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European sea bass (Dicentrarchus labrax) is a large, economically important fish species with a long generation time whose long-term resilience to ocean acidification (OA) and warming (OW) is not clear. We incubated sea bass from Brittany (France) for two generations (>5 yearsin total) under ambient and predicted OA conditions (P CO2: 650 and 1700 µatm) crossed with ambient and predicted OW conditions in F1 (temperature: 15–18°C and 20–23°C) to investigate the effects of climate change on larval and juvenile growth and metabolic rate. We found that in F1, OA as a single stressor at ambient temperature did not affect larval or juvenile growth and OW increased developmental time and growth rate, but OAW decreased larval size at metamorphosis. Larval routine and juvenile standard metabolic rate were significantly lower in cold compared with warm conditioned fish and also lower in F0 compared with F1 fish. We did not find any effect of OA as a single stressor on metabolic rate. Juvenile PO2,crit was not affected by OA or OAW in both generations. We discuss the potential underlying mechanisms resulting in the resilience of F0 and F1 larvae and juveniles to OA and in the beneficial effects of OW on F1 larval growth and metabolic rate, but contrastingly in the vulnerability of F1, but not F0 larvae to OAW. With regard to the ecological perspective, we conclude that recruitment of larvae and early juveniles to nursery areas might decrease under OAW conditions but individuals reaching juvenile phase might benefit from increased performance at higher temperatures.

Repeatability of behavioural and physiological traits is increasingly a focus for animal researchers, for which fish have become important models. Almost all of this work has been done in the context of evolutionary ecology, with few explicit attempts to apply repeatability and context dependency of trait variation toward understanding conservation-related issues. Here, we review work examining the degree to which repeatability of traits (such as boldness, swimming performance, metabolic rate and stress responsiveness) is context dependent. We review methods for quantifying repeatability (distinguishing between within-context and across-context repeatability) and confounding factors that may be especially problematic when attempting to measure repeatability in wild fish. Environmental factors such temperature, food availability, oxygen availability, hypercapnia, flow regime and pollutants all appear to alter trait repeat

The state of the art of research on the environmental physiology of marine fishes is reviewed from the perspective of how it can contribute to conservation of biodiversity and fishery resources. A major constraint to application of physiological knowledge for conservation of marine fishes is the limited knowledge base; international collaboration is needed to study the environmental physiology of a wider range of species. Multifactorial field and laboratory studies on biomarkers hold promise to relate ecophysiology directly to habitat quality and population status. The ‘Fry paradigm’ could have broad applications for conservation physiology research if it provides a universal mechanism to link physiological function with ecological performance and population dynamics of fishes, through effects of abiotic conditions on aerobic metabolic scope. The available data indicate, however, that the paradigm is not universal, so further research is required on a wide diversity of species. Fish physiologists should interact closely with researchers developing ecological models, in order to investigate how integrating physiological information improves confidence in projecting effects of global change; for example, with mechanistic models that define habitat suitability based upon potential for aerobic scope or outputs of a dynamic energy budget. One major challenge to upscaling from physiology of individuals to the level of species and communities is incorporating intraspecific variation, which could be a crucial component of species’ resilience to global change. Understanding what fishes do in the wild is also a challenge, but techniques of biotelemetry and biologging are providing novel information towards effective conservation. Overall, fish physiologists must strive to render research outputs more applicable to management and decision-making. There are various potential avenues for information flow, in the shorter term directly through biomarker studies and in the longer t

Studies of inter-individual variation in hypoxia tolerance and fish swimming performance may provide insight into how selection has influenced diversity in phenotypic traits that may be important for responding to climate change. We investigated individual variation and short-term repeatability of individual hypoxia tolerance and its relationship to swimming performance in European sea bass measured with a constant acceleration test (CAT). We measured maximum anaerobic speed at exhaustion (UCAT), gait transition speed from steady aerobic to unsteady anaerobic swimming (Ugt), routine metabolic rate (RMR), post-CAT maximum metabolic rate (MMR) and aerobic scope. Fish were subsequently released into artificial estuaries for five months at densities that ensured competition for natural forage. Individual variation in UCAT could be accounted for almost exclusively by variation in anaerobic burst-and-coast performance beyond Ugt. The Ugt itself varied substantially between individuals. Individual RMR and MMR varied considerably, but the rank order of metabolic rates was repeatable and inversely related to hypoxia tolerance. Survival in the estuaries was 40% and the relationship between mortality selection, hypoxia tolerance, metabolic rates and swimming performances will be discussed.

The efficiency and adaptive plasticity of mitochondrial metabolism is one of the key factors shaping organismal tolerance towards environmental change.We thus investigated the adaptive capacities of mitochondrial metabolism in Antarctic & Austral notothenioids (Nothothenia rossii, N. coriiceps & N. angustata) and temperate Sea Bass (Dicentrarchus labrax) with respect to some important factors that will influence the survival of marine life in the near future: global warming (elevated sea temperatures), ocean acidification (elevated CO2 levels) and hypoxia tolerance.We namely analysed the function and contribution of the single respiratory complexes to total mitochondrial metabolism, as well as membrane potential and proton leak. In all experiments, mitochondrial measurements were made under acute thermal challenges, compairing liver and heart mitochondria from either differently acclimated individuals (thermal acclimation, CO2 acclimation the combination thereof) or from individuals selected for a specific phenotypic trait (hypoxia tolerance in D. labrax).The implications of mitochondrial plasticity for long-term adaptation in a changing marine environment will be discussed.

Acidification of ocean surface waters by anthropogenic carbon dioxide (CO2) emissions is a currently developing scenario that warrants a broadening of research foci in the study of acid–base physiology. Recent studies working with environmentally relevant CO2 levels, indicate that some echinoderms and molluscs reduce metabolic rates, soft tissue growth and calcification during hypercapnic exposure. In contrast to all prior invertebrate species studied so far, growth trials with the cuttlefish Sepia officinalis found no indication of reduced growth or calcification performance during long-term exposure to 0.6 kPa CO2. It is hypothesized that the differing sensitivities to elevated seawater pCO2 could be explained by taxa specific differences in acid–base regulatory capacity. In this study, we examined the acid–base regulatory ability of S. officinalis in vivo, using a specially modified cannulation technique as well as 31P NMR spectroscopy. During acute exposure to 0.6 kPa CO2, S. officinalis rapidly increased its blood [HCO3 −] to 10.4 mM through active ion-transport processes, and partially compensated the hypercapnia induced respiratory acidosis. A minor decrease in intracellular pH (pHi) and stable intracellular phosphagen levels indicated efficient pHi regulation. We conclude that S. officinalis is not only an efficient acid–base regulator, but is also able to do so without disturbing metabolic equilibria in characteristic tissues or compromising aerobic capacities. The cuttlefish did not exhibit acute intolerance to hypercapnia that has been hypothesized for more active cephalopod species (squid). Even though blood pH (pHe) remained 0.18 pH units below control values, arterial O2 saturation was not compromised in S. officinalis because of the comparatively lower pH sensitivity of oxygen binding to its blood pigment. This raises questions concerning the potentially broad range of sensitivity to changes in acid–base status amongst invertebrates, as well as to the

Cephalopods are the largest, most active invertebrates and there is considerable evidence for their convergent evolution with fishes. However, most active cephalopods display standard and active metabolic rates that are several-fold higher than comparably sized fishes. Shifting habitat temperatures due to climate change will therefore affect a cephalopods energy metabolism much more than that of a fish. Prediction of the probable outcome of cephalopod-fish competition thus requires quantitative information concerning whole animal energetics and corresponding efficiencies. Migrating cephalopods such as squid and cuttlefish grow rapidly to maturity, carry few food reserves and have little overlap of generations. This "live fast, die young" life history strategy means that they require niches capable of sustaining high power requirements and rapid growth. This presentation aims to draw a bottom-up picture of the cellular basis of energy metabolism of the cuttlefish Sepia officinalis, from its molecular basis to whole animal energetics based on laboratory experiments and field data. We assessed the proportionality of standard vs active metabolic rate and the daily energetic requirements using field tracking data in combination with lab based respirometry and video analysis. Effects of environmental temperature on mitochondrial energy coupling were investigated in whole animals using in vivo 31P-NMR spectroscopy. As efficient energy turnover needs sufficient oxygen supply, also thermal effects on the blood oxygen-binding capacities of the respiratory pigment haemocyanin and the differential expression of its isoforms were investigated.Supported by NERC grant NERC/A/S/2002/00812.

Cephalopods are the largest, most active invertebrates and there is considerable evidence for their convergent evolution with fishes. However, most active cephalopods display standard and active metabolic rates that are several-fold higher than comparably sized fishes. Shifting habitat temperatures due to climate change will therefore affect a cephalopods energy metabolism much more than that of a fish. Prediction of the probable outcome of cephalopod-fish competition thus requires quantitative information concerning whole animal energetics and corresponding efficiencies. Migrating cephalopods such as squid and cuttlefish grow rapidly to maturity, carry few food reserves and have little overlap of generations. This "live fast, die young" life history strategy means that they require niches capable of sustaining high power requirements and rapid growth. This presentation aims to draw a bottom-up picture of the cellular basis of energy metabolism of the cuttlefish Sepia officinalis, from its molecular basis to whole animal energetics based on laboratory experiments and field data. We assessed the proportionality of standard vs active metabolic rate and the daily energetic requirements using field tracking data in combination with lab based respirometry and video analysis. Effects of environmental temperature on mitochondrial energy coupling were investigated in whole animals using in vivo 31P-NMR spectroscopy. As efficient energy turnover needs sufficient oxygen supply, also thermal effects on the blood oxygen-binding capacities of the respiratory pigment haemocyanin and the differential expression of its isoforms were investigated.Supported by NERC grant NERC/A/S/2002/00812.

In trout and salmon, the metabolic costs of exercise and feeding are additive, which would suggest that gastrointestinal blood flow during exercise is maintained to preserve digestive and absorptive processes related to the specific dynamic action (SDA) of food. However, in most published studies, gastrointestinal blood flow drops during swimming, hypoxia, and general stress. To test whether gastrointestinal blood flow is spared during exercise after feeding, sea bass were instrumented with flow probes to measure cardiac output and celiacomesenteric blood flow while swimming in a respirometer before and after feeding. Swimming at 2 body lengths per second (bl s-1) increased metabolic rate considerably more than did feeding (208% vs. 32% increase, respectively, relative to resting), and a similar pattern was observed for cardiac output. In unfed fish, resting gastrointestinal blood flow was mL 13.8 ± 0.5 min-1 kg-1. After feeding, resting gastrointestinal blood flow increased by 82% but then decreased progressively with increasing swimming speeds. At 2 bl s-1, gastrointestinal blood flow in fed fish was not significantly different compared with that in unfed swimming fish, and, therefore, the data do not support the gastrointestinal sparing hypothesis. The magnitude of the SDA was maintained despite the decrease in gastrointestinal blood flow and the consequent reduction in oxygen supply to the gut. An estimate of maximal oxygen flow to the gastrointestinal tract after feeding yielded 2.6 mmol O2 h-1 kg-1, but this amount is not able to cover the oxygen demand of 3.16 mmol O2 h -1 kg-1. Therefore, the SDA must reflect metabolic processes in tissues other than those directly perfused by the celiacomesenteric artery. © 2008 by The University of Chicago. All rights reserved.

Cuttlefish (Sepia officinalis) display diurnal changes in activity levels that are linked to the gas loading of the cuttlebone, which regulates buoyancy (Denton and Gilpin-Brown, 1961).To investigate diurnal changes of standard and active metabolic rates, we analysed activity patterns of S. officinalis using new techniques of video tracking. We monitored S. officinalis activity by video continuously for 5 days. In a parallel experiment we measured their rates of oxygen consumption in order to explore whether metabolic rate changes in parallel with activity levels. Both measurements of activity and oxygen consumption indicate a strong diurnal pattern with a maximum physical activity shortly after midnight and a relatively constant minimum value during daytime.In order to determine whether patterns of metabolic regulation go hand in hand with the diurnal rhythm of activity-dependent metabolic slowing (daytime) and stimulation (nighttime), we analysed the activities of enzymes involved in standard and digestive metabolism in mantle and hepatopancreas tissues to complete the picture. Moreover, we could show that different feeding schemes strongly affect the distinctiveness of the diurnal activity pattern.Supported by NERC grant NERC/A/S/2002/00812.

Denton and Gilpin-Brown hypothesized in 1961 that the cuttlefish Sepia officinalis displays diurnal changes in activity levels. We therefore analysed activity patterns of S. officinalis using new techniques of video recordings and analysis. We monitored S. officinalis activity by video continuously for 5 days. In a parallel experiment we measured their rates of oxygen consumption in order to see whether metabolic rate changes in parallel with activity levels. Preliminary tests support the original hypothesis of a diurnal pattern. Measurements of oxygen consumption indicate maximum physical activity between 0 and 3 am and a relatively constant minimum value during daytime. Enzyme activities are currently being analysed in mantle and hepatopancreas tissues in order to determine whether patterns of metabolic regulation go hand in hand with the diurnal rhythm of activity dependent metabolic slowing (daytime) and stimulation (nighttime).Supported by NERC grant NERC/A/S/2002/00812.