Posts Tagged 'fish'



Ecological-economic sustainability of the Baltic cod fisheries under ocean warming and acidification

Highlights
• Ocean warming and acidification (OAW) will drastically decrease cod fishing opportunities in the Baltic.

• Ecological-economic modeling shows high losses in catch, and profits due to OAW.

• There is a high risk of cod stock collapse under mid-term climate change.

• Improved management could temporarily counteract OAW stressors.

• Adaptation includes a reduction in fishing mortality, and increased mesh size.

Abstract
Human-induced climate change such as ocean warming and acidification, threatens marine ecosystems and associated fisheries. In the Western Baltic cod stock socio-ecological links are particularly important, with many relying on cod for their livelihoods. A series of recent experiments revealed that cod populations are negatively affected by climate change, but an ecological-economic assessment of the combined effects, and advice on optimal adaptive management are still missing. For Western Baltic cod, the increase in larval mortality due to ocean acidification has experimentally been quantified. Time-series analysis allows calculating the temperature effect on recruitment. Here, we include both processes in a stock-recruitment relationship, which is part of an ecological-economic optimization model. The goal was to quantify the effects of climate change on the triple bottom line (ecological, economic, social) of the Western Baltic cod fishery. Ocean warming has an overall negative effect on cod recruitment in the Baltic. Optimal management would react by lowering fishing mortality with increasing temperature, to create a buffer against climate change impacts. The negative effects cannot be fully compensated, but even at 3 °C warming above the 2014 level, a reduced but viable fishery would be possible. However, when accounting for combined effects of ocean warming and acidification, even optimal fisheries management cannot adapt to changes beyond a warming of +1.5° above the current level. Our results highlight the need for multi-factorial climate change research, in order to provide the best available, most realistic, and precautionary advice for conservation of exploited species as well as their connected socio-economic systems.

Continue reading ‘Ecological-economic sustainability of the Baltic cod fisheries under ocean warming and acidification’

Future ocean warming may prove beneficial for the northern population of European seabass, but ocean acidification does not

The world’s oceans are acidifying and warming due to increasing amounts of atmospheric CO2. Thermal tolerance of fish much depends on the cardiovascular ability to supply the tissues with oxygen. The heart itself is highly dependent on oxygen and heart mitochondria thus might play a key role in shaping an organism’s tolerance to temperature. The present study aimed to investigate the effects of acute and chronic warming on respiratory capacities of European sea bass (Dicentrarchus labrax L.) heart mitochondria. We hypothesized that acute warming would impair mitochondrial respiratory capacities, but be compensated after long-term. Increasing PCO2 may cause intracellular changes, likely further constricting cellular energy metabolism. We found increased leak respiration rates in acutely warmed heart mitochondria of cold-conditioned fish in comparison to measurements at their rearing temperature, suggesting a lower aerobic capacity to synthesize ATP. However, thermal acclimation led to increased mitochondrial functionality, e.g. higher RCRo in heart mitochondria of warm-conditioned compared to cold-conditioned fish. Exposure to high PCO2 synergistically amplified the effects of acute and long-term warming, but did not result in changes by itself. We explained the high ability to maintain mitochondrial function under OA with the fact that seabass are moving between various environmental conditions. Improved mitochondrial capacities after warm conditioning could be due to the origin of this species in the warm waters of the Mediterranean. Our results also indicate that seabass are not yet fully adapted to the colder temperatures in their northern distribution range and might benefit from warmer temperatures.

Continue reading ‘Future ocean warming may prove beneficial for the northern population of European seabass, but ocean acidification does not’

Impact of climate change and contamination in the oxidative stress response of marine organisms

Atmospheric carbon dioxide (CO2) levels are increasing at an unprecedented rate, changing the carbonate chemistry (in a process known as ocean acidification) and temperature of the worlds ocean. Moreover, the simultaneous occurrence of highly toxic and persistent contaminants, such as mercury, will play a key role in further shaping the ecophysiology of marine organisms. Thus, the main goal of the present dissertation was to undertake the first comprehensive and comparative analysis of the biochemical strategies, namely antioxidant defense (both enzymatic and non-enzymatic antioxidants) and protein repair and removal mechanisms, of several marine organisms – from invertebrate (Veretillum cynomorium and Gammarus locusta) to vertebrate species (Argyrosomus regius, Chiloscyllium plagiosum and Scyliorhinus canicula) – encompassing different life-stages and life-strategies to the predicted climate-mediated changes. The findings provided in the present dissertation proved that organisms’ responses were mostly underpinned by temperature (increasing lipid, protein and nucleic acid damage), that also culminated into increased mercury bioaccumulation and toxicity, while ocean acidification as a sole stressor usually played a minor role in defining species vulnerability (i.e. responsible for increased oxidative damage in the marine calcifying organisms G. locusta). Nonetheless when co-occurring with warming and contamination scenarios, acidification was usually responsible for the reduction of heavy metal accumulation and toxicity, as well as decreased warming and contamination-elicited oxidative stress. Additionally, organisms’ responses were species-specific, and organisms that usually occupy more variable environments (e.g. daily changes in abiotic conditions) usually displayed greater responses towards environmental change than organisms inhabiting more stable environments. Furthermore, and assuming the relevance of transgenerational effects, it seems that the negative effects of OA are potentially being inherited by the offspring’s, compromising the efficiency of future generations to endure the upcoming conditions.

Continue reading ‘Impact of climate change and contamination in the oxidative stress response of marine organisms’

Elevated CO2 alters behavior, growth, and lipid composition of Pacific cod larvae

Highlights

• Ocean acidification has been shown to induce a range of effects on early life stages of commercially important marine fishes.

• Elevated CO2 levels strengthened behavioral phototaxis in larval Pacific cod.

• High CO2 reduced growth and energy storage during the first 2 weeks of life, but this effect was reversed by 5 weeks of age.

Abstract

High-latitude seas, which support a number of commercially important fisheries, are predicted to be most immediately impacted by ongoing ocean acidification (OA). Elevated CO2 levels have been shown to induce a range of impacts on the physiology and behavior of marine fish larvae. However, these responses have yet to be characterized for most fishery species, including Pacific cod (Gadus macrocephalus). Based on laboratory experiments, we present a multi-faceted analysis of the sensitivity of Pacific cod larvae to elevated CO2. Fish behavior in a horizontal light gradient was used to evaluate the sensitivity of behavioral phototaxis in 4–5 week old cod larvae. Fish at elevated CO2 levels (∼1500 and 2250 μatm) exhibited a stronger phototaxis (moved more quickly to regions of higher light levels) than fish at ambient CO2 levels (∼600 μatm). In an independent experiment, we examined the effects of elevated CO2 levels on growth of larval Pacific cod over the first 5 weeks of life under two different feeding treatments. Fish exposed to elevated CO2 levels (∼1700 μatm) were smaller and had lower lipid levels at 2 weeks of age than fish at low (ambient) CO2 levels (∼500 μatm). However, by 5 weeks of age, this effect had reversed: fish reared at elevated CO2 levels were slightly (but not significantly) larger and had higher total lipid levels and storage lipids than fish reared at low CO2. Fatty acid composition differed significantly between fish reared at high and low CO2 levels (p < 0.01) after 2 weeks of feeding, but this effect diminished by week 5. Effects of CO2 on FA composition of the larvae differed between the two diets, an effect possibly related more to dietary equilibrium and differential lipid class storage than a fundamental effect of CO2 on fatty acid metabolism. These experiments point to a stage-specific sensitivity of Pacific cod to the effects of OA. Further understanding of these effects will be required to predict the impacts on production of Pacific cod fisheries.

Continue reading ‘Elevated CO2 alters behavior, growth, and lipid composition of Pacific cod larvae’

Ocean acidification affects somatic and otolith growth relationship in fish: evidence from an in situ study

Ocean acidification (OA) may have varied effects on fish eco-physiological responses. Most OA studies have been carried out in laboratory conditions without considering the in situ pCO2/pH variability documented for many marine coastal ecosystems. Using a standard otolith ageing technique, we assessed how in situ ocean acidification (ambient, versus end-of-century CO2 levels) can affect somatic and otolith growth, and their relationship in a coastal fish. Somatic and otolith growth rates of juveniles of the ocellated wrasse Symphodus ocellatus living off a Mediterranean CO2 seep increased at the high-pCO2 site. Also, we detected that slower-growing individuals living at ambient pCO2 levels tend to have larger otoliths at the same somatic length (i.e. higher relative size of otoliths to fish body length) than faster-growing conspecifics living under high pCO2 conditions, with this being attributable to the so-called ‘growth effect’. Our findings suggest the possibility of contrasting OA effects on fish fitness, with higher somatic growth rate and possibly higher survival associated with smaller relative size of otoliths that could impair fish auditory and vestibular sensitivity.

Continue reading ‘Ocean acidification affects somatic and otolith growth relationship in fish: evidence from an in situ study’

Divergent gene expression in the gills of juvenile turbot (Psetta maxima) exposed to chronic severe hypercapnia indicates dose-dependent increase in intracellular oxidative stress and hypoxia

Highlights
• We investigated the impact of chronic hypercapnia on gene expression in the gills of turbot (Psetta maxima) via RT-qPCR.

• Data indicated enhanced concentrations of reactive oxygen species (ROS) in the two highest treatment levels.

• Further, dose-dependent modulations of transcriptional adjustments implied different underlying coping mechanisms.

• These modulations seemed to comprise hypoxia-mediated suppressed protein synthesis in the highest tested treatment level.

• We discuss our results within a model of capacity limitation and draw conclusions regarding the condition of the gills.

Abstract
Elevated concentrations of carbon dioxide are a common stressor for fish and other aquatic animals. In particular, intensive aquaculture can impose prolonged periods of severe environmental hypercapnia, manifold exceeding CO2 concentrations of natural habitats. In order to cope with this stressor, gills are essential and constitute the primary organ in the acclimatization process. Yet, despite a general understanding of changes in ion regulation, not much is known with regard to other cellular mechanisms. In this study, we apply RT-qPCR to investigate changes in the expression of several genes associated with metabolism, stress and immunity within gills of juvenile turbot (Psetta maxima) after an eight-week exposure to different concentrations of CO2 (low = ∼3000 μatm, medium = ∼15,000 μatm and high = ∼25,000 μatm CO2). Histological examination of the gill tissue only found a significant increase of hypertrophied secondary lamella in the highest tested treatment level. gene expression results, on the other hand, implied both, mutual and dose-dependent transcriptional adjustments. Comparable up-regulation of IL-1ß, LMP7 and Grim19 at medium and high hypercapnia indicated an increase of reactive oxygen species (ROS) within gill cells. Simultaneous increase in Akirin and PRDX transcripts at medium CO2 indicated enhanced anti-oxidant activity and regulation of transcription, while reduced mRNA concentrations of COX, EF1α and STAT2 at high CO2 denoted suppressed protein synthesis and reduced metabolic capacity. In addition to upregulated DFAD and ApoE expression, implying compensating repair measures, gills exposed to the highest tested treatment level seemed to operate close to or even beyond their maximum capacity. Thus, fitting the model of capacity limitation, our results provide evidence for accretive intracellular hypoxia and oxidative stress in the gills of turbot, dependent on the level of environmental hypercapnia. Further, genes, such as COX, may be valuable biomarkers when attempting to discriminate between a successful and an overpowered stress response.

Continue reading ‘Divergent gene expression in the gills of juvenile turbot (Psetta maxima) exposed to chronic severe hypercapnia indicates dose-dependent increase in intracellular oxidative stress and hypoxia’

Diel CO2 cycles and parental effects have similar benefits to growth of a coral reef fish under ocean acidification

Parental effects have been shown to buffer the negative effects of within-generation exposure to ocean acidification (OA) conditions on the offspring of shallow water marine organisms. However, it remains unknown if parental effects will be impacted by the presence of diel CO2 cycles that are prevalent in many shallow water marine habitats. Here, we examined the effects that parental exposure to stable elevated (1000 µatm) and diel-cycling elevated (1000 ± 300 µatm) CO2 had on the survival and growth of juvenile coral reef anemonefish, Amphiprion melanopus. Juvenile survival was unaffected by within-generation exposure to either elevated CO2 treatment but was significantly increased (8%) by parental exposure to diel-cycling elevated CO2. Within-generation exposure to stable elevated CO2 caused a significant reduction in juvenile growth (10.7–18.5%); however, there was no effect of elevated CO2 on growth when diel CO2 cycles were present. Parental exposure to stable elevated CO2 also ameliorated the negative effects of elevated CO2 on juvenile growth, and parental exposure to diel CO2 cycles did not alter the effects of diel CO2 cycles on juveniles. Our results demonstrate that within-generation exposure to diel-cycling elevated CO2 and parental exposure to stable elevated CO2 had similar outcomes on juvenile condition. This study illustrates the importance of considering natural CO2 cycles when predicting the long-term impacts of OA on marine ecosystems.

Continue reading ‘Diel CO2 cycles and parental effects have similar benefits to growth of a coral reef fish under ocean acidification’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book