| 1. |
- Ketzer, João Marcelo, et al.
(författare)
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Near seafloor methane flux in the world's largest human-induced dead zone is regulated by sediment accumulation rate
- 2024
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Ingår i: Marine Geology. - : Elsevier. - 0025-3227 .- 1872-6151. ; 468
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Tidskriftsartikel (refereegranskat)abstract
- The vast oxygen-depleted area of the central Baltic Sea is the largest human-induced dead zone in the world with 70,000 km(2) or approximately three times the second largest one in the Gulf of Mexico. Methane occurs in high concentrations in bottom waters (3200 nM) and sediments (30 mM), and its dynamics is better constrained for the water column, but still poorly understood on sediments. Here we show that sediment accumulation rate plays a major role in regulating the quantity of organic matter and its residence time in the sulphate reduction and methanogenesis zones and, therefore, affects methane generation, consumption, and diffusive flux in sediments near the seafloor (< 1 m). High fluxes found in high sediment accumulation rate areas and competition for substrate (organoclastic sulphate reduction vs. anaerobic oxidation of methane with sulphate), compromise the ability of the thin microbial filter to consume and prevent methane diffusion through the seafloor.
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| 2. |
- Li, Songjun, et al.
(författare)
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Baltic Sea coastal sediment-bound eukaryotes have increased year-round activities under predicted climate change related warming
- 2024
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Ingår i: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Climate change related warming is a serious environmental problem attributed to anthropogenic activities, causing ocean water temperatures to rise in the coastal marine ecosystem since the last century. This particularly affects benthic microbial communities, which are crucial for biogeochemical cycles. While bacterial communities have received considerable scientific attention, the benthic eukaryotic community response to climate change remains relatively overlooked. In this study, sediments were sampled from a heated (average 5°C increase over the whole year for over 50 years) and a control (contemporary conditions) Baltic Sea bay during four different seasons across a year. RNA transcript counts were then used to investigate eukaryotic community changes under long-term warming. The composition of active species in the heated and control bay sediment eukaryotic communities differed, which was mainly attributed to salinity and temperature. The family level RNA transcript alpha diversity in the heated bay was higher during May but lower in November, compared with the control bay, suggesting altered seasonal activity patterns and dynamics. In addition, structures of the active eukaryotic communities varied between the two bays during the same season. Hence, this study revealed that long-term warming can change seasonality in eukaryotic diversity patterns. Relative abundances and transcript expression comparisons between bays suggested that some taxa that now have lower mRNA transcripts numbers could be favored by future warming. Furthermore, long-term warming can lead to a more active metabolism in these communities throughout the year, such as higher transcript numbers associated with diatom energy production and protein synthesis in the heated bay during winter. In all, these data can help predict how future global warming will affect the ecology and metabolism of eukaryotic community in coastal sediments.
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| 3. |
- Seidel, Laura, 1989-, et al.
(författare)
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Climate change-related warming reduces thermal sensitivity and modifies metabolic activity of coastal benthic bacterial communities
- 2023
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Ingår i: The ISME Journal. - : Springer Nature. - 1751-7362 .- 1751-7370. ; 17, s. 855-869
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Tidskriftsartikel (refereegranskat)abstract
- Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming.
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| 4. |
- Seidel, Laura, et al.
(författare)
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Weakened resilience of benthic microbial communities in the face of climate change
- 2022
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Ingår i: ISME Communications. - : Springer Nature. - 2730-6151. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbialcommunities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The systemdemonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction.Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer tothe sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesistranscripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface,with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that mayresult in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energyproduction in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increasedtemperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures mayamplify negative effects at the base of coastal biochemical cycling.
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| 5. |
- Stranne, Christian, 1979-, et al.
(författare)
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Anaerobic oxidation has a minor effect on mitigating seafloor methane emissions from gas hydrate dissociation
- 2022
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Ingår i: Communications Earth & Environment. - : Springer Nature. - 2662-4435. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Continental margin sediments contain large reservoirs of methane stored as gas hydrate. Ocean warming will partly destabilize these reservoirs which may lead to the release of substantial, yet unconstrained, amounts of methane. Anaerobic oxidation of methane is the dominant biogeochemical process to reduce methane flux, estimated to consume 90% of the methane produced in marine sediments today. This process is however neglected in the current projections of seafloor methane release from gas hydrate dissociation. Here, we introduce a fully coupled oxidation module to a hydraulic-thermodynamic-geomechanical hydrate model. Our results show that for seafloor warming rates > 1 degrees C century(-1), the efficiency of anaerobic oxidation of methane in low permeability sediments is poor, reducing the seafloor methane emissions by <5%. The results imply an extremely low mitigating effect of anaerobic oxidation of methane on climate warming-induced seafloor methane emissions. Microbial anaerobic oxidation of methane may not substantially mitigate projected warming-induced emissions of methane from marine hydrate-bearing sediments, according to a coupled hydraulic-thermodynamic-geomechanical hydrate model.
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| 6. |
- Stranne, Christian, et al.
(författare)
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Can anaerobic oxidation of methane prevent seafloor gas escape in a warming climate?
- 2019
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Ingår i: Solid Earth. - : Copernicus GmbH. - 1869-9510 .- 1869-9529. ; 10:5, s. 1541-1554
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Tidskriftsartikel (refereegranskat)abstract
- Assessments of future climate-warming-induced seafloor methane (CH4) release rarely include anaerobic ox- idation of methane (AOM) within the sediments. Consider- ing that more than 90 % of the CH4 produced in ocean sed- iments today is consumed by AOM, this may result in sub- stantial overestimations of future seafloor CH4 release. Here, we integrate a fully coupled AOM module with a numerical hydrate model to investigate under what conditions rapid re- lease of CH4 can bypass AOM and result in significant fluxes to the ocean and atmosphere. We run a number of different model simulations for different permeabilities and maximum AOM rates. In all simulations, a future climate warming sce- nario is simulated by imposing a linear seafloor temperature increase of 3 ◦C over the first 100 years. The results presented in this study should be seen as a first step towards under- standing AOM dynamics in relation to climate change and hydrate dissociation. Although the model is somewhat poorly constrained, our results indicate that vertical CH4 migration through hydraulic fractures can result in low AOM efficien- cies. Fracture flow is the predicted mode of methane trans- port under warming-induced dissociation of hydrates on up- per continental slopes. Therefore, in a future climate warm- ing scenario, AOM might not significantly reduce methane release from marine sediments.
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