| 1. |
- Huser, Brian, et al.
(författare)
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Spatial and temporal variation in Arctic freshwater chemistry : Reflecting climate-induced landscape alterations and a changing template for biodiversity
- 2022
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Ingår i: Freshwater Biology. - : John Wiley & Sons. - 0046-5070 .- 1365-2427. ; 67:1, s. 14-29
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Tidskriftsartikel (refereegranskat)abstract
- 1. Freshwater chemistry across the circumpolar region was characterised using a pan-Arctic data set from 1,032 lake and 482 river stations. Temporal trends were estimated for Early (1970-1985), Middle (1986-2000), and Late (2001-2015) periods. Spatial patterns were assessed using data collected since 2001.2. Alkalinity, pH, conductivity, sulfate, chloride, sodium, calcium, and magnesium (major ions) were generally higher in the northern-most Arctic regions than in the Near Arctic (southern-most) region. In particular, spatial patterns in pH, alkalinity, calcium, and magnesium appeared to reflect underlying geology, with more alkaline waters in the High Arctic and Sub Arctic, where sedimentary bedrock dominated.3. Carbon and nutrients displayed latitudinal trends, with lower levels of dissolved organic carbon (DOC), total nitrogen, and (to a lesser extent) total phosphorus (TP) in the High and Low Arctic than at lower latitudes. Significantly higher nutrient levels were observed in systems impacted by permafrost thaw slumps.4. Bulk temporal trends indicated that TP was higher during the Late period in the High Arctic, whereas it was lower in the Near Arctic. In contrast, DOC and total nitrogen were both lower during the Late period in the High Arctic sites. Major ion concentrations were higher in the Near, Sub, and Low Arctic during the Late period, but the opposite bulk trend was found in the High Arctic.5. Significant pan-Arctic temporal trends were detected for all variables, with the most prevalent being negative TP trends in the Near and Sub Arctic, and positive trends in the High and Low Arctic (mean trends ranged from +0.57%/year in the High/Low Arctic to -2.2%/year in the Near Arctic), indicating widespread nutrient enrichment at higher latitudes and oligotrophication at lower latitudes.6. The divergent P trends across regions may be explained by changes in deposition and climate, causing decreased catchment transport of P in the south (e.g. increased soil binding and trapping in terrestrial vegetation) and increased P availability in the north (deepening of the active layer of the permafrost and soil/sediment sloughing). Other changes in concentrations of major ions and DOC were consistent with projected effects of ongoing climate change. Given the ongoing warming across the Arctic, these region-specific changes are likely to have even greater effects on Arctic water quality, biota, ecosystem function and services, and human well-being in the future.
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| 2. |
- Harper, Meagan, et al.
(författare)
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A multi-realm perspective on applying potential tipping points to environmental decision-making
- 2024
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Ingår i: Environmental Reviews. - 1181-8700 .- 1208-6053. ; 32, s. 131-144
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Forskningsöversikt (refereegranskat)abstract
- Ecosystems experiencing pressures are at risk of rapidly transitioning (“tipping”) from one state to another. Identifying and managing these so-called tipping points continue to be a challenge in marine, freshwater, and terrestrial ecosystems, particularly when multiple potentially interacting drivers are present. Knowledge of tipping points, the mechanisms that cause them, and their implications for management practices are evolving, but often in isolation within specific ecological realms. Here, we summarize current knowledge of tipping points in marine, freshwater, and terrestrial realms and provide a multi-realm perspective of the challenges and opportunities for applying this knowledge to ecosystem management. We brought together conservation practitioners and global experts in marine, freshwater, and terrestrial tipping points and identified seven challenges that environmental policymakers and managers contend with including (1) predictability, (2) spatiotemporal scales, (3) interactions, (4) reversibility, (5) socio-ecological context, (6) complexity and heterogeneity, and (7) selecting appropriate action. We highlight opportunities for cross-scalar and cross-realm knowledge production and provide recommendations for enabling the management of tipping points. Although knowledge of tipping points is imperfect, we stress the need to continue working toward incorporating tipping points perspectives in environmental management across all realms.
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| 3. |
- King, Connor, et al.
(författare)
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Diatoms and other siliceous indicators track the ontogeny of a “bofedal” (Wetland) ecosystem in the peruvian andes
- 2021
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Ingår i: Botany. - : Canadian Science Publishing. - 1916-2790 .- 1916-2804. ; 99:8, s. 491-505
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Tidskriftsartikel (refereegranskat)abstract
- Recent warming in the Andes is affecting the region’s water resources including glaciers and lakes, which supply water to tens of millions of people downstream. High-elevation wetlands, known locally as “bofedales”, are an understudied Andean ecosystem despite their key role in carbon sequestration, maintenance of biodiversity, and regulation of water flow. Here, we analyze subfossil diatom assemblages and other siliceous bioindicators preserved in a peat core collected from a bofedal in Peru’s Cordillera Vilcanota. Basal radiocarbon ages show the bofedal likely formed during a wet period of the Little Ice Age (1520–1680 CE), as inferred from nearby ice core data. The subfossil diatom record is marked by several dynamic assemblage shifts documenting a hydrosere succession from an open-water system to mature peatland. The diatoms appear to be responding largely to changes in hydrology that occur within the natural development of the bofedal, but also to pH and possibly nutrient enrichment from grazing animals. The rapid peat accretion recorded post-1950 at this site is consistent with recent peat growth rates elsewhere in the Andes. Given the many threats to Peruvian bofedales including climate change, overgrazing, peat extraction, and mining, these baseline data will be critical to assessing future change in these important ecosystems.
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| 4. |
- Kritzberg, Emma S., et al.
(författare)
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Other Important Elements
- 2023
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Ingår i: Wetzel's Limnology : Lake and River Ecosystems, Fourth Edition - Lake and River Ecosystems, Fourth Edition. - 9780128227015 - 9780128227107 ; , s. 427-461
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Bokkapitel (refereegranskat)abstract
- In addition to the major nutrients carbon, nitrogen, and phosphorus, many minor elements play an important role in the function of freshwater systems. Such elements may function as essential micronutrients, or they may affect the biota by being toxic, or they play an indirect role by influencing the mobility and availability of other elements. This chapter covers the fundamentals of important minor elements in freshwaters, including their sources, forms, cycling, and transformations. This chapter also includes the biogeochemical cycle of sulfur, which is in fact an abundant macronutrient but is included here due to its close interaction with iron and manganese. The chapter also includes silicon, which is an element of key importance to specific organisms in freshwaters.
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| 5. |
- Meyer-Jacob, Carsten, 1984-, et al.
(författare)
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Re-browning of Sudbury (Ontario, Canada) lakes now approaches pre-acid deposition lake-water dissolved organic carbon levels
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 725
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Tidskriftsartikel (refereegranskat)abstract
- Since the implementation of large-scale lake monitoring in the similar to 1980s, water color and dissolved organic carbon (DOC) concentrations have increased in many northern lakes (i.e., lake browning), impacting the functioning of aquatic ecosystems. In regions that formerly experienced high levels of acid deposition, this browning trend has been largely attributed to the recovery from the impacts of past acid deposition. However, the extent to which DOC levels have now returned to naturally higher, pre-industrial conditions is still poorly understood. In this study, we assessed whether DOC levels are still influenced by acid deposition in lakes near Sudbury, Ontario, a region that has been heavily affected by sulfur dioxide emissions from local metal smelting during the 20th century. We analyzed water chemistry monitoring data (1981-2018), together with comparisons between modern and pre-industrial DOC levels inferred from sediment spectroscopy, for 51 acid-sensitive and 24 buffered reference lakes across the Sudbury landscape. Since 1981, DOC concentrations doubled in acid-sensitive lakes, with a mean increase of +1.6 mg/L, whereas in more buffered reference lakes, mean DOC levels increased by only 0.8 mg/L. Similarly, sediment-inferred DOC trends indicate that current DOC levels are, on average, similar to 22% below pre-industrial levels in acid sensitive systems compared to only similar to 10% in buffered lakes. Weakening correlations between DOC and acidification-related water chemistry variables (e.g., pH, alkalinity, metals) further indicate a diminishing influence of acid deposition on DOC in Sudbury lakes. These results highlight the strong impact that acid deposition has historically had on lake-water DOC dynamics in this region, but also suggest that DOC levels are approaching natural baseline levels in less acid-sensitive lakes, and that other drivers, such as changes in climate or vegetation cover, are now becoming the dominant controls on changes in DOC concentrations.
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| 6. |
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Tracking environmental change using lake sediments : volume 6: sedimentary DNA
- 2023. - 1
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Samlingsverk (redaktörskap) (refereegranskat)abstract
- This book, entitled Tracking Environmental Change Using Lake Sediments: Volume 6 – Sedimentary DNA, provides an overview of the applications of sedimentary DNA-based approaches to paleolimnological studies. These approaches have shown considerable potential in providing information about the long-term changes of overall biodiversity in lakes and their watersheds in response to natural and anthropogenic changes, as well as tracking human migrations over the last thousands of years.Although the first studies investigating the preservation of these molecular proxies in sediments originate from the late-1990s, the number of scientific publications on this topic has increased greatly over the last five years. Alongside numerous ecological findings, several sedimentary DNA studies have been dedicated to understanding the reliability of this approach to reconstruct past ecosystem changes. Despite the major surge of interest, a comprehensive compilation of sedimentary DNA approaches and applications has yet to be attempted. The overall aim of this DPER volume is to fill this knowledge gap.
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