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Mitigation or disturbance? Effects of liming on macroinvertebrate assemblage structure and leaf-litter decomposition in the humic streams of northern Sweden
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2006 (English)In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 43, no 4, 780-791 p.Article in journal (Refereed) Published
Abstract [en]
  1. Stream liming can alleviate the effects of anthropogenic acidification but itself constitutes a substantial ecosystem-level perturbation. Acidity in the humic streams of northern Sweden largely arises from natural causes but liming is extensively practised, with uncertain ecological outcomes.
  2. We investigated macroinvertebrate assemblage structure and leaf-litter decomposition in seven humic Swedish streams, each of which is limed at a single point using a dosing tower. Grey alder Alnus incana leaves were enclosed in replicate fine (mesh size 0·5 mm) and coarse (10 mm) mesh bags at three locations in each stream: upstream of the dosing tower, in the transitional ‘mixing zone’ immediately downstream of the tower, and at a site further downstream where the lime powder is completely dissolved, with marked changes to water chemistry. Benthic macroinvertebrate assemblages were characterized from each site via five replicate Surber samples.
  3. Alkalinity, pH, conductivity and calcium (Ca) concentrations increased following liming, whereas dissolved organic carbon and aluminium concentrations decreased.
  4. Decomposition in fine mesh bags, primarily mediated by microbes, was positively associated with pH and Ca and was significantly elevated by liming, probably attributable to stimulation of fungal pectin-degrading enzymes that require Ca as a cofactor.
  5. Decomposition attributable to detritivorous insects (shredders), assessed by subtracting decomposition observed in fine mesh bags from that observed in coarse bags, was reduced following liming, in concert with changes to shredder assemblages. Abundance of large caddisfly shredders declined in limed stream sections, whereas some smaller stoneflies increased in number. Shredder diversity declined following liming during spring. Species evenness fell overall, and richness was reduced in four of six streams.
  6. Synthesis and applications. Water chemistry changes following stream liming in northern Sweden appear to overcompensate for the limited acid deposition observed in the region, with important ecosystem consequences. The potential deleterious impacts of liming need to be balanced against its desired outcomes in regions where acidity is largely attributable to natural causes.
Place, publisher, year, edition, pages
Oxford: Blackwell , 2006. Vol. 43, no 4, 780-791 p.
Keyword [en]
alkalinization, biodiversity, ecosystem function, hyphomycete, natural acidity, restoration
Identifiers
URN: urn:nbn:se:umu:diva-2489DOI: 10.1111/j.1365-2664.2006.01196.xOAI: oai:DiVA.org:umu-2489DiVA: diva2:140637
Available from: 2007-08-28 Created: 2007-08-28 Last updated: 2017-12-14Bibliographically approved
In thesis
1. What are the effects of natural versus human-caused acidity on stream species diversity and ecosystem functioning?
Open this publication in new window or tab >>What are the effects of natural versus human-caused acidity on stream species diversity and ecosystem functioning?
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human activities have caused acidification of freshwater systems on a large scale resulting in reduced species diversity and ecological functioning in many lakes and streams. However, many naturally acidic freshwater systems have also been found, for instance in northern Sweden. In regions where such naturally acidic aquatic ecosystems have prevailed over evolutionary periods, species diversity and ecological functioning are not automatically impaired due to possible adaptation to the putatively adverse environmental conditions. I studied species diversity patterns and ecological functioning in anthropogenically acidified, naturally acidic, circumneutral, and limed streams to test the adaptation hypothesis and examine the ecological effects of variation in naturally acidic water chemistry. Species diversity was studied using benthic macroinvertebrates, while functioning was modelled using the decomposition rates of leaf litter. In accordance with the evolutionary species pool hypothesis, species richness was reduced more strongly in regions with anthropogenic than natural acidity when compared to circumneutral streams, supporting the adaptation hypothesis. In contrast, the patterns in ecological functioning along the pH-gradients did not differ between regions with anthropogenic and natural acidity, likely resulting from compensation: the biomass of tolerant taxa probably increased which thus rescued the loss in functioning otherwise mediated by the more sensitive taxa. Furthermore, the naturally variable acidic water chemistry clearly supported distinct macroinvertebrate assemblages, as was reflected in differing patterns of species diversity and ecological functioning. Such naturally acidic waters that were rich in dissolved organic carbon supported higher ecosystem process rates and lower species diversity than waters that contained little dissolved organic carbon. Upon liming naturally acidic streams microbial leaf decomposition increased, whereas shredding decreased along with changes in shredder abundances. The abundance of large caddisflies decreased, while the abundance of small stoneflies increased. The results suggest that various types of benthic macroinvertebrates with varying levels of adaptation and tolerance inhabited the hydrochemically variable naturally acidic streams. The distributions of macroinvertebrates in response to different pH levels and differences in acid quality and how these distributions translate into varying patterns of species diversity and ecological functioning are worthy of further investigation. This will likely improve our understanding of how such naturally acidic streams and their biota can be successfully managed.

Place, publisher, year, edition, pages
Umeå: Ekologi, miljö och geovetenskap, 2007. 19 p.
Keyword
acid rain, aquatic insects, biodiversity, ecosystem function
National Category
Biological Sciences
Identifiers
urn:nbn:se:umu:diva-1318 (URN)978-91-7264-345-1 (ISBN)
Public defence
2007-09-22, KB3A9, KBC, Ekologi, miljö och geovetenskap, Umeå, 10:00
Opponent
Supervisors
Available from: 2007-08-28 Created: 2007-08-28 Last updated: 2011-03-23Bibliographically approved

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Publisher's full texthttp://dx.doi.org/10.1111/j.1365-2664.2006.01196.x

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