Posts Tagged 'temperature'



Impairment of swimming performance in Tritia reticulata (L.) veligers under projected ocean acidification and warming scenarios

Highlights

Tritia reticulata survival relies on the swimming performance of planktotrophic larva.

•Swimming and histological integrity of related organs assessed after exposure to OA-W

•Veligers travelled slower, for shorter distances, under end of century OA-W scenarios.

•Foot secretor epithelium alteration suggests pre and post-settlement motor impairment.

•Veliger competence is proved to be threatened if OA-W projections are realised.

Abstract

Tritia reticulata (L.) is a neogastropod ubiquitous in the intertidal communities of the NE Atlantic. Its life cycle relies on the swimming performance of planktonic early life stages, whose sensitivity to the climate conditions projected for the near future, namely of ocean acidification (OA) and warming (W), is, to our best knowledge, unknown. To examine the resilience of larval stages to future environmental conditions, this work investigates the effect of OA-W on the swimming performance of T. reticulata veligers under a range of experimental conditions, based on the end-of-century projections of the Intergovernmental Panel on Climate Change. Veligers were exposed to six experimental scenarios for 14 days, employing a full factorial design with three temperatures (T°C: 18, 20 and 22 °C) and two pH levels (pHtarget: 8.1 and 7.8). Mortality was assessed throughout the trial, after which swimming behaviour – characterised by the activity, speed and the distance travelled by veligers – was analysed by automated video recordings in a Zebrabox® device. Mortality increased with OA-W and, although more active, larvae travelled shorter distances revealing reduced swimming speed under acidic and warmer conditions, with the interaction of the tested stressors – pH and T°C – being highly significant. Results motivated the morpho-histological analysis of larvae preserved at the end of the trial, to check for the integrity of the organs involved in veligers’ motion: statocysts, velum and foot. Statocyst and velar morpho-structure were conserved but histological damage of metapodial epithelia was evident under acidity, namely an apparent hypertrophy and protrusion of the secretory cells, with dispersed pigmented granules and, at 22 °C, less cilia, with potential functional implications. Negative consequences of the OA-W scenarios tested on veligers’ competence are unveiled, pointing towards the eminent threat these phenomena constitute to T. reticulata perpetuation in case no mitigation measures are taken, and projections become effective.

Continue reading ‘Impairment of swimming performance in Tritia reticulata (L.) veligers under projected ocean acidification and warming scenarios’

The effect of climate change on the escape kinematics and performance of fishes: implications for future predator–prey interactions

Climate change can have a pronounced impact on the physiology and behaviour of fishes. Notably, many climate change stressors, such as global warming, hypoxia and ocean acidification (OA), have been shown to alter the kinematics of predator–prey interactions in fishes, with potential effects at ecological levels. Here, we review the main effects of each of these stressors on fish escape responses using an integrative approach that encompasses behavioural and kinematic variables. Elevated temperature was shown to affect many components of the escape response, including escape latencies, kinematics and maximum swimming performance, while the main effect of hypoxia was on escape responsiveness and directionality. OA had a negative effect on the escape response of juvenile fish by decreasing their directionality, responsiveness and locomotor performance, although some studies show no effect of acidification. The few studies that have explored the effects of multiple stressors show that temperature tends to have a stronger effect on escape performance than OA. Overall, the effects of climate change on escape responses may occur through decreased muscle performance and/or an interference with brain and sensory functions. In all of these cases, since the escape response is a behaviour directly related to survival, these effects are likely to be fundamental drivers of changes in marine communities. The overall future impact of these stressors is discussed by including their potential effects on predator attack behaviour, thereby allowing the development of potential future scenarios for predator–prey interactions.

Continue reading ‘The effect of climate change on the escape kinematics and performance of fishes: implications for future predator–prey interactions’

Elevated CO2 concentrations promote growth and photosynthesis of the brown alga Saccharina japonica

Non-photochemical quenching (NPQ) is one of the most important photo-protection mechanisms in brown macroalgae. Global warming and ocean acidification are predicted to impact physiological characteristics of marine algae. However, little is known about the effects of co-occurrence of the elevation of pCO2 and temperature on photochemical capacity, especially regarding photoprotective mechanisms in brown macroalgae. Here, we studied the separate and combined effects of increases in pCO2 and temperature on the photochemical characteristics and growth performance in sporophytes of the brown macroalga Saccharina japonica. The results showed that the NPQ of S. japonica is mainly dependent on the xanthophyll cycle (XC) which appears to be related only to the activation of the enzyme violaxanthin de-epoxidase (VDE), and the transthylakoid proton gradient (ΔpH) could not induce NPQ alone. The elevation of pCO2 reduced NPQ value of S. japonica under high-temperature stress. After 60-day cultivation under the ambient and elevated pCO2 (400 and 1000 μatm), we further found that the elevation of pCO2 promoted growth and increased the photosynthetic performance of all three cultivar strains of S. japonica that have been traditionally cultured for many years in China.

Continue reading ‘Elevated CO2 concentrations promote growth and photosynthesis of the brown alga Saccharina japonica’

Impact of temperature, low pH and NH4+ enrichment on ecophysiological responses of a green tide Species Ulva australis Areschoug

Ulva are ubiquitous and opportunistic green algae species that easily adapt to various environmental conditions. These algae are responsible for the green tides that cause many environmental and ecological problems in coastal waters. We investigated the physiological responses of Ulva australis under warming, acidification, and eutrophication conditions. The physiological changes in the algae were observed under various combinations of temperature, pH, and NH4+ levels. Combinations of three temperatures (10°C, 20°C, and 30°C), two pH levels (7.80 and 8.20), and two NH4+ concentrations (4 μM and 120 μM) were considered under laboratory conditions. Temperature, NH4+, and pH had significant impact on the photosynthetic and nutrient uptake rates. However, the 12 h observation could not stimulate the seaweed to change the pH in the cultured media. Changes in relative growth rates, photosynthetic efficiency, and variations in tissue C and N were not affected by the interactions between temperature, pH level, and nutrient concentration. It is probable that, due to global warming, the bloom of Ulva australis may continue in warm, acidic, coastal waters with high nutrient levels.

Continue reading ‘Impact of temperature, low pH and NH4+ enrichment on ecophysiological responses of a green tide Species Ulva australis Areschoug’

Ocean warming and acidification may drag down the commercial Arctic cod fishery by 2100

The Arctic Ocean is an early warning system for indicators and effects of climate change. We use a novel combination of experimental and time-series data on effects of ocean warming and acidification on the commercially important Northeast Arctic cod (Gadus morhua) to incorporate these physiological processes into the recruitment model of the fish population. By running an ecological-economic optimization model, we investigate how the interaction of ocean warming, acidification and fishing pressure affects the sustainability of the fishery in terms of ecological, economic, social and consumer-related indicators, ranging from present day conditions up to future climate change scenarios. We find that near-term climate change will benefit the fishery, but under likely future warming and acidification this large fishery is at risk of collapse by the end of the century, even with the best adaptation effort in terms of reduced fishing pressure.

Continue reading ‘Ocean warming and acidification may drag down the commercial Arctic cod fishery by 2100’

Planktonic stages of the ecologically important sea urchin, Diadema africanum: larval performance under near future ocean conditions

Diadema africanum is a recently described sea urchin from the Eastern Atlantic archipelagos, and adults play a major ecological role mediating the transition between two alternative ecosystem states: macroalgal beds and urchin barrens. The aim of this study was to describe for the first time the egg characteristics, fertilization and larval development. To determine basic life-history characteristics for this species, we reared larvae through to metamorphic competence under an energy shortage experiment and temperature–pH experiments to characterize the morphological plasticity of larval responses to actual and future oceanic conditions. D. africanum produces eggs that are larger both in diameter (82.7 μm) and volume (0.30 nl) than the eggs of both Diadema antillarum (70.0 μm, 0.18 nl) and Diadema mexicanum (68.0 μm, 0.16 nl). Larval development is similar to other species within the Family Diadematidae, with a Echinopluteus transversus larval type morphology. The combined effects of the climate change-related environmental factors resulted in a reduction in fitness of D. africanum at the warmer limit of its thermal range when combined with low pH. Results suggest that the egg and larval life-history characteristics of D. africanum may have evolved to facilitate long-distance oceanic transport; however, near-future oceanic conditions may compromise larval survival.

Continue reading ‘Planktonic stages of the ecologically important sea urchin, Diadema africanum: larval performance under near future ocean conditions’

Molecular response of a coral reef fish (Acanthochromis polyacanthus) to climate change

Marine ecosystems are already threatened by the effects of climate change through increases in ocean temperatures and pCO2 levels due to increasing atmospheric CO2. Marine fish living close to their thermal maximum have been shown to be especially vulnerable to temperatures exceeding that threshold, and even relatively small increases in elevated pCO2 levels have led to behavioral impairments with amplified predation risks. These ongoing threats highlight the need for further understanding of how these changes will impact fish and if any potential for adaptation or acclimation exists. The coral reef fish, Acanthochromis polyacanthus, has been well studied in response to singular environmental changes both through its phenotype and molecular expression profiles within and across generations. However, key questions regarding transgenerational heritability and molecular responses to multiple environmental changes have not been addressed. To further understand A. polyacanthus I examined the mechanisms behind heritability of behavioral tolerance to elevated pCO2 in an attempt to determine the maternal and paternal contributions to this phenotype. There was a strong impact of parental phenotype on the expression profiles of their offspring regardless of environmental exposure. Offspring from both parental pairs expressed mechanisms involved in tolerance to ocean acidification suggesting this phenotype is reliant on input from both parents. Creation of a new proteomic resource, a SWATH spectral library, delivered a closer examination of the link between phenotypic and expression changes. Analysis on different constructed libraries led to the use of an organism whole library combined with study specific data to analyze proteomic changes in A. polyacanthus under the combined environmental changes of ocean acidification and warming. With direct comparisons to transcriptomic changes in the same individuals I identified an additive effect of elevated pCO2 and temperature associated with decreases in growth and development. However, a strong role of parental identity on the expression profiles of offspring reinforced the high genetic variability of this species. This thesis provides novel insights into the heritability of phenotypic traits and the molecular responses to combined stressors in A. polyacanthus, as well as presenting a new resource for proteomic studies in this fish and other non-model species.

Continue reading ‘Molecular response of a coral reef fish (Acanthochromis polyacanthus) to climate change’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book