Proteinsynthesekapazität und Wachstum bei Kammmuscheln (Pectiniden) und Fischen (Zoarciden) aus polaren und gemäßigten Breiten

Polar marine invertebrates and fish grow slowly. At present there are three basic explanations for this slow growth: 1. a direct limitation by temperature, 2. rising costs of maintenance at the expense of a reduction in growth, 3. seasonal resource limitation. On the cellular level the rate-limiting effect of temperature on growth could be excluded for the cold stenothermal scallop Adamussium colbecki and for the Antarctic eelpout Pachycara brachycephalum. The protein synthesis, measured in vitro, was cold compensated in these species compared to related eurythermal species, the European scallop Aequipecten opercularis and the North Sea eelpout Zoarces viviparus. Within the temperature tolerance of P. brachycephalum the cold adapted protein synthesis apparatus could still be acclimated to various temperatures. Compensated protein synthesis capacities in Antarctic scallops and eelpout have been achieved by low activation energies and high RNA translation capacities and indicate the development of a cost efficient growth apparatus. Unlike Antarctic fish, Antarctic invertebrates exhibit higher RNA contents when compared to related species from warmer waters. These over compensated protein synthesis capacities due to high RNA contents seem specific for Antarctic invertebrates and support high growth efficiencies during the austral summer. A comparison of in vivo and in vitro protein synthesis rates suggests that actual in vivo rates remain far below capacity. Therefore the regulation must occur on a higher level. A sensible regulation factor could be the pHi. Differing energy budgets and trade-offs between lifestyle, exercise and growth performance of cold stenothermal and eurythermal animals are discussed. A basic requirement is that the energetic costs for the protein synthesis are the same as demonstrated for both scallop species. Despite even low maintenance costs, cold stenothermal animals exhibit slow annual growth rates suggesting seasonal resource limitation

Climate sensitivity: Can we identify bottlenecks during early development and its effects on subsequent larval stages in crustaceans and fish?

Environmental drivers such as temperature and CO2 have in effect on early live stages. This overview will show different sensitivities of eggs and early larvae of crustaceans and fish. We measured mortality, developmental time, oxygen consumption and heart beat to get a comprehensive overview about the performance of these life stages and effects on later stages. Our experiments show synergistic effects of ocean warming and acidification on eggs and hatching larvae of crustaceans and fish. Interestingly, crab larvae hatching from eggs that were incubated at high CO2 showed higher mortality and prolonged developmental time compared to eggs that were kept at ambient CO2. Embryonic survival (p = 0.015) and larval size at hatch (p < 0,01) were significantly reduced under high PCO2, especially towards unfavourably cold temperatures. In turn, respiration rates of developing embryos were significantly (p < 0.05) increased under high PCO2, suggesting higher energy demand due to e.g. increased acid-base regulation leaving less energy for larval growth. These experiments suggest that life history stages and transition phases with lowered physiological capacities will be most sensitive to ocean warming and acidification

MR imaging as a monitoring tool for gonadal growth in fish

An in vivo approach of magnetic resonance imaging (MRI) will be presented to follow the gonadal development of unanaesthetised male and female polar cod (Boreogadus saida). The first screening procedure was carried out on a set of reproductive polar cod every four weeks. Gonad maturation was followed from November until shortly before spawning in February. The resolution of the MR images allowed for specific sex determination and calculation of gonads volumes. The results of calculated gonad volume in vivo was in agreement with the in vitro gonad weight

Effects of Ocean Acidification and Warming on the mitochondrial physiology of Atlantic cod

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

Broodstock exposure to warming and elevated pCO<inf>2</inf> impairs gamete quality and narrows the temperature window of fertilisation in Atlantic cod

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Latitudinal variation in maternal investment traits of the kelp crab Taliepus dentatus along the coast of Chile

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

Early life stages of an arctic keystone species (Boreogadus saida) show high sensitivity to a water-soluble fraction of crude oil

Source: doi: 10.1016/j.envpol.2016.07.044Increasing 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

Temperature tolerance of different larval stages of the spider crab Hyas araneus exposed to elevated seawater PCO2

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