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| 2. |
- Larson, Daniel, et al.
(author)
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Bioaccumulation of microcystins in the food web : a field study of four Swedish lakes
- 2014
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In: Inland Waters. - 2044-2041 .- 2044-205X. ; 4:1, s. 91-104
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Journal article (peer-reviewed)abstract
- The transfer of microcystins (MC) up the food chain was measured in 4 lakes in central Sweden; Ekoln, Lilla Ullfjärden, Valloxen, and Storsjön. In lakes Ekoln and Valloxen, Microcystis aeruginosa was the dominant cyanobacterium, while the oscillatorian species Planktothrix prolifica form dense blooms in Lake Lilla Ullfjärden. The cyanobacterial composition in Lake Storsjön was more diverse with several Microcystis andDolichospermum species. All dominant taxa are well-known producers of hepatotoxic MC. The highest recorded MC in the water samples from Lake Lilla Ullfjärden was measured in the bloom of P. prolifica (35 µg L−1). The highest MC content was measured in invertebrates; however, the MC concentration was usually low in fish. Maximum levels were 9 µg g−1 dry weight (dw) in zooplankton, 10 µg g−1 dw in benthos, and 2.7 µg g−1 dw in fish (smelt) liver. In fish muscle the highest recorded levels were 0.10–0.18 µg g−1 dw in bleak and smelt from Lake Lilla Ullfjärden and in pike-perch and roach from Lake Storsjön. Based on the World Health Organization’s tolerable daily intake value of 0.04 µg kg−1 body weight, we conclude that any risk related to MC from human consumption of fish from these lakes is minimal.
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| 3. |
- Weyhenmeyer, Gesa, et al.
(author)
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Shifts in phytoplankton species richness and biomass along a latitudinal gradient : consequences for relationships between biodiversity and ecosystem functioning
- 2013
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In: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 58:3 (SI), s. 612-623
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Journal article (peer-reviewed)abstract
- 1. Analysing phytoplankton community data from 205 small, mainly oligotrophic Swedish lakes along a 13 degrees latitudinal gradient, we found that the duration of the open-water season (DT>0) was best related to phytoplankton speciesrichness and biomass, probably because DT>0 can be used as a proxy for nutrient concentrations, as well as for light and temperature conditions in lakes. 2. The relationships between DT>0 and phytoplankton species richness and biomass were not linear but showed significant shifts, that is, richness suddenly doubled at DT>0=170days and phytoplankton biomass began to strongly increase at DT>0 around 220days. 3. The doubling in species richness corresponded to a change in the seasonal plankton succession from one to two peaks per year, and the shift in biomass corresponded to ashift in nutrient concentrations. 4. The geographical differences in richness and biomassshifts resulted in an exponential biodiversityecosystem functioning relationship along aDT>0 gradient. 5. We conclude that phytoplankton species richness and biomass are driven by different environmental factors, resulting in a nonlinear biodiversityecosystem functioning relationship. The shape of the diversityfunctioning relationship varies alongwith variations in environmental drivers, which is of highest importance for ongoing discussions about impacts of global change on biodiversity and ecosystem functioning.
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| 4. |
- Willen, Eva, et al.
(author)
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Cyanotoxin production in seven Ethiopian Rift Valley lakes
- 2011
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In: Inland Waters. - 2044-2041 .- 2044-205X. ; 1:2, s. 81-91
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Journal article (peer-reviewed)abstract
- We hypothesized that unusual deaths and illnesses in wild and domestic animals in lake areas of the Rift Valley south of Addis Ababa were caused by toxic cyanobacteria. In the first cyanotoxic analyses conducted in samples from Ethiopia, we found lakes Chamo, Abaya, Awassa, Chitu, Langano, Ziway, and Koka all had concentrations of microcystins (MC) ranging from trace to hazardous, whereas only traces less than limits of detection (LOD) of cylindrospermopsin (CYN) were found. In the December 2006 dry season we sampled the lakes for analyses of MC, CYN, species structures, and calculations of cyanobacteria biomass. We used the Utermol technique to analyse cyanobacterial biomass and monitored MC toxins using HPLC-DAD, LC-ESI-MS-MRM, and ELISA-test and CYN with HPLC-DAD and ELISA. The various toxicity tests coincided well. In 4 of the lakes (Chamo, Langano, Ziway, and Koka), the inter-lake range of total MC concentration was 1.3-48 mu g L-1; in 3 (Abaya, Awassa, and Chitu), we found only traces of MC. Microcystis aeruginosa was the dominant species, with Microcystis panniformis, Anabaena spiroides, and Cylindrospermopsis spp. as subdominants. The MC concentration, especially in Lake Koka, exceeded levels for serious health hazards for humans, cattle, and wildlife.
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| 5. |
- Willen, Eva
(author)
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Regional species pools control community saturation in lake phytoplankton
- 2010
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In: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 277, s. 3755-3764
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Journal article (peer-reviewed)abstract
- Recent research has highlighted that positive biodiversity-ecosystem functioning relationships hold for all groups of organisms, including microbes. Yet, we still lack understanding regarding the drivers of microbial diversity, in particular, whether diversity of microbial communities is a matter of local factors, or whether metacommunities are of similar importance to what is known from higher organisms. Here, we explore the driving forces behind spatial variability in lake phytoplankton diversity in Fennoscandia. While phytoplankton biovolume is best predicted by local phosphorus concentrations, phytoplankton diversity (measured as genus richness, G) only showed weak correlations with local concentrations of total phosphorus. By estimating spatial averages of total phosphorus concentrations on various scales from an independent, spatially representative lake survey, we found that close to 70 per cent of the variability in local phytoplankton diversity can be explained by regionally averaged phosphorus concentrations on a scale between 100 and 400 km. Thus, the data strongly indicate the existence of metacommunities on this scale. Furthermore, we show a strong dependency between lake productivity and spatial community turnover. Thus, regional productivity affects beta-diversity by controlling spatial community turnover, resulting in scale-dependent productivity-diversity relationships. As an illustration of the interaction between local and regional processes in shaping microbial diversity, our results offer both empirical support and a plausible mechanism for the existence of common scaling rules in both the macrobial and the microbial worlds. We argue that awareness of regional species pools in phytoplankton and other unicellular organisms may critically improve our understanding of ecosystems and their susceptibility to anthropogenic stressors.
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