| 1. |
- Costello, David M., et al.
(författare)
-
Global patterns and controls of nutrient immobilization on decomposing cellulose in riverine ecosystems
- 2022
-
Ingår i: Global Biogeochemical Cycles. - : John Wiley & Sons. - 0886-6236 .- 1944-9224. ; 36:3
-
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.
|
|
| 2. |
- Tiegs, Scott D., et al.
(författare)
-
Global patterns and drivers of ecosystem functioning in rivers and riparian zones
- 2019
-
Ingår i: Science Advances. - Washington : American Association of Advancement in Science. - 2375-2548. ; 5:1
-
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.
|
|
| 3. |
- Mckie, Brendan, et al.
(författare)
-
Evaluating the properties, fate and individual-to-ecosystem level impacts of contrasting microplastics in freshwaters
- 2023
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Microplastic particles (MPs) are fragments, fibres and other shapes derived fromplastic polymers in the size range of 1–5 000 μm. Concern about the environmentalimpacts of MPs and their implications for human wellbeing has never been higher.Unfortunately, growth in the empirical understanding of the dynamics and impactsof MPs lags behind. This hinders the capacity of scientists, managers and policymakers to address public concerns about the true level of risk posed by MPs, andto develop effective management, policy and governance strategies for eliminatingor reducing those risks.Research on the behaviour and impacts of MPs in freshwater ecosystems is especiallydeficient, despite their vulnerability to inputs of plastic waste (e.g. via storm waterand other terrestrial runoff), and their capacity to act as key transport pathwaysthrough the landscape. This represents a substantial black box in our understandingof the dynamics of MPs from inland to the ocean.In seven research activities (5 mesocosm experiments, 1 field study and 1 literaturereview) we addressed two broad research questions:a) Initial fate and environmental interactions of MP particles in streams, includingbiofilm formation and sorption of chemical stressorsb) Ecological impacts of MPs on resource consumption, growth and survival oforganisms, and on key ecosystem processes.Among our key results addressing the initial fate and biofilm formation of MPparticles, we found that (i) biofilm formation generally made denser particles morebuoyant and caused more buoyant particles to sink faster, (ii) biofilms on polystyreneMPs supported more cyanobacteria than other polymers, and (iii) aquatic macrophytesincrease MP retention by up to 94 %.Among our key results addressing the ecological impacts of MPs, we found that almostall MP shapes and polymers studied had one or more effects on stream microbialorganisms and associated ecosystem processes (e.g. microbial respiration, detritusbreakdown), and/or on the life history of a model macroinvertebrate detritivore.We also provide evidence that effects of MPs on microbial organisms can propagateup food-chains to affect consumer growth and fat storage.Some MP impacts were similar to those of naturally occurring organic and inorganicparticles, whilst others represented a risk over and above that associated with naturalparticles.The number of MP impacts detected in our experiments provides sufficient basis for“moving beyond the precautionary principle” when motivating a need for monitoringand management – there is now sufficient evidence that MPs alter key aspects of thefunctioning of stream benthic food webs to motivate a need for action.Based on our results, we further provide a series of recommendations formonitoring,policy and management targeting MPs, and for future research.
|
|
| 4. |
- Ramberg, Ellinor, et al.
(författare)
-
The Structure of Riparian Vegetation in Agricultural Landscapes Influences Spider Communities and Aquatic-Terrestrial Linkages
- 2020
-
Ingår i: Water. - : MDPI. - 2073-4441. ; 12:10
-
Tidskriftsartikel (refereegranskat)abstract
- Riparian habitats are important ecotones connecting aquatic and terrestrial ecosystems, but are often highly degraded by human activities. Riparian buffers might help support impacted riparian communities, and improve trophic connectivity. We sampled spider communities from riparian habitats in an agricultural catchment, and analyzed their polyunsaturated fatty acid (PUFA) content to quantify trophic connectivity. Specific PUFAs are exclusively produced by stream algae, and thus are used to track uptake of aquatic resources by terrestrial consumers. Riparian spiders were collected from 10 site pairs situated along agricultural streams, and from five forest sites (25 sites total). Each agricultural site pair comprised an unshaded site with predominantly herbaceous vegetation cover, and a second with a woody riparian buffer. Spider communities differed between site types, with web-building spiders dominating woody buffered sites and free-living spiders associated with more open habitats. PUFA concentrations were greatest overall in free-living spiders, but there was also evidence for increased PUFA uptake by some spider groups when a woody riparian buffer was present. Our results reveal the different roles of open and wooded riparian habitats in supporting terrestrial consumers and aquatic-terrestrial connectivity, and highlight the value of incorporating patches of woody vegetation within riparian networks in highly modified landscapes.
|
|
| 5. |
- Salo, Tiina, et al.
(författare)
-
Diurnal variation around an optimum and near-critically high temperature does not alter the performance of an ectothermic aquatic grazer
- 2019
-
Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 9:20, s. 11695-11706
-
Tidskriftsartikel (refereegranskat)abstract
- The growing threat of global climate change has led to a profusion of studies examining the effects of warming on biota. Despite the potential importance of natural variability such as diurnal temperature fluctuations, most experimental studies on warming are conducted under stable temperatures. Here, we investigated whether the responses of an aquatic invertebrate grazer (Lymnaea stagnalis) to an increased average temperature differ when the thermal regime is either constant or fluctuates diurnally. Using thermal response curves for several life-history and immune defense traits, we first identified the optimum and near-critically high temperatures that Lymnaea potentially experience during summer heat waves. We then exposed individuals that originated from three different populations to these two temperatures under constant or fluctuating thermal conditions. After 7 days, we assessed growth, reproduction, and two immune parameters (phenoloxidase-like activity and antibacterial activity of hemolymph) from each individual. Exposure to the near-critically high temperature led to increased growth rates and decreased antibacterial activity of hemolymph compared to the optimum temperature, whilst temperature fluctuations had no effect on these traits. The results indicate that the temperature level per se, rather than the variability in temperature was the main driver altering trait responses in our study species. Forecasting responses in temperature-related responses remains challenging, due to system-specific properties that can include intraspecific variation. However, our study indicates that experiments examining the effects of warming using constant temperatures can give similar predictions as studies with fluctuating thermal dynamics, and may thus be useful indicators of responses in nature.
|
|
| 6. |
- Salo, Tiina, et al.
(författare)
-
Resilience to heat waves in the aquatic snail Lymnaea stagnalis : Additive and interactive effects with micropollutants
- 2017
-
Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 62:11, s. 1831-1846
-
Tidskriftsartikel (refereegranskat)abstract
- 1. Multiple anthropogenic changes, such as climate change and chemical pollution, threaten the persistence of natural populations. Yet, their potential additive and interactive effects on organismal performance and fitness are poorly understood, thus limiting our ability to predict the effects of the global change. 2. We conducted a laboratory experiment to study the singular and combined effects of experimental heat waves and micropollutants (i.e. low-concentration toxicants; henceforth micropollutants [MPs]) on the freshwater snail, Lymnaea stagnalis. To comprehensively understand physiological and ecological consequences of stress, we studied a broad range of traits from respiration rate to feeding performance and growth. We also determined traits contributing to fitness and immune responses, as these are key traits in determining both organismal fitness and interspecific (e.g. host-parasite) interactions. We tested whether a constant exposure to MPs affects the ability of snails to tolerate heat waves (8days of 23.5 degrees C), and subsequently to recover from them, and whether the effects are immediate or delayed. 3. We found strong immediate additive effects of both stressors on reproduction, while they synergistically increased respiration and antagonistically decreased food consumption. Moreover, these effects were transient. Although the heat wave increased metabolic rates, individuals did not increase their resource uptake. This caused an apparent imbalance in resource levelsa probable cause for the observed trade-off between immune function and reproductive traits (i.e. phenoloxidase-like activity decreased, while reproductive output increased). In addition, exposure to MPs led to a temporarily reduced reproductive output. 4. Our results indicate that even short-term heat waves and low concentrations of chemical pollution can have large, mainly additive impacts on organismal fitness (e.g. altering susceptibility to infections and reproductive output). This suggests that long-term effects of existing stressors and heat waves need to be considered when assessing the resilience of natural populations.
|
|
| 7. |
- Salo, Tiina, et al.
(författare)
-
Simultaneous exposure to a pulsed and a prolonged anthropogenic stressor can alter consumer multifunctionality
- 2018
-
Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 127:10, s. 1437-1448
-
Tidskriftsartikel (refereegranskat)abstract
- Ecosystems face multiple anthropogenic threats globally, and the effects of these environmental stressors range from individual-level organismal responses to altered system functioning. Understanding the combined effects of stressors on process rates mediated by individuals in ecosystems would greatly improve our ability to predict organismal multifunctionality (e.g. multiple consumer-mediated functions). We conducted a laboratory experiment to test direct and indirect, as well as immediate and delayed effects of a heat wave (pulsed stress) and micropollutants (MPs) (prolonged stress) on individual consumers (the great pond snail Lymnaea stagnalis) and their multifunctionality (i.e. consumption of basal resources, growth, reproduction, nutrient excretion and organic-matter cycling). We found that stressful conditions increased the process rates of multiple functions mediated by individual consumers. Specifically, the artificial heat wave increased process rates in the majority of the quantified functions (either directly or indirectly), whereas exposure to MPs increased consumption of basal resources which led to increases in the release of nutrients and fine particulate organic matter. Moreover, snails exposed to a heat wave showed decreased reproduction and nutrient excretion after the heat-wave, indicating the potential for ecologically relevant delayed effects. Our study indicates that the immediate and delayed effects of stressors on individual organisms may directly and indirectly impact multiple ecosystem functions. In particular, delayed effects of environmental stress on individual consumers may cumulatively impede recovery due to decreased functioning following a perturbation. Reconciling these results with studies incorporating responses at higher levels of biological complexity will enhance our ability to forecast how individual responses upscale to ecosystem multifunctionality.
|
|
