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  • Wiley  (2)
  • AMER SOC LIMNOLOGY OCEANOGRAPHY  (1)
  • Elsvier  (1)
  • Macmillian Magazines Ltd.  (1)
  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Stable associations of more than one species of symbiont within a single host cell or tissue are assumed to be rare in metazoans because competition for space and resources between symbionts can be detrimental to the host. In animals with multiple endosymbionts, such as mussels from deep-sea ...
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2020-07-20
    Description: Low seawater pH can be harmful to many calcifying marine organisms, but the calcifying macroalgae Padina spp. flourish at natural submarine carbon dioxide seeps where seawater pH is low. We show that the microenvironment created by the rolled thallus margin of Padina australis facilitates supersaturation of CaCO3 and calcifi-cation via photosynthesis-induced elevated pH. Using microsensors to investigate oxygen and pH dynamics in the microenvironment of P. australis at a shallow CO2 seep, we found that, under saturating light, the pH inside the microenvironment (pHME) was higher than the external seawater (pHSW) at all pHSW levels investigated, and the difference (i.e., pHME − pHSW) increased with decreasing pHSW (0.9 units at pHSW 7.0). Gross photosynthesis (Pg) inside the microenvironment increased with decreasing pHSW, but algae from the control site reached a threshold at pH 6.5. Seep algae showed no pH threshold with respect to Pg within the pHSW range investigated. The external carbonic anhydrase (CA) inhibitor, acetazolamide, strongly inhibited Pg of P. australis at pHSW 8.2, but the effect was diminished under low pHSW (6.4–7.5), suggesting a greater dependence on membrane-bound CA for the dehydration of HCO3− ions during dissolved inorganic carbon uptake at the higher pHSW. In comparison, a calcifying green alga, Halimeda cuneata f. digitata, was not inhibited by AZ, suggesting efficient bicarbonate transport. The ability of P. australis to elevate pHME at the site of calcification and its strong dependence on CA may explain why it can thrive at low pHSW.
    Type: Article , PeerReviewed
    Format: text
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  • 3
    Publication Date: 2016-11-04
    Description: Natural CO2 venting systems can mimic conditions that resemble intermediate to high pCO2 levels as predicted for our future oceans. They represent ideal sites to investigate potential long-term effects of ocean acidification on marine life. To test whether microbes are affected by prolonged exposure to pCO2 levels, we examined the composition and diversity of microbial communities in oxic sandy sediments along a natural CO2 gradient. Increasing pCO2 was accompanied by higher bacterial richness and by a strong increase in rare members in both bacterial and archaeal communities. Microbial communities from sites with CO2 concentrations close to today's conditions had different structures than those of sites with elevated CO2 levels. We also observed increasing sequence abundance of several organic matter degrading types of Flavobacteriaceae and Rhodobacteraceae, which paralleled concurrent shifts in benthic cover and enhanced primary productivity. With increasing pCO2, sequences related to bacterial nitrifying organisms such as Nitrosococcus and Nitrospirales decreased, and sequences affiliated to the archaeal ammonia-oxidizing Thaumarchaeota Nitrosopumilus maritimus increased. Our study suggests that microbial community structure and diversity, and likely key ecosystem functions, may be altered in coastal sediments by long-term CO2 exposure to levels predicted for the end of the century.
    Type: Article , PeerReviewed
    Format: text
    Format: archive
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  • 4
    Publication Date: 2024-02-07
    Description: Highlights • A mechanistic explanation is provided for the observed CO2 loss in the sediments. • Reactions of CO2 with the sediment lead to significant heating. • The observations were modeled including reactions and losses due to lateral transport. • CO2 leakage will lead to very local effects. Abstract We investigated the effect of an artificial CO2 vent (0.0015−0.037 mol s−1), simulating a leak from a reservoir for carbon capture and storage (CCS), on the sediment geochemistry. CO2 was injected 3 m deep into the seafloor at 120 m depth. With increasing mass flow an increasing number of vents were observed, distributed over an area of approximately 3 m. In situ profiling with microsensors for pH, T, O2 and ORP showed the geochemical effects are localized in a small area around the vents and highly variable. In measurements remote from the vent, the pH reached a value of 7.6 at a depth of 0.06 m. In a CO2 venting channel, pH reduced to below 5. Steep temperature profiles were indicative of a heat source inside the sediment. Elevated total alkalinity and Ca2+ levels showed calcite dissolution. Venting decreased sulfate reduction rates, but not aerobic respiration. A transport-reaction model confirmed that a large fraction of the injected CO2 is transported laterally into the sediment and that the reactions between CO2 and sediment generate enough heat to elevate the temperature significantly. A CO2 leak will have only local consequences for sediment biogeochemistry, and only a small fraction of the escaped CO2 will reach the sediment surface.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 5
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    AMER SOC LIMNOLOGY OCEANOGRAPHY
    In:  EPIC3Limnology and Oceanography, AMER SOC LIMNOLOGY OCEANOGRAPHY, ISSN: 0024-3590
    Publication Date: 2020-09-07
    Description: We investigated the impact of kelp deposition on the geochemistry and microbial community composition of beach sands on the island of Helgoland (North Sea). The composition of the microbial community at a beach with regular kelp deposition appeared shaped by this regular input of organic material, as indicated by significantly higher proportions of aerobic degraders, fermenters, and sulfur cycling microorganisms. Rapid degradation of deposited kelp by this community leads to high levels of dissolved organic and inorganic carbon and nutrients, a lower pH and anoxia. Aerobic respiration, fermentation, Fe- and SO42- reduction and methanogenesis were strongly enhanced, with SO42- reduction being the main process in kelp degradation. SO42- reduction rates increased 20 to 25-fold upon addition of kelp. The main route of electrons from kelp to SO42- was not via CO and H2, as expected, but via organic fermentation products. O2 supply by the tides was not sufficient and reduced intermediates escaped from the sediment with tidal water retraction. The resulting extremely high levels of free sulfide (〉10 mmol L-1) lead to abundant filamentous growth of sulfur-oxidizing bacteria largely composed of a rare O2-adapted Sulfurovum lacking the expected denitrification genes. Our results show that regular kelp deposition strongly enhances the thermodynamic disequilibrium in the beach sand habitat, leading to a dramatic enhancement of the sulfur cycle.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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