Search

The ecophysiology of marine ectotherms is regulated by the interaction of temperature with environmental drivers, such as dissolved oxygen (DO). The combination of low levels of DO and temperature in the ocean affects physiological and behavioral responses, especially in early life history traits of marine species. Here, we aimed to investigate the combined effect of ecologically relevant values of temperature and DO on female brooding behavior as well as on the early ontogeny of the Chilean kelp crabTaliepus dentatus. In a laboratory experiment, after acclimation and mating of females and males in constant temperatures (11 or 14°C), we exposed brooding females to 1 of 2 temperatures (11 or 14°C) and 1 of 2 DO levels (normoxia or cycling hypoxia). We tested the effects of these 4 treatments on embryo and larval sizes, embryo developmental time, female brooding behavior (i.e. embryo ventilation), larval hatching (i.e. number of hatched larvae), Zoea 1 survival to starvation, and swimming speed. We found a negative effect of temperature on the size of early embryos, but no interactions were detected in embryo size during development. High temperature and low DO increased female brooding behavior and larval size, reduced the number of hatched larvae, and affected larval swimming speed. Embryo development time and larval survival were negatively affected by temperature. These results suggest that an increasing frequency of hypoxic events, combined with ocean warming, might have important consequences on marine invertebrate brooders, affecting female fecundity, larval performance and, potentially, their dispersal ability even well within their optimal thermal range.

Mitochondrial respiration is a multi-step pathway that involves matrix and membrane-associated enzymes and plays a key role in acclimation to variable environmental conditions, but until now it has not been clear which of these steps would be most important in acclimation to changing temperatures and CO2 levels. Considering scenarios of ocean warming and acidification we assessed the role and limitation to phenotypic plasticity in the hearts of two Gadoid species adapted to different thermal ranges: the polar cod (Boreogadus saida), an Arctic stenotherm, and the Northeast Arctic population of Atlantic cod (NEAC, Gadus morhua), a cold eurytherm. We analysed the capacity of single enzymes involved in mitochondrial respiration [citrate synthase (CS), succinate dehydrogenase (SDH), cytochrome c oxidase (CCO)], the capacity of the electron transport system and the lipid class composition of the cellular membranes. Juveniles of the two species were held for four months at four temperatures (0, 3, 6, 8 °C for polar cod and 3, 8, 12, 16 °C for NEAC), at both ambient and elevated $$P_{{{\text{CO}}_{2} }}$$ (400 µatm and 1170 µatm, respectively). Polar cod showed no changes in mitochondrial enzyme capacities and in the relative lipid class composition in response to altered temperature or elevated $$P_{{{\text{CO}}_{2} }} .$$ The lack of cardiac cellular plasticity together with evidence at the whole-animal level coming from other studies is indicative of little or no ability to overcome stenothermy, in particular during acclimation to 8 °C. In contrast, eurythermal NEAC exhibited modifications of membrane composition towards a more rigid structure and altered enzyme capacities to preserve functionality at higher temperatures. Furthermore, in NEAC, the capacities of SDH, CCO and CS were increased by high levels of CO2 if combined with high temperatures (12 and 16 °C), suggesting the compensation of an inhibitory effect. These results indicate that the cold eurythermal species (NEAC) is able to alter its mitochondrial function to a far greater extent than the Arctic stenotherm (polar cod), indicating greater resilience to variable environmental conditions. This difference in plasticity may underpin differences in the resilience to climate change and affect future species distributions and, eventually, survival.

Impacts of global warming and CO

Ocean acidification induces strong behavioural alterations in marine fish as a conse- quence of acid−base regulatory processes in response to increasing environmental CO2 partial pressure. While these changes have been investigated in tropical and temperate fish species, nothing is known about behavioural effects on polar species. In particular, fishes of the Arctic Ocean will experience much greater acidification and warming than temperate or tropical species. Also, possible interactions of ocean warming and acidification are still understudied. Here we analysed the combined effects of warming and acidification on behavioural patterns of 2 fish species co-occurring around Svalbard, viz. polar cod Boreogadus saida and Atlantic cod Gadus morhua. We found a significant temperature effect on the spontaneous activity of B. saida, but not of G. morhua. Environmental CO2 did not significantly influence activity of either species. In con- trast, behavioural laterality of B. saida was affected by CO2 but not by temperature. Behavioural laterality of G. morhua was not affected by temperature or CO2; however, in this species, a possi- ble temperature dependency of CO2 effects on relative laterality may have been missed due to sample size restrictions. This study indicates that fish in polar ecosystems may undergo some, albeit less intense, behavioural disturbances under ocean acidification and in combination with ocean warming than observed in tropical species. It further accentuates species-specific differ- ences in vulnerability.

Ocean acidification (OA) and hypoxic events are increasing worldwide problems, their interactive effects have not been well clarified, although their co-occurrence is prevalent. The East China Sea (the Yangtze River estuary area) suffers from not only coastal hypoxia but also pH fluctuation, representing an ideal study site to explore the combined effect of OA and hypoxia on marine bivalves. We experimentally evaluated the antioxidant response of the mussel Mytilus coruscus exposed to three pH levels (8.1, 7.7 and 7.3) at two dissolved oxygen (DO) levels (2.0mgL-1 and 6.0mgL-1) for 72h. Activities of superoxide dismutase, catalase, glutathione peroxidase, acid phosphatase, and alkaline phosphatase and levels of malondialdehyde were measured in gills and hemolymph. All enzymatic activities in hemolymph and gills followed a similar pattern throughout the experiment duration. Generally, low DO showed greater effects on enzyme activities than elevated CO2. Significant interactions between DO, pH and time were only observed at superoxide dismutase and catalase in both tissues. PCA revealed positive relationships between most enzyme activities in both gills and hemolymph with the exception of alkaline phosphatase activity and the level of malondialdehyde in the hemolymph. Overall, our results suggested that decreased pH and low DO induced similar antioxidant responses in the hard shelled mussel, and showed an additive effect on most enzyme activities. The evaluation of multiple environmental stressors, a more realistic scenario than single ones, is crucial to predict the effect of future global changes on coastal species and our results supply some insights on the potential combined effects of reduced pH and DO on marine bivalves.

The vulnerability of fish embryos and larvae to environmental factors is often attributed to a lack of adult-like organ systems (gills) and thus insufficient homeostatic capacity. However, experimental data supporting this hypothesis are scarce. Here, by using Atlantic cod (Gadus morhua) as a model, the relationship between embryo vulnerability (to projected ocean acidification and warming) and homeostatic capacity was explored through parallel analyses of stage-specific mortality and in vitro activity and expression of major ion pumps (ATP-Synthase, Na+/K+-ATPase, H+-ATPase) and co-transporters (NBC1, NKCC1). Immunolocalization of these transporters was used to study ionocyte morphology in newly-hatched larvae. Treatment-related embryo mortality until hatch (+20% due to acidification and warming) occurred primarily during an early period (gastrulation) characterized by extremely low ion transport capacities. Thereafter, embryo mortality decreased in parallel with an exponential increase in activity and expression of all investigated ion transporters. Significant changes in transporter activity and expression in response to acidification (+15% activity) and warming (-30% expression) indicate some potential for short-term acclimatization, although likely associated with energetic trade-offs. Interestingly, whole-larvae enzyme capacities (supported by abundant epidermal ionocytes) reached levels similar to those previously measured in gill tissue of adult cod, suggesting that early-life stages without functional gills are better equipped in terms of ion homeostasis than previously thought. This study implies that the gastrulation period represents a critical transition from inherited (maternal) defenses to active homeostatic regulation, which facilitates enhanced resilience of later stages to environmental factors.

Source: doi: 10.1016/j.envpol.2016.07.044 Increasing anthropogenic activities in the Arctic represent an enhanced threat for oil pollution in a marine environment that is already at risk from climate warming. In particular, this applies to species with free-living pelagic larvae that aggregate in surface waters and under the sea ice where hydrocarbons are likely to remain for extended periods of time due to low temperatures. We exposed the positively buoyant eggs of polar cod (Boreogadus saida), an arctic keystone species, to realistic concentrations of a crude oil water-soluble fraction (WSF), mimicking exposure of eggs aggregating under the ice to oil WSF leaking from brine channels following encapsulation in ice. Total hydrocarbon and polycyclic aromatic hydrocarbon levels were in the ng/L range, with most exposure concentrations below the limits of detection throughout the experiment for all treatments. The proportion of viable, free-swimming larvae decreased significantly with dose and showed increases in the incidence and severity of spine curvature, yolk sac alterations and a reduction in spine length. These effects are expected to compromise the motility, feeding capacity, and predator avoidance during critical early life stages for this important species. Our results imply that the viability and fitness of polar cod early life stages is significantly reduced when exposed to extremely low and environmentally realistic levels of aqueous hydrocarbons, which may have important implications for arctic food web dynamics and ecosystem functioning.

Atlantic herring (

Maternal investment (MI), the energy allocated by mothers to offspring, has important effects on the life-history traits of marine organisms. Variation in such traits shows strong correlation with latitude for several marine taxa (Thorson’s rule). Large-scale latitudinal variation in MI within a single species suggests population genetic divergence, while temporal changes in MI, rather, reflect plasticity. At higher latitudes (i.e., colder waters), traits associated with MI (brood weight, fecundity, egg volume, and energy content) increase. To identify phenotypic plasticity along a latitudinal gradient in MI traits (brood weight, egg volume, density number, and egg lipid composition), five populations of the kelp crab Taliepus dentatus along the coast of Chile (30°S–42°S) were investigated during the summer (December–February) and winter months (June–August) of 2015–2016. Despite this wide latitudinal range, the sea surface temperature (SST) difference between the northernmost and the southernmost sites was only approximately 2.0 °C in winter and 5.5 °C in summer. In summer, when latitudinal variation in SST was highest, brood weight, egg density, fecundity, and egg lipids increased with latitude, while egg volume decreased. No trends in MI were observed in winter when the SST gradient was almost non-existent. These results suggest that the relationship between MI and latitude is shaped by temperature rather than being site-specific. The seasonality of latitudinal MI traits also suggests a trade-off between the costs of female maintenance and/or brooding behaviours and MI. When investigating latitudinal and temporal variation in marine brooder MI, the effect of temperature on life-history traits and the associated costs of female brooding should be quantified.

Atlantic herring (Clupea harengus) is a benthic spawner, therefore its eggs are prone to encounter different water conditions during embryonic development, with bottom waters often depleted of oxygen and enriched in CO2. Some Atlantic herring spawning grounds are predicted to be highly affected by ongoing Ocean Acidification and Warming with water temperature increasing by up to +3°C and CO2 levels reaching ca. 1000 μatm (RCP 8.5). Although many studies investigated the effects of high levels of CO2 on the embryonic development of Atlantic herring, little is known about the combination of temperature and ecologically relevant levels of CO2. In this study, we investigated the effects of Ocean Acidification and Warming on embryonic metabolic and developmental performance such as mitochondrial function, respiration, hatching success (HS) and growth in Atlantic herring from the Oslo Fjord, one of the spawning grounds predicted to be greatly affected by climate change. Fertilized eggs were incubated under combinations of two PCO2 conditions (400 μatm and 1100 μatm) and three temperatures (6, 10 and 14°C), which correspond to current and end-of-the-century conditions. We analysed HS, oxygen consumption (MO2) and mitochondrial function of embryos as well as larval length at hatch. The capacity of the electron transport system (ETS) increased with temperature, reaching a plateau at 14°C, where the contribution of Complex I to the ETS declined in favour of Complex II. This relative shift was coupled with a dramatic increase in MO2 at 14°C. HS was high under ambient spawning conditions (6–10°C), but decreased at 14°C and hatched larvae at this temperature were smaller. Elevated PCO2 increased larval malformations, indicating sub-lethal effects. These results indicate that energetic limitations due to thermally affected mitochondria and higher energy demand for maintenance occur at the expense of embryonic development and growth.

Acidification narrows thermal ranges of Arctic fish embryos and thereby constraints reproductive opportunities in a warming ocean., Rapid climate change in the Northeast Atlantic and Arctic poses a threat to some of the world’s largest fish populations. Impacts of warming and acidification may become accessible through mechanism-based risk assessments and projections of future habitat suitability. We show that ocean acidification causes a narrowing of embryonic thermal ranges, which identifies the suitability of spawning habitats as a critical life-history bottleneck for two abundant cod species. Embryonic tolerance ranges linked to climate simulations reveal that ever-increasing CO2 emissions [Representative Concentration Pathway (RCP) 8.5] will deteriorate suitability of present spawning habitat for both Atlantic cod (Gadus morhua) and Polar cod (Boreogadus saida) by 2100. Moderate warming (RCP4.5) may avert dangerous climate impacts on Atlantic cod but still leaves few spawning areas for the more vulnerable Polar cod, which also loses the benefits of an ice-covered ocean. Emissions following RCP2.6, however, support largely unchanged habitat suitability for both species, suggesting that risks are minimized if warming is held “below 2°C, if not 1.5°C,” as pledged by the Paris Agreement.

Thermal tolerance windows serve as a powerful tool for estimating the vulnerability of marine species and their life stages to increasing temperature means and extremes. However, it remains uncertain to which extent additional drivers, such as ocean acidification, modify organismal responses to temperature. This study investigated the effects of CO2 -driven ocean acidification on embryonic thermal sensitivity and performance in Atlantic cod, Gadus morhua, from the Kattegat. Fertilized eggs were exposed to factorial combinations of two PCO2 conditions (400 μatm vs. 1100 μatm) and five temperature treatments (0, 3, 6, 9 and 12 °C), which allow identifying both lower and upper thermal tolerance thresholds. We quantified hatching success, oxygen consumption (MO2 ) and mitochondrial functioning of embryos as well as larval morphometrics at hatch and the abundance of acid-base-relevant ionocytes on the yolk sac epithelium of newly hatched larvae. Hatching success was high under ambient spawning conditions (3-6 °C), but decreased towards both cold and warm temperature extremes. Elevated PCO2 caused a significant decrease in hatching success, particularly at cold (3 and 0 °C) and warm (12 °C) temperatures. Warming imposed limitations to MO2 and mitochondrial capacities. Elevated PCO2 stimulated MO2 at cold and intermediate temperatures, but exacerbated warming-induced constraints on MO2 , indicating a synergistic interaction with temperature. Mitochondrial functioning was not affected by PCO2 . Increased MO2 in response to elevated PCO2 was paralleled by reduced larval size at hatch. Finally, ionocyte abundance decreased with increasing temperature, but did not differ between PCO2 treatments. Our results demonstrate increased thermal sensitivity of cod embryos under future PCO2 conditions and suggest that acclimation to elevated PCO2 requires reallocation of limited resources at the expense of embryonic growth. We conclude that ocean acidification constrains the thermal performance window of embryos, which has important implication for the susceptibility of cod to projected climate change.

Marine brachyuran and anomuran crustaceans are completely absent from the extremely cold (− 1.8 °C) Antarctic continental shelf, but caridean shrimps are abundant. This has at least partly been attributed to low capacities for magnesium excretion in brachyuran and anomuran lithodid crabs ([Mg2+]HL = 20–50 mmol L− 1) compared to caridean shrimp species ([Mg2+]HL = 5–12 mmol L− 1). Magnesium has an anaesthetizing effect and reduces cold tolerance and activity of adult brachyuran crabs. We investigated whether the capacity for magnesium regulation is a factor that influences temperature-dependent activity of early ontogenetic stages of the Sub-Antarctic lithodid crab Paralomis granulosa. Ion composition (Na+, Mg2+, Ca2+, Cl−, SO42−) was measured in haemolymph withdrawn from larval stages, the first and second juvenile instars (crabs I and II) and adult males and females. Magnesium excretion improved during ontogeny, but haemolymph sulphate concentration was lowest in the zoeal stages. Neither haemolymph magnesium concentrations nor Ca2+:Mg2+ ratios paralleled activity levels of the life stages. Long-term (3 week) cold exposure of crab I to 1 °C caused a significant rise of haemolymph sulphate concentration and a decrease in magnesium and calcium concentrations compared to control temperature (9 °C). Spontaneous swimming activity of the zoeal stages was determined at 1, 4 and 9 °C in natural sea water (NSW, [Mg2+] = 51 mmol L− 1) and in sea water enriched with magnesium (NSW + Mg2+, [Mg2+] = 97 mmol L− 1). It declined significantly with temperature but only insignificantly with increased magnesium concentration. Spontaneous velocities were low, reflecting the demersal life style of the zoeae. Heart rate, scaphognathite beat rate and forced swimming activity (maxilliped beat rate, zoea I) or antennule beat rate (crab I) were investigated in response to acute temperature change (9, 6, 3, 1, − 1 °C) in NSW or NSW + Mg2+. High magnesium concentration reduced heart rates in both stages. The temperature–frequency curve of the maxilliped beat (maximum: 9.6 beats s− 1 at 6.6 °C in NSW) of zoea I was depressed and shifted towards warmer temperatures by 2 °C in NSW + Mg2+, but antennule beat rate of crab I was not affected. Magnesium may therefore influence cold tolerance of highly active larvae, but it remains questionable whether the slow-moving lithodid crabs with demersal larvae would benefit from an enhanced magnesium excretion in nature.

Hypoxia and ocean acidification are two consequences of anthropogenic activities. These global trends occur on top of natural variability. In environments such as estuarine areas, short-term acute pH and O2 fluctuations are occurring simultaneously. The present study tested the combined effects of short-term seawater acidification and hypoxia on the physiology and energy budget of the thick shell mussel Mytilus coruscus. Mussels were exposed for 72 h to six combined treatments with three pH levels (8.1, 7.7 and 7.3) and two dissolved oxygen (DO) levels (2 mg L−1, 6 mg L−1). Clearance rate (CR), food absorption efficiency (AE), respiration rate (RR), ammonium excretion rate (ER), O:N ratio and scope for growth (SFG) were significantly reduced, and faecal organic dry weight ratio (E) was significantly increased at low DO. Low pH did not lead to a reduced SFG. Interactive effects of pH and DO were observed for CR, E and RR. Principal component analysis (PCA) revealed positive relationships among most physiological indicators, especially between SFG and CR under normal DO conditions. These results demonstrate that Mytilus coruscus was sensitive to short-term (72 h) exposure to decreased O2 especially if combined with decreased pH levels. In conclusion, the short-term oxygen and pH variation significantly induced physiological changes of mussels with some interactive effects.

Capacities and effects of cold or warm acclimation were investigated in two zoarcid species from the North Sea (Zoarces viviparus) and the Antarctic (Pachycara brachycephalum) by investigating temperature dependent mitochondrial respiration and activities of citrate synthase (CS) and NADP+ -dependent isocitrate dehydrogenase (IDH) in the liver. Antarctic eelpout were acclimated to 5°C and 0°C (controls) for at least 10 months, whereas boreal eelpout, Z. viviparus (North Sea) were acclimated to 5°C and to 10°C (controls). Liver sizes were found to be increased in both species in the cold, with a concomitant rise in liver mitochondrial protein content. As a result, total liver state III rates were elevated in both cold-versus and warm-exposed P. brachycephalum and Z. viviparus, with the highest rates in boreal eelpout acclimated to 5°C. CS and IDH activities in the total liver were similar in Z. viviparus acclimated to 5°C and 10°C, but decreased in those warm acclimated versus control P. brachycephalum. Enzyme capacities in the total liver were higher in eelpout from Antarctica than those from the North Sea. In conclusion, cold compensation of aerobic capacities in the liver seems to be linked to an increase in organ size with unchanged specific mitochondrial protein content. Despite its life in permanently cold climate, P. brachycephalum was able to reduce liver aerobic capacities in warm climate and thus, displayed a capacity for temperature acclimation.

Population dynamics of the queen scallop, Aequipecten opercularis, was investigated in the western English Channel off Roscoff. Annual formation of natural growth rings on the shell surface was validated by stable isotope (y 18 O and y 13 C) analysis. A von Bertalanffy growth function (Ht = 58.9 mm . (1� e � 0.604 .(t + 0.235) )) was fitted to size-at-age data of 249 individuals. Annual somatic and gonad production amounted to 19.74 kJ m � 2 and 0.98 kJ m � 2 y � 1 , respectively. Total mortality rate Z was estimated to be 1.716 y � 1 . Net growth efficiencies (ranging from 45% in 1-y-old to 11% in 6-y-old individuals) were in the same range as in other short-lived scallops. Individual growth, however, was distinctly slower in this population than in other A. opercularis populations from similar latitudes, most likely due to a more stressful environment. D 2004 Elsevier B.V. All rights reserved.

Translationally active cell-free systems from gills of the Antarctic scallop Adamussium colbecki and the European scallop Aequipecten opercularis were developed, characterised, and optimised for an analysis of translational capacity. The aim was to determine the energetic cost of protein synthesis in the in vitro cell-free system by directly measuring the required energy equivalents in the lysates. Protein synthesis rate in assays conducted with lysates of A. colbecki (1.029+/-0.061 micromol Phe min(-1) at 15 degrees C; Phe=phenylalanine) were higher compared with lysates of A. opercularis (0.087+/-0.013 micromol Phe min(-1) at 15 degrees C and 0.156+/-0.023 micromol Phe min(-1) at 25 degrees C). This can in part be attributed to the naturally occurring higher RNA content in lysates of A. colbecki (0.883+/-0.037 mg RNA mL(-1) lysate) compared with A. opercularis (0.468+/-0.013 mg RNA mL(-1) lysate). There was no significant difference in the energetic costs of protein synthesis in cell-free systems of gill lysates of the cold stenothermal A. colbecki with 4.3+/-0.7 energy equivalents per peptide bond formed and the eurythermal A. opercularis with 5.6+/-0.6 energy equivalents, indicating that there are no differences in the efficiency of the translation machinery. The energetic costs specified for protein synthesis correspond with the generally accepted theoretical value of four energy equivalents per peptide bond formed, especially in gill lysates of A. colbecki, whereas the value for gill lysates of A. opercularis was slightly higher.

Introduction Exposure to elevated seawater PCO2 limits the thermal tolerance of crustaceans but the underlying mechanisms have not been comprehensively explored. Larval stages of crustaceans are even more sensitive to environmental hypercapnia and possess narrower thermal windows than adults. Results In a mechanistic approach, we analysed the impact of high seawater CO2 on parameters at different levels of biological organization, from the molecular to the whole animal level. At the whole animal level we measured oxygen consumption, heart rate and activity during acute warming in zoea and megalopa larvae of the spider crab Hyas araneus exposed to different levels of seawater PCO2. Furthermore, the expression of genes responsible for acid–base regulation and mitochondrial energy metabolism, and cellular responses to thermal stress (e.g. the heat shock response) was analysed before and after larvae were heat shocked by rapidly raising the seawater temperature from 10°C rearing temperature to 20°C. Zoea larvae showed a high heat tolerance, which decreased at elevated seawater PCO2, while the already low heat tolerance of megalopa larvae was not limited further by hypercapnic exposure. There was a combined effect of elevated seawater CO2 and heat shock in zoea larvae causing elevated transcript levels of heat shock proteins. In all three larval stages, hypercapnic exposure elicited an up-regulation of genes involved in oxidative phosphorylation, which was, however, not accompanied by increased energetic demands. Conclusion The combined effect of seawater CO2 and heat shock on the gene expression of heat shock proteins reflects the downward shift in thermal limits seen on the whole animal level and indicates an associated capacity to elicit passive thermal tolerance. The up-regulation of genes involved in oxidative phosphorylation might compensate for enzyme activities being lowered through bicarbonate inhibition and maintain larval standard metabolic rates at high seawater CO2 levels. The present study underlines the necessity to align transcriptomic data with physiological responses when addressing mechanisms affected by an interaction of elevated seawater PCO2 and temperature extremes. Electronic supplementary material The online version of this article (doi:10.1186/s12983-014-0087-4) contains supplementary material, which is available to authorized users.

The Atlantic cod (Gadus morhua) is an economically important marine fish species exploited by both fishery and aquaculture, especially in the North Atlantic and Arctic oceans. Ongoing climate changes are happening faster in the high latitude oceans with a higher increase of temperature and a steeper decrease in water pH due to anthropogenic CO2 than in the temperate regions threatening the existence of the Atlantic cod in the areas of its maximum exploitation. In this study, we investigated the mitochondrial physiology of two life-stages of cod under the sea water temperatures and pCO2 conditions forecasted for the year 2100 in the North Atlantic (+ 5 °C, 1000 μatm CO2). In embryos, the metabolism during development showed to be sensitive to rising temperatures with a general increase in respiratory activity until 9 °C (5 °C over the natural range) and a drop in activity at 12 °C mainly caused by a dramatic decrease in Complex I activity, which was not compensated by Complex II. In the adults, already well known for their metabolic plasticity, mitochondria from liver and heart are not affected by either increasing temperature or pCO2. However, in heart mitochondria of animals that were reared under warm hypercapnia (10 °C + 1000 μatm CO2), we found OXPHOS to exploit already 100% of the ETS capacity. This suggests that a further increase in temperature or pCO2 might lead to a mismatch in the ATP demand/production and consequently decrease heart performances. The different mitochondrial plasticities of the two life-stages reflect the sensitivity range at population level and thus can provide a more realistic reading frame of the potential survival of the North Atlantic cod population under climate change.

Organisms in all domains, Archaea, Bacteria, and Eukarya will respond to climate change with differential vulnerabilities resulting in shifts in species distribution, coexistence, and interactions. The identification of unifying principles of organism functioning across all domains would facilitate a cause and effect understanding of such changes and their implications for ecosystem shifts. For example, the functional specialization of all organisms in limited temperature ranges leads us to ask for unifying functional reasons. Organisms also specialize in either anoxic or various oxygen ranges, with animals and plants depending on high oxygen levels. Here, we identify thermal ranges, heat limits of growth, and critically low (hypoxic) oxygen concentrations as proxies of tolerance in a meta-analysis of data available for marine organisms, with special reference to domain-specific limits. For an explanation of the patterns and differences observed, we define and quantify a proxy for organismic complexity across species from all domains. Rising complexity causes heat (and hypoxia) tolerances to decrease from Archaea to Bacteria to uni- and then multicellular Eukarya. Within and across domains, taxon-specific tolerance limits likely reflect ultimate evolutionary limits of its species to acclimatization and adaptation. We hypothesize that rising taxon-specific complexities in structure and function constrain organisms to narrower environmental ranges. Low complexity as in Archaea and some Bacteria provide life options in extreme environments. In the warmest oceans, temperature maxima reach and will surpass the permanent limits to the existence of multicellular animals, plants and unicellular phytoplankter. Smaller, less complex unicellular Eukarya, Bacteria, and Archaea will thus benefit and predominate even more in a future, warmer, and hypoxic ocean.

Sensitivity of marine crustaceans to anthropogenic CO2 emissions and the associated acidification of the oceans may be less than that of other, especially lower, invertebrates. However, effects on critical transition phases or carry-over effects between life stages have not comprehensively been explored. Here we report the impact of elevated seawater PCO2 values (3100 µatm) on Hyas araneus during the last 2 weeks of their embryonic development (pre-hatching phase) and during development while in the consecutive zoea I and zoea II larval stages (post-hatching phase). We measured oxygen consumption, dry weight, developmental time and mortality in zoea I to assess changes in performance. Feeding rates and survival under starvation were investigated at different temperatures to detect differences in thermal sensitivities of zoea I and zoea II larvae depending on pre-hatch history. When embryos were pre-exposed to elevated PCO2 during maternal care, mortality increased about 60% under continued CO2 exposure during the zoea I phase. The larvae that moulted into zoea II, displayed a developmental delay by about 20 days compared to larvae exposed to control PCO2 during embryonic and zoeal phases. Elevated PCO2 caused a reduction in zoea I dry weight and feeding rates, while survival of the starved larvae was not affected by the seawater CO2 concentration. In conclusion, CO2 effects on egg masses under maternal care carried over to the first larval stages of crustaceans and reduced their survival and development to levels below those previously reported in studies exclusively focussing on acute PCO2 effects on the larval stages.

Early life stages of marine crustaceans respond sensitively to elevated seawater P CO 2 . However, the underlying physiological mechanisms have not been studied well. We therefore investigated the effects of elevated seawater P CO 2 on oxygen consumption, dry weight, elemental composition, median developmental time (MDT) and mortality in zoea I larvae of the spider crab Hyas araneus (Svalbard 79°N/11°E; collection, May 2009; hatch, December 2009). At the time of moulting, oxygen consumption rate had reached a steady state level under control conditions. In contrast, elevated seawater P CO 2 caused the metabolic rate to rise continuously leading to a maximum 1.5-fold increase beyond control level a few days before moulting into the second stage (zoea II), followed by a pronounced decrease. Dry weight of larvae reared under high CO 2 conditions was lower than in control larvae at the beginning of the moult cycle, yet this difference had disappeared at the time of moulting. MDT of zoea I varied between 45 ± 1 days under control conditions and 42 ± 2 days under the highest seawater CO 2 concentration. The present study indicates that larval development under elevated seawater P CO 2 levels results in higher metabolic costs during premoulting events in zoea I. However, H. araneus zoea I larvae seem to be able to compensate for higher metabolic costs as larval MDT and survival was not affected by elevated P CO 2 level

Research investigating the genetic basis of physiological responses has significantly broadened our understanding of the mechanisms underlying organismic response to environmental change. However, genomic data are currently available for few taxa only, thus excluding physiological model species from this approach. In this study we report the transcriptome of the model organism Hyas araneus from Spitsbergen (Arctic). We generated 20,479 transcripts, using the 454 {GS} {FLX} sequencing technology in combination with an Illumina HiSeq sequencing approach. Annotation by Blastx revealed 7159 blast hits in the {NCBI} non-redundant protein database. The comparison between the spider crab H. araneus transcriptome and {EST} libraries of the European lobster Homarus americanus and the porcelain crab Petrolisthes cinctipes yielded 3229/2581 sequences with a significant hit, respectively. The clustering by the Markov Clustering Algorithm (MCL) revealed a common core of 1710 clusters present in all three species and 5903 unique clusters for H. araneus. The combined sequencing approaches generated transcripts that will greatly expand the limited genomic data available for crustaceans. We introduce the {MCL} clustering for transcriptome comparisons as a simple approach to estimate similarities between transcriptomic libraries of different size and quality and to analyze homologies within the selected group of species. In particular, we identified a large variety of reverse transcriptase (RT) sequences not only in the H. araneus transcriptome and other decapod crustaceans, but also sea urchin, supporting the hypothesis of a heritable, anti-viral immunity and the proposed viral fragment integration by host-derived {RTs} in marine invertebrates.

SUMMARY Studies of thermal tolerance in marine ectotherms are key in understanding climate effects on ecosystems; however, tolerance of their larval stages has rarely been analyzed. Larval stages are expected to be particularly sensitive. Thermal stress may affect their potential for dispersal and zoogeographical distribution. A mismatch between oxygen demand and the limited capacity of oxygen supply to tissues has been hypothesized to be the first mechanism restricting survival at thermal extremes. Therefore, thermal tolerance of stage zoea I larvae was examined in two populations of the Chilean kelp crab Taliepus dentatus, which are separated by latitude and the thermal regime. We measured temperature-dependent activity, oxygen consumption,cardiac performance, body mass and the carbon (C) and nitrogen (N) composition in order to: (1) examine thermal effects from organismal to cellular levels,and (2) compare the thermal tolerance of larvae from two environmental temperature regimes. We found that larval performance is affected at thermal extremes indicated by decreases in activity, mainly in maxilliped beat rates,followed by decreases in oxygen consumption rates. Cardiac stroke volume was almost temperature-independent. Through changes in heart rate, cardiac output supported oxygen demand within the thermal window whereas at low and high temperature extremes heart rate declined. The comparison between southern and central populations suggests the adaptation of southern larvae to a colder temperature regime, with higher cardiac outputs due to increased cardiac stroke volumes, larger body sizes but similar body composition as indicated by similar C:N ratios. This limited but clear differentiation of thermal windows between populations allows the species to widen its biogeographical range.

SUMMARY For an evaluation of effects of seasonal cold acclimation and evolutionary cold adaptation on protein synthesis capacity, the protein synthesis apparatus was isolated from the gills and white muscle of Antarctic eelpout Pachycara brachycephalum and North Sea eelpout Zoarces viviparus. Both species had been acclimated to 0°C (control) and 5°C (Antarctic) and 5°C and 10°C (North Sea control). The translational capacities of the protein synthesis machineries were determined in an optimised cell-free in vitro system. The results demonstrate that tissues from the polar zoarcid possess cold-adapted protein synthesis machineries, indicated by low activation energies and, especially, high RNA translational capacities at similar RNA:protein ratios when compared to temperate zoarcids at 10°C. When both species were brought to 5°C, the temperate species displayed cold compensated protein synthesis capacities caused by elevated RNA:protein ratios. Warm exposure (from 0 to 5°C) of the Antarctic zoarcid revealed a capacity for thermal acclimation indicated by a reduction in protein synthesis capacities associated with lower RNA:protein ratios.

Publisher Summary Marine life in the polar, especially Antarctic, cold is characterized by a low to moderate pace at permanently low temperatures. This chapter discusses the special characteristics of metabolism in the cold by considering their role in tissue and whole‐organism functional adjustments to cold, as well as the environmental forces that cause temperature‐dependent trade‐offs in biochemical and physiological tissue and cellular design. The chapter highlights the knowledge of metabolic biochemistry of polar fishes, including molecular and cellular design and of individual tissue, functioning toward an understanding of the animal, its thermal specialization, and its integration into the ecosystem. The hypothesis of an oxygen‐limited thermal tolerance as a unifying principle in animals is important and is briefly discussed in the chapter.

The translational system was isolated from the gills of the Antarctic scallop Adamussium colbecki (Smith) and the European scallop Aequipecten opercularis (Linnaeus) for in vitro protein synthesis capacities microg protein mg FW(-1) day(-1)) and the translational capacities of RNA (k(RNA in vitro) mg protein mg RNA(-1) day(-1)). In vitro protein synthesis capacity in the cold-adapted pectinid at 0 degrees C was similar to the one found in the temperate scallop at 25 degrees C. These findings might reflect cold compensated rates in Adamussium colbecki, partly explainable by high tissue levels of RNA. Cold-compensated in vitro protein synthesis capacities may further result from increments in the translational capacity of RNA. The thermal sensitivity of the translation machinery was slightly different in the two species, with significantly lower levels of Arrhenius activation energies E(a) and Q(10) in Adamussium colbecki in the temperature range 0-15 degrees C. Reduced protein synthesis and translational capacities were found in vitro in gills of long-term aquarium-maintained Adamussium colbecki and were accounted for by a loss of protein synthesis machinery, i.e. a reduction in RNA levels, as well as a decrease in the amount of protein synthesized per milligram of RNA (RNA translational capacity, k(RNA in vitro)). Such changes may involve food uptake or mirror metabolic depression strategies, like those occurring during winter. Consequences of high in vitro RNA translational capacities found in the permanently cold-adapted species are discussed in the context of seasonal food availability and growth rates at high latitudes.

The effect of hydrogen peroxide on the rate of tissue oxygen consumption, on intracellular pH (pH i ) and on malondialdehyde (MDA) accumulation was studied in isolated body wall tissue of the lugworm Arenicola marina (L.). H 2 O 2 effects were investigated at various levels of pH i by changing medium pH (pH e ). The largest decrease of tissue oxygen consumption (by 17% below controls), as well as the highest degree of MDA accumulation (four-fold compared to control values) after H 2 O 2 exposure were found at acidic pH e of 6.4. This was attributed to the higher redox potential of H 2 O 2 in acidic solutions. Oxygen consumption at alkaline pH e (8.5) was not affected by H 2 O 2 . MDA accumulation in the tissue was considerably lower than at pH e 7.4 or 6.4. Despite pH dependent alterations of H 2 O 2 redox potential, we observed more or less constant pH e independent acidification of the tissue upon exposure to H 2 O 2 . We attributed the acidification to an inhibition of ATP consuming proton equivalent ion transport across the cellular membrane. Inactivation of carrier proteins is discussed to be responsible for the decrease in tissue oxygen consumption. However, with a larger effect on oxygen consumption at acidic pH e values, the latter may not be the only explanation, but additional impairment of other energy demanding processes may be involved.

Thermal tolerance of single larval stages has rarely been studied, eventhough the larva might be the actual physiological bottleneck of all life history stages setting distribution limits. Therefore, temperature tolerance of Zoea I was examined in two different population of the Chilean kelp crab Taliepus dentatus. We measured activity, oxygen consumption, cardiac performance and the CN composition of larval T. dentatus of two populations from central and southern Chile at various temperatures (1) to determine at which organisational level T. dentatus larvae get first affected by temperature, integrating variables from the organismal, tissue functional to the biochemical elemental level, and (2) to compare the thermal tolerance of larvae from varying environmental temperature regimes to look at functional differences between populations as a correlate of adaptation capacities of the Zoea. Our mechanistic analysis explicitly sheds light on how temperature affects the physiology of crab larvae. We found that the highest organisational level gets affected first, seen in activity decrements at unsuitably high or low temperatures, paralleled by decreases in oxygen consumption rates. Cardiac performance is more robust to temperature changes. Heart beat rate decreases only at very high and low temperature extremes and stroke volume is almost temperature independent. The comparison between the southern and central populations showed a limited but clear adaptation of larvae from the southern sampling site to the colder environmental temperature regime, visible at all organisational levels.

Background Hypercapnia and elevated temperatures resulting from climate change may have adverse consequences for many marine organisms. While diverse physiological and ecological effects have been identified, changes in those molecular mechanisms, which shape the physiological phenotype of a species and limit its capacity to compensate, remain poorly understood. Here, we use global gene expression profiling through RNA-Sequencing to study the transcriptional responses to ocean acidification and warming in gills of the boreal spider crab Hyas araneus exposed medium-term (10 weeks) to intermediate (1,120 μatm) and high (1,960 μatm) PCO2 at different temperatures (5°C and 10°C). Results The analyses reveal shifts in steady state gene expression from control to intermediate and from intermediate to high CO2 exposures. At 5°C acid–base, energy metabolism and stress response related genes were upregulated at intermediate PCO2, whereas high PCO2 induced a relative reduction in expression to levels closer to controls. A similar pattern was found at elevated temperature (10°C). There was a strong coordination between acid–base, metabolic and stress-related processes. Hemolymph parameters at intermediate PCO2 indicate enhanced capacity in acid–base compensation potentially supported by upregulation of a V-ATPase. The likely enhanced energy demand might be met by the upregulation of the electron transport system (ETS), but may lead to increased oxidative stress reflected in upregulated antioxidant defense transcripts. These mechanisms were attenuated by high PCO2, possibly as a result of limited acid–base compensation and metabolic down-regulation. Conclusion Our findings indicate a PCO2 dependent threshold beyond which compensation by acclimation fails progressively. They also indicate a limited ability of this stenoecious crustacean to compensate for the effects of ocean acidification with and without concomitant warming. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-789) contains supplementary material, which is available to authorized users.