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- Bohman, Irene, 1960-
(author)
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Coarse detritus in oligotrophic lake littoral zones : utilization by intervertebrates and contribution to carbon flow
- 2005
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Doctoral thesis (other academic/artistic)abstract
- Syftet med denna avhandling är att öka förståelsen av hur grovt organiskt material, sk grovdetritus, tex löv och makrofytrester, bryts ner i sjöars strandzoner. Motivet bakom intresset för detta är att små näringsfattiga sjöar i skogsrika områden ofta är beroende av tillförsel av energi utifrån och att nedbrytningen av grovdetritus är relativt lite undersökt i sjöar. Utifrån tillförd detritus, i löst och partikulär form kan utgöra extra energikälla för sjöekosystem, men bara om några organismer kan tillgodogöra sig detta organiska material. I sötvatten kan sådana organismer vara bakterier, svampar och ryggradslösa djur. Under nedbrytningsförloppet produceras en mängd mellanprodukter som kan användas av andra konsumenter tex fisk. På så sätt återcirkuleras energi och näring från detritus utan fullständig nedbrytning. Vidare har det föreslagits att hög biodiversitet kan resultera i hög ekosystemfunktion, t ex effektiv nedbryning. Därför kan studier av både samhällen och enskilda arter av nedbrytare öka förståelsen av förändringar i hela ekosystemets funktion. Inom ramen för avhandlingen har jag studerat vilka arter som deltar i nedbrytningen av grovdetritus och vilka möjliga vägar för det fortsatta nyttjandet av detta material som finns. Jag har särskilt betonat det säsongsmässiga mönstret för omsättningen av grovdetritus och för tillgängligheten av mellanprodukter. Resultaten visar att både mikroorganismer och ryggradslösa djur successivt processar tillgängligt grovt organiskt material under hela året. Viktminskningsmönstret över året hos löv och makrofytrester är nära kopplat till förekomst och tillväxt hos olika arter av nedbrytande ryggradslösa djur, sk fragmenterare. Av de vanligaste förekommande tio arterna fragmenterare, var nio nattsländelarver. Därför drar jag slutsatsen att dessa arter av nattsländelarver spelar en avgörande roll för omsättningen av grovdetritus i sjöstränder i sydöstra Sverige. Samtidigt visar resultaten att sötvattengråsuggan spelar mindre roll för nedbrytningen av grovdetritus än förväntat. Denna art föredrar andra födoämnen åtminstone under våren och undviker de grunda bottnarna där grovdetritus finns under vintern. I laboratorieexperiment har jag visat att nedbrytning av löv i närvaro av fragmenterare huvudsakligen ger upphov till två olika produkter: löst organiskt material och finpartikulära rester. Därmed har jag visat att fragmenterare kan omsätta grovdetritus snabbare än mikroorganismer. Slutsatsen blir att mikroorganismernas kvantitativa bidrag till nedbrytning av grov grovdetritus är beroende av mängden fragmenterare. Jag har också visat att olika kombinationer detritussorter och fragmenterararter kan påverka när olika nedbryningsprodukter blir tillgängliga för andra organismer. Sammanfatningsvis har jag visat att grovdetritus är en attraktiv födoresurs för ryggradslösa djur i näringsfattiga sjöars strandzoner, precis som i små bäckar. Dessutom visar jag att de arter av fragmenterare som är speciella för sjöar, tillsammans omsätter tillgängligt grovdetritus i ett finskaligt tidsmönster över året. Detta mönster har utvecklats genom anpassning till trädens lövfällning och nedvissningen av vattenväxter som sker på hösten i vårt klimat. Jag vill också betona att ökade kunskaper om nedbrytning av grovdetritus krävs för att kunna förutsäga effekter av olika störningar i dessa ekosystem. Slutligen rekommenderar jag att nedbrytningshastigheten för grovdetritus testas som mått på ekosystemfunktion också i sjöar.
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- Bohman, Irene, et al.
(author)
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The timing for winter-growing shredder species and leaf litter turnover rate in an oligotrophic lake, SE Sweden
- 2006
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 556:1, s. 99-108
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Journal article (peer-reviewed)abstract
- Small freshwater systems often depend on allochthonous organic subsidies to sustain productivity. Benthic invertebrates consuming coarse detritus maintain the energy flow by conveying dead organic matter into prey items and increase the food availability for other consumers. Compared to lotic systems, the dynamics of coarse detritus decomposition has not received much attention in lakes. The objectives of this study were to investigate the seasonality of leaf litter turnover and the timing of abundance of potential shredder species in a typical oligotrophic boreal lake. Leaf litter was experimentally exposed in litterbags in the littoral zone in Lake Välen from autumn to late spring two consecutive years. The weight loss rate of leaf litter initially followed the same pattern during both winter periods, but was markedly influenced by freezing in late winter the second year. Further, the seasonal variation patterns in abundance in litterbags were quite different among the potential shredder species. Only the limnephilid caddis larvae showed a density variation pattern possible to connect to the weight loss of leaf litter in litterbags. Otherwise frequent detritivores such as Asellus aquaticus and Leptophlebia marginata displayed lowest density in litterbags during the main weight loss period. However, after the long ice period the second winter the remaining leaf litter seemed to be consumed by A. aquaticus. With increasing knowledge of the initial leaf breakdown process and the guild of shredders in lakes, the decomposition rate may also in this habitat become a useful instrument when evaluating the impact from perturbations on ecosystem function.
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- Bohman, Tony, et al.
(author)
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Does a healthy lifestyle behaviour influence the prognosis of low back pain among men and women in a general population? A population-based cohort study
- 2014
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In: BMJ Open. - : BMJ. - 2044-6055. ; 4:12
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Journal article (peer-reviewed)abstract
- OBJECTIVES:To study the influence of healthy lifestyle behaviour on the prognosis of occasional low back pain among men and women in a general population.DESIGN:Cohort study with a 4-year follow-up.SETTINGS:General population in Stockholm County, Sweden.PARTICIPANTS:The study sample comprised 3938 men and 5056 women aged 18-84 from the Stockholm Public Health Cohort reporting occasional low back pain in the baseline questionnaire 2006.MEASURES:Lifestyle factors and potential confounders were assessed at baseline. The lifestyle factors smoking habits, alcohol consumption, leisure physical activity and consumption of fruit and vegetables were dichotomised using recommendations for a health-enhancing lifestyle and combined to form the exposure variable 'healthy lifestyle behaviour'. The exposure was categorised into five levels according to the number of healthy lifestyle factors met. The follow-up questionnaire in 2010 gave information about the outcome, long duration troublesome low back pain. Crude and adjusted binomial regression models were applied to estimate the association between the exposure and the outcome analysing men and women separately.RESULTS:The risk of developing long duration troublesome low back pain among women with occasional low back pain decreased with increasing healthy lifestyle behaviour (trend test: p=0.006). 21% (28/131) among women with no healthy lifestyle factor (reference) experienced the outcome compared to 9% (36/420) among women with all four factors. Compared to the reference group, the risk was reduced by 35% (RR 0.65, 95% CI 0.44 to 0.96) for women with one healthy lifestyle factor and 52% (RR 0.48, 95% CI 0.31 to 0.77) for women with all four healthy lifestyle factors. There were no clear associations found among men.CONCLUSIONS:Healthy lifestyle behaviour seems to decrease the risk of developing long duration troublesome low back pain among women with occasional low back pain and may be recommended to improve the prognosis.
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- Leberfinger, Karolina, et al.
(author)
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Drought impact on stream detritivores - experimental effects on leaf litter breakdown and life cycles
- 2010
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 652:1, s. 247-254
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Journal article (peer-reviewed)abstract
- Predictions of effects of global climate change include decreased runoff for many parts of the world, which will result in drying of streams. Information of the effects of drought on aquatic ecosystems is limited and little is known of the effects on ecosystem functions. Our main objective was to measure the direct effects of drought on leaf litter breakdown by invertebrate shredders in a controlled laboratory experiment. We hypothesized a decreased breakdown at high drought level. Single-species and multi-species treatments with three shredder species (Asellus aquaticus, Limnephilus bipunctatus, and L. flavicornis) were set up in an experiment with three drought level treatments, control, medium, and high drought (6 cm water level, 1 cm water level, and water level below sediment surface, respectively). Breakdown measured as leaf litter loss was significantly lower in both medium and high drought treatments compared to the control. Previously, decreased breakdown due to drying has been reported, but attributed to low densities of invertebrate shredders. We show that even when shredders are present, drought decreases the breakdown. Drought treatments also induced earlier pupation for the caddisfly L. flavicornis. Shifts in species phenology due to drought, e.g., earlier emergence, may affect species ability to adult survival and reproduction. Shifts in timing of emergence may also affect terrestrial food webs, where emerging aquatic insects may constitute an important food subsidy. Our knowledge of the complex effects of droughts in aquatic systems is limited with an urgent need of extended knowledge of the ecological effects of droughts on freshwater ecosystem functioning.
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- Leberfinger, Karolina, et al.
(author)
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Grass, mosses, algae or leaves? Food preference among shredders from open-canopy streams
- 2010
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In: Aquatic Ecology. - : Springer Science and Business Media LLC. - 1386-2588 .- 1573-5125. ; 44:1, s. 195-203
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Journal article (peer-reviewed)abstract
- Shredder feeding is a vital process in making decomposition products available to biota in streams. To investigate which food sources shredders in open-canopy streams exploit, we conducted a feeding preference experiment with the invertebrate detritivores Limnephilus bipunctatus and Nemoura sp., which are commonly found in open-canopy streams on the Swedish island of A-land in the southern Baltic Sea. Leaves of birch, Swedish whitebeam, and shrubby cinquefoil; dead and fresh grass; water moss; and algae were offered to the shredders in multi- and single treatments. We hypothesized that food with high nutritional value would be preferred. Both taxa preferred leaves of shrubby cinquefoil, a bush common in the riparian zone of A-land streams; additionally Nemoura sp. also chose algae. Dead grass, the most abundant food source in the streams during the whole year, was the least consumed food type. The fresh food types had highest nutritional value, measured as carbon to nitrogen content. Therefore, food quality could not alone explain the preference of shrubby cinquefoil. However, among the detritus type offered, shrubby cinquefoil had the highest nutritional value. Shrubby cinquefoil may constitute one important energy source to these open-canopy stream ecosystems and may be essential in maintaining an abundant shredder community in these streams. Thus, the results of this study indicate that detrital resources are indeed important in open-canopy stream systems.
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