Posts Tagged 'Cnidaria'

Extreme, but not moderate climate scenarios, impart sublethal effects on polyps of the Irukandji jellyfish, Carukia barnesi

Highlights
• Sublethal effects on Carukia barnesi polyps only manifested in extreme conditions.

• Individual metabolites were suppressed in extreme pH and elevated temperature treatments.

• C. barnesi polyps are unaffected by the most optimistic climate scenario and can survive in extreme conditions.

Abstract
Ocean acidification and warming, fueled by excess atmospheric carbon dioxide, can impose stress on marine organisms. Most studies testing the effects of climate change on marine organisms, however, use extreme climate projection scenarios, despite moderate projections scenarios being most likely to occur. Here, we examined the interactive effects of warming and acidification on reproduction, respiration, mobility and metabolic composition of polyps of the Irukandji jellyfish, Carukia barnesi, to determine the responses of a cubozoan jellyfish to moderate and extreme climate scenarios in Queensland, Australia. The experiment consisted two orthogonal factors: temperature (current 25 °C and future 28 °C) and pH (current (8.0) moderate (7.9) and extreme (7.7)). All polyps survived in the experiment but fewer polyps were produced in the pH 7.7 treatment compared to pH 7.9 and pH 8.0. Respiration rates were elevated in the lowest pH treatment throughout most of the experiment and polyps were approximately half as mobile in this treatment compared to pH 7.9 and pH 8.0, regardless of temperature. We identified metabolites occurring at significantly lower relative abundance in the lowest pH (i.e. glutamate, acetate, betaine, methylguanidine, lysine, sarcosine, glycine) and elevated temperature (i.e. proline, trigonelline, creatinine, mannose, acetate, betaine, methylguanidine, lysine, sarcosine) treatments. Glycine was the only metabolite exhibiting an interactive effect between pH and temperature. Our results suggest that C. barnesi polyps are unaffected by the most optimistic climate scenario and may tolerate even extreme climate conditions to some extent.

Continue reading ‘Extreme, but not moderate climate scenarios, impart sublethal effects on polyps of the Irukandji jellyfish, Carukia barnesi’

Ocean acidification at a coastal CO2 vent induces expression of stress-related transcripts and transposable elements in the sea anemone Anemonia viridis

Ocean acidification threatens to disrupt interactions between organisms throughout marine ecosystems. The diversity of reef-building organisms decreases as seawater CO2 increases along natural gradients, yet soft-bodied animals, such as sea anemones, are often resilient. We sequenced the polyA-enriched transcriptome of adult sea anemone Anemonia viridis and its dinoflagellate symbiont sampled along a natural CO2 gradient in Italy to assess stress levels in these organisms. We found that about 3.1% of the anemone transcripts, but <1% of the Symbiodinium sp. transcripts were differentially expressed. Processes enriched at high seawater CO2 were linked to cellular stress and inflammation, including significant up-regulation of protective cellular functions and down-regulation of metabolic pathways. Transposable elements were differentially expressed at high seawater CO2, with an extreme up-regulation (> 100-fold) of the BEL-family of long terminal repeat retrotransposons. Seawater acidified by CO2 generated a significant stress reaction in A. viridis, but no bleaching was observed and Symbiodinium sp. appeared to be less affected. These observed changes indicate the mechanisms by which A. viridis acclimate to survive chronic exposure to ocean acidification conditions. We conclude that many organisms that are common in acidified conditions may nevertheless incur costs due to hypercapnia and/or lowered carbonate saturation states.

Continue reading ‘Ocean acidification at a coastal CO2 vent induces expression of stress-related transcripts and transposable elements in the sea anemone Anemonia viridis’

Ocean acidification causes mortality in the medusa stage of the cubozoan Carybdea xaymacana

Ocean pH is decreasing due to anthropogenic activities, and the consequences of this acidification on marine fauna and ecosystems are the subject of an increasing number of studies. Yet, the impact of ocean acidification (OA) on several abundant and ecologically important taxa, such as medusozoans, is poorly documented. To date there have been no studies on the effect of post-2050 OA projections on the medusa stage of jellyfish. As medusae represent the reproductive stage of cnidarians, negative impacts on adult jellyfish could severely impact the long-term survival of this group. Using a laboratory experiment, we investigated the effect of 2300 OA projections (i.e. pH of 7.5) on the mortality rate of the medusa-stage of the cubozoan species Carybdea xaymacana, compared to ambient seawater pH conditions (i.e. pH of 8.1). After a 12-h exposure to OA, Cxaymacana medusae suffered higher mortality rates compared to ambient conditions. This study represents the first evidence of the potential lethal effects of post-2050 OA projections on jellyfish. The higher metabolic rates of cubozoans compared to other cnidarians might make box jellyfish more vulnerable to OA. A decrease in the density of cnidarians could lead to harmful ecological events, such as algal blooms.

Continue reading ‘Ocean acidification causes mortality in the medusa stage of the cubozoan Carybdea xaymacana’

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’

The weakest link: sensitivity to climate extremes across life stages of marine invertebrates

Predicting the effects of climate change on Earth’s biota becomes even more challenging when acknowledging that most species have life cycles consisting of multiple stages, each of which may respond differently to extreme environmental conditions. There is currently no clear consensus regarding which stages are most susceptible to increasing environmental stress, or ‘climate extremes’. We used a meta‐analytic approach to quantify variation in responses to environmental stress across multiple life stages of marine invertebrates. We identified 287 experiments in 29 papers which examined the lethal thresholds of multiple life stages (embryo, larva, juvenile, and adult) of both holoplanktonic and meroplanktonic marine invertebrates subjected to the same experimental conditions of warming, acidification, and hypoxia stress. Most studies considered short acute exposure to stressors. We calculated effect sizes (log response ratio) for each life stage (unpaired analysis) and the difference in effect sizes between stages of each species (paired analysis) included in each experiment. In the unpaired analysis, all significant responses were negative, indicating that warming, acidification and hypoxia tended to increase mortality. Furthermore, embryos, larvae, and juveniles were more negatively affected by warming than adults. The paired analysis revealed that, when subjected to the same experimental conditions, younger life stages were more negatively affected by warming than older life stages, specifically among pairings of adults vs. juveniles and larvae vs. embryos. Although responses to warming are well documented, few studies of the effects of acidification and hypoxia met the criteria for inclusion in our analyses. Our results suggest that while most life stages will be negatively affected by climate change, younger stages of marine invertebrates are more sensitive to extreme heating events.

Continue reading ‘The weakest link: sensitivity to climate extremes across life stages of marine invertebrates’

Eating in an acidifying ocean: a quantitative review of elevated CO2 effects on the feeding rates of calcifying marine invertebrates

Feeding is fundamental for all heterotrophic organisms, providing the means to acquire energy for basic life processes. Recent studies have suggested that experimental ocean acidification (OA) can alter the feeding performance of marine calcifying invertebrates, but results have been inconsistent. While several reviews pertaining to the biological effects of OA exist, none provide a synthesis of OA effects on feeding performance. Here, we provide a quantitative analysis of published experiments testing for effects of elevated CO2 on feeding rates of marine calcifying invertebrates. Results revealed that suspension-feeding molluscs and predatory and grazing echinoderms experienced depressed feeding rates under elevated CO2, while arthropods appeared unaffected; larval and juvenile animals were more susceptible to CO2 effects than adults. Feeding strategy did not appear to influence the overall taxonomic trend, nor did habitat, although exposure time did have an effect. AIC model selection revealed that Phylum best predicted effect size; life stage and exposure time were also included in candidate models. Based on these results, we synthesize potential physiological attributes of different taxa that may drive OA sensitivities in feeding rates, which could potentially result in community-level impacts. We also discuss CO2 effects on calcifier feeding in the context of elevated temperature and other global marine change stressors, and highlight other areas for future research.

Continue reading ‘Eating in an acidifying ocean: a quantitative review of elevated CO2 effects on the feeding rates of calcifying marine invertebrates’

The effects of ocean acidification on feeding and contest behaviour by the beadlet anemone Actinia equina

Increasing concentrations of atmospheric carbon dioxide are causing oceanic pH to decline worldwide, a phenomenon termed ocean acidification. Mounting experimental evidence indicates that near-future levels of CO2 will affect calcareous invertebrates such as corals, molluscs and gastropods, by reducing their scope for calcification. Despite extensive research into ocean acidification in recent years, the effects on non-calcifying anthozoans, such as sea anemones, remain little explored. In Western Europe, intertidal anemones such as Actinia equina are abundant, lower trophic-level organisms that function as important ecosystem engineers. Changes to behaviours of these simple predators could have implications for intertidal assemblages. This investigation identified the effects of reduced seawater pH on feeding and contest behaviour by A. equina. Video footage was recorded for A. equina feeding at current-day seawater (pH 8.1), and the least (pH 7.9) and most (pH 7.6) severe end-of-century predictions. Footage was also taken of contests over ownership of space between anemones exposed to reduced pH and those that were not. No statistically significant differences were identified in feeding duration or various aspects of contest behaviour including initiating, winning, inflating acrorhagi, inflicting acrorhagial peels and contest duration. Multivariate analyses showed no effect of pH on a combination of these variables. This provides contrast with other studies where anemones with symbiotic algae thrive in areas of natural increased acidity. Thus, novel experiments using intraspecific contests and resource-holding potential may prove an effective approach to understand sub-lethal consequences of ocean acidification for A. equina, other sea anemones and more broadly for marine ecosystems.

Continue reading ‘The effects of ocean acidification on feeding and contest behaviour by the beadlet anemone Actinia equina’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book