Posts Tagged 'fish'

Impacts of CO2-induced ocean acidification on predator detection ability and developementof temperate fish

Ocean acidification, caused by elevated levels of atmospheric carbon dioxide (CO2), is recognized as a serious threat to marine ecosystems. Until now, most studies have focused on marine calcifying organisms, due to dependence on calcium carbonate, which is likely to become limited under future acidification scenarios. Less attention has been given to fish, but recent studies on the early life stages suggest that behavior, growth, development and otolith size may be highly affected by increasing CO2 levels. Other studies, on the other hand, fail to detect negative effects, suggesting species-specific vulnerabilities to increasing concentrations of CO2 and point to a need of further research. Here we tested the effects of CO2-induced ocean acidification on the early life stages of a temperate marine fish, the clingfish Lepadogaster lepadogaster, by rearing larvae since hatching in control and high pCO2 conditions. Size-at-age metrics and otolith size were examined in pre-settlement stage larvae. Additionally, behavioral response to a predator odour was tested in L. lepadogaster larvae and in Atherina presbyter larvae, maintained in high pCO2 conditions. Recognition of predator odours is a key behavior for predator avoidance and survival, and is one of the most commonly affected behaviors in fishes exposed to high CO2 levels. Results suggest that early life stages of L. lepadogaster might be resilient to future scenarios of ocean acidification, whereas A. presbyter might be more susceptible, with potential impacts on its future survival. Future studies should address species capacity to adapt to the predicted ocean acidification over the next century.

Continue reading ‘Impacts of CO2-induced ocean acidification on predator detection ability and developementof temperate fish’

Trophic transfer of essential elements in the clownfish Amphiprion ocellaris in the context of ocean acidification

Little information exists on the effects of ocean acidification (OA) on the digestive and post-digestive processes in marine fish. Here, we investigated OA impacts (Δ pH = 0.5) on the trophic transfer of select trace elements in the clownfish Amphiprion ocellaris using radiotracer techniques. Assimilation efficiencies of three essential elements (Co, Mn and Zn) as well as their other short-term and long-term kinetic parameters in juvenile clownfish were not affected by this experimental pH change. In complement, their stomach pH during digestion were not affected by the variation in seawater pH. Such observations suggest that OA impacts do not affect element assimilation in these fish. This apparent pCO2 tolerance may imply that clownfish have the ability to self-regulate pH shifts in their digestive tract, or that they can metabolically accommodate such shifts. Such results are important to accurately assess future OA impacts on diverse marine biota, as such impacts are highly species specific, complex, and may be modulated by species-specific metabolic processes.

Continue reading ‘Trophic transfer of essential elements in the clownfish Amphiprion ocellaris in the context of ocean acidification’

Mitochondrial acclimation potential to ocean acidification and warming of Polar cod (Boreogadus saida) and Atlantic cod (Gadus morhua)

Background

Ocean acidification and warming are happening fast in the Arctic but little is known about the effects of ocean acidification and warming on the physiological performance and survival of Arctic fish.

Results

In this study we investigated the metabolic background of performance through analyses of cardiac mitochondrial function in response to control and elevated water temperatures and PCO2 of two gadoid fish species, Polar cod (Boreogadus saida), an endemic Arctic species, and Atlantic cod (Gadus morhua), which is a temperate to cold eurytherm and currently expanding into Arctic waters in the wake of ocean warming. We studied their responses to the above-mentioned drivers and their acclimation potential through analysing the cardiac mitochondrial function in permeabilised cardiac muscle fibres after 4 months of incubation at different temperatures (Polar cod: 0, 3, 6, 8 °C and Atlantic cod: 3, 8, 12, 16 °C), combined with exposure to present (400μatm) and year 2100 (1170μatm) levels of CO2.

OXPHOS, proton leak and ATP production efficiency in Polar cod were similar in the groups acclimated at 400μatm and 1170μatm of CO2, while incubation at 8 °C evoked increased proton leak resulting in decreased ATP production efficiency and decreased Complex IV capacity. In contrast, OXPHOS of Atlantic cod increased with temperature without compromising the ATP production efficiency, whereas the combination of high temperature and high PCO2 depressed OXPHOS and ATP production efficiency.

Conclusions

Polar cod mitochondrial efficiency decreased at 8 °C while Atlantic cod mitochondria were more resilient to elevated temperature; however, this resilience was constrained by high PCO2. In line with its lower habitat temperature and higher degree of stenothermy, Polar cod has a lower acclimation potential to warming than Atlantic cod.

Continue reading ‘Mitochondrial acclimation potential to ocean acidification and warming of Polar cod (Boreogadus saida) and Atlantic cod (Gadus morhua)’

Carbon dioxide induced plasticity of branchial acid-base pathways in an estuarine teleost

Anthropogenic CO2 is expected to drive ocean pCO2 above 1,000 μatm by 2100 – inducing respiratory acidosis in fish that must be corrected through branchial ion transport. This study examined the time course and plasticity of branchial metabolic compensation in response to varying levels of CO2 in an estuarine fish, the red drum, which regularly encounters elevated CO2 and may therefore have intrinsic resilience. Under control conditions fish exhibited net base excretion; however, CO2 exposure resulted in a dose dependent increase in acid excretion during the initial 2 h. This returned to baseline levels during the second 2 h interval for exposures up to 5,000 μatm, but remained elevated for exposures above 15,000 μatm. Plasticity was assessed via gene expression in three CO2 treatments: environmentally realistic 1,000 and 6,000 μatm exposures, and a proof-of-principle 30,000 μatm exposure. Few differences were observed at 1,000 or 6,000 μatm; however, 30,000 μatm stimulated widespread up-regulation. Translocation of V-type ATPase after 1 h of exposure to 30,000 μatm was also assessed; however, no evidence of translocation was found. These results indicate that red drum can quickly compensate to environmentally relevant acid-base disturbances using baseline cellular machinery, yet are capable of plasticity in response to extreme acid-base challenges.

Continue reading ‘Carbon dioxide induced plasticity of branchial acid-base pathways in an estuarine teleost’

Biological responses of sharks to ocean acidification

Sharks play a key role in the structure of marine food webs, but are facing major threats due to overfishing and habitat degradation. Although sharks are also assumed to be at relatively high risk from climate change due to a low intrinsic rate of population growth and slow rates of evolution, ocean acidification (OA) has not, until recently, been considered a direct threat. New studies have been evaluating the potential effects of end-of-century elevated CO2 levels on sharks and their relatives’ early development, physiology and behaviour. Here, we review those findings and use a meta-analysis approach to quantify the overall direction and magnitude of biological responses to OA in the species of sharks that have been investigated to date. While embryo survival and development time are mostly unaffected by elevated CO2, there are clear effects on body condition, growth, aerobic potential and behaviour (e.g. lateralization, hunting and prey detection). Furthermore, studies to date suggest that the effects of OA could be as substantial as those due to warming in some species. A major limitation is that all past studies have involved relatively sedentary, benthic sharks that are capable of buccal ventilation—no studies have investigated pelagic sharks that depend on ram ventilation. Future research should focus on species with different life strategies (e.g. pelagic, ram ventilators), climate zones (e.g. polar regions), habitats (e.g. open ocean), and distinct phases of ontogeny in order to fully predict how OA and climate change will impact higher-order predators and therefore marine ecosystem dynamics.

Continue reading ‘Biological responses of sharks to ocean acidification’

Marine fish intestine responds to ocean acidification producing more carbonate aggregates

Marine fish contribute to the carbon cycle by producing mineralized intestinal aggregates generated as by-products of their osmoregulation. Here we aimed at characterizing the control of intestinal aggregate production in the gilthead sea bream in response to near future increases of environmental CO2. Our results demonstrate that hypercapnia (800 and 1200 μatm CO2) elicits higher intestine epithelial HCO3- secretion and the subsequent parallel increase of intestinal aggregate production when compared to present values (400 μatm CO2). Intestinal gene expression analysis revealed the up-regulation of crucial transport mechanisms involved not only in the intestinal secretion cascade (Slc4a4, Slc26a3 and Slc26a6) of sea bream, but also in other mechanisms involved in intestinal ion uptake linked to water absorption such as NKCC2 and the Aquaporin 1b. These results highlight the important role of fish in the marine carbon cycle, and their potential growing impact of intestinal biomineralization processes in the scenario of ocean acidification.

Continue reading ‘Marine fish intestine responds to ocean acidification producing more carbonate aggregates’

Extinction selectivity among marine fishes during multistressor global change in the end-Permian and end-Triassic crises

Ancient mass extinction events such as the end-Permian and end-Triassic crises provide analogues for multistressor global change of ocean warming, pH reduction, and deoxygenation. Organism physiology is hypothesized to be a key trait influencing vulnerability to these stressors, but it is not certain how physiology predicts survival over evolutionary time scales and when organisms are faced with opposing or synergistic stressors. Fishes (bony fishes and chondrichthyan fishes) are active organisms with high aerobic scope for thermal tolerance and well-developed acid-base regulation, traits that should confer resilience to global change. To test this, we compiled a database of fossil marine fish occurrences to quantify extinction rates during background and mass extinctions from the Permian through Early Jurassic, using maximum likelihood estimation to compare extinction trajectories with marine invertebrates. Our results show that fewer chondrichthyan fishes underwent extinction than marine invertebrates during the end-Permian crisis. End-Triassic chondrichthyan extinction rates also were not elevated above background levels. In contrast, bony fishes underwent an end-Triassic extinction comparable to that of marine invertebrates. The differing responses of these two groups imply that a more active physiology can be advantageous during global change, although not uniformly. Permian–Triassic chondrichthyan fishes may have had broader environmental tolerances, facilitating survival. Alternatively, the larger offspring size of chondrichthyan fishes may provide greater energy reserves to offset the demands of warming and acidification. Although more active organisms have adult adaptations for thermal tolerance and pH regulation, some may nevertheless be susceptible to global change during early life stages.

Continue reading ‘Extinction selectivity among marine fishes during multistressor global change in the end-Permian and end-Triassic crises’


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Ocean acidification in the IPCC AR5 WG II

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