Following worldwide bans and restrictions on the use of many persistent organic pollutants (POPs) from the late 1970s, their regional and global distributions have become governed increasingly by ...phase partitioning between environmental reservoirs, such as air, water, soil, vegetation and ice, where POPs accumulated during the original applications. Presently, further transport occurs within the atmospheric and aquatic reservoirs. Increasing temperatures provide thermodynamic forcing to drive these chemicals out of reservoirs, like soil, vegetation, water and ice, and into the atmosphere where they can be transported rapidly by winds and then recycled among environmental media to reach locations where lower temperatures prevail (e.g., polar regions and high elevations). Global climate change, widely considered as global warming, is also manifested by changes in hydrological systems and in the cryosphere; with the latter now exhibiting widespread loss of ice cover on the Arctic Ocean and thawing of permafrost. All of these changes alter the cycling and fate of POPs. There is abundant evidence from observations and modeling showing that climate variation has an effect on POPs levels in biotic and abiotic environments. This article reviews recent progress in research on the effects of climate change on POPs with the intention of promoting awareness of the importance of interactions between climate and POPs in the geophysical and ecological systems.
•POPs are distributed globally due to their volatility and persistence in the environment.•The environmental fate of POPs are associated strongly with temperature and organic carbon content.•Climate change may alter the stability of POPs and affect their re-cycling between their environmental reservoirs.•Releasing of POPs from their reservoirs accumulated from the past under climate warming may pose potential risks to eco-sensitive environment.•The adverse effect of POPs subject climate warming might be most significant in the Arctic
Arctic contaminant research in the marine environment has focused on organohalogen compounds and mercury mainly because they are bioaccumulative, persistent and toxic. This review summarizes and ...discusses the patterns and trends of persistent organic pollutants (POPs) and mercury in ringed seals (Pusa hispida) and polar bears (Ursus maritimus) in the Eastern Canadian Arctic relative to the rest of the Canadian Arctic. The review provides explanations for these trends and looks at the implications of climate-related changes on contaminants in these marine mammals in a region that has been reviewed little. Presently, the highest levels of total mercury (THg) and the legacy pesticide HCH in ringed seals and polar bears are found in the Western Canadian Arctic relative to other locations. Whereas, highest levels of some legacy contaminants, including ∑PCBs, PCB 153, ∑DDTs, p,p′-DDE, ∑CHLs, ClBz are found in the east (i.e., Ungava Bay and Labrador) and in the Beaufort Sea relative to other locations. The highest levels of recent contaminants, including PBDEs and PFOS are found at lower latitudes. Feeding ecology (e.g., feeding at a higher trophic position) is shaping the elevated levels of THg and some legacy contaminants in the west compared to the east. Spatial and temporal trends for POPs and THg are underpinned by historical loadings of surface ocean reservoirs including the Western Arctic Ocean and the North Atlantic Ocean. Trends set up by the distribution of water masses across the Canadian Arctic Archipelago are then acted upon locally by on-going atmospheric deposition, which is the dominant contributor for more recent contaminants. Warming and continued decline in sea ice are likely to result in further shifts in food web structure, which are likely to increase contaminant burdens in marine mammals. Monitoring of seawater and a range of trophic levels would provide a better basis to inform communities about contaminants in traditionally harvested foods, allow us to understand the causes of contaminant trends in marine ecosystems, and to track environmental response to source controls instituted under international conventions.
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•Mercury and legacy HCH in marine mammals are highest in the Western Arctic.•Most legacy POPs in marine mammals are highest in the East and the Beaufort Sea.•More recent POPs are highest in seals and polar bears at lower latitudes.•Food web structure is shaping spatial trends of mercury and some legacy POPs.•Water is driving legacy POPs whereas atmospheric deposition is driving recent POPs.
Blue carbon, the carbon fixed by vegetated coastal ecosystems including seagrasses, is reported to have a large potential to sequester atmospheric carbon dioxide. Planting, expanding or protecting ...seagrass meadows has, accordingly, been proposed as a form of geoengineering. Seagrasses are reported to account for up to 18% of the carbon burial in the world's oceans, which is on the same order of magnitude as other proposed geoengineering techniques, including iron fertilization. International protocols have been developed to quantify carbon sequestration in seagrass meadows, with a view to awarding carbon credits under the Verified Carbon Standard. Unfortunately, because these protocols do not adequately account for post-depositional processes in marine sediment, they significantly overestimate carbon capture by seagrass beds and give an incorrect view of its distribution. Specifically, neglecting biomixing and remineralization of carbon in surface sediments biases burial rates high, while using sediment carbon inventory (soil carbon stock) over the top 1 m as a proxy for burial rate incorrectly identifies areas of high carbon burial. Seagrass beds likely provide a limited setting for geoengineering, because they generally comprise slowly-accumulating, fine to medium sand, which captures organic carbon less efficiently than fine-grained sediments or rapidly-accumulating delta deposits. While there is no question that seagrass meadows provide valuable habitat, nor that they are disappearing rapidly, their contribution to the global burial of carbon has not yet been established. The danger of geoengineering with seagrasses before reliable assessment methods have been established is that overestimated carbon offsets could lead to a net increase in emissions of carbon dioxide to the atmosphere.
The Strait of Georgia (SoG) is a large semienclosed estuary that spatially dominates the Salish Sea on the North American Pacific coast. The region is well populated, harbors significant aquaculture, ...and is vulnerable to climate change. We present the first inorganic carbon data collected in the SoG covering all seasons (2003 and 2010–2012) and put them into the context of local circulation and oxygen cycles. Results show that the SoG has a higher carbon content and lower pH than surrounding waters. Aragonite saturation horizons in the SoG do not become deeper than 20–30 m and shoal to the surface for extended periods. Furthermore, incoming upwelled “acidified” water from the outer coast actually increases local pH. Finally, intense mixing in the physically restricted channels connecting the SoG to the outer coast allows significant oxygen uptake but minimal CO2 out gassing, protecting the SoG from hypoxia but not from ocean acidification.
Key Points
Semienclosed estuarine seas may be protected from hypoxia but not from ocean acidification
Significant O2 uptake occurs during intense tidal mixing in narrows, while little CO2 is out gassed
The Strait of Georgia is enriched in carbon and has low pH relative to the surrounding ocean
Natural organic matter was collected from the upper Yukon River and size fractionated into the <1 kDa low‐molecular‐weight dissolved (LMW‐DOC), colloidal (COC, 1 kDa to 0.45 μm) and particulate ...organic carbon (POC, >0.45 μm) phases for characterization of elemental (C and N) and isotopic (13C, 14C and 15N) composition to examine their sources and transport. Concentrations of total organic carbon (TOC) decreased from 3010 μM in mid‐May to 608 μM in September, accompanying an increase in river water δ18O from the snowmelt to summer and early fall. COC was the predominant OC species, comprising, on average, 63 ± 8% of the TOC, with 23 ± 5% partitioned in the LMW‐DOC and 14 ± 5% in the POC fraction. Annual riverine export flux to the ocean was 2.02 × 1012 g‐C for TOC, 7.66 × 1010 g‐N for total organic nitrogen (TON), and 3.53 × 1012 g‐C for dissolved inorganic carbon (DIC), respectively. The C/N molar ratios were distinctly different between colloidal organic matter (COM, 46 ± 3) and particulate organic matter (POM, 15 ± 1.4). Similar δ13C values were found for LMW‐DOM (−27.9 ± 0.5‰), COM (−27.4 ± 0.2‰), and POM (−26.2 ± 0.7‰), although there was a general increase with increasing size, suggesting a common terrigenous organic source. In contrast, distinct Δ14C values were found for LMW‐DOC (−155 to +91‰), COC (40 to 140‰), and POC (−467 to −253‰) with a decreasing trend from snowmelt to ice‐open season, suggesting that turnover pathways and transport mechanisms vary with organic matter size fractions. The high abundance of COC and its contemporary 14C ages points to a predominant source from modern terrestrial primary production, likely from the leaching/decomposition of fresh plant litter in the upper soil horizon. The predominately old POC (average 3698 ± 902 years B.P.), in contrast, was largely derived from riverbank erosion and melting of permafrost. These results imply that ice‐opening Yukon River flows are dominated by snowmelt (low δ18O) with high DOC (high Δ14C) but low DIC and Si(OH)4 concentrations, whereas late summer flows contain more products of permafrost or ice melt and rain (high δ18O), with low DOC (low Δ14C) but high DIC and Si(OH)4 concentrations. A warming climate with a deeper permafrost active layer in the Yukon River watershed would enhance the mobilization and export of old terrestrial OC, but largely in the particulate form into the Bering Sea and Arctic Ocean.
The recent warming in the Arctic is affecting a broad spectrum of physical, ecological, and human/cultural systems that may be irreversible on century time scales and have the potential to cause ...rapid changes in the earth system. The response of the carbon cycle of the Arctic to changes in climate is a major issue of global concern, yet there has not been a comprehensive review of the status of the contemporary carbon cycle of the Arctic and its response to climate change. This review is designed to clarify key uncertainties and vulnerabilities in the response of the carbon cycle of the Arctic to ongoing climatic change. While it is clear that there are substantial stocks of carbon in the Arctic, there are also significant uncertainties associated with the magnitude of organic matter stocks contained in permafrost and the storage of methane hydrates beneath both subterranean and submerged permafrost of the Arctic. In the context of the global carbon cycle, this review demonstrates that the Arctic plays an important role in the global dynamics of both CO₂ and CH₄ . Studies suggest that the Arctic has been a sink for atmospheric CO₂ of between 0 and 0.8 Pg C/yr in recent decades, which is between 0% and 25% of the global net land/ocean flux during the 1990s. The Arctic is a substantial source of CH₄ to the atmosphere (between 32 and 112 Tg CH₄/yr), primarily because of the large area of wetlands throughout the region. Analyses to date indicate that the sensitivity of the carbon cycle of the Arctic during the remainder of the 21st century is highly uncertain. To improve the capability to assess the sensitivity of the carbon cycle of the Arctic to projected climate change, we recommend that (1) integrated regional studies be conducted to link observations of carbon dynamics to the processes that are likely to influence those dynamics, and (2) the understanding gained from these integrated studies be incorporated into both uncoupled and fully coupled carbon-climate modeling efforts.
There is now general consensus that climate change is a global threat and a challenge for the 21st century. More and more information is available demonstrating how increased temperature may affect ...aquatic ecosystems and living resources or how increased water levels may impact coastal zones and their management. Many ecosystems are also affected by human releases of contaminants, for example from land based sources or the atmosphere, which also may cause severe effects. So far these two important stresses on ecosystems have mainly been discussed independently. The present paper is intended to increase awareness among scientists, coastal zone managers and decision makers that climate change will affect contaminant exposure and toxic effects and that both forms of stress will impact aquatic ecosystems and biota. Based on examples from different ecosystems, we discuss risks anticipated from contaminants in a rapidly changing environment and the research required to understand and predict how on-going and future climate change may alter risks from chemical pollution.
Arctic warming may cause the release of vast amounts of soil organic carbon (SOC) from permafrost, which will manifest itself in the fluxes and composition of organic carbon in northern rivers and ...Arctic coastal regions. To elucidate the transport pathways of SOC, radiocarbon composition was measured for dissolved organic carbon (DOC), particulate organic carbon (POC), sediments and SOC from the Mackenzie, Sagavanirktok, and Yukon river basins, and soil leaching experiments were conducted. The radiocarbon ages of riverine suspended POC and sediments ranged from 4430 to ∼7970 yr BP, while DOC was much younger (390–1440 yr BP) except samples from the Sag River. Soil leaching experiments released <1% of SOC as DOC. The decoupling in age and partitioning between POC and DOC indicates that POC in these rivers is dominated by old SOC derived from permafrost thawing and river‐bank erosion in contrast to DOC, which is more readily influenced by modern terrestrial biomass, especially in large river basins which also drain subarctic regions. These observations imply that melting of permafrost will be manifest in the age and amounts of POC in arctic rivers whereas change in DOC will reflect altered plant ecology.
Mercury (Hg) is a contaminant of major concern in Arctic marine ecosystems. Decades of Hg observations in marine biota from across the Canadian Arctic show generally higher concentrations in the west ...than in the east. Various hypotheses have attributed this longitudinal biotic Hg gradient to regional differences in atmospheric or terrestrial inputs of inorganic Hg, but it is methylmercury (MeHg) that accumulates and biomagnifies in marine biota. Here, we present high-resolution vertical profiles of total Hg and MeHg in seawater along a transect from the Canada Basin, across the Canadian Arctic Archipelago (CAA) and Baffin Bay, and into the Labrador Sea. Total Hg concentrations are lower in the western Arctic, opposing the biotic Hg distributions. In contrast, MeHg exhibits a distinctive subsurface maximum at shallow depths of 100-300 m, with its peak concentration decreasing eastwards. As this subsurface MeHg maximum lies within the habitat of zooplankton and other lower trophic-level biota, biological uptake of subsurface MeHg and subsequent biomagnification readily explains the biotic Hg concentration gradient. Understanding the risk of MeHg to the Arctic marine ecosystem and Indigenous Peoples will thus require an elucidation of the processes that generate and maintain this subsurface MeHg maximum.
Climate and environmental changes are having profound impacts on Arctic river basins, but the biogeochemical response remains poorly understood. To examine the effect of ice formation on temporal ...variations in composition and fluxes of carbon and nutrient species, monthly water and particulate samples collected from the lower Yukon River between July 2004 and September 2005 were measured for concentrations of organic and inorganic C, N, and P, dissolved silicate (Si(OH)₄), and stable isotope composition (δD and δ¹ɸO). All organic carbon and nutrient species had the highest concentration during spring freshet and the lowest during the winter season under the ice, indicating dominant sources from snowmelt and flushing of soils in the drainage basin. In contrast, inorganic species such as dissolved inorganic carbon (DIC) and Si(OH)₄ had the highest concentrations in winter and the lowest during spring freshet, suggesting dilution during snowmelt and sources from groundwater and leaching/weathering of mineral layer. The contrasting relation with discharge between organic, such as dissolved organic carbon (DOC), and inorganic, such as DIC and Si(OH)₄, indicates hydrological control of solute concentration but different sources and transport mechanisms for organic and inorganic carbon and nutrient species. Concentration of DOC also shows an inter-annual variability with higher DOC in 2005 (higher stream flow) than 2004 (lower stream flow). Average inorganic N/P molar ratio was 110 ± 124, with up to 442 under the ice and 38-70 during the ice-open season. While dissolved organic matter had a higher C/N ratio under the ice (45-62), the particulate C/N ratio was lower during winter (21-26) and spring freshet (19). Apparent fractionation factors of C, N, P, Si and δD and δ¹ɸO between ice and river water varied considerably, with high values for inorganic species such as DIC and Si(OH)₄ (45 and 9550, respectively) but lower values for DOC (4.7). River ice formation may result in fractionation of inorganic and organic solutes and the repartitioning of seasonal flux of carbon and nutrient species. Annual export flux from the Yukon River basin was 1.6 x 10¹² g-DOC, 4.4 x 10¹² g-DIC, and 0.89 x 10¹² g-POC during 2004-2005. Flux estimation without spring freshet sampling results in considerable underestimation for organic species but significant overestimation for inorganic species regardless of the flux estimation methods used. Without time-series sampling that includes frozen season, an over-or under-estimation in carbon and nutrient fluxes will occur depending on chemical species. Large differences in carbon export fluxes between studies and sampling years indicate that intensive sampling together with long-term observations are needed to determine the response of the Yukon River to a changing climate. sources from snowmelt and flushing of soils in the drainage basin. In contrast, inorganic species such as dissolved inorganic carbon (DIC) and Si(OH)₄ had the highest concentrations in winter and the lowest during spring freshet, suggesting dilution during snowmelt and sources from groundwater and leaching/weathering of mineral layer. The contrasting relation with discharge between organic, such as dissolved organic carbon (DOC), and inorganic, such as DIC and Si(OH)₄, indicates hydrological control of solute concentration but different sources and transport mechanisms for organic and inorganic carbon and nutrient species. Concentration of DOC also shows an inter-annual variability with higher DOC in 2005 (higher stream flow) than 2004 (lower stream flow). Average inorganic N/P molar ratio was 110 ± 124, with up to 442 under the ice and 38-70 during the ice-open season. While dissolved organic matter had a higher C/N ratio under the ice (45-62), the particulate C/N ratio was lower during winter (21-26) and spring freshet (19). Apparent fractionation factors of C, N, P, Si and δD and δ¹ɸO between ice and river water varied considerably, with high values for inorganic species such as DIC and Si(OH)₄ (45 and 9550, respectively) but lower values for DOC (4.7). River ice formation may result in fractionation of inorganic and organic solutes and the repartitioning of seasonal flux of carbon and nutrient species. Annual export flux from the Yukon River basin was 1.6 x 10¹² g-DOC, 4.4 x 10¹² g-DIC, and 0.89 x 10¹² g-POC during 2004-2005. Flux estimation without spring freshet sampling results in considerable underestimation for organic species but significant overestimation for inorganic species regardless of the flux estimation methods used. Without time-series sampling that includes frozen season, an over- or under-estimation in carbon and nutrient fluxes will occur depending on chemical species. Large differences in carbon export fluxes between studies and sampling years indicate that intensive sampling together with long-term observations are needed to determine the response of the Yukon River to a changing climate.
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