Inter University Center for Aquatic Ecosystem Research

Lunz am See, Austria

Inter University Center for Aquatic Ecosystem Research

Lunz am See, Austria
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Khomich M.,University of Oslo | Davey M.L.,University of Oslo | Kauserud H.,University of Oslo | Rasconi S.,Inter University Center for Aquatic Ecosystem Research | Andersen T.,University of Oslo
Fungal Ecology | Year: 2017

This study investigates the diversity and distribution of fungal communities in 77 oligotrophic lakes in southern Norway and Sweden using 454-sequencing with fungal-specific primers targeting ITS2 region of the rRNA gene. A total of 232 operational taxonomic units (OTUs) belonging to four recognized phyla were detected. A large proportion (70.69%) of the detected OTUs were Dikarya (Ascomycota and Basidiomycota), while Chytridiomycota dominated quantitatively (63.37% reads). The most abundant aquatic fungi were taxonomically assigned to Chytridiomycota, whose members are known to be saprobes on a large variety of substrates and parasites of phytoplankton, zooplankton, fungi and invertebrates, suggesting that resident fungi strictly depend on surfaces and, therefore, are closely associated with other types of aquatic organisms. Our results indicate that surface waters of oligotrophic lakes harbour a diverse pool of fungi, both with tentative terrestrial and true aquatic origin. Longitude and environmental factors were important in structuring the fungal community composition. © 2017 Elsevier Ltd and British Mycological Society

Rasconi S.,Inter University Center for Aquatic Ecosystem Research | Winter K.,Inter University Center for Aquatic Ecosystem Research | Kainz M.J.,Inter University Center for Aquatic Ecosystem Research
Ecology and Evolution | Year: 2017

Global climate change scenarios predict lake water temperatures to increase up to 4°C and extreme weather events, including heat waves and large temperature fluctuations, to occur more frequently. Such changes may result in a reorganization of the plankton community structure, causing shifts in diversity and structure toward a community dominated by fewer species that are more adapted to endure warmer and irregular temperature conditions. We designed a long-term (8 months) mesocosm experiment to explore how ambient water temperature (C: control), induced increased temperature (T: +4°C), and temperature fluctuations (F: ±4°C relative to T) change phytoplankton phenology, taxonomical diversity, and community structure, and how such changes affected zooplankton abundance and composition. Synthesis. Our results show that T and F relative to C significantly decreased phytoplankton diversity. Moreover, there was a clear effect of the temperature treatments (T and F) on phytoplankton size structure that resulted in a significantly lower growth of large species (i.e., large Chlorophyta) compared to C. Decreased diversity and evenness in the T and F treatments pushed the community toward the dominance of only a few phytoplankton taxa (mainly Cyanobacteria and Chlorophyta) that are better adapted to endure warmer and more irregular temperature conditions. The observed shift toward Cyanobacteria dominance may affect trophic energy transfer along the aquatic food web. © 2017 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

Kainz M.J.,Inter University Center for Aquatic Ecosystem Research | Ptacnik R.,Inter University Center for Aquatic Ecosystem Research | Rasconi S.,Inter University Center for Aquatic Ecosystem Research | Hager H.H.,Inter University Center for Aquatic Ecosystem Research
Inland Waters | Year: 2017

Evidence is growing that the surface water temperature increases and the duration of ice cover has decreased in many lakes worldwide during the past few decades. Here, we present changes in surface water temperature and ice-cover duration of Lake Lunz from 1921 to 2015 and evaluate how fast these changes occur over time, in particular with respect to other lakes with similar long-term data series. Since 1921, the surface water temperature of this Austrian subalpine lake has increased by 0.8 °C, with the most intense increase recorded during the spring and summer months (~1-2 °C) and less during fall (~0.3 °C). The duration of full lake ice cover has decreased significantly since 1921. During the 1921-2015 study period, Lake Lunz was ice covered for 92 of 94 winters, with icefree winters in 2006 and 2013. The interannual decrease of the lake ice cover corresponds to 0.36 days less ice cover per year from 1921 to 2015. Freeze dates now occur 17.4 d/100 yr later, and the ice breakup date change is similar to the freeze date, 17.6 d/100 yr earlier. Although the duration of interannual ice cover varied by only 8.3 days between 1921 and 1930, on 32 days between 2006 and 2015 this interannual variability increased by almost 4 times. Thus, the observed decrease of ice cover is accompanied by increasing interannual variability, during which the lake was fully ice covered. When comparing days of full ice cover to other lakes until 2005, Lake Lunz had a similar decline in ice-cover duration (1.85 d/decade), but a dramatic decrease in full ice cover during 2005 and 2015 indicates that the overall decline in lake ice-cover duration was sensitive to changes in lake ice cover during the past decade. This study emphasizes the importance of continuous and collaborative measurements in other (subalpine) lakes worldwide to test, and also manage, the sensitivity of lakes to ongoing effects of climate change. © 2017 International Society of Limnology (SIL).

Colombo S.M.,Ryerson University | Wacker A.,University of Potsdam | Parrish C.C.,Memorial University of Newfoundland | Kainz M.J.,Inter University Center for Aquatic Ecosystem Research | Arts M.T.,Ryerson University
Environmental Reviews | Year: 2017

Polyunsaturated fatty acids (PUFA), especially long-chain (i.e., ≥20 carbons) polyunsaturated fatty acids (LC-PUFA), are fundamental to the health and survival of marine and terrestrial organisms. Therefore, it is imperative that we gain a better understanding of their origin, abundance, and transfer between and within these ecosystems. We evaluated the natural variation in PUFA distribution and abundance that exists between and within these ecosystems by amassing and analyzing, using multivariate and analysis of variance (ANOVA) methods, >3000 fatty acid (FA) profiles from marine and terrestrial organisms. There was a clear dichotomy in LC-PUFA abundance between organisms in marine and terrestrial ecosystems, mainly driven by the C18 PUFA in terrestrial organisms and omega-3 (n-3) LC-PUFA in marine organisms. The PUFA content of an organism depended on both its biome (marine vs terrestrial) and taxonomic group. Within the marine biome, the PUFA content varied among taxonomic groups. PUFA content of marine organisms was dependent on both geographic zone (i.e., latitude, and thus broadly related to temperature) and trophic level (a function of diet). The contents of n-3 LC-PUFA were higher in polar and temperate marine organisms than those from the tropics. Therefore, we conclude that, on a per capita basis, high latitude marine organisms provide a disproportionately large global share of these essential nutrients to consumers, including terrestrial predators. Our analysis also hints at how climate change, and other anthropogenic stressors, might act to negatively impact the global distribution and abundance of n-3 LC-PUFA within marine ecosystems and on the terrestrial consumers that depend on these subsidies. © 2017 Published by NRC Research Press.

PubMed | CSIC - Institute of Marine Sciences, University of Oslo and Inter University Center for Aquatic Ecosystem Research
Type: | Journal: FEMS microbiology ecology | Year: 2016

Despite their obvious importance, our knowledge about the eukaryotic microbial diversity of inland waters is still limited and poorly documented. We applied 18S rDNA amplicon sequencing to provide a comprehensive analysis of eukaryotic diversity in 74 low-productivity lakes along a 750 km longitudinal transect (5.40-18.52E) across southern Scandinavia. We detected a wide diversity of pelagic microbial eukaryotes, classified into 1882 operational taxonomic units (OTUs). The highest OTU richness was found in traditional phytoplankton groups like Dinoflagellata, Chrysophyceae, Chlorophyta and Cryptophyta. A total of 53.6% OTUs were primarily autotrophic while 19.4% of the heterotrophic OTUs belonged to putative parasitic taxa. Except for a longitudinal trend in the relative influence of mixotrophs, there were no significant associations between major functional groups (auto-, heterotrophs and parasites) and spatial and environmental variables. Community dissimilarity increased significantly with increasing geographical distance between lakes. In accordance with earlier, microscopy-based surveys in this region, we demonstrate distinct gradients in protistan diversity and community composition, which are better explained by spatial structure than local environment. The strong association between longitude and protistan diversity is probably better explained by differences in regional species pools due to differences in landscape productivity than by dispersal limitation or climatic constraints.

Welti N.,University of Natural Resources and Life Sciences, Vienna | Welti N.,Inter University Center for Aquatic Ecosystem Research | Bondar-Kunze E.,University of Natural Resources and Life Sciences, Vienna | Bondar-Kunze E.,Inter University Center for Aquatic Ecosystem Research | And 7 more authors.
Ecological Engineering | Year: 2012

Restoration measures of deteriorated river ecosystems generally aim at increasing the spatial heterogeneity and connectivity of these systems in order to increase biodiversity and ecosystem stability. While this is believed to benefit overall ecological integrity, consequences of such restoration projects on biogeochemical processes per se (i.e. ecosystem functioning) in fluvial systems are rarely considered. We address these issues by evaluating the characteristics of surface water connection between side arms and the main river channel in a former braided river section and the role and degree of connectivity (i.e. duration of surface water connection) on the sediment biogeochemistry. We hypothesized that potential respiration and denitrification would be controlled by the degree of hydrological connectivity, which was increased after floodplain restoration. We measured potential microbial respiration (SIR) and denitrification (DEA) and compared a degraded floodplain section of the Danube River with a reconnected and restored floodplain in the same river section. Re-establishing surface water connection altered the controls on sediment microbial respiration and denitrification ultimately impacting potential microbial activities. Meta-variables were created to characterize the effects of hydrology, morphology, and the available carbon and nutrient pools on potential microbial processing. Mantel statistics and path analysis were performed and demonstrate a hierarchy where the effects of hydrology on the available substrates and microbial processing are mediated by the morphology of the floodplain. In addition, these processes are highest in the least connected sites. Surface water connection, mediated by morphology regulates the potential denitrification rate and the ratio of N 2O to N 2 emissions, demonstrating the effects of restoration in floodplain systems. © 2012 Elsevier B.V.

Mariash H.L.,University of Jyväskylä | Cazzanelli M.,Copenhagen University | Kainz M.J.,Inter University Center for Aquatic Ecosystem Research | Rautio M.,University of Jyväskylä | Rautio M.,University of Quebec at Chicoutimi
Freshwater Biology | Year: 2011

Subarctic ponds are seasonal aquatic habitats subject to short summers but often have surprisingly numerous planktonic consumers relative to phytoplankton productivity. Because subarctic ponds have low pelagic productivity but a high biomass of benthic algae, we hypothesised that benthic mats provide a complementary and important food source for the zooplankton. To test this, we used a combination of fatty acid and stable isotope analyses to evaluate the nutritional content of benthic and pelagic food and their contributions to the diets of crustacean zooplankton in 10 Finnish subarctic ponds. Benthic mats and seston differed significantly in total lipids, with seston (62.5μgmg-1) having approximately eight times higher total lipid concentrations than benthic mats (7.0μgmg-1). Moreover, the two potential food sources differed in their lipid quality, with benthic organic matter completely lacking some nutritionally important polyunsaturated fatty acids (PUFA), most notably docosahexaenoic acid and arachidonic acid. Zooplankton had higher PUFA concentrations (27-67μgmg-1) than either of the food sources (mean benthic mats: 1.2μgmg-1; mean seston: 9.9μgmg-1), indicating that zooplankton metabolically regulate their accumulation of PUFA. In addition, when each pond was evaluated independently, the zooplankton was consistently more 13C-depleted (δ13C -20 to -33‰) than seston (-23 to -29‰) or benthic (-15 to -27‰) food sources. In three ponds, a subset of the zooplankton (Eudiaptomus graciloides, Bosmina sp., Daphnia sp. and Branchinecta paludosa) showed evidence of feeding on both benthic and planktonic resources, whereas in most (seven out of 10) ponds the zooplankton appeared to feed primarily on plankton. Our results indicate that pelagic primary production was consistently the principal food resource of most metazoans. While benthic mats were highly productive, they did not appear to be a major food source for zooplankton. The pond zooplankton, faced by strong seasonal food limitation, acquires particular dietary elements selectively. © 2011 Blackwell Publishing Ltd.

Sanon S.,UNESCO-IHE Institute for Water Education | Hein T.,University of Natural Resources and Life Sciences, Vienna | Hein T.,Inter University Center for Aquatic Ecosystem Research | Douven W.,UNESCO-IHE Institute for Water Education | And 2 more authors.
Journal of Environmental Management | Year: 2012

Wetland ecosystems provide multiple functions and services for the well-being of humans. In urban environments, planning and decision making about wetland restoration inevitably involves conflicting objectives, trade-offs, uncertainties and conflicting value judgments. This study applied trade-off and multi criteria decision analysis to analyze and quantify the explicit trade-offs between the stakeholder's objectives related to management options for the restoration of an urban floodplain, the Lobau, in Vienna, Austria. The Lobau has been disconnected from the main channel of the Danube River through flood protection schemes 130 years ago that have reduced the hydraulic exchange processes. Urban expansion has also changed the adjacent areas and led to increased numbers of visitors, which hampers the maximum potential for ecosystem development and exerts additional pressure on the sensitive habitats in the national park area. The study showed that increased hydraulic connectivity would benefit several stakeholders that preferred the ecological development of the floodplain habitats. However, multiple uses including fishery, agriculture and recreation, exploring the maximum potential in line with national park regulations, were also possible under the increased hydraulic connectivity options. The largest trade-offs were quantified to be at 0.50 score between the ecological condition of the aquatic habitats and the drinking water production and 0.49 score between the ecological condition of the terrestrial habitats and the drinking water production. At this point, the drinking water production was traded-off with 0.40 score, while the ecological condition of the aquatic habitats and the ecological condition of the terrestrial habitats were traded off with 0.30 and 0.23 score, respectively. The majority of the stakeholders involved preferred the management options that increased the hydraulic connectivity compared with the current situation which was not preferred by any stakeholders. These findings highlight the need for targeted restoration measures. By that, it is recommended that additional measures to ensure reliable drinking water production should be developed, if the higher connectivity options would be implemented. In the next step it is recommended to include cost and flood risk criteria in the decision matrix for more specific developed measures. The research showed that pair-wise trade-off figures provided a useful means to elaborate and quantify the real trade-offs. Finally, the research also showed that the use of multi criteria decision analyses should be based on a participatory approach, in which the process of arriving at the final ranking should be equal or more important than the outcome of the ranking itself. © 2012 Elsevier Ltd.

Baart I.,University of Natural Resources and Life Sciences, Vienna | Baart I.,Inter University Center for Aquatic Ecosystem Research | Gschopf C.,Vienna University of Technology | Blaschke A.P.,Vienna University of Technology | And 4 more authors.
Aquatic Botany | Year: 2010

Wetland restoration efforts require practical models for predicting the effects of various measures on ecosystem structure and function. The present study examined the species diversity and abundance of macrophytes in relation to hydrological parameters in the Alluvial Zone National Park along the Austrian Danube with a main focus on the Lobau, an urban riverine wetland within the city limits of Vienna. A macrophyte regression model was developed based on the output of a 2D hydraulic model for different wetland management options. These management options describe possible rehabilitation measures by re-connecting the riverine wetland with the Danube. Stepwise multiple regressions revealed that the most important predictors of macrophyte diversity and abundance were water velocity at bankfull discharge (maximum water velocity) and size of shallow water areas (<1m depth) during the growing season. Macrophyte abundance and diversity increased with decreasing water velocity and increasing shallow water area. These parameters integrate information about environmental features such as nutrients, light availability and hydrological disturbance for macrophytes and explained between 65 and 85% of the macrophyte distribution in an analysis. The model results enabled us to predict quantitatively the development and spatial distribution of macrophytes for different management options in this urban riverine wetland. These predictions suggest that partial reconnection could be a compromise solution at the scale of the whole riverine wetland, increasing the availability of suitable aquatic habitats and diversifying the types of existing wetland water bodies to establish potential new habitats for macrophyte species. © 2010 Elsevier B.V.

PubMed | Inter University Center for Aquatic Ecosystem Research
Type: Journal Article | Journal: PloS one | Year: 2015

Climate change scenarios predict that lake water temperatures will increase up to 4C and rainfall events will become more intense and frequent by the end of this century. Concurrently, supply of humic substances from terrestrial runoff is expected to increase, resulting in darker watercolor (brownification) of aquatic ecosystems. Using a multi-seasonal, low trophic state mesocosm experiment, we investigated how higher water temperature and brownification affect plankton community composition, phenology, and functioning. We tested the hypothesis that higher water temperature (+3C) and brownification will, a) cause plankton community composition to shift toward small sized phytoplankton and cyanobacteria, and, b) extend the length of the growing season entailing higher phytoplankton production later in the season. We demonstrate that the 3C increase of water temperature favored the growth of heterotrophic bacteria and small sized autotrophic picophytoplankton cells with significantly higher primary production during warmer fall periods. However, 3X darker water (effect of brownification) caused no significant changes in the plankton community composition or functioning relative to control conditions. Our findings reveal that increased temperature change plankton community structure by favoring smaller sized species proliferation (autotrophic phytoplankton and small size cladocerans), and increase primary productivity and community turnover. Finally, results of this multi-seasonal experiment suggest that warming by 3C in aquatic ecosystems of low trophic state may cause planktonic food web functioning to become more dominated by fast growing, r-trait species (i.e., small sizes and rapid development).

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