| 1. |
- Roth, Florian, et al.
(författare)
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High spatiotemporal variability of methane concentrations challenges estimates of emissions across vegetated coastal ecosystems.
- 2022
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Ingår i: Global change biology. - : Wiley. - 1365-2486 .- 1354-1013. ; 28:14, s. 4308-4322
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Tidskriftsartikel (refereegranskat)abstract
- Coastal methane (CH4 ) emissions dominate the global ocean CH4 budget and can offset the "blue carbon" storage capacity of vegetated coastal ecosystems. However, current estimates lack systematic, high-resolution, and long-term data from these intrinsically heterogeneous environments, making coastal budgets sensitive to statistical assumptions and uncertainties. Using continuous CH4 concentrations, δ13 C-CH4 values, and CH4 sea-air fluxes across four seasons in three globally pervasive coastal habitats, we show that the CH4 distribution is spatially patchy over meter-scales and highly variable in time. Areas with mixed vegetation, macroalgae, and their surrounding sediments exhibited a spatiotemporal variability of surface water CH4 concentrations ranging two orders of magnitude (i.e., 6-460nM CH4 ) with habitat-specific seasonal and diurnal patterns. We observed (1) δ13 C-CH4 signatures that revealed habitat-specific CH4 production and consumption pathways, (2) daily peak concentration events that could change >100% within hours across all habitats, and (3) a high thermal sensitivity of the CH4 distribution signified by apparent activation energies of ~1eV that drove seasonal changes. Bootstrapping simulations show that scaling the CH4 distribution from few samples involves large errors, and that ~50 concentration samples per day are needed to resolve the scale and drivers of the natural variability and improve the certainty of flux calculations by up to 70%. Finally, we identify northern temperate coastal habitats with mixed vegetation and macroalgae as understudied but seasonally relevant atmospheric CH4 sources (i.e., releasing≥100μmol CH4 m-2 day-1 in summer). Due to the large spatial and temporal heterogeneity of coastal environments, high-resolution measurements will improve the reliability of CH4 estimates and confine the habitat-specific contribution to regional and global CH4 budgets.
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| 2. |
- Cheung, Henry Lok Shan, et al.
(författare)
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Denitrification, anammox, and DNRA in oligotrophic continental shelf sediments
- 2024
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Ingår i: Limnology and Oceanography. - 1939-5590 .- 0024-3590.
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Tidskriftsartikel (refereegranskat)abstract
- Continental shelf sediments are considered hotspots for nitrogen (N) removal. While most investigations have quantified denitrification in shelves receiving large amounts of anthropogenic nutrient supply, we lack insight into the key drivers of N removal on oligotrophic shelves. Here, we measured rates of N removal through denitrification and anammox by the revised-isotope pairing technique (r-IPT) along the Northeastern New Zealand shelf. Denitrification dominated total N2 production at depths between 30 and 128 m with average rates (± SE) ranging from 65 ± 28 to 284 ± 72 μmol N m−2 d−1. N2 production by anammox ranged from 3 ± 1 to 28 ± 11 μmol N m−2 d−1 and accounted for 2–19% of total N2 production. DNRA was negligible in these oligotrophic settings. Parallel microbial community analysis showed that both Proteobacteria and Planctomycetota were key taxa driving denitrification. Denitrification displayed a negative correlation with oxygen penetration depth, and a positive correlation with macrofauna abundance. Our denitrification rates were comparable to oligotrophic shelves from the Arctic, but were lower than those from nutrient-rich Pacific and Atlantic shelves. Based on our results and existing IPT measurements, the global shelf denitrification rate was reassessed to be 53.5 ± 8.1 Tg N yr−1, equivalent to 20 ± 2% of marine N removal. We suggest that previous estimates of global shelf N loss might have been overestimated due to sampling bias toward areas with high N loads in the Northern Hemisphere.
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| 3. |
- Drake, Henrik, 1979-, et al.
(författare)
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Ancient microbial activity in deep hydraulically conductive fracture zones within the Forsmark target area for deep geological nuclear waste disposal, Sweden
- 2018
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Ingår i: Geosciences. - : MDPI AG. - 2076-3263. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies reveal that organisms from all three domains of life—Archaea, Bacteria, and even Eukarya—can thrive under energy-poor, dark, and anoxic conditions at large depths in the fractured crystalline continental crust. There is a need for an increased understanding of the processes and lifeforms in this vast realm, for example, regarding the spatiotemporal extent and variability of the different processes in the crust. Here, we present a study that set out to detect signs of ancient microbial life in the Forsmark area—the target area for deep geological nuclear waste disposal in Sweden. Stable isotope compositions were determined with high spatial resolution analyses within mineral coatings, and mineralized remains of putative microorganisms were studied in several deep water-conducting fracture zones (down to 663 m depth), from which hydrochemical and gas data exist. Large isotopic variabilities of 13Ccalcite (?36.2 to +20.2‰V-PDB) and 34Spyrite (?11.7 to +37.8‰V-CDT) disclose discrete periods of methanogenesis, and potentially, anaerobic oxidation of methane and related microbial sulfate reduction at several depth intervals. Dominant calcite–water disequilibrium of 18O and 87Sr/86Sr precludes abundant recent precipitation. Instead, the mineral coatings largely reflect an ancient archive of episodic microbial processes in the fracture system, which, according to our microscale Rb–Sr dating of co-genetic adularia and calcite, date back to the mid-Paleozoic. Potential Quaternary precipitation exists mainly at ~400 m depth in one of the boreholes, where mineral–water compositions corresponded.
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| 4. |
- Omstedt, Anders, 1949
(författare)
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The Development of Climate Science of the Baltic Sea Region
- 2017
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Ingår i: Oxford Research Encyclopedia of Climate Science. - : Oxford University Press.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Dramatic climate changes have occurred in the Baltic Sea region caused by changes in orbital movement in the earth–sun system and the melting of the Fennoscandian Ice Sheet. Added to these longer-term changes, changes have occurred at all timescales, caused mainly by variations in large-scale atmospheric pressure systems due to competition between the meandering midlatitude low-pressure systems and highpressure systems. Here we follow the development of climate science of the Baltic Sea from when observations began in the 18th century to the early 21st century. The question of why the water level is sinking around the Baltic Sea coasts could not be answered until the ideas of postglacial uplift and the thermal history of the earth were better understood in the 19th century and periodic behavior in climate related time series attracted scientific interest. Herring and sardine fishing successes and failures have led to investigations of fishery and climate change and to the realization that fisheries themselves have strongly negative effects on the marine environment, calling for international assessment efforts. Scientists later introduced the concept of regime shifts when interpreting their data, attributing these to various causes. The increasing amount of anoxic deep water in the Baltic Sea and eutrophication have prompted debate about what is natural and what is anthropogenic, and the scientific outcome of these debates now forms the basis of international management efforts to reduce nutrient leakage from land. The observed increase in atmospheric CO and its effects on global warming have focused the climate debate on trends and generated a series of international and regional assessments and research programs that have greatly improved our understanding of climate and environmental changes, bolstering the efforts of earth system science, in which both climate and environmental factors are analyzed together.
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| 5. |
- Björk, Mats, 1960-, et al.
(författare)
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Methane emissions from macrophyte beach wrack on Baltic seashores
- 2023
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Ingår i: Ambio. - : Springer Nature. - 0044-7447 .- 1654-7209. ; 52:1, s. 171-181
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Tidskriftsartikel (refereegranskat)abstract
- Beach wrack of marine macrophytes is a natural component of many beaches. To test if such wrack emits the potent greenhouse gas methane, field measurements were made at different seasons on beach wrack depositions of different ages, exposure, and distance from the water. Methane emissions varied greatly, from 0 to 176 mg CH4-C m−2 day−1, with a clear positive correlation between emission and temperature. Dry wrack had lower emissions than wet. Using temperature data from 2016 to 2020, seasonal changes in fluxes were calculated for a natural wrack accumulation area. Such calculated average emissions were close to zero during winter, but peaked in summer, with very high emissions when daily temperatures exceeded 20 °C. We conclude that waterlogged beach wrack significantly contributes to greenhouse gas emissions and that emissions might drastically increase with increasing global temperatures. When beach wrack is collected into heaps away from the water, the emissions are however close to zero.
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| 6. |
- Hassellöv, Ida-Maja, 1974, et al.
(författare)
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Miljörisker sjunkna vrak II. Undersökningsmetoder och miljöaspekter
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- During 2015 the Swedish Maritime Administration continued the second phase of thegovernmental task Environmental risks from sunken wrecks which first report was finalized2014-10-31 (Dnr: 1399-14-01942-6).The main conclusions from the 2014 report remain; for future handling of potentially pollutingshipwrecks it is recommended that the Swedish Agency for Water and Marine Management isgiven a coordinating responsibility in close cooperation with other competent nationalauthorities, such as Swedish Maritime Administration, Swedish Coastguard, Swedish NationalMaritime Museums, the Geological Survey of Sweden, SMHI, Swedish EPA, and SwedishCivil Contingencies Agency. Through coordination of wreck related operations and activitieswithin the concerned competent authorities’ ordinary areas of responsibility, resourceefficiency is improved. The estimated extra cost for implementation of a national strategy forhandling of the wrecks are estimated to be 10-15 MSEK which should be allocated to thecompetent authorities by the Swedish Agency for Water and Marine Management.The conclusions from 2014 was reinforced during 2015, e.g. through the validation of the riskassessment model VRAKA, which is now available in a first operative version. Additionalecotoxicological experiments on the development of tolerance against PAHs in meiofauna andmicroorganism communities were conducted in a field study in Brofjorden. The mainconclusions from this work is that comprehensive analyzes of PAHs should include alkylatedPAHs, and that exposure to PAHs over time can lead to tolerance development in ammoniumoxidizing bacteria, at the expense of their ability to perform the essential ecosystem servicenitrification.Continued measurements of the bottom currents were made at the wrecks Villon and Skytteren,and at the dumping area west of Måseskär. Measurement series yielded important informationon how measuring equipment at the wreck can be deployed in an optimized way in futuremonitoring program; to calculate the possible spreading of pollution from a wreck, currentmeasurements should be performed upstream from the wreck site, while sensors for thedetection of, for example, oil should be put into the turbulence downstream of the wreck.The current measurement instruments (RDCP) deployed at the Måseskär dump site was trawledup after only three weeks of measurements, but still gave valuable information on the extensivebottom trawling that resuspend (stir up) sediments. Earlier geochemical surveys have shownsignificantly elevated arsenic concentrations in the area and sediment resuspension greatlyincreased the risk for spread of any contaminants in the area. Trawling is not prohibited in thearea, and the current lack of knowledge regarding potential effects on human health whenconsuming seafood from dump areas calls for reflection upon the suitability of trawling in thearea.In addition to the current measurements Swedish Maritime Administration and the SwedishNavy conducted hydrographic survey with multibeam and side scan sonar and ROVinvestigation of the wrecks in the dumping area at Måseskär. 28 wrecks were found, and ROVinvestigation showed cargo holds with dumped torpedoes or mines and other containers in some SjöfartsverketDnr: 1399-14-01942-156of the wrecks. There is some discrepancy between the previously measured elevated arsenicconcentrations in the Måseskär area and recently presented data from historical archives thatdoes not support the theory that chemical weapons were dumped in the area. However, there isa very good correlation between the dominant current direction in the area, and the highestmeasured arsenic concentrations in the area downstream of the wrecks, suggesting some formof arsenic source in the area.
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| 7. |
- Weyhenmeyer, Gesa A., et al.
(författare)
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Towards critical white ice conditions in lakes under global warming.
- 2022
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- The quality of lake ice is of uppermost importance for ice safety and under-ice ecology, but its temporal and spatial variability is largely unknown. Here we conducted a coordinated lake ice quality sampling campaign across the Northern Hemisphere during one of the warmest winters since 1880 and show that lake ice during 2020/2021 commonly consisted of unstable white ice, at times contributing up to 100% to the total ice thickness. We observed that white ice increased over the winter season, becoming thickest and constituting the largest proportion of the ice layer towards the end of the ice cover season when fatal winter drownings occur most often and light limits the growth and reproduction of primary producers. We attribute the dominance of white ice before ice-off to air temperatures varying around the freezing point, a condition which occurs more frequently during warmer winters. Thus, under continued global warming, the prevalence of white ice is likely to substantially increase during the critical period before ice-off, for which we adjusted commonly used equations for human ice safety and light transmittance through ice.
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| 8. |
- Chan, Phoebe, et al.
(författare)
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Freshening of the Alaska Coastal Current recorded by coralline algal Ba/Ca ratios
- 2011
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Ingår i: Journal of Geophysical Research-Biogeosciences. - 0148-0227. ; 116
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Tidskriftsartikel (refereegranskat)abstract
- Arctic Ocean freshening can exert a controlling influence on global climate, triggering strong feedbacks on ocean-atmospheric processes and affecting the global cycling of the world's oceans. Glacier-fed ocean currents such as the Alaska Coastal Current are important sources of freshwater for the Bering Sea shelf, and may also influence the Arctic Ocean freshwater budget. Instrumental data indicate a multiyear freshening episode of the Alaska Coastal Current in the early 21st century. It is uncertain whether this freshening is part of natural multidecadal climate variability or a unique feature of anthropogenically induced warming. In order to answer this, a better understanding of past variations in the Alaska Coastal Current is needed. However, continuous long-term high-resolution observations of the Alaska Coastal Current have only been available for the last 2 decades. In this study, specimens of the long-lived crustose coralline alga Clathromorphum nereostratum were collected within the pathway of the Alaska Coastal Current and utilized as archives of past temperature and salinity. Results indicate that coralline algal Mg/Ca ratios provide a 60 year record of sea surface temperatures and track changes of the Pacific Decadal Oscillation, a pattern of decadal-to-multidecadal ocean-atmosphere climate variability centered over the North Pacific. Algal Ba/Ca ratios (used as indicators of coastal freshwater runoff) are inversely correlated to instrumentally measured Alaska Coastal Current salinity and record the period of freshening from 2001 to 2006. Similar multiyear freshening events are not evident in the earlier portion of the 60 year Ba/Ca record. This suggests that the 21st century freshening of the Alaska Coastal Current is a unique feature related to increasing glacial melt and precipitation on mainland Alaska.
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| 9. |
- Gamboa, G., et al.
(författare)
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Mg/Ca ratios in coralline algae record northwest Atlantic temperature variations and North Atlantic Oscillation relationships
- 2010
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Ingår i: Journal of Geophysical Research-Oceans. - 0148-0227. ; 115
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Tidskriftsartikel (refereegranskat)abstract
- [1] Climate variability in the North Atlantic has been linked in part to the North Atlantic Oscillation (NAO). The NAO influences marine ecosystems in the northwestern Atlantic and transport variability of the cold Labrador Current. Understanding historic patterns of NAO variability requires long-term and high-resolution climate records that are not available from instrumental data. Here we present the first century-scale proxy record of sea surface temperature (SST) variability from the Newfoundland shelf, a region from which other annual-resolution shallow marine proxies are unavailable. The 116 year record was obtained from three sites along the eastern Newfoundland shelf using laser ablation inductively coupled mass spectrometry-determined Mg/Ca ratios in the crustose coralline alga Clathromorphum compactum. The alga is characterized by a high Mg-calcite skeleton exhibiting annual growth increments and a century-scale lifespan. Results indicate positive correlations between interannual variations in Mg/Ca ratios and both station-based and gridded instrumental SST. In addition, the record shows high spatial correlations to SST across the Newfoundland shelf and the Gulf of St. Lawrence. Before 1950 the Mg/Ca proxy record reveals significant departures from gridded temperature records. While the Newfoundland shelf is generally considered a region of negative correlations to the NAO, the algal time series as well as a recent modeling study suggest a variable negative relationship with the NAO which is strongest after similar to 1960 and before the mid-1930s.
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| 10. |
- Broman, Elias, 1985-, et al.
(författare)
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Biotic interactions between benthic infauna and aerobic methanotrophs mediate methane fluxes from coastal sediments
- 2024
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Ingår i: The ISME journal. - 1751-7370 .- 1751-7362. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- Coastal ecosystems dominate oceanic methane (CH4) emissions. However, there is limited knowledge about how biotic interactions between infauna and aerobic methanotrophs (i.e. CH4 oxidizing bacteria) drive the spatial-temporal dynamics of these emissions. Here, we investigated the role of meio- and macrofauna in mediating CH4 sediment-water fluxes and aerobic methanotrophic activity that can oxidize significant portions of CH4. We show that macrofauna increases CH4 fluxes by enhancing vertical solute transport through bioturbation, but this effect is somewhat offset by high meiofauna abundance. The increase in CH4 flux reduces CH4 pore-water availability, resulting in lower abundance and activity of aerobic methanotrophs, an effect that counterbalances the potential stimulation of these bacteria by higher oxygen flux to the sediment via bioturbation. These findings indicate that a larger than previously thought portion of CH4 emissions from coastal ecosystems is due to faunal activity and multiple complex interactions with methanotrophs.
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