Archive for October, 2018

Ocean warming, but not acidification, accelerates seagrass decomposition under near-future climate scenarios

The majority of marine macrophyte production is not consumed by herbivores but instead is channeled into detrital pathways where it supports biodiversity and drives coastal productivity, nutrient cycling and blue carbon sequestration. While it is clear that detrital pathways will be affected by ocean climate change, the relative importance of changing temperature or pH, or their interactions, has not been assessed. We used outdoor mesocosm experiments to assess the relative importance of ocean warming, acidification and latitude of litter origin on the decomposition and biomechanical properties of seagrass Zostera muelleri. Seagrass, collected from 2 sites at each of 2 latitudes (29° and 35°S), was subjected to an orthogonal combination of current and predicted future ocean warming (+3°C) and acidification (-0.3 pH unit). Elevated temperatures resulted in a 15% greater loss of seagrass detrital mass. Mass loss of seagrass detritus was also greater in seagrass from higher than from lower latitudes. The stiffness (Young’s modulus) of decomposing seagrass was greater at 22°C than at 25°C. Elevated sea temperatures also weakened decomposing seagrass, but the magnitude of these effects was greater for Z. muelleri originating from higher than from lower latitudes. Overall, ocean warming is likely to have a much larger influence on seagrass decomposition than ocean acidification. As climate changes, however, if seagrass from higher latitudes takes on similar characteristics to seagrass currently growing at lower latitudes, there may be a negative feedback against the impacts of ocean warming on decomposition, moderating changes in associated primary and secondary productivity that supports coastal fisheries and ecosystem processes.

Continue reading ‘Ocean warming, but not acidification, accelerates seagrass decomposition under near-future climate scenarios’

Quantifying sensitivity and adaptive capacity of shellfish in the Northern California Current Ecosystem to increasing prevalence of ocean acidification and hypoxia

The severity of carbonate chemistry changes from ocean acidification is predicted to increase greatly in the coming decades, with serious consequences for marine species-­ especially those reliant on calcium carbonate for structure and function (Fabry et al. 2008). The Northern California Current Ecosystem off the coast of US West Coast experiences seasonal variations in upwelling and downwelling patterns creating natural episodes of hypoxia and calcite/aragonite undersaturation, exacerbating global trends of increasing ocean acidification and hypoxia (OAH) (Chan et al. 2008) (Gruber et al. 2012). The goal of these experiments was to identify thresholds of tolerance and attempt to quantify a point at which variance in responses to stress collapses. This study focuses on two species: Cancer magister (Dungeness crab) and Haliotis rufescens (red abalone). These species were selected for this study based on their economic and ecological value, as well as their taxonomic differences. Respirometry was used as a proxy for metabolic activity at four different scenarios mimicking preindustrial, upwelling, contemporary upwelling, and distant future conditions by manipulating dissolved oxygen and inorganic carbon (DIC) concentrations. Both species showed a decrease in mean respiration rate as OAH stressors increase, including an effect in contemporary upwelling conditions. These results suggest that current exposure to ocean acidification (OA) and hypoxia do not confer resilience to these stressors for either taxa. In teasing apart the effects of OAH as multiple stressors, it was found that Dungeness crab response was more strongly driven by concentration of dissolved oxygen, while red abalone data suggested a strong interactive effect between OA and hypoxia. Not only did these two different taxa exhibit different responses to a multiple stressors, but the fact that the Dungeness crab were secondarily impacted by acidification could suggest that current management concerns may need to be focus more strongly on deoxygenation.

Continue reading ‘Quantifying sensitivity and adaptive capacity of shellfish in the Northern California Current Ecosystem to increasing prevalence of ocean acidification and hypoxia’

Alterations to seabed raise fears for future

The ocean floor as we know it is dissolving rapidly as a result of human activity.

Normally the deep sea bottom is a chalky white. It’s composed, to a large extent, of the mineral calcite (CaCO3) formed from the skeletons and shells of many planktonic organisms and corals. The seafloor plays a crucial role in controlling the degree of ocean acidification. The dissolution of calcite neutralizes the acidity of the CO2, and in the process prevents seawater from becoming too acidic. But these days, at least in certain hotspots such as the Northern Atlantic and the southern Oceans, the ocean’s chalky bed is becoming more of a murky brown. As a result of human activities the level of CO2 in the water is so high, and the water is so acidic, that the calcite is simply being dissolved.

The McGill-led research team who published their results this week in a study in PNAS believe that what they are seeing today is only a foretaste of the way that the ocean floor will most likely be affected in future.

Continue reading ‘Alterations to seabed raise fears for future’

New version of seacarb R package available

The R package seacarb calculates parameters of the seawater carbonate system and includes functions useful for ocean acidification research. There was a major update of seacarb with its version 3.2.6. It is an important update with major contributions from Jim Orr, Jean-Marie Epitalon and Mathilde Hagens. You are urged to use this version, or even better more recent versions (currently v3.2.10) rather than any of the earlier ones. Support from the Ocean Acidification International Coordination Centre was critical for this update.

Continue reading ‘New version of seacarb R package available’

Routine uncertainty propagation for the marine carbon dioxide system

Highlights

• Add ons to four public packages used to make CO2 system calculations were developed to make uncertainty propagation easy.

• A new type of diagram further simplifies propagating and interpreting uncertainties.

• Large changes in the uncertainties in the measured input pair of CO2 system variables often have little effect on propagated uncertainties because they are dominated by uncertainties from the equilibrium constants, particularly K1 and K2.

• Relative uncertainties for the saturation states of aragonite and calcite are larger than for the carbonate ion concentration, being dominated by the contribution of their respective solubility products.

Abstract

Pairs of marine carbonate system variables are often used to calculate others, but those results are seldom reported with estimates of uncertainties. Although the procedure to propagate these uncertainties is well known, it has not been offered in public packages that compute marine carbonate chemistry, fundamental tools that are relied on by the community. To remedy this shortcoming, four of these packages were expanded to calculate sensitivities of computed variables with respect to each input variable and to use those sensitivities along with user-specified estimates of input uncertainties (standard uncertainties) to propagate uncertainties of calculated variables (combined standard uncertainties). Sensitivities from these packages agree with one another and with analytical solutions to within 0.01%; similar agreement among packages was found for the combined standard uncertainties. One package was used to quantify how propagated uncertainties vary among computed variables, seawater conditions, and the chosen pair of carbonate system variables that is used as input. The relative contributions to propagated uncertainties from the standard uncertainties of the input pair of measurements and various other input data (equilibrium constants etc) were explored with a new type of diagram. These error-space diagrams illustrate that further improvement beyond today’s state-of-the-art measurement uncertainties for the input pair would generally be ineffective at reducing the combined standard uncertainties because the contribution from the constants is larger. Likewise, using much more uncertain measurements of the input pair does not always substantially worsen combined standard uncertainty. The constants that contribute most to combined standard uncertainties are generally K1 and K2, as expected. Yet more of the propagated uncertainty in the computed saturation states of aragonite and calcite comes from their solubility products. Thus percent relative combined standard uncertainties for the saturation states are larger than for the carbonate ion concentration. Routine propagation of these uncertainties should become standard practice.

Continue reading ‘Routine uncertainty propagation for the marine carbon dioxide system’

Le CO₂ d’origine humaine laisse sa trace au fond des mers (in French)

Photo: NEON_ja / Wikimedia Commons

Après avoir perturbé la composition, la température et la dynamique de l’atmosphère, l’humain bouscule maintenant l’océan jusqu’aux profondeurs des abysses. Une étude publiée le 29 octobre montre pour la première fois que les émissions anthropiques de CO₂ dissolvent des minéraux dans les sédiments aux fonds des mers.

« On a découvert que le CO₂ émis par les humains acidifiait assez l’eau des océans pour dissoudre les sédiments qu’on retrouve au fond des mers », explique Olivier Sulpis, candidat au doctorat à l’Université McGill et premier auteur de l’étude.

Chaque année, environ le tiers du CO₂ que l’humanité envoie dans l’atmosphère est absorbé par les océans. Cette part du carbone ne contribue donc pas au réchauffement climatique, mais acidifie l’eau des océans. Les eaux plus corrosives dissolvent plus facilement la calcite (CaCO₃), le minéral blanc qui compose la craie ou les coquillages et qui se retrouve souvent dans les sédiments marins. La calcite qui s’accumule au fond des mers provient des coquilles de certains organismes planctoniques qui, à leur mort, tombent vers le plancher océanique.

Continue reading ‘Le CO₂ d’origine humaine laisse sa trace au fond des mers (in French)’

Current CaCO3 dissolution at the seafloor caused by anthropogenic CO2

Oceanic uptake of anthropogenic CO2 leads to decreased pH, carbonate ion concentration, and saturation state with respect to CaCO3 minerals, causing increased dissolution of these minerals at the deep seafloor. This additional dissolution will figure prominently in the neutralization of man-made CO2. However, there has been no concerted assessment of the current extent of anthropogenic CaCO3 dissolution at the deep seafloor. Here, recent databases of bottom-water chemistry, benthic currents, and CaCO3 content of deep-sea sediments are combined with a rate model to derive the global distribution of benthic calcite dissolution rates and obtain primary confirmation of an anthropogenic component. By comparing preindustrial with present-day rates, we determine that significant anthropogenic dissolution now occurs in the western North Atlantic, amounting to 40–100% of the total seafloor dissolution at its most intense locations. At these locations, the calcite compensation depth has risen ∼300 m. Increased benthic dissolution was also revealed at various hot spots in the southern extent of the Atlantic, Indian, and Pacific Oceans. Our findings place constraints on future predictions of ocean acidification, are consequential to the fate of benthic calcifiers, and indicate that a by-product of human activities is currently altering the geological record of the deep sea.

Continue reading ‘Current CaCO3 dissolution at the seafloor caused by anthropogenic CO2’

Living in a multi-stressors environment: an integrated biomarker approach to assess the ecotoxicological response of meagre (Argyrosomus regius) to venlafaxine, warming and acidification

Highlights
• VFX toxicity was influenced by exposure route, as well as by abiotic stressors
• VFX water exposure induced more severe biomarker responses than VFX feed exposure
• Muscle, liver and brain biomarker responses were significantly affected by warming
• Biomarker changes due to acidification were more evident in fish gills
• The combination of the three stressors simultaneously increased stress severity
• The importance of assessing potential interaction between stressors was evidenced

Abstract
Pharmaceuticals, such as the antidepressant venlafaxine (VFX), have been frequently detected in coastal waters and marine biota, and there is a growing body of evidence that these pollutants can be toxic to non-target marine biota, even at low concentrations. Alongside, climate change effects (e.g. warming and acidification) can also affect marine species’ physiological fitness and, consequently, compromising their ability to cope with the presence of pollutants. Yet, information regarding interactive effects between pollutants and climate change-related stressors is still scarce. Within this context, the present study aims to assess the differential ecotoxicological responses (antioxidant activity, heat shock response, protein degradation, endocrine disruption and neurotoxicity) of juvenile fish (Argyrosomus regius) tissues (muscle, gills, liver and brain) exposed to VFX (via water or feed), as well as to the interactive effects of warming (ΔT°C = +5 °C) and acidification (ΔpCO2 ~ +1000 µatm, equivalent to ΔpH = −0.4 units), using an integrated multi-biomarker response (IBR) approach.

Overall, results showed that VFX toxicity was strongly influenced by the uptake pathway, as well as by warming and acidification. More significant changes (e.g. increases surpassing 100% in lipid peroxidation, LPO, heat shock response protein content, HSP70/HSC70, and total ubiquitin content, Ub,) and higher IBR index values were observed when VFX exposure occurred via water (i.e. average IBR = 19, against 17 in VFX-feed treatment). The co-exposure to climate change-related stressors either enhanced (e.g. glutathione S-transferases activity (GST) in fish muscle was further increased by warming) or attenuated the changes elicited by VFX (e.g. vitellogenin, VTG, liver content increased with VFX feed exposure acting alone, but not when co-exposed with acidification). Yet, increased stress severity was observed when the three stressors acted simultaneously, particularly in fish exposed to VFX via water (i.e. average IBR = 21). Hence, the distinct fish tissues responses elicited by the different scenarios emphasized the relevance of performing multi-stressors ecotoxicological studies, as such approach enables a better estimation of the environmental hazards posed by pollutants in a changing ocean and, consequently, the development of strategies to mitigate them.

Continue reading ‘Living in a multi-stressors environment: an integrated biomarker approach to assess the ecotoxicological response of meagre (Argyrosomus regius) to venlafaxine, warming and acidification’

Non-linear physiology and gene expression responses of harmful alga Heterosigma akashiwo to rising CO2

Heterosigma akashiwo is a raphidophyte known for forming ichthyotoxic blooms. In order to predict the potential impacts of rising CO2 on H. akashiwo it is necessary to understand the factors influencing growth rates over a range of CO2 concentrations. Here we examined the physiology and gene expression response of H. akashiwo to concentrations from 200 to 1000 ppm CO2. Growth rate data were combined from this and previous studies and fit with a CO2 limitation-inhibition model that revealed an apparent growth optimum around 600–800 ppm CO2. Physiological changes included a significant increase in C:N ratio at ∼800 ppm CO2 and a significant decrease in hydrogen peroxide concentration at ∼1000 ppm. Whole transcriptome sequencing of H. akashiwo revealed sharp distinctions in metabolic pathway gene expression between ∼600 and ∼800 ppm CO2. Hierarchical clustering by co-expression identified groups of genes with significant correlations to CO2 and growth rate. Genes with significant differential expression with CO2 included carbon concentrating mechanism genes such as beta-carbonic anhydrases and a bicarbonate transporter, which may underpin shifts in physiology. Genes involved in cell motility were significantly changed by both elevated CO2 and growth rate, suggesting that future ocean conditions could modify swimming behavior in this species.

Continue reading ‘Non-linear physiology and gene expression responses of harmful alga Heterosigma akashiwo to rising CO2’

The rise of sponges in Anthropocene reef ecosystems

Many Caribbean reefs are now dominated by sponges. Credit:  CC BY-ND

Coral reefs across the world have been altered dramatically in recent decades. Human activities have contributed to mass coral die-offs in tropical oceans.

The degradation of reef-building corals is expected to worsen under current climate trajectories, but our work shows that most reef sponges are resilient enough to tolerate climate conditions projected for 2100.

In our latest research, we examine how future reefs that include more sponges might function compared to the current coral‐dominated ecosystems.

Sponge resilience

In our most recent research, we explored the potential mechanisms that underpin sponge tolerance to warming and acidification. We measured the composition of lipids and fatty acids in sponge species with different environmental sensitivities. We found that sponges with greater proportions of storage lipids and certain long‐chain polyunsaturated fatty acids were more resistant to warming.

These specific lipids and fatty acids likely preserve cell membrane function and other cellular processes in the face of temperature stress. Further exploration of how sponges alter their membrane lipids in response to rising temperatures revealed a potential mechanism through which ocean acidification may increase resistance to thermal stress by increasing production of membrane‐stabilising sterols. Our research shows that lipids and fatty acids are an important component of how sponges respond and may support their survival in future oceans.

Continue reading ‘The rise of sponges in Anthropocene reef ecosystems’


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