Juvenile rockfish show resilience to CO\u3csub\u3e2\u3c/sub\u3e-acidification and hypoxia across multiple biological scales

California’s coastal ecosystems are forecasted to undergo shifting ocean conditions due to climate change, some of which may negatively impact recreational and commercial fish populations. To understand if fish populations have the capacity to respond to multiple stressors, it is critical to examine interactive effects across multiple biological scales, from cellular metabolism to species interactions. This study examined the effects of CO2-acidification and hypoxia on two naturally cooccurring species, juvenile rockfish (genus Sebastes) and a known predator, cabezon (Scorpaenichthys marmoratus). Fishes were exposed to two PCO2 levels at two dissolved oxygen (DO) levels: ~600 (ambient) and ~1600 (high) μatm PCO2 and 8.0 (normoxic) and 4.5 mg l−1 DO (hypoxic) and assessments of cellular metabolism, prey behavior and predation mortality rates were quantified after 1 and 3 weeks. Physiologically, rockfish showed acute alterations in cellular metabolic enzyme activity after 1 week of acclimation to elevated PCO2 and hypoxia that were not evident in cabezon. Alterations in rockfish energy metabolism were driven by increases in anaerobic LDH activity, and adjustments in enzyme activity ratios of cytochrome c oxidase and citrate synthase and LDH:CS. Correlated changes in rockfish behavior were also apparent after 1 week of acclimation to elevated PCO2 and hypoxia. Exploration behavior increased in rockfish exposed to elevated PCO2 and spatial analysis of activity indicated short-term interference with anti-predator responses. Predation rate after 1 week increased with elevated PCO2; however, no mortality was observed under the multiple-stressor treatment suggesting negative effects on cabezon predators. Most noteworthy, metabolic and behavioral changes were moderately compensated after 3 weeks of acclimation, and predation mortality rates also decreased suggesting that these rockfish may be resilient to changes in environmental stressors predicted by climate models. Linking physiological and behavioral responses to multiple stressors is vital to understand impacts on populations and community dynamics

New Frontiers for Organismal Biology

Understanding how complex organisms function as integrated units that constantly interact with their environment is a long-standing challenge in biology. To address this challenge, organismal biology reveals general organizing principles of physiological systems and behavior—in particular, in complex multicellular animals. Organismal biology also focuses on the role of individual variability in the evolutionary maintenance of diversity. To broadly advance these frontiers, cross-compatibility of experimental designs, methodological approaches, and data interpretation pipelines represents a key prerequisite. It is now possible to rapidly and systematically analyze complete genomes to elucidate genetic variation associated with traits and conditions that define individuals, populations, and species. However, genetic variation alone does not explain the varied individual physiology and behavior of complex organisms. We propose that such emergent properties of complex organisms can best be explained through a renewed emphasis on the context and life-history dependence of individual phenotypes to complement genetic data.Organismic and Evolutionary Biolog

Reframing conservation physiology to be more inclusive, integrative, relevant and forward-looking: reflections and a horizon scan

Applying physiological tools, knowledge and concepts to understand conservation problems (i.e. conservation physiology) has become common place and confers an ability to understand mechanistic processes, develop predictive models and identify cause-and-effect relationships. Conservation physiology is making contributions to conservation solutions; the number of 'success stories' is growing, but there remain unexplored opportunities for which conservation physiology shows immense promise and has the potential to contribute to major advances in protecting and restoring biodiversity. Here, we consider howconservation physiology has evolved with a focus on reframing the discipline to be more inclusive and integrative. Using a 'horizon scan', we further exploreways in which conservation physiology can be more relevant to pressing conservation issues of today (e.g. addressing the Sustainable Development Goals; delivering science to support the UN Decade on Ecosystem Restoration), as well as more forward-looking to inform emerging issues and policies for tomorrow. Our horizon scan provides evidence that, as the discipline of conservation physiology continues to mature, it provides a wealth of opportunities to promote integration, inclusivity and forward-thinking goals that contribute to achieving conservation gains. To advance environmenta lmanagement and ecosystem restoration, we need to ensure that the underlying science (such as that generated by conservation physiology) is relevant with accompanying messaging that is straightforward and accessible to end users

Thermal windows and metabolic performance curves in a developing Antarctic fish.

For ectotherms, temperature modifies the rate of physiological function across a temperature tolerance window depending on thermal history, ontogeny, and evolutionary history. Some adult Antarctic fishes, with comparatively narrow thermal windows, exhibit thermal plasticity in standard metabolic rate; however, little is known about the shape or breadth of thermal performance curves of earlier life stages of Antarctic fishes. We tested the effects of acute warming (- 1 to 8 °C) and temperature acclimation (2 weeks at - 1, 2, 4 °C) on survival and standard metabolic rate in early embryos of the dragonfish Gymnodraco acuticeps from McMurdo Sound, Ross Island, Antarctica. Contrary to predictions, embryos acclimated to warmer temperatures did not experience greater mortality and nearly all embryos survived acute warming to 8 °C. Metabolic performance curve height and shape were both significantly altered after 2 weeks of development at - 1 °C, with further increase in curve height, but not alteration of shape, with warm temperature acclimation. Overall metabolic rate temperature sensitivity (Q 10) from - 1 to 8 °C varied from 2.6 to 3.6, with the greatest thermal sensitivity exhibited by embryos at earlier developmental stages. Interclutch variation in metabolic rates, mass, and development of simultaneously collected embryos was also documented. Taken together, metabolic performance curves provide insight into the costs of early development under warming temperatures, with the potential for thermal sensitivity to be modified by dragonfish phenology and magnitude of seasonal changes in temperature

Thermal windows and metabolic performance curves in a developing Antarctic fish.

For ectotherms, temperature modifies the rate of physiological function across a temperature tolerance window depending on thermal history, ontogeny, and evolutionary history. Some adult Antarctic fishes, with comparatively narrow thermal windows, exhibit thermal plasticity in standard metabolic rate; however, little is known about the shape or breadth of thermal performance curves of earlier life stages of Antarctic fishes. We tested the effects of acute warming (- 1 to 8 °C) and temperature acclimation (2 weeks at - 1, 2, 4 °C) on survival and standard metabolic rate in early embryos of the dragonfish Gymnodraco acuticeps from McMurdo Sound, Ross Island, Antarctica. Contrary to predictions, embryos acclimated to warmer temperatures did not experience greater mortality and nearly all embryos survived acute warming to 8 °C. Metabolic performance curve height and shape were both significantly altered after 2 weeks of development at - 1 °C, with further increase in curve height, but not alteration of shape, with warm temperature acclimation. Overall metabolic rate temperature sensitivity (Q 10) from - 1 to 8 °C varied from 2.6 to 3.6, with the greatest thermal sensitivity exhibited by embryos at earlier developmental stages. Interclutch variation in metabolic rates, mass, and development of simultaneously collected embryos was also documented. Taken together, metabolic performance curves provide insight into the costs of early development under warming temperatures, with the potential for thermal sensitivity to be modified by dragonfish phenology and magnitude of seasonal changes in temperature

Effect of food availability on the growth and thermal physiology of juvenile Dungeness crabs (Metacarcinus magister).

Juvenile Dungeness crabs spend ~1 year in the San Francisco Estuary, where they undergo considerable growth before returning to the coastal ocean. Previous studies suggest that competition, food scarcity and avoidance of conspecifics may cause some juvenile Dungeness crabs in the San Francisco Estuary to become food limited. Food limitation may force these crabs to forage in higher temperature intertidal environments in the estuary, exposing them to stressful conditions in order to sustain growth and, potentially, necessitating physiological trade-offs in energy allocation between growth and stress tolerance. To investigate the effects of food limitation on aerobic metabolism and physiological performance of crabs, we assessed growth, moulting frequency, metabolic rate, citrate synthase and malate dehydrogenase enzyme activity and cardiac performance, as an index of temperature sensitivity and upper temperature tolerance. Summer- and winter-caught crabs were acclimated to either a high- or a low-food ration for 5 weeks. Overall, our results demonstrated that while food limitation had a negative effect on growth of juvenile Dungeness crabs in both the summer and the winter feeding trials, crabs in the low-food group maintained both metabolic rate at ambient San Francisco Estuary temperatures (15°C; summer trial only) and upper temperature tolerance as determined by failure of cardiac function when compared with crabs in the high-food group (summer and winter trials). Therefore, the ability to maintain stress tolerance when food is limited appears to come as a physiological trade-off to growth. Food-limited crabs were unable to increase their metabolic rate to the same level as that achieved by well-fed crabs; therefore, if exposure to elevated temperatures persists and requires more energy than can be met by crabs in their food-limited state, physiological performance may be compromised

Effect of food availability on the growth and thermal physiology of juvenile Dungeness crabs (Metacarcinus magister).

Juvenile Dungeness crabs spend ~1 year in the San Francisco Estuary, where they undergo considerable growth before returning to the coastal ocean. Previous studies suggest that competition, food scarcity and avoidance of conspecifics may cause some juvenile Dungeness crabs in the San Francisco Estuary to become food limited. Food limitation may force these crabs to forage in higher temperature intertidal environments in the estuary, exposing them to stressful conditions in order to sustain growth and, potentially, necessitating physiological trade-offs in energy allocation between growth and stress tolerance. To investigate the effects of food limitation on aerobic metabolism and physiological performance of crabs, we assessed growth, moulting frequency, metabolic rate, citrate synthase and malate dehydrogenase enzyme activity and cardiac performance, as an index of temperature sensitivity and upper temperature tolerance. Summer- and winter-caught crabs were acclimated to either a high- or a low-food ration for 5 weeks. Overall, our results demonstrated that while food limitation had a negative effect on growth of juvenile Dungeness crabs in both the summer and the winter feeding trials, crabs in the low-food group maintained both metabolic rate at ambient San Francisco Estuary temperatures (15°C; summer trial only) and upper temperature tolerance as determined by failure of cardiac function when compared with crabs in the high-food group (summer and winter trials). Therefore, the ability to maintain stress tolerance when food is limited appears to come as a physiological trade-off to growth. Food-limited crabs were unable to increase their metabolic rate to the same level as that achieved by well-fed crabs; therefore, if exposure to elevated temperatures persists and requires more energy than can be met by crabs in their food-limited state, physiological performance may be compromised

Physiological responses to shifts in multiple environmental stressors: relevance in a changing world.

Population response to global change will depend on responses to a multivariate set of changes in abiotic habitat characteristics and biotic interactions. Organismal biologists seeking to make ecological inferences about the impacts of global change by studying physiological performance have traditionally performed carefully controlled experimental studies that examine one variable at a time. Those studies, while of high value, may not lead to accurate predictions of organismal responses in the natural habitat, where organisms experience concomitant changes in multiple environmental factors. The symposium "Physiological Responses to Simultaneous Shifts in Multiple Environmental Stressors: Relevance in a Changing World" focused on physiological studies in which multiple environmental variables were simultaneously examined and brought together an international group of early-career and established speakers with unique perspectives on studies of multistressors. In doing so, the objective of the symposium was to frame the necessary next steps for increasing predictive capacity of organismal responses to environmental shifts in the natural habitat, establish novel collaborations among researchers actively investigating physiological responses to a multivariate environment, and broaden the number of researchers conducting such studies