| 1. |
- Heibati, Masoumeh, 1986, et al.
(författare)
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Assessment of drinking water quality at the tap using fluorescence spectroscopy.
- 2017
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Ingår i: Water research. - : Elsevier BV. - 1879-2448 .- 0043-1354. ; 125, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Treated drinking water may become contaminated while travelling in the distribution system on the way to consumers. Elevated dissolved organic matter (DOM) at the tap relative to the water leaving the treatment plant is a potential indicator of contamination, and can be measured sensitively, inexpensively and potentially on-line via fluorescence and absorbance spectroscopy. Detecting elevated DOM requires potential contamination events to be distinguished from natural fluctuations in the system, but how much natural variation to expect in a stable distribution system is unknown. In this study, relationships between DOM optical properties, microbial indicator organisms and trace elements were investigated for households connected to a biologically-stable drinking water distribution system. Across the network, humic-like fluorescence intensities showed limited variation (RSD = 3.5-4.4%), with half of measured variation explained by interactions with copper. After accounting for quenching by copper, fluorescence provided a very stable background signal (RSD
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| 2. |
- Jonsson, Micael, et al.
(författare)
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Catchment properties predict autochthony in stream filter feeders
- 2018
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Ingår i: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 815:1, s. 83-95
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Tidskriftsartikel (refereegranskat)abstract
- Stream ecological theory predicts that the use of allochthonous resources declines with increasing channel width, while at the same time primary production and autochthonous carbon use by consumers increase. Although these expectations have found support in several studies, it is not well known how terrestrial runoff and/or inputs of primary production from lakes alter these longitudinal patterns. To investigate this, we analyzed the diet of filter-feeding black fly and caddisfly larvae from 23 boreal streams, encompassing gradients in drainage area, land cover and land use, and distance to nearest upstream lake outlet. In five of these streams, we also sampled repeatedly during autumn to test if allochthony of filter feeders increases over time as new litter inputs are processed. Across sites, filter-feeder autochthony was 21.1-75.1%, did not differ between black fly and caddisfly larvae, was not positively related to drainage area, and did not decrease with distance from lakes. Instead, lake and wetland cover promoted filter-feeder autochthony independently of stream size, whereas catchment-scale forest cover and forestry reduced autochthony. Further, we found no seasonal increase in allochthony, indicating low assimilation of particles derived from autumn litter fall. Hence, catchment properties, rather than local conditions, can influence levels of autochthony in boreal streams.
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| 3. |
- Jonsson, Micael, et al.
(författare)
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Climate change modifies the size structure of assemblages of emerging aquatic insects
- 2015
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Ingår i: Freshwater Biology. - : Wiley-Blackwell. - 0046-5070 .- 1365-2427. ; 60:1, s. 78-88
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to not only raise water temperatures, but also to cause brownification of aquatic ecosystems via increased inputs of terrestrial dissolved organic matter. While efforts have been made to understand how increased temperature and brownification separately influence aquatic food webs, their interactive effects have been less investigated. Further, although climate change effects on aquatic ecosystems likely will propagate to terrestrial consumers via changes in aquatic insect emergence, this has rarely been studied. We investigated the effect of climate change on aquatic insect emergence, in a large-scale outdoor pond facility where 16 sections - each containing natural food webs including a fish top-consumer population - were subjected to warming (3 degrees C above ambient temperatures) and/or brownification (by adding naturally humic stream water). Aquatic insect emergence was measured biweekly over 18weeks. We found no effect of warming or brownification on total emergent insect dry mass. However, warming significantly reduced the number of emergent Chironomidae, while numbers of larger taxa, Trichoptera and Ephemeroptera, remained unchanged. On average, 57% and 58% fewer Chironomidae emerged from the warmed clear and humic pond sections, respectively. This substantial decrease in emergent Chironomidae resulted in a changed community structure and on average larger individuals emerging from warm sections as well as from humic sections under ambient conditions. There was also a weak influence of fish biomass on the size structure of emergent aquatic insects, with a positive relationship between individual insect size and total fish biomass, but effects of fish were clearly subordinate to those of warming. Climate change impacts on aquatic systems can have widespread consequences also for terrestrial systems, as aquatic insects are ubiquitous and their emergence represents an important resource flow from aquatic to terrestrial environments. While we found that neither warming nor brownification quantitatively changed total aquatic insect emergence biomass, the warming-induced decrease in number of emergent Chironomidae and the subsequent increase in average body size will likely impact terrestrial consumers relying on emergent aquatic insect as prey.
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| 4. |
- Jonsson, Micael, et al.
(författare)
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True autochthony and allochthony in aquatic-terrestrial resource fluxes along a landuse gradient
- 2016
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Ingår i: Freshwater Science. - : University of Chicago Press. - 2161-9549 .- 2161-9565. ; 35:3, s. 882-894
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Tidskriftsartikel (refereegranskat)abstract
- Freshwater and terrestrial ecosystems are connected via reciprocal cross-boundary resource fluxes, where terrestrially derived (allochthonous) organic matter is a critical energy source to freshwater food webs. Therefore, some proportion of aquatic-to-terrestrial resource fluxes, which consist primarily of emergent aquatic insects, are of allochthonous origin (i.e., recycled terrestrial matter). Landuse activities modify basal resources and consumer community composition in aquatic systems and, thereby, aquatic resource fluxes to terrestrial systems. The origin of aquatic terrestrial resource fluxes and alterations to them caused by land use should be considered to understand these fluxes better. Resource fluxes at the aquatic terrestrial interface were measured at 10 streams along a forest-to-agriculture gradient. Autochthony in emergent aquatic insects ranged from 10 to 97%. Hence, aquatic fluxes to terrestrial systems drive the flux of matter of aquatic origin (true aquatic flux) and the recycling of terrestrial matter to the terrestrial environment. Land use indirectly affected autochthony of emergent aquatic insects via changes in water chemistry, high-quality resource availability, and in-stream consumer composition. Chironomidae diet shifts along the landuse gradient strengthened the aquatic flux to the land. For every 10% increase in agricultural land cover, aquatically derived matter deposited on land via emergent Chironomidae increased 0.005 g dry mass m(-2) d(-1). Plecoptera strengthened the aquatic flux and the recycling of terrestrial matter via changes in abundance across the landuse gradient. Aquatically derived matter deposited on land via emergent Plecoptera increased 0.002 g dry mass m(-2) d(-1) for every 10% increase in coniferous forest cover. Qualitative changes in resource fluxes across the aquatic terrestrial interface may be driven indirectly by the influences of land use on diets and composition of emergent aquatic insects.
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| 5. |
- Stenroth, Karolina, et al.
(författare)
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A model-based comparison of organic matter dynamics in forested and open-canopy streams
- 2014
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Ingår i: Riparian Ecology and Conservation. - : Portico. - 2299-1042. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- The food webs of forest streams are primarily based upon inputs of organic matter from adjacent terrestrial ecosystems. However, streams that run through open landscapes generally lack closed riparian canopies, and an increasing number of studies indicate that terrestrial organic matter may be an important resource in these systems as well. Combining key abiotically-controlled factors (stream discharge, water temperature, and litter input rate) with relevant biotic processes (e.g. macroinvertebrate CPOM consumption, microbial processing), we constructed a model to predict and contrast organic matter dynamics (including temporal variation in CPOM standing crop, CPOM processing rate, FPOM production, and detritivore biomass) in small riparian-forested and open-canopy streams. Our modeled results showed that the standing crop of CPOM was similar between riparian-forested and open-canopy streams, despite considerable differences in litter input rate. This unexpected result was partly due to linkages between CPOM supply and consumer abundance that produced higher detritivore biomass in the forest stream than the open-canopy stream. CPOM standing crop in the forest stream was mainly regulated by top-down consumer control, depressing it to a level similar to that of the open-canopy stream. In contrast, CPOM standing crop in the open-canopy stream was primarily controlled by physical factors (litter input rates and discharge), not consumption. This suggests that abiotic processes (e.g. discharge) may play a greater role in limiting detrital resource availability and consumer biomass in open-canopy streams than in forest streams. These model results give insight on functional differences that exists among streams and they can be used to predict effects of anthropogenic influences such as forestry, agriculture, urbanization, and climate change on streams and how riparian management and conservation tools can be employed to mitigate undesirable effects.
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| 6. |
- Stenroth, Karolina, et al.
(författare)
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Land-use effects on terrestrial consumers through changed size structure of aquatic insects
- 2015
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Ingår i: Freshwater Biology. - : Wiley-Blackwell. - 0046-5070 .- 1365-2427. ; 60:1, s. 136-149
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Tidskriftsartikel (refereegranskat)abstract
- We assessed the influence of agricultural land use on aquatic-terrestrial linkages along streams arising from changes in the emergence of aquatic insects. We expected that terrestrial predators would respond to a change in the abundance and/or the size structure of the emerging aquatic insects by an increase or decrease in population size. We measured the flux of emergent aquatic insects and the abundance of terrestrial invertebrate predators and birds along 10 streams across a forest-to-agriculture land-use gradient. We also performed stable isotope analyses (hydrogen, carbon and nitrogen) of terrestrial invertebrate predators. Small aquatic insects (Nematocera) were most abundant under agricultural land use, whereas larger bodied aquatic insects (Plecoptera and Trichoptera) were more associated with forest land use. Carabid beetles and linyphiid spiders were associated with agricultural streams (where there was a high abundance of small aquatic insects), whereas lycosid spiders and birds were associated with forest streams and a high abundance of large-sized aquatic insects. The contribution of aquatic insects to the diets of riparian Lycosidae, Linyphiidae and Carabidae was estimated to be 44%, 60% and 43%, respectively, indicating the importance of aquatic subsidies to the terrestrial system. Our results show that agricultural land use in an overall forested landscape can have significant effects on the abundance and diet of terrestrial consumers through its impact on the size structure of the assemblage of emerging insects, rather than the overall magnitude (numbers) of the aquatic subsidy. Hence, our results suggest that the composition, not just quantity, of a cross-habitat resource may influence the recipient system.
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| 7. |
- Yeung, Alex C. Y., et al.
(författare)
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Modelling biophysical controls on stream organic matter standing stocks under a range of forest harvesting impacts
- 2019
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Ingår i: Limnologica. - : Elsevier. - 0075-9511 .- 1873-5851. ; 78
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Tidskriftsartikel (refereegranskat)abstract
- Forest harvesting could induce diverse responses of terrestrial-derived coarse particulate organic matter (CPOM) quantity in small streams. Understanding the basis of such variation requires the assessment of the independent and interactive effects of the controlling processes of stream CPOM quantity. Here we simulated post-harvest responses of leaf litter-derived CPOM quantity in a coastal rainforest stream in British Columbia, Canada, using a published process-based model. We compared the relative importance of major biophysical controls of CPOM quantity, including riparian litterfall, discharge, and stream temperature, across a range of severity of forest harvesting disturbance, using a sensitivity analysis. This range represented published post-harvest responses of these model drivers in temperate North America. We then varied the values of model drivers to examine possible changes in CPOM quantity (within (similar to)4 years post-harvest) under different harvesting scenarios, and to characterise the interactions among pairs of drivers. The effects of litterfall reductions due to forest harvesting on depleting CPOM quantity were at least an order of magnitude greater than those of elevated peak flows. Summer stream warming of 4 degrees C or more could lead to a smaller magnitude of CPOM reductions, possibly due to decreases in CPOM consumption and shredder biomass that lasted until fall. Warming-induced CPOM increases could counteract the effects of reduced litterfall and elevated peak flows on lowering CPOM quantity, depending on disturbance severity. CPOM depletions were highly likely when litterfall was below 50% of that in undisturbed conditions. Our heuristic modelling revealed that non-additive, antagonistic interactions between paired model drivers could emerge at higher severity levels of disturbance. We suggest that establishing riparian buffer zones would more likely mitigate post-harvest changes in CPOM quantity through minimising alterations in litter inputs and stream summer temperature. Our study illustrates the utility of process-based simulations and scenario analysis in evaluating the ecological impacts of biophysical processes operating at reach to catchment scales. A wider adoption of these modelling approaches can improve the predictions of stream ecological responses to watershed disturbances.
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