Posts Tagged 'vents'

How calorie-rich food could help marine calcifiers in a CO2-rich future

Increasing carbon emissions not only enrich oceans with CO2 but also make them more acidic. This acidifying process has caused considerable concern because laboratory studies show that ocean acidification impairs calcification (or shell building) and survival of calcifiers by the end of this century. Whether this impairment in shell building also occurs in natural communities remains largely unexplored, but requires re-examination because of the recent counterintuitive finding that populations of calcifiers can be boosted by CO2 enrichment. Using natural CO2 vents, we found that ocean acidification resulted in the production of thicker, more crystalline and more mechanically resilient shells of a herbivorous gastropod, which was associated with the consumption of energy-enriched food (i.e. algae). This discovery suggests that boosted energy transfer may not only compensate for the energetic burden of ocean acidification but also enable calcifiers to build energetically costly shells that are robust to acidified conditions. We unlock a possible mechanism underlying the persistence of calcifiers in acidifying oceans.

Continue reading ‘How calorie-rich food could help marine calcifiers in a CO2-rich future’

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 impacts on coastal ecosystem services due to habitat degradation

The oceanic uptake of anthropogenic carbon dioxide emissions is changing seawater chemistry in a process known as ocean acidification. The chemistry of this rapid change in surface waters is well understood and readily detectable in oceanic observations, yet there is uncertainty about the effects of ocean acidification on society since it is difficult to scale-up from laboratory and mesocosm tests. Here, we provide a synthesis of the likely effects of ocean acidification on ecosystem properties, functions and services based on observations along natural gradients in pCO2. Studies at CO2 seeps worldwide show that biogenic habitats are particularly sensitive to ocean acidification and that their degradation results in less coastal protection and less habitat provisioning for fisheries. The risks to marine goods and services amplify with increasing acidification causing shifts to macroalgal dominance, habitat degradation and a loss of biodiversity at seep sites in the tropics, the sub-tropics and on temperate coasts. Based on this empirical evidence, we expect ocean acidification to have serious consequences for the millions of people who are dependent on coastal protection, fisheries and aquaculture. If humanity is able to make cuts in fossil fuel emissions, this will reduce costs to society and avoid the changes in coastal ecosystems seen in areas with projected pCO2 levels. A binding international agreement for the oceans should build on the United Nations Sustainable Development Goal to ‘minimise and address the impacts of ocean acidification’.

Continue reading ‘Ocean acidification impacts on coastal ecosystem services due to habitat degradation’

Transport of carbon dioxide and heavy metals from hydrothermal vents to shallow water by hydrate-coated gas bubbles

Deep-sea hydrothermal plumes are of major importance in the biogeochemical ocean cycles and in this study we focus on plumes emitted from the Jan Mayen vent fields in the Norwegian-Greenland Sea. These vent fields are of interest because of the high CO2 concentrations and also due to the different styles of venting occurring here. Venting at these sites occurs between 550 and 700 m depth and is characterized by the release of hydrate coated bubbles as well as focused flow venting. This study aims to enhance our current understanding of the impact of CO2 rich hydrate coated bubbles on the water column as well as the interaction between hydrothermally derived gases and metals in the water column. Three water column surveys were conducted in this area in between 2012 and 2014, in which the non-buoyant plume (NBP) produced by focused flow venting from both the Troll Wall and the Perle & Bruse vent sites was identified by primordial helium (3He), methane (CH4), carbon dioxide (CO2) and dissolved manganese (Mn) enrichments close to 500 m water depth. Our results show that venting of hydrate coated CO2 rich bubbles increases bubble rise height, which results in shallow acidification locally above the vent sites. A polymetallic anomaly in the mid-depth water column above the NBP is also hypothesized to be a result of the hydrate coated bubbles. We argue that nanoparticles get sequestered to the hydrate lattice and travel with the bubbles until the lattice becomes unstable due to gas expansion upon depressurization during ascent. This process could fuel the primary production in the pelagic water column.

Continue reading ‘Transport of carbon dioxide and heavy metals from hydrothermal vents to shallow water by hydrate-coated gas bubbles’

Bottom water methane sources along the high latitude eastern Canadian continental shelf and their effects on the marine carbonate system

Highlights
• Evidence of sedimentary methane seepage at three sites along the high latitude eastern Canadian Shelf.

• Stable isotope measurements at one of the sites suggest methane originates from microbial methanogenesis.

• Near bottom spikes in pH seen at two sites suggest the presence of an unidentified proton acceptor in the seep fluid.

Abstract
Measurements of dissolved methane (CH4) and carbonate system parameters were conducted in shelf and slope waters off Baffin Island and northern Labrador during September 2012 and August 2016 in order to investigate potential cold seeps and their influence on the marine carbonate system. Evidence of a strong near-bottom methane source was found at two sites along the Baffin Island Shelf (Scott Inlet and Cape Dyer) and above a pair of reported sea floor mounds in the Saglek Basin between Baffin Island and northern Labrador. Stable carbon isotope measurements of dissolved methane made at the Cape Dyer site give an estimated δ13C value of −71.2‰ for the source, consistent with microbial methanogenesis. The distributions of pCO2, pH and aragonite and calcite saturation states showed no evidence of enhanced ocean acidification in the vicinity of these sites, so it would seem that these seeps were not significant local sources of carbon dioxide, either as a component in the seep fluid or produced subsequent to release by water column microbial methane oxidation, nonetheless, aragonite saturation states of one or less were seen along the Baffin Island Shelf suggesting that ecosystems here may be vulnerable to further acidification. Spectrophotometric pH measurements of fresh samples in 2012 revealed a bottom water spike in pH at two seep sites that were not replicated by measurements of preserved seawater samples. We hypothesise that this was due to an unstable anionic compound present in seep fluid that can locally increase total alkalinity, pH and calcium carbonate saturation with HS− being a likely candidate, possibly to the benefit of calcifying organisms in an environment bordering on aragonite under-saturation.

Continue reading ‘Bottom water methane sources along the high latitude eastern Canadian continental shelf and their effects on the marine carbonate system’

Geochemistry of hot-springs at the SuSu Knolls Hydrothermal Field, Eastern Manus Basin: advanced argillic alteration and vent fluid acidity

SuSu Knolls is an area of ongoing magmatic activity and recent volcanism located in the back-arc spreading environment of the Manus Basin in the Bismarck Sea, Papua New Guinea. In 2006, hydrothermal fluids were collected from three areas of submarine hot-spring venting and analyzed for the chemical and isotopic composition of major and trace species. Fluids were characterized by temperatures that varied from 226 to 325 °C, and formed grey to black smoke as they mixed with bottom seawater. The compositions of seawater derived vent fluids are regulated by the relative contributions of fluid-rock and fluid-sediment interaction, phase separation, and the addition of volatiles from magmatic degassing. In addition to phase separation, leaching of Cl from felsic rocks that compose the lithosphere in back-arc environments may produce measured Cl concentrations in excess of seawater values.

The measured pH25°C of SuSu Knolls smoker fluids varied from 1.5 to 3.7, a range that includes values substantially more acidic than typically observed in fluids at mid-ocean ridge spreading centers. Late stage addition of magmatic volatiles in the shallow seafloor is directly responsible for the most acidic fluids (pH25°C values below 2). In contrast, the acidity of vent fluids characterized by pH25°C values between 2 and 3 is not the direct result of the direct addition of magmatically-derived acidic species. Instead, the pH of these fluids likely reflects reaction with rocks that were previously altered by highly acidic magmatic fluids to an advanced argillic alteration assemblage containing quartz-illite-pyrophyllite-anhydrite±alunite in hydrothermal upflow zones. Fluids that do not react with advanced argillic alteration assemblages during upflow have measured pH25°Cvalues between 3 and 4.

Continue reading ‘Geochemistry of hot-springs at the SuSu Knolls Hydrothermal Field, Eastern Manus Basin: advanced argillic alteration and vent fluid acidity’

Living in future ocean acidification, physiological adaptive responses of the immune systems of sea urchins resident at a CO2 vent system

Highlights

• Paracentrotus lividus living at CO2 vents was compared to those at two control sites.
• Sea urchins are adapted to life at vent site by altering immune cells metabolism.
• Vent animals show a rearrangement of defensive abilities and antioxidant processes.

Abstract

The effects of ocean acidification, a major anthropogenic impact on marine life, have been mainly investigated in laboratory/mesocosm experiments. We used the CO2 vents at Ischia as a natural laboratory to study the long-term effects of ocean acidification on the sea urchin Paracentrotus lividus population resident in low-pH (7.8 ± 0.2) compared to that at two control sites (pH 8.02 ± 0.00; 8.02 ± 0.01). The novelty of the present study is the analysis of the sea urchin immune cells, the sentinels of environmental stress responses, by a wide-ranging approach, including cell morphology, biochemistry and proteomics. Immune cell proteomics showed that 311 proteins were differentially expressed in urchins across sites with a general shift towards antioxidant processes in the vent urchins. The vent urchin immune cells showed higher levels of total antioxidant capacity, up-regulation of phagosome and microsomal proteins, enzymes of ammonium metabolism, amino-acid degradation, and modulation of carbon metabolism proteins. Lipid-hydroperoxides and nitric oxide levels were not different in urchins from the different sites. No differences in the coelomic fluid pH, immune cell composition, animal respiration, nitrogen excretion and skeletal mineralogy were observed. Our results reveal the phenotypic plasticity of the immune system of sea urchins adapted to life at vent site, under conditions commensurate with near-future ocean acidification projections.

Continue reading ‘Living in future ocean acidification, physiological adaptive responses of the immune systems of sea urchins resident at a CO2 vent system’


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Ocean acidification in the IPCC AR5 WG II

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