Endurance swimming performance and physiology of juvenile Green Sturgeon () at different temperatures.

Sturgeon are threatened by anthropogenic changes to river systems, including entrainment or impingement at water diversions (i.e. the unwanted passage of fish through a water intake or physical contact with a barrier screen, likely caused by high intake velocities).

Prior thermal acclimation gives White Sturgeon a fin up dealing with low oxygen.

Assessing how at-risk species respond to co-occurring stressors is critical for predicting climate change vulnerability. In this study, we characterized how young-of-the-year White Sturgeon () cope with warming and low oxygen (hypoxia) and investigated whether prior exposure to one stressor may improve the tolerance to a subsequent stressor through "cross-tolerance". Fish were acclimated to five temperatures within their natural range (14-22°C) for one month prior to assessment of thermal tolerance (critical thermal maxima, CTmax) and hypoxia tolerance (incipient lethal oxygen saturation, ILOS; tested at 20°C).

Effects of acclimation temperature and feed restriction on the metabolic performance of green sturgeon.

Green sturgeon () are an anadromous threatened species of sturgeon found along the Pacific coast of North America. The southern distinct population segment only spawns in the Sacramento River and is exposed to water temperatures kept artificially cold for the conservation and management of winter-run Chinook salmon (). Past research has demonstrated costs of cold-water rearing including reduced growth rates, condition and survivorship of juvenile green sturgeon.

Enhanced oxygen unloading in two marine percomorph teleosts.

Teleost fishes are diverse and successful, comprising almost half of all extant vertebrate species. It has been suggested that their success as a group is related, in part, to their unique O transport system, which includes pH-sensitive hemoglobin, a red blood cell β-adrenergic Na/H exchanger (RBC β-NHE) that protects red blood cell pH, and plasma accessible carbonic anhydrase which is absent at the gills but present in some tissues, that short-circuits the β-NHE to enhance O unloading during periods of stress. However, direct support for this has only been examined in a few species of salmonids.

Contrasting effects of constant and fluctuating pCO conditions on the exercise physiology of coral reef fishes.

Ocean acidification (OA) is predicted to affect the physiology of some fishes. To date, most studies have investigated this issue using stable pCO levels based on open ocean projections. Yet, most shallow, nearshore systems experience temporal and spatial pCO fluctuations.

The effects of constant and fluctuating elevated pCO levels on oxygen uptake rates of coral reef fishes.

Ocean acidification, resulting from increasing atmospheric carbon dioxide (CO) emissions, can affect the physiological performance of some fishes. Most studies investigating ocean acidification have used stable pCO treatments based on open ocean predictions. However, nearshore systems can experience substantial spatial and temporal variations in pCO.

Hot and bothered: effects of elevated Pco and temperature on juvenile freshwater mussels.

Multiple environmental stressors may interact in complex ways to exceed or diminish the impacts of individual stressors. In the present study, the interactive effects of two ecologically relevant stressors [increased temperature and partial pressure of carbon dioxide (Pco)] were assessed for freshwater mussels, a group of organisms that are among the most sensitive and rapidly declining worldwide. The individual and combined effects of elevated temperature (22°C-34°C) and Pco (~230, 58,000 µatm) on juvenile Lampsilis siliquoidea were quantified over a 5- or 14-day period, during which physiological and whole animal responses were measured.

Aquatic acidification: a mechanism underpinning maintained oxygen transport and performance in fish experiencing elevated carbon dioxide conditions.

Aquatic acidification, caused by elevating levels of atmospheric carbon dioxide (CO), is increasing in both freshwater and marine ecosystems worldwide. However, few studies have examined how acidification will affect oxygen (O) transport and, therefore, performance in fishes. Although data are generally lacking, the majority of fishes investigated in this meta-analysis exhibited no effect of elevated CO at the level of O uptake, suggesting that they are able to maintain metabolic performance during a period of acidosis.

Chronic exposure of a freshwater mussel to elevated pCO : Effects on the control of biomineralization and ion-regulatory responses.

Freshwater mussels may be exposed to elevations in mean partial pressure of carbon dioxide (pCO ) caused by both natural and anthropogenic factors. The goal of the present study was to assess the effects of a 28-d elevation in pCO at 15 000 and 50 000 μatm on processes associated with biomineralization, ion regulation, and cellular stress in adult Lampsilis siliquoidea (Barnes, 1823). In addition, the capacity for mussels to compensate for acid-base disturbances experienced after exposure to elevated pCO was assessed over a 14-d recovery period.

Valve movement of three species of North American freshwater mussels exposed to elevated carbon dioxide.

Freshwater mussels are at-risk taxa and may be exposed to high levels of carbon dioxide (CO) because of the potential use of CO to control the movement of invasive aquatic fish species. One potential behavioral response to a change in the partial pressure of CO (pCO) may be altered valve movement. In this study, three species of mussels were fitted with modified sensors and exposed to two regimes of pCO to define thresholds of impaired valve movement.

Physiological responses of three species of unionid mussels to intermittent exposure to elevated carbon dioxide.

Freshwater systems are at risk owing to increasing carbon dioxide (CO) levels, and one of the possible reasons for these elevations is the deployment of non-physical fish barriers to prevent invasive fish movements. Carbon dioxide barriers have the potential to create short, chronic and intermittent exposures of CO for surrounding freshwater biota. Although intermittent exposures to a stressor may be more ecologically relevant, the majority of laboratory tests use chronic or short-term time periods to determine how organisms will respond to an environmental stressor.

The response of two species of unionid mussels to extended exposure to elevated carbon dioxide.

Changes in environmental conditions can act as stressors, with potential consequences for the health and fitness of organisms. Rising levels of carbon dioxide (CO2) is one potential environmental stressor that is occurring more frequently in the environment and can be a stressor for aquatic organisms. In this study, the physiological responses of two species of unionid mussel, Lampsilis siliquoidea and Amblema plicata, were assessed in response to exposure to two levels of elevated partial pressure of CO2 (pCO2) (~20,000 and ~55,000μatm) over a 28d period, followed by a subsequent 14d recovery period.

Responses to elevated CO exposure in a freshwater mussel, Fusconaia flava.

Freshwater mussels are some of the most imperiled species in North America and are particularly susceptible to environmental change. One environmental disturbance that mussels may encounter that remains understudied is an increase in the partial pressure of CO (pCO). The present study quantified the impacts of acute (6 h) and chronic (up to 32 days) exposures to elevated pCO on genes associated with shell formation (chitin synthase; cs) and the stress response (heat shock protein 70; hsp70) in Fusconaia flava.