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  • 1.
    Bergfur, Jenny
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Temporal variation in carbon and nitrogen isotope ratios of aquatic biota in two contrasting boreal streams2013In: Fundamental and Applied Limnology, ISSN 1863-9135, Vol. 182, no 3, p. 205-218Article in journal (Refereed)
    Abstract [en]

    Natural abundant isotopes of carbon and nitrogen are frequently used to elucidate food webs and trace energy flows in aquatic ecosystems. Seasonal events such as leaf fall and algal blooms can influence temporal patterns and hence also affect interpretations of isotope data. This study examined such patterns in two contrasting streams in Sweden: Vadsbacken, which is heavily impacted by agriculture and has high nitrogen levels, and Pinnarpsbacken, which has a primarily forested catchment and lower nitrogen levels. Different organic compartments (e.g., detritus, biofilm, and invertebrates) were sampled in September, November, April, and June. Effects of sampling date on isotope signatures of leaf litter (delta N-15: p = 0.0001, delta C-13: p = 0.03), seston (delta N-15: p = 0.001, delta C-13: p = 0.001), FPOM (delta N-15: p = 0.03, delta C-13: p = 0.003), wood (delta C-13: p = 0.05) and invertebrates (delta N-15: p = 0.04) were found. However, there were site-specific temporal patterns in isotope signatures, probably reflecting disparate origins of allochthonous material related to the differences in catchment land use. Mixing models revealed no changes in resource partitioning that could be attributed to the above-mentioned seasonal events. The site-specific patterns recorded here indicate that generalisation regarding ecosystems with different perturbations should be done with caution.

  • 2.
    Bergfur, Jenny
    et al.
    The James Hutton Institute, Craigiebuckler, Aberdeen, UK.
    Demars, B.O.I
    The James Hutton Institute, Craigiebuckler, Aberdeen, UK.
    Stutter, M.I.
    The James Hutton Institute, Craigiebuckler, Aberdeen, UK.
    Langan, S.J.
    The James Hutton Institute, Craigiebuckler, Aberdeen, UK.
    Friberg, N
    The James Hutton Institute, Craigiebuckler, Aberdeen, UK.
    The Tarland Catchment Initiative and Its Effect on Stream Water Quality and Macroinvertebrate Indices2012In: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 41, no 2, p. 314-321Article in journal (Refereed)
    Abstract [en]

    The Tarland Catchment Initiative is a partnership venture between researchers, land managers, regulators, and the local community. Its aims are to improve water quality, promote biodiversity, and increase awareness of catchment management. In this study, the effects of buffer strip installations and remediation of a large septic tank effluent were appraised by water physico-chemistry (suspended solids, NO3, NH4, soluble reactive P) and stream macroinvertebrate indices used by the Scottish Environmental Protection Agency. It was done during before and after interventions over an 8-yr period using a paired catchment approach. Because macroinvertebrate indices were previously shown to respond negatively to suspended solid concentrations in the study area, the installation of buffer strips along the headwaters was expected to improve macroinvertebrate scores. Although water quality (soluble reactive P, NH4) improved downstream of the septic tank effluent after remediation, there was no detectable change in macroinvertebrate scores. Buffer strip installations in the headwaters had no measurable effects (beyond possible weak trends) on water quality or macroinvertebrate scores. Either the buffer strips have so far been ineffective or ineffectiveness of assessment methods and sampling frequency and time lags in recovery prevent us detecting reliable effects. To explain and appreciate these constraints on measuring stream recovery, continuous capacity building with land managers and other stakeholders is essential; otherwise, the feasibility of undertaking sufficient management interventions is likely to be compromised and projects deemed unsuccessful.

  • 3.
    Bergfur, Jenny
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Friberg, Nikolai
    Department of Bioscience, Aarhus University, Silkeborg, Denmark.
    Trade-offs between fungal and bacterial respiration along gradients in temperature, nutrients and substrata: Experiments with stream derived microbial communities2012In: Fungal ecology, ISSN 1754-5048, E-ISSN 1878-0083, Vol. 5, no 1, p. 46-52Article in journal (Refereed)
    Abstract [en]

    We examined the effects of temperature, nutrients and substrata on microbial respiration rates. Leaves of alder and oak were incubated in a natural stream. Leaf discs were incubated in antibiotics to manipulate the ratio of fungi to bacteria with three treatments: antifungal, antibacterial, and combined antifungal and antibacterial treatment in addition to controls. Discs were subsequently incubated in different nutrient set-ups and temperature regimes. Significant effects of temperature, nutrients, microbial treatment and leaf type on respiration rates were found. However, temperature did not significantly add to the effect of eutrophication on microbial respiration rates. A stronger effect of temperature on fungal mediated respiration than on bacterial mediated respiration was found. In streams where leaf litter constitutes the main energy source, fungi constitute the dominant microbial decomposer. Our results indicate that increased temperature due to global warming might have serious implications for ecosystem functioning when leaf litter constitutes the main energy source.

  • 4.
    Bergfur, Jenny
    et al.
    Department of Aquatic Sciences and Assessment, Swedish Agricultural University, Uppsala, Sweden; The Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen, UK .
    Johnson, Richard K
    Department of Aquatic Sciences and Assessment, Swedish Agricultural University, Uppsala, Sweden.
    Sandin, Leonard
    Department of Aquatic Sciences and Assessment, Swedish Agricultural University, Uppsala, Sweden.
    Goedkoop, Willem
    Department of Aquatic Sciences and Assessment, Swedish Agricultural University, Uppsala, Sweden.
    Effects of nutrient enrichment on C and N stable isotope ratios of invertebrates, fish and their food resources in boreal streams2009In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 628, p. 67-79Article in journal (Refereed)
    Abstract [en]

    Carbon and nitrogen stable isotopes are frequently used to study energy sources and food web structure in ecosystems, and more recently, to study the effects of anthropogenic stress on aquatic ecosystems. We investigated the effect of nutrient enrichment on  d13C and d15N in fine (FPOM), coarse (CPOM) particulate organic matter, periphyton, invertebrates and fish in nine boreal streams in south-central Sweden. In addition, we analysed the diet of benthic consumers using stable isotope data. Increases in d15N of periphyton (R2 = 0.88), CPOM (0.78), invertebrates (0.92) and fish (0.89) were related to nutrient enrichment. In contrast, d13C signatures did not change along the nutrient gradient. Our results show that d15N has potential as a sensitive indicator of nutrient enrichment in boreal streams. Carbon and nitrogen isotopes failed to elucidate putative diets of selected aquatic consumers. Indeed, comparison of low- and high-impact sites showed that d13C of many consumers were found outside the ranges of basal resource d13C. Moreover, ranges of basal resource d13C and d15N overlapped at both low and high sites, making discrimination between the importance of allochthonous and autochthonous production difficult. Our findings show that a fractionation rate of 3.4% is not always be appropriate to assess trophic interactions, suggesting that more studies are needed on fractionation rates along gradients of impairment.

  • 5.
    Bergfur, Jenny
    et al.
    Linköping University, The Tema Institute, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Sundberg, Carina
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Leaf-litter-associated fungi and bacteria along temporal and environmental gradients in boreal streams2014In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 73, no 3, p. 225-234Article in journal (Refereed)
    Abstract [en]

    Aquatic fungi and bacteria have long been recognized as key drivers in ecosystem processes such as leaf litter decomposition. We examined fungal and bacterial communities on decaying alder Alnus glutinosa (L.) Gaertner leaves along a gradient of increasing agricultural land use and associated nutrient enrichment in 9 boreal streams during 4 separate seasons (fall 2003, spring 2005, fall 2005, and spring 2006). Denaturing gradient gel electrophoresis (DGGE) and quantitative polymerase chain reactions (qPCR) showed that agricultural land use had significant effects on both bacterial and fungal communities, and on the ratios of fungi to total microbes associated with decomposing leaf litter. Furthermore, landscape factors and fluvial geomorphology appeared to influence the community composition of fungi and bacteria. Seasonal effects were found for fungal community structure only, indicating a higher temperature sensitivity of fungi compared to bacteria.

  • 6.
    Fischer, Helmut
    et al.
    Limnology/Department of Ecology and Evolution, Uppsala University, Sweden.
    Bergfur, Jenny
    Department of Aquatic Sciences, Swedish Agricultural University, Sweden.
    Goedkoop, Willem
    Department of Aquatic Sciences, Swedish Agricultural University, Sweden.
    Tranvik, Lars
    Limnology/Department of Ecology and Evolution, Uppsala University, Sweden.
    Microbial leaf degraders in boreal streams: bringing together stochastic and deterministic regulators ofcommunity composition2009In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 54, p. 2276-2289Article in journal (Refereed)
    Abstract [en]

    1. Leaves that fall into the water represent a new habitat for microorganisms to colonise in streams, providing an opportunity to study colonisation and the subsequent regulation of community structure. We explored community composition of bacteria and fungi on decomposing alder leaves in nine streams in central Sweden, and describe their relationship with environmental variables. Succession of the microbial community was studied in one of the streams for 118 days. Microbial community composition was examined by denaturing gradient gel electrophoresis on replicate samples of leaves from each stream.

    2. During succession in one stream, maximum taxon richness was reached after 34 days for bacteria and 20 days for fungi respectively. Replicate samples within this stream differed between each other earlier in colonisation, while subsequently such variation among replicate communities was low and remained stable for several weeks. Replicate samples taken from all the nine streams after 34 days of succession showed striking similarities in microbial communities within-streams, although communities differed more strongly between streams.

    3. Canonical analysis of microbial communities and environmental variables revealed that water chemistry had a significant influence on community composition. This influence was superimposed on a statistical relationship between the properties of stream catchments and microbial community composition.

    4. The catchment regulates microbial communities in two different ways. It harbours the species pool from which the in-stream microbial community is drawn and it governs stream chemistry and the composition of organic substrates that further shape the communities. We suggest that there is a random element to colonisation early in succession, whereas other factors such as species interactions, stream chemistry and organic substrate properties, result in a more deterministic regulation of communities during later stages.

  • 7.
    Friberg, Nikolai
    et al.
    Department of Bioscience, Aarhus University, Silkeborg, Denmark.
    Bergfur, Jenny
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Rasmussen, Jes
    Department of Bioscience, Aarhus University, Silkeborg, Denmark.
    Sandin, Leonard
    Changing Northern catchments: Is altered hydrology, temperature or both going to shape future stream communities and ecosystem processes?2013In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 27, no 5, p. 734-740Article in journal (Refereed)
    Abstract [en]

    Global change is predicted to increase temperature substantially in the North as well as altering run-off regimes with less synchronicity as the importance of snow melt declines. River biota and ecosystem processes will be influenced across all levels of organization, both in concert and individually. It is of vital importance that the impacts, and their likely magnitude, can be identified in order to deploy suitable adaptation strategies at the catchment scale. In this paper, we re-analyse four data sets from studies conducted in Greenland (66–69oN), Iceland (64oN), Sweden (60oN) and Denmark (55–57oN) to try and tease out the likely impacts of water temperature and hydrology in shaping the stream communities and ecosystem processes in high-latitude catchments. Water temperature was the environmental variable that best explained macroinvertebrate community composition across latitudes. In contrast, no significant relationship between macroinvertebrate community composition and measures of hydraulic stability (or nutrients) was found. We found a strong linear relationship between decay rate of leaf litter and water temperature (r2 = 0.68; p < 0.0001) independent of latitudes. Our study suggests that temperature could be the primary driver of ecosystem change in future with northern catchments likely to be especially vulnerable.

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