scholarly journals Are Arctic Ocean ecosystems exceptionally vulnerable to global emissions of mercury? A call for emphasised research on methylation and the consequences of climate change

2010 ◽  
Vol 7 (2) ◽  
pp. 133 ◽  
Author(s):  
R. W. Macdonald ◽  
L. L. Loseto
Keyword(s):  
Climate Change ◽  
Arctic Ocean ◽  
Food Webs ◽  
Deposition Process ◽  
The Arctic ◽  
Marine Biota ◽  
Mercury Deposition ◽  
Photochemical Process ◽  
The Arctic Ocean ◽  
Emission Controls

Environmental context. Mercury is a global contaminant that has entered Arctic food webs in sufficient quantity to put at risk the health of top predators and humans that consume them. Recent research has discovered a photochemical process unique to the Arctic that leads to mercury deposition on frozen surfaces after polar sunrise, but the connection between mercury deposition and entry into food webs remains tenuous and poorly understood. We propose here that the Arctic Ocean’s sensitivity to the global mercury cycle depends far more on neglected post-deposition processes that lead to methylation within the ice–ocean system, and the vulnerability of these processes to changes occurring in the cryosphere. Abstract. Emissions, atmospheric transport and deposition have formed the emphasis of recent research to understand Hg trends in Arctic marine biota, with the expressed objective of predicting how biotic trends might respond to emission controls. To answer the question of whether the Arctic Ocean might be especially vulnerable to global mercury (Hg) contamination and how biota might respond to emission controls requires a distinction between the supply of Hg from source regions and the processes within the Arctic Ocean that sequester and convert mercury to monomethyl Hg (MeHg). Atmospheric Mercury Depletion Events (AMDEs) provide a unique Hg deposition process in the Arctic; however, AMDEs have yet to be linked quantitatively with Hg uptake in marine food webs. The difficulty in implicating AMDEs or emissions to biotic trends lie in the ocean where several poorly understood processes lead to MeHg production and biomagnification. We propose that sensitivity of the Arctic Ocean’s ecosystem to Hg lies not so much in the deposition process as in methylation processes within the ocean, Hg inputs from large drainage basins, and the vulnerability these to climate change. Future research needs to be better balanced across the entire Hg cycle.

Methylmercury in arctic Alaskan mosquitoes: implications for impact of atmospheric mercury depletion events

2008 ◽  
Vol 5 (2) ◽  
pp. 127 ◽  
Author(s):  
Chad R. Hammerschmidt ◽  
William F. Fitzgerald
Keyword(s):  
Arctic Ocean ◽  
Food Webs ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Health Concern ◽  
Initial Assessment ◽  
Mercury Deposition ◽  
Enhanced Production ◽  
The Arctic Ocean ◽  
The Impact

Environmental context. Recent research suggests that gross mercury deposition in the Arctic is increased significantly as a result of springtime Atmospheric Mercury Depletion Events (AMDE). A primary environmental and human health concern is whether mercury deposited with these events leads to enhanced production and uptake of the toxic methylmercury species in polar ecosystems. Here, we present an initial assessment of potential impact from AMDE utilising mosquitoes as bioindicators of methylmercury accumulation in freshwater and terrestrial food webs within 200 km of the Arctic Ocean. Abstract. Atmospheric Mercury Depletion Events (AMDE) – phenomena in which elemental Hg is oxidised and stripped from the atmosphere over an 8–12-week period following polar sunrise – appear to increase Hg deposition to environs near the Arctic Ocean with a lesser impact inland. A key concern is whether such events lead to enhanced production and uptake of the toxic methylmercury (MeHg) species into arctic food webs. Here, we used mosquitoes, which are sensitive and site-specific bioindicators of Hg loadings, to assess the impact of AMDE on ecosystem MeHg contamination along a 200-km transect between the Arctic Ocean coast and foothills of the Brooks Range, where gross atmospheric Hg deposition appears to be ~20-fold less than that near the coast. This preliminary survey revealed little variation and no gradient in mosquito MeHg levels, which suggests comparable ecosystem impact. This may also point to significant cycling and reemission (e.g. via photoreduction) of Hg deposited during AMDE from the snow and ice pack to the atmosphere.

The role of permafrost soils in Arctic mercury cycling: source tracing with Hg stable isotopes and revised soil pool estimate

2020 ◽  
Author(s):  
Martin Jiskra ◽  
Jeroen E. Sonke ◽  
Artem G. Lim ◽  
Sergey V. Loiko ◽  
Natalia Kosykh ◽  
...  
Keyword(s):  
Climate Change ◽  
Arctic Ocean ◽  
Coastal Plain ◽  
River Runoff ◽  
Indigenous Populations ◽  
The Arctic ◽  
Marine Biota ◽  
Arctic Coastal Plain ◽  
The Arctic Ocean ◽  
Permafrost Soils

<p>Mercury (Hg) is a pollutant of great concern for indigenous populations in the Arctic, which are exposed to high dietary Hg from fish and marine mammal consumption. Hg in marine biota can be derived from direct atmospheric deposition to the Arctic Ocean or from terrestrial sources by river runoff. Permafrost soils thereby play a pivotal role in the Arctic Hg cycle by storing atmospheric Hg deposition and providing a reservoir for later mobilization to the Arctic Ocean. The stability of Hg in permafrost soils depends on the pathway of atmospheric Hg deposition and Hg release processes, i.e. reduction and re-emission to the atmosphere and transfer to river runoff. We combined Hg stable isotope with Hg flux measurements in a field study on the Arctic Coastal Plain in northern Alaska. We could show that gaseous elemental Hg uptake by vegetation represents 70% of total atmospheric Hg deposition. Atmospheric Hg uptake by vegetation results in a characteristic Hg isotope fingerprint. This fingerprint dominates Hg signatures in permafrost soils measured across the Arctic coastal plain and is also imprinted in marine mammals and Ocean sediments, suggesting that Hg from Arctic permafrost soils represent a major source to the Arctic Ocean. Knowing the pool and spatial distribution of Hg in permafrost soils is therefore essential to assess current Hg mobilization to aquatic ecosystems and potential future changes due to permafrost thaw and climate change. Two recent studies have used Hg to carbon (C) ratios, R<sub>HgC</sub>, measured in Alaskan permafrost mineral and peat soils, together with a northern soil carbon inventory, to estimate that these soils contain large amounts, 184 to 755 Gg of Hg in the upper 1 m. In a second part, we present new Hg and C data for six peat cores, down to mineral horizons, across a latitudinal permafrost gradient in the Western Siberian lowlands. Hg concentrations increase from south to north in all soil horizons, reflecting enhanced net accumulation of atmospheric gaseous elemental Hg by the vegetation Hg pump. We reviewed and estimate pan-arctic organic and mineral soil R<sub>HgC</sub> to be 0.19 and 0.77 Gg Pg<sup>-1</sup>, and use a soil C budget to revise the northern soil Hg pool to be 67 Gg (37-88 Gg, interquartile range (IQR)) in the upper 30 cm and 225 Gg (102-320 Gg, IQR) in the upper 1 m. Finally, we discuss how climate change may affect the mobilization of Hg from permafrost soils to the atmosphere and the Arctic Ocean.</p>

scholarly journals Regional variability of acidification in the Arctic: a sea of contrasts

2014 ◽  
Vol 11 (2) ◽  
pp. 293-308 ◽  
Author(s):  
E. E. Popova ◽  
A. Yool ◽  
Y. Aksenov ◽  
A. C. Coward ◽  
T. R. Anderson
Keyword(s):  
Climate Change ◽  
Primary Production ◽  
Arctic Ocean ◽  
Canadian Arctic ◽  
Atmospheric Co2 ◽  
The Arctic ◽  
Canadian Arctic Archipelago ◽  
Regional Variability ◽  
The Arctic Ocean ◽  
The Impact

Abstract. The Arctic Ocean is a region that is particularly vulnerable to the impact of ocean acidification driven by rising atmospheric CO2, with potentially negative consequences for calcifying organisms such as coccolithophorids and foraminiferans. In this study, we use an ocean-only general circulation model, with embedded biogeochemistry and a comprehensive description of the ocean carbon cycle, to study the response of pH and saturation states of calcite and aragonite to rising atmospheric pCO2 and changing climate in the Arctic Ocean. Particular attention is paid to the strong regional variability within the Arctic, and, for comparison, simulation results are contrasted with those for the global ocean. Simulations were run to year 2099 using the RCP8.5 (an Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) scenario with the highest concentrations of atmospheric CO2). The separate impacts of the direct increase in atmospheric CO2 and indirect effects via impact of climate change (changing temperature, stratification, primary production and freshwater fluxes) were examined by undertaking two simulations, one with the full system and the other in which atmospheric CO2 was prevented from increasing beyond its preindustrial level (year 1860). Results indicate that the impact of climate change, and spatial heterogeneity thereof, plays a strong role in the declines in pH and carbonate saturation (Ω) seen in the Arctic. The central Arctic, Canadian Arctic Archipelago and Baffin Bay show greatest rates of acidification and Ω decline as a result of melting sea ice. In contrast, areas affected by Atlantic inflow including the Greenland Sea and outer shelves of the Barents, Kara and Laptev seas, had minimal decreases in pH and Ω because diminishing ice cover led to greater vertical mixing and primary production. As a consequence, the projected onset of undersaturation in respect to aragonite is highly variable regionally within the Arctic, occurring during the decade of 2000–2010 in the Siberian shelves and Canadian Arctic Archipelago, but as late as the 2080s in the Barents and Norwegian seas. We conclude that, for future projections of acidification and carbonate saturation state in the Arctic, regional variability is significant and needs to be adequately resolved, with particular emphasis on reliable projections of the rates of retreat of the sea ice, which are a major source of uncertainty.

scholarly journals Nitrogen Fixation in a Changing Arctic Ocean: An Overlooked Source of Nitrogen?

2020 ◽  
Vol 11 ◽  
Author(s):  
Lisa W. von Friesen ◽  
Lasse Riemann
Keyword(s):  
Climate Change ◽  
Nitrogen Fixation ◽  
Primary Production ◽  
Arctic Ocean ◽  
Current Knowledge ◽  
Carbon Sink ◽  
Spatial Scales ◽  
The Arctic ◽  
Future Research ◽  
The Arctic Ocean

The Arctic Ocean is the smallest ocean on Earth, yet estimated to play a substantial role as a global carbon sink. As climate change is rapidly changing fundamental components of the Arctic, it is of local and global importance to understand and predict consequences for its carbon dynamics. Primary production in the Arctic Ocean is often nitrogen-limited, and this is predicted to increase in some regions. It is therefore of critical interest that biological nitrogen fixation, a process where some bacteria and archaea termed diazotrophs convert nitrogen gas to bioavailable ammonia, has now been detected in the Arctic Ocean. Several studies report diverse and active diazotrophs on various temporal and spatial scales across the Arctic Ocean. Their ecology and biogeochemical impact remain poorly known, and nitrogen fixation is so far absent from models of primary production in the Arctic Ocean. The composition of the diazotroph community appears distinct from other oceans – challenging paradigms of function and regulation of nitrogen fixation. There is evidence of both symbiotic cyanobacterial nitrogen fixation and heterotrophic diazotrophy, but large regions are not yet sampled, and the sparse quantitative data hamper conclusive insights. Hence, it remains to be determined to what extent nitrogen fixation represents a hitherto overlooked source of new nitrogen to consider when predicting future productivity of the Arctic Ocean. Here, we discuss current knowledge on diazotroph distribution, composition, and activity in pelagic and sea ice-associated environments of the Arctic Ocean. Based on this, we identify gaps and outline pertinent research questions in the context of a climate change-influenced Arctic Ocean – with the aim of guiding and encouraging future research on nitrogen fixation in this region.

Atmospheric HCH Concentrations over the Marine Boundary Layer from Shanghai, China to the Arctic Ocean: Role of Human Activity and Climate Change

2010 ◽  
Vol 44 (22) ◽  
pp. 8422-8428 ◽  
Author(s):  
Xiaoguo Wu ◽  
James C. W. Lam ◽  
Chonghuan Xia ◽  
Hui Kang ◽  
Liguang Sun ◽  
...  
Keyword(s):  
Climate Change ◽  
Boundary Layer ◽  
Arctic Ocean ◽  
Human Activity ◽  
Marine Boundary Layer ◽  
The Arctic ◽  
The Arctic Ocean
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