| 1. |
- Tiegs, Scott D., et al.
(författare)
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Global patterns and drivers of ecosystem functioning in rivers and riparian zones
- 2019
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Ingår i: Science Advances. - Washington : American Association of Advancement in Science. - 2375-2548. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth's biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented "next-generation biomonitoring" by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.
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| 2. |
- Costello, David M., et al.
(författare)
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Global patterns and controls of nutrient immobilization on decomposing cellulose in riverine ecosystems
- 2022
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Ingår i: Global Biogeochemical Cycles. - : John Wiley & Sons. - 0886-6236 .- 1944-9224. ; 36:3
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Tidskriftsartikel (refereegranskat)abstract
- Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.
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| 3. |
- Hampton, Stephanie E., et al.
(författare)
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Ecology under lake ice
- 2017
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 20:1, s. 98-111
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Forskningsöversikt (refereegranskat)abstract
- Winter conditions are rapidly changing in temperate ecosystems, particularly for those that experience periods of snow and ice cover. Relatively little is known of winter ecology in these systems, due to a historical research focus on summer ‘growing seasons’. We executed the first global quantitative synthesis on under-ice lake ecology, including 36 abiotic and biotic variables from 42 research groups and 101 lakes, examining seasonal differences and connections as well as how seasonal differences vary with geophysical factors. Plankton were more abundant under ice than expected; mean winter values were 43.2% of summer values for chlorophyll a, 15.8% of summer phytoplankton biovolume and 25.3% of summer zooplankton density. Dissolved nitrogen concentrations were typically higher during winter, and these differences were exaggerated in smaller lakes. Lake size also influenced winter-summer patterns for dissolved organic carbon (DOC), with higher winter DOC in smaller lakes. At coarse levels of taxonomic aggregation, phytoplankton and zooplankton community composition showed few systematic differences between seasons, although literature suggests that seasonal differences are frequently lake-specific, species-specific, or occur at the level of functional group. Within the subset of lakes that had longer time series, winter influenced the subsequent summer for some nutrient variables and zooplankton biomass.
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| 4. |
- Weyhenmeyer, Gesa A., Professor, et al.
(författare)
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Global Lake Health in the Anthropocene : Societal Implications and Treatment Strategies
- 2024
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Ingår i: Earth's Future. - : American Geophysical Union (AGU). - 2328-4277. ; 12:4
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Forskningsöversikt (refereegranskat)abstract
- The world's 1.4 million lakes (>= 10 ha) provide many ecosystem services that are essential for human well-being; however, only if their health status is good. Here, we reviewed common lake health issues and classified them using a simple human health-based approach to outline that lakes are living systems that are in need of oxygen, clean water and a balanced energy and nutrient supply. The main reason for adopting some of the human health terminology for the lake health classification is to increase the awareness and understanding of global lake health issues. We show that lakes are exposed to various anthropogenic stressors which can result in many lake health issues, ranging from thermal, circulatory, respiratory, nutritional and metabolic issues to infections and poisoning. Of particular concern for human well-being is the widespread lake drying, which is a severe circulatory issue with many cascading effects on lake health. We estimated that similar to 115,000 lakes evaporate twice as much water as they gain from direct precipitation, making them vulnerable to potential drying if inflowing waters follow the drying trend, putting more than 153 million people at risk who live in close vicinity to those lakes. Where lake health issues remain untreated, essential ecosystem services will decline or even vanish, posing a threat to the well-being of millions of people. We recommend coordinated multisectoral and multidisciplinary prevention and treatment strategies, which need to include a follow-up of the progress and an assessment of the resilience of lakes to intensifying threats. Priority should be given to implementing sewage water treatment, mitigating climate change, counteracting introductions of non-native species to lakes and decreasing uncontrolled anthropogenic releases of chemicals into the hydro-, bio-, and atmosphere. Lakes around the world come in an array of sizes, shapes and colors, each telling a unique story of geological history and environmental importance. When lakes are healthy they contribute to the achievement of the global sustainable development goals by providing many important ecosystem services. Lakes are, however, not always healthy. Here, it is shown that lakes can suffer from a large variety of health issues, ranging from thermal, circulatory, respiratory, nutritional and metabolic issues to infections and poisoning. Without improved treatment strategies, many of the health issues may become chronic, affecting millions of people who are dependent on the ecosystem services from the lakes. To prevent and cure lakes from critical health conditions, strategies that are similar to those used in human healthcare should be applied: intervention and preventative actions before health problems occur, regular screening and early identification of lake health issues, and remediation and mitigation efforts at an appropriate scale, spanning from local to global. Anthropogenic stressors can cause lake health issues that range from thermal, circulatory, respiratory, nutritional and metabolic issues to infections and poisoning Lake health varies geographically, with the highest risk of critical conditions occurring in densely populated low-income countries There is an urgent need to follow-up the progress of treatments and to make adjustments whenever needed
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| 5. |
- Nydahl, Anna Cecilia
(författare)
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Carbon Dioxide in Inland Waters : Drivers and Mechanisms Across Spatial and Temporal Scales
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inland waters are an essential component of the global carbon cycle as they are very active sites for carbon transformation processes. Much of this carbon is transformed into the greenhouse gas carbon dioxide (CO2) and emitted into the atmosphere. The biogeochemical and hydrological mechanisms driving CO2 concentrations in inland waters are manifold. Although some of them have been studied in detail, there are still knowledge gaps regarding the relative importance of the different CO2-driving mechanisms, both on a spatial and a temporal scale. The main aim of this thesis was to fill some of the knowledge gaps by studying long- and short-term effects of enhanced dissolved organic carbon (DOC) concentrations on surface water partial pressure of CO2 (pCO2) as well as to investigate both internal (i.e., within the water body) and external (i.e., catchment) drivers of pCO2 in inland waters. Based on analyses of long-term data from more than 300 boreal lakes and streams and on results from two mesocosm experiments as well as a detailed catchment study, one of the main results of the thesis was that DOC concentrations were, on a temporal scale, generally uncoupled to pCO2. Indeed, additions of allochthonous DOC to lake water could result in increased pCO2 in waters but not as originally expected by stimulation of bacterial activity but instead by light driven suppression of primary production, at least in mesotrophic waters. Changes in the carbonate system was also found to be a main driver for surface water pCO2. Finally, also external processes such as groundwater inputs contributed substantially to variations of surface water pCO2. In a detailed study on carbon in groundwater, pCO2 in groundwater was found to decrease with soil depth and correlated negatively with pH, which increased with soil depth. Conclusively, this thesis show that pCO2 does not follow the trends of increased DOC in boreal surface waters but instead correlates with changes in primary production and shifts in the carbonate system. Additionally, the dominating mechanisms driving pCO2 clearly differ between lakes and streams. Consequently, simulations of future CO2 dynamics and emissions from inland waters cannot rely on DOC concentrations as a pCO2 predictor, but rather need to incorporate several pCO2 driving mechanisms, and consider the difference between lakes and streams.
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| 6. |
- Song, Keunyea, et al.
(författare)
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Phosphorus cycling in urban aquatic ecosystems: connecting biological processes and water chemistry to sediment P fractions in urban stormwater management ponds
- 2017
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Ingår i: Biogeochemistry. - : Springer. - 0168-2563 .- 1573-515X. ; 132:1, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- Phosphorus (P) dynamics in urban landscapes may differ from that in natural landscapes due to different P sources and unique environmental conditions. However, many aspects of P cycles in urban areas, especially within engineered aquatic ecosystems, remain largely unknown. Through this work, we aim to contribute to better understanding of P cycling in urban aquatic ecosystems by investigating P fractions in sediment and their relationship with ambient chemistry in surface water from six urban stormwater management ponds located in Ontario, Canada. We found that organic P contributed up to 75% of total P in pond sediment, but this percentage decreased significantly between our two sampling events in June and September 2012. This decrease coincided with increased rates of extracellular enzyme (especially phosphatase) activities, which is indicative of fast mineralization processes in these ecosystems. Moreover, the decreased sediment organic P was matched by increased water column P concentration. This inverse relationship suggests that the large organic P pool in pond sediment, and its fast decomposition, contributed to internal release of P from sediment and increased water column P concentrations. The dominance of organic P in sediment and the putative role of relevant biological processes (i.e., decomposition and productivity) in urban ponds found in this study strongly contrast with classic water management expectations of physicochemically controlled P dynamics and long-term P storage in sediment of aquatic ecosystems. This difference suggests that urban stormwater ponds may perform poorly in terms of P retention and thereby contribute to poor water quality in terms of P pollution to downstream urban watersheds. Thus, stormwater pond design and future management strategies should consider these biogeochemical features of urban ponds, including internal P release, to help prevent eutrophication of downstream ecosystems.
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| 7. |
- Williams, Clayton J., et al.
(författare)
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Add a dash of salt? Effects of road de-icing salt (NaCl) on benthic respiration and nutrient fluxes in freshwater sediments : [¿Agregar una pizca de sal? Efectos de la sal usada en carreteras (NaCl) sobre la respiración béntónica y los flujos de nutrientes en los sedimentos de agua dulce]
- 2023
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Ingår i: Limnetica. - : Asociación Ibérica de Limnología. - 0213-8409. ; 42:2, s. 233-250
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Tidskriftsartikel (refereegranskat)abstract
- Winter road salt applications are increasing chloride concentrations in many freshwater ecosystems. This trend is alarming, given chloride’s potential to impair aquatic ecosystems. Short- and long-term exposure to salt could affect ecosystem metabolism and nutrient cycles. Here, we examine connections between chloride concentrations, water quality conditions, benthic respiration, and sediment-water nutrient flux throughout a large (722 km2) lake and its catchment. Aquatic locations experiencing high concentrations of chloride are indicators of anthropogenic activities and are often associated with additional pollutants. We used sediment core flow-through incubations under ambient and enriched chloride concentrations to determine the effects of road salt on benthic respiration and nutrient fluxes in stream, stormwater pond, and lake sites. Salt (as sodium chloride) additions caused a significant overall increase in benthic respiration. Acute exposure to road salt caused the strongest increase in benthic respiration when water was warm and at sites that had low (< 50 mg Cl-/L) or high (> 400 mg Cl-/L) ambient chloride concentrations or when water was cold and sites had intermediate (100-400 mg Cl-/L) ambient chloride concentrations. Nitrate flux responded less uniformly to salt additions. Depending on waterbody type and season, ambient nitrate flux into the sediment was similar, increased, or decreased post-chloride addition. Dissolved phosphorus flux was not significantly impacted by salt additions. Across lake and stream sites, our results supported the hypothesis that chloride causes increased respiration while nutrient cycles were weakly and inconsistently altered under experimental pulse road salt additions.
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| 8. |
- Xenopoulos, Marguerite A., et al.
(författare)
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How humans alter dissolved organic matter composition in freshwater: relevance for the Earth’s biogeochemistry
- 2021
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Ingår i: Biogeochemistry. - : Springer Nature. - 0168-2563 .- 1573-515X. ; 154:2, s. 323-348
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved organic matter (DOM) is recognized for its importance in freshwater ecosystems, but historical reliance on DOM quantity rather than indicators of DOM composition has led to an incomplete understanding of DOM and an underestimation of its role and importance in biogeochemical processes. A single sample of DOM can be composed of tens of thousands of distinct molecules. Each of these unique DOM molecules has their own chemical properties and reactivity or role in the environment. Human activities can modify DOM composition and recent research has uncovered distinct DOM pools laced with human markers and footprints. Here we review how land use change, climate change, nutrient pollution, browning, wildfires, and dams can change DOM composition which in turn will affect internal processing of freshwater DOM. We then describe how human-modified DOM can affect biogeochemical processes. Drought, wildfires, cultivated land use, eutrophication, climate change driven permafrost thaw, and other human stressors can shift the composition of DOM in freshwater ecosystems increasing the relative contribution of microbial-like and aliphatic components. In contrast, increases in precipitation may shift DOM towards more relatively humic-rich, allochthonous forms of DOM. These shifts in DOM pools will likely have highly contrasting effects on carbon outgassing and burial, nutrient cycles, ecosystem metabolism, metal toxicity, and the treatments needed to produce clean drinking water. A deeper understanding of the links between the chemical properties of DOM and biogeochemical dynamics can help to address important future environmental issues, such as the transfer of organic contaminants through food webs, alterations to nitrogen cycling, impacts on drinking water quality, and biogeochemical effects of global climate change.
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