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171.
The toxicities and bioavailabilities of total mercury (THg) and methylmercury (MeHg) in aquatic systems have made them the subjects of recent research. In this study, we collected a lake sediment core from Ny-Ålesund in Svalbard and analyzed the distributions of THg and MeHg in the sediments. The increased trend of THg was caused by anthropogenic contamination since the 14th century through long-range transportation, especially after the industrial era. However, the peak values of Hg in surface sediment samples could be explained by the increased algal scavenging process in recent decades. All the biogeochemical proxies (e.g., pigments and diatom biomass) revealed recent sharp increases in aquatic primary production due to the current climate warming. Rock-Eval analyses indicated that algal-derived organic matter took up a large portion, and quantitative calculation showed that 89.6-95.8% of the Hg in post-1950 could be explained by scavenging. The distribution of MeHg has a close relationship with total Hg and organic matter. The oxidation-reduction condition is one of the possible factors affecting the methylation rates in H2 lake sediments. Higher algal productivity and organic matter actually led to the increased trend of methylation in the uppermost sediment. This study supports some new key hypotheses on climate-driven factors affecting Hg and MeHg cycling in High Arctic lake sediments. 相似文献
172.
Birgit M. Braune Mark L. Mallory Scott A. Mabury 《Environmental pollution (Barking, Essex : 1987)》2010,158(12):3513-3519
Northern fulmars from two breeding colonies in the Canadian Arctic, Cape Vera and Prince Leopold Island, were analyzed for organochlorine pesticides, PCBs, perfluorinated compounds (PFCs) and total mercury (Hg). Hepatic concentrations of organochlorines and Hg were highest in the male fulmars from Cape Vera. Perfluorooctane sulfonate (PFOS) concentrations did not vary significantly between sexes or colonies. However, concentrations of the perfluorinated carboxylates (PFCAs) were higher in fulmars from Cape Vera than Prince Leopold Island. The C11-C15 PFCAs averaged 90% of the PFCA profile at both colonies. Polychorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and non-ortho PCBs (NO-PCBs) were measured only in birds from Prince Leopold Island. Concentrations of PCDDs, PCDFs, NO-PCBs and Toxic Equivalents (TEQs) did not differ significantly between sexes. ΣTEQ was comprised mainly of ΣTEQPCDF. Concentrations of Hg and the persistent halogenated compounds reported in this study were below published toxicological threshold values for wild birds. 相似文献
173.
It seems inevitable that the ongoing and rapid changes in the physical environment of the marine Arctic will push components
of the region’s existing social-ecological systems—small and large—beyond tipping points and into new regimes. Ongoing changes
include warming, freshening, acidification, and alterations to food web structure. In anticipation we pose three distinct
but interrelated challenges: (1) to explore existing connectivities within components of the marine system; (2) to seek indicators
(if they exist) of approaching regime change through observation and modeling; and (3) to build functional resilience into
existing systems through adaptation-oriented policy and to have in hand transformative options when tipping points are crossed
and new development trajectories are required. Each of the above challenges is scale dependent, and each requires a much deeper
understanding than we currently have of connectivity within existing systems and their response to external forcing. Here,
we argue from a global perspective the need to understand the Arctic’s role in an increasingly nonlinear world; then describe
emerging evidence from new observations on the connectivity of processes and system components from the Canada Basin and subarctic
seas surrounding northern North America; and finally posit an approach founded in “resilience thinking” to allow northern
residents living in small coastal communities to participate in the observation, adaption and—if necessary—transformation
of the social-ecological system with which they live. 相似文献
174.
Arctic Climate Tipping Points 总被引:1,自引:0,他引:1
There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a
long history of natural, abrupt climate changes, which together with current observations and model projections, can help
us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points
are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate changes
in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead,
a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate
tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available
responses are considered, especially the prospects for avoiding Arctic climate tipping points. 相似文献
175.
Anders Omstedt Christoph Humborg Janusz Pempkowiak Matti Perttilä Anna Rutgersson Bernd Schneider Benjamin Smith 《Ambio》2014,43(1):49-59
Past, present, and possible future changes in the Baltic Sea acid–base and oxygen balances were studied using different numerical experiments and a catchment–sea model system in several scenarios including business as usual, medium scenario, and the Baltic Sea Action Plan. New CO2 partial pressure data provided guidance for improving the marine biogeochemical model. Continuous CO2 and nutrient measurements with high temporal resolution helped disentangle the biogeochemical processes. These data and modeling indicate that traditional understandings of the nutrient availability–organic matter production relationship do not necessarily apply to the Baltic Sea. Modeling indicates that increased nutrient loads will not inhibit future Baltic Sea acidification; instead, increased mineralization and biological production will amplify the seasonal surface pH cycle. The direction and magnitude of future pH changes are mainly controlled by atmospheric CO2 concentration. Apart from decreasing pH, we project a decreasing calcium carbonate saturation state and increasing hypoxic area. 相似文献
176.
177.
Alessa L Kliskey A Lammers R Arp C White D Hinzman L Busey R 《Environmental management》2008,42(3):523-541
People in the Arctic face uncertainty in their daily lives as they contend with environmental changes at a range of scales from local to global. Freshwater is a critical resource to people, and although water resource indicators have been developed that operate from regional to global scales and for midlatitude to equatorial environments, no appropriate index exists for assessing the vulnerability of Arctic communities to changing water resources at the local scale. The Arctic Water Resource Vulnerability Index (AWRVI) is proposed as a tool that Arctic communities can use to assess their relative vulnerability-resilience to changes in their water resources from a variety of biophysical and socioeconomic processes. The AWRVI is based on a social-ecological systems perspective that includes physical and social indicators of change and is demonstrated in three case study communities/watersheds in Alaska. These results highlight the value of communities engaging in the process of using the AWRVI and the diagnostic capability of examining the suite of constituent physical and social scores rather than the total AWRVI score alone. 相似文献
178.
Objective assessment of habitat compensation is a central yet challenging issue for restoration ecologists. In 1997, a 3.4-km stream channel, designed to divert water around an open pit diamond mine, was excavated in the Barrenlands region of the Canadian Arctic to create productive stream habitat. We evaluated the initial success of this compensation program by comparing multiple biological attributes of the constructed stream during its first three years to those of natural reference streams in the area. The riparian zone of the constructed stream was largely devoid of vegetation throughout the period, in contrast to the densely vegetated zones of reference streams. The constructed stream also contained lower amounts of woody debris, coarse particulate organic matter (CPOM), and epilithon; had lower coverage by macrophytes and bryophytes; and processed leaf litter at a lower rate than reference streams. Species richness and densities of macroinvertebrates were consistently lower in the constructed stream compared to natural streams. This contributed to differences in macroinvertebrate assemblage structure throughout the period, although assemblages showed some convergence by year 3. The effectiveness of the constructed stream to emulate natural streams varied somewhat depending on the biological attribute being evaluated. Assessments based on individual attributes showed that minimal to moderate levels of similarity between the constructed stream and natural streams were achieved. A collective assessment of all biological and ecosystem attributes suggested that the constructed stream was not a good surrogate for natural streams during these first years. Additional time would be required before many characteristics of the constructed stream would resemble those of reference streams. Because initial efforts to improve fish habitat in the constructed stream focused on physical structures (e.g., weirs, vanes, rock, groins), ecological factors limiting fish growth were not considered and likely constrained success. We suggest that a greater focus on organic characteristics and vegetation within the stream and its riparian zone could have accelerated compensation. The addition of woody debris and CPOM, combined with planting of shrubs and herbs along the stream, should provide a source of allochthonous matter for the biotic community while large cobble and boulders should improve the physical stability of stream system, protecting its organic components. 相似文献
179.
Paul J. Mann Jens Strauss Juri Palmtag Kelsey Dowdy Olga Ogneva Matthias Fuchs Michael Bedington Ricardo Torres Luca Polimene Paul Overduin Gesine Mollenhauer Guido Grosse Volker Rachold William V. Sobczak Robert G. M. Spencer Bennet Juhls 《Ambio》2022,51(2):439
Arctic warming is causing ancient perennially frozen ground (permafrost) to thaw, resulting in ground collapse, and reshaping of landscapes. This threatens Arctic peoples'' infrastructure, cultural sites, and land-based natural resources. Terrestrial permafrost thaw and ongoing intensification of hydrological cycles also enhance the amount and alter the type of organic carbon (OC) delivered from land to Arctic nearshore environments. These changes may affect coastal processes, food web dynamics and marine resources on which many traditional ways of life rely. Here, we examine how future projected increases in runoff and permafrost thaw from two permafrost-dominated Siberian watersheds—the Kolyma and Lena, may alter carbon turnover rates and OC distributions through river networks. We demonstrate that the unique composition of terrestrial permafrost-derived OC can cause significant increases to aquatic carbon degradation rates (20 to 60% faster rates with 1% permafrost OC). We compile results on aquatic OC degradation and examine how strengthening Arctic hydrological cycles may increase the connectivity between terrestrial landscapes and receiving nearshore ecosystems, with potential ramifications for coastal carbon budgets and ecosystem structure. To address the future challenges Arctic coastal communities will face, we argue that it will become essential to consider how nearshore ecosystems will respond to changing coastal inputs and identify how these may affect the resiliency and availability of essential food resources.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01666-z. 相似文献
180.
Geraint A. Tarling Jennifer J. Freer Neil S. Banas Anna Belcher Mayleen Blackwell Claudia Castellani Kathryn B. Cook Finlo R. Cottier Malin Daase Magnus L. Johnson Kim S. Last Penelope K. Lindeque Daniel J. Mayor Elaine Mitchell Helen E. Parry Douglas C. Speirs Gabriele Stowasser Marianne Wootton 《Ambio》2022,51(2):333
The changing Arctic environment is affecting zooplankton that support its abundant wildlife. We examined how these changes are influencing a key zooplankton species, Calanus finmarchicus, principally found in the North Atlantic but expatriated to the Arctic. Close to the ice-edge in the Fram Strait, we identified areas that, since the 1980s, are increasingly favourable to C. finmarchicus. Field-sampling revealed part of the population there to be capable of amassing enough reserves to overwinter. Early developmental stages were also present in early summer, suggesting successful local recruitment. This extension to suitable C. finmarchicus habitat is most likely facilitated by the long-term retreat of the ice-edge, allowing phytoplankton to bloom earlier and for longer and through higher temperatures increasing copepod developmental rates. The increased capacity for this species to complete its life-cycle and prosper in the Fram Strait can change community structure, with large consequences to regional food-webs.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01667-y. 相似文献