. Results suggest that effects of increasing temperature on energetic requirements are more important than effects on hypoxia tolerance. Management strategies considering physiological differences among species and/or subpopulations are likely to be more effective than a simple “one-size-fits-all” approach.
KeywordsDissolved oxygen Respiration Energy demand Climate change Valve closure Temperature Hypoxia
This research was supported by the Alabama Agricultural Experiment Station and the Hatch program of the National Institute of Food and Agriculture, U.S. Department of Agriculture. Funding was provided by the Texas Comptroller of Public Accounts and Texas State University Subcontract 17,012-82683-1. We thank B. Littrell, K. Sullivan, J. Guajardo, and J. Jenkerson of BIOWEST, Inc. for mussel field collections. Lab members Ryan Fluharty, Kaelyn Fogelman, and Rebecca Gibson provided much appreciated help throughout this project.
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