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Bravo, A. G., Kothawala, D., Attermeyer, K., Tessier, E., Bodmer, P. & Amouroux, D. (2018). Cleaning and sampling protocol for analysis of mercury and dissolved organic matter in freshwater systems. MethodsX, 5, 1017-1026
Open this publication in new window or tab >>Cleaning and sampling protocol for analysis of mercury and dissolved organic matter in freshwater systems
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2018 (English)In: MethodsX, ISSN 1258-780X, E-ISSN 2215-0161, Vol. 5, p. 1017-1026Article in journal (Refereed) Published
Abstract [en]

Mercury (Hg), and in particular its methylated form (methylmercury, MeHg), is a hazardous substance with the potential to produce significant adverse neurological and other health effects. Enhanced anthropogenic emissions and long-range transport of atmospheric Hg have increased Hg concentrations above background levels in aquatic systems. In this context, the Minamata Convention, a global legally binding agreement that seeks to prevent human exposure to Hg, was signed and enforced by 128 countries, and today more than 90 Parties have ratified it. All these Parties have committed to develop Hg monitoring programs to report the effectiveness of the convention. For this purpose, we provide a standardized cleaning and water sampling protocol for the determination of total-Hg and MeHg in freshwaters at ambient levels. As Hg and organic matter are tightly bound, the protocol also describes sample collection for dissolved organic carbon (DOC) concentration and characterization of dissolved organic matter (DOM) composition by fluorescence spectroscopy. This protocol is highly useful to non-experts without a prior background in Hg sampling and analysis, and can serve as a useful basis for national monitoring programs. Furthermore, this protocol should help increase quantitative inventories of DOC, inorganic-Hg (IHg) and MeHg concentrations and DOM composition in freshwater, which are severely lacking at a global scale. • Provides a standardized method to collect water samples for IHg, MeHg, DOC and DOM composition from freshwater ecosystems.

Keywords
Sampling, Preservation, Mercury, Methylmercury, Water, DOC, Fluorescence
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-369285 (URN)10.1016/j.mex.2018.08.002 (DOI)
Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2018-12-12Bibliographically approved
Nydahl, A., Wallin, M., Tranvik, L., Hiller, C., Attermeyer, K., Garrison, J., . . . Weyhenmeyer, G. A. (2018). Colored organic matter increases CO2 in meso-eutrophic lake water through altered light climate and acidity. Limnology and Oceanography
Open this publication in new window or tab >>Colored organic matter increases CO2 in meso-eutrophic lake water through altered light climate and acidity
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2018 (English)In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590Article in journal (Refereed) Published
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-366220 (URN)10.1002/lno.11072 (DOI)
Available from: 2018-11-18 Created: 2018-11-18 Last updated: 2018-12-12
Mehner, T., Lischke, B., Scharnweber, K., Attermeyer, K., Brothers, S., Gaedke, U., . . . Brucet, S. (2018). Empirical correspondence between trophic transfer efficiency in freshwater food webs and the slope of their size spectra. Ecology, 99(6), 1463-1472
Open this publication in new window or tab >>Empirical correspondence between trophic transfer efficiency in freshwater food webs and the slope of their size spectra
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2018 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 99, no 6, p. 1463-1472Article in journal (Refereed) Published
Abstract [en]

The density of organisms declines with size, because larger organisms need more energy than smaller ones and energetic losses occur when larger organisms feed on smaller ones. A potential expression of density-size distributions are Normalized Biomass Size Spectra (NBSS), which plot the logarithm of biomass independent of taxonomy within bins of logarithmic organismal size, divided by the bin width. Theoretically, the NBSS slope of multi-trophic communities is exactly - 1.0 if the trophic transfer efficiency (TTE, ratio of production rates between adjacent trophic levels) is 10% and the predator-prey mass ratio (PPMR) is fixed at 10(4). Here we provide evidence from four multi-trophic lake food webs that empirically estimated TTEs correspond to empirically estimated slopes of the respective community NBSS. Each of the NBSS considered pelagic and benthic organisms spanning size ranges from bacteria to fish, all sampled over three seasons in 1 yr. The four NBSS slopes were significantly steeper than -1.0 (range -1.14 to -1.19, with 95% CIs excluding -1). The corresponding average TTEs were substantially lower than 10% in each of the four food webs (range 1.0% to 3.6%, mean 1.85%). The overall slope merging all biomass-size data pairs from the four systems (-1.17) was almost identical to the slope predicted from the arithmetic mean TTE of the four food webs (-1.18) assuming a constant PPMR of 10(4). Accordingly, our empirical data confirm the theoretically predicted quantitative relationship between TTE and the slope of the biomass-size distribution. Furthermore, we show that benthic and pelagic organisms can be merged into a community NBSS, but future studies have yet to explore potential differences in habitat-specific TTEs and PPMRs. We suggest that community NBSS may provide valuable information on the structure of food webs and their energetic pathways, and can result in improved accuracy of TTE-estimates.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-347754 (URN)10.1002/ecy.2347 (DOI)000434094400021 ()29856494 (PubMedID)
Funder
German Research Foundation (DFG), Me 1686/7-1
Available from: 2018-04-06 Created: 2018-04-06 Last updated: 2018-08-31Bibliographically approved
Bengtsson, M. M., Attermeyer, K. & Catalan, N. (2018). Interactive effects on organic matter processing from soils to the ocean: are priming effects relevant in aquatic ecosystems?. Hydrobiologia, 822(1), 1-17
Open this publication in new window or tab >>Interactive effects on organic matter processing from soils to the ocean: are priming effects relevant in aquatic ecosystems?
2018 (English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 822, no 1, p. 1-17Article, review/survey (Refereed) Published
Abstract [en]

Organic matter (OM) is degraded during transport from soils to oceans. However, there are spatial and temporal variabilities along the aquatic continuum, which hamper the development of carbon cycling models. One concept that has been applied in this context is the priming effect (PE), describing non-additive effects on OM degradation after mixing sources of contrasting bioavailability. Studies on the aquatic PE report divergent results from positive (increased OM degradation rates) to neutral, to negative (decreased OM degradation rates) effects upon mixing. Here, we aim to condense the outcomes of these studies on aquatic PE. Based on a literature review, we discuss differences in the reported PEs across freshwater and marine ecosystems, identifying system-specific features that could favour non-additive effects on OM degradation. Using a quantitative meta-analysis approach, we evaluated the occurrence, direction (positive vs. negative) and magnitude of aquatic PE. The meta-analysis revealed a mean PE of 12.6%, which was not significantly different from zero across studies. Hence, mixing of contrasting OM sources in aquatic ecosystems does not necessarily result in a change in OM degradation rates. Therefore, we suggest to focus on molecular and microbial diversity and function, which could provide a better mechanistic understanding of processes driving OM interactions.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Aquatic continuum, DOM, Ecotones, Priming effect, Soil
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-366303 (URN)10.1007/s10750-018-3672-2 (DOI)000440587800001 ()
Funder
EU, FP7, Seventh Framework Programme
Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2018-11-20Bibliographically approved
Attermeyer, K., Catalan, N., Einarsdóttir, K., Freixa, A., Groeneveld, M. M., Hawkes, J. A., . . . Tranvik, L. (2018). Organic Carbon Processing During Transport Through Boreal Inland Waters: Particles as Important Sites. Journal of Geophysical Research - Biogeosciences, 123(8), 2412-2428
Open this publication in new window or tab >>Organic Carbon Processing During Transport Through Boreal Inland Waters: Particles as Important Sites
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2018 (English)In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 123, no 8, p. 2412-2428Article in journal (Refereed) Published
Abstract [en]

The degradation and transformation of organic carbon (C) in inland waters result in significant CO2 emissions from inland waters. Even though most of the C in inland waters occurs as dissolved organic carbon (DOC), studies on particulate organic carbon (POC) and how it influences the overall reactivity of organic C in transport are still scarce. We sampled 30 aquatic ecosystems following an aquatic continuum including peat surface waters, streams, rivers, and lakes. We report DOC and POC degradation rates, relate degradation patterns to environmental data across these systems, and present qualitative changes in dissolved organic matter and particulate organic matter during degradation. Microbial degradation rates of POC were approximately 15 times higher compared to degradation of DOC, with POC half-lives of only 17 +/- 3 (mean +/- SE) days across all sampled aquatic ecosystems. Rapid POC decay was accompanied by a shift in particulate C: N ratios, whereas dissolved organic matter composition did not change at the time scale of incubations. The faster degradation of the POC implies a constant replenishment to sustain natural POC concentrations. We suggest that degradation of organic matter transported through the inland water continuum might occur to a large extent via transition of DOC into more rapidly cycling POC in nature, for example, triggered by light. In this way, particles would be a dominant pool of organic C processing across the boreal aquatic continuum, partially sustained by replenishment via flocculation of DOC.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2018
National Category
Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-363637 (URN)10.1029/2018JG004500 (DOI)000445731100009 ()
Funder
Knut and Alice Wallenberg Foundation, KAW 2013.0091Swedish Research Council, 2014-04264Swedish Research Council, 2015-4870
Available from: 2018-10-18 Created: 2018-10-18 Last updated: 2018-12-19Bibliographically approved
Bravo, A. G., Kothawala, D., Attermeyer, K., Tessier, E., Bodmer, P., Ledesma, J. L. .., . . . Amouroux, D. (2018). The interplay between total mercury, methylmercury and dissolved organic matter in fluvial systems: A latitudinal study across Europe. Water Research, 144, 172-182
Open this publication in new window or tab >>The interplay between total mercury, methylmercury and dissolved organic matter in fluvial systems: A latitudinal study across Europe
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2018 (English)In: Water Research, ISSN 0043-1354, Vol. 144, p. 172-182Article in journal (Refereed) Published
Abstract [en]

Large-scale studies are needed to identify the drivers of total mercury (THg) and monomethyl-mercury (MeHg) concentrations in aquatic ecosystems. Studies attempting to link dissolved organic matter (DOM) to levels of THg or MeHg are few and geographically constrained. Additionally, stream and river systems have been understudied as compared to lakes. Hence, the aim of this study was to examine the influence of DOM concentration and composition, morphological descriptors, land uses and water chemistry on THg and MeHg concentrations and the percentage of THg as MeHg (%MeHg) in 29 streams across Europe spanning from 41°N to 64 °N. THg concentrations (0.06–2.78 ng L−1) were highest in streams characterized by DOM with a high terrestrial soil signature and low nutrient content. MeHg concentrations (7.8–159 pg L−1) varied non-systematically across systems. Relationships between DOM bulk characteristics and THg and MeHg suggest that while soil derived DOM inputs control THg concentrations, autochthonous DOM (aquatically produced) and the availability of electron acceptors for Hg methylating microorganisms (e.g. sulfate) drive %MeHg and potentially MeHg concentration. Overall, these results highlight the large spatial variability in THg and MeHg concentrations at the European scale, and underscore the importance of DOM composition on mercury cycling in fluvial systems.

Place, publisher, year, edition, pages
Pergamon, 2018
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-369339 (URN)10.1016/J.WATRES.2018.06.064 (DOI)000447569300016 ()30029076 (PubMedID)
Funder
Swedish Research Council
Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2018-12-12Bibliographically approved
Attermeyer, K., Grossart, H.-P., Flury, S. & Premke, K. (2017). Bacterial processes and biogeochemical changes in the water body of kettle holes: mainly driven by autochthonous organic matter?. Aquatic Sciences, 79(3), 675-687
Open this publication in new window or tab >>Bacterial processes and biogeochemical changes in the water body of kettle holes: mainly driven by autochthonous organic matter?
2017 (English)In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 79, no 3, p. 675-687Article in journal (Refereed) Published
Abstract [en]

Kettle holes are small inland waters formed from glacially-created depressions often situated in agricultural landscapes. Due to their high perimeter-to-area ratio facilitating a high aquatic-terrestrial coupling, kettle holes can accumulate high concentrations of organic carbon and nutrients, fueling microbial activities and turnover rates. Thus, they represent hotspots of carbon turnover in the landscape, but their bacterial activities and controlling factors have not been well investigated. Therefore, we aimed to assess the relative importance of various environmental factors on bacterial and biogeochemical processes in the water column of kettle holes and to disentangle their variations. In the water body of ten kettle holes in north-eastern Germany, we measured several physico-chemical and biological parameters such as carbon quantity and quality, as well as bacterial protein production (BP) and community respiration (CR) in spring, early summer and autumn 2014. Particulate organic matter served as an indicator of autochthonous production and represented an important parameter to explain variations in BP and CR. This notion is supported by qualitative absorbance indices of dissolved molecules in water samples and C:N ratios of the sediments, which demonstrate high fractions of autochthonous organic matter (OM) in the studied kettle holes. In contrast, dissolved chemical parameters were less important for bacterial activities although they revealed strong differences throughout the growing season. Pelagic bacterial activities and dynamics might thus be regulated by autochthonous OM in kettle holes implying a control of important biogeochemical processes by internal primary production rather than facilitated exchange with the terrestrial surrounding due to a high perimeter-to-area ratio.

Keywords
Bacterial production, Carbon turnover, Growth efficiency, Ponds, Respiration, DOC quality, LC-OCD
National Category
Ecology Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-323614 (URN)10.1007/s00027-017-0528-1 (DOI)000405798900019 ()
Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2018-01-13Bibliographically approved
Lischke, B., Mehner, T., Hilt, S., Attermeyer, K., Brauns, M., Brothers, S., . . . Gaedke, U. (2017). Benthic carbon is inefficiently transferred in the food webs of two eutrophic shallow lakes. Freshwater Biology, 62(10), 1693-1706
Open this publication in new window or tab >>Benthic carbon is inefficiently transferred in the food webs of two eutrophic shallow lakes
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2017 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 62, no 10, p. 1693-1706Article in journal (Refereed) Published
Abstract [en]

1. The sum of benthic autotrophic and bacterial production often exceeds the sum of pelagic autotrophic and bacterial production, and hence may contribute sub- stantially to whole-lake carbon fluxes, especially in shallow lakes. Furthermore, both benthic and pelagic autotrophic and bacterial production are highly edible and of sufficient nutritional quality for animal consumers. We thus hypothesised that pelagic and benthic transfer efficiencies (ratios of production at adjacent trophic levels) in shallow lakes should be similar. 2. We performed whole ecosystem studies in two shallow lakes (3.5 ha, mean depth 2 m), one with and one without submerged macrophytes, and quantified pelagic and benthic biomass, production and transfer efficiencies for bacteria, phytoplank- ton, epipelon, epiphyton, macrophytes, zooplankton, macrozoobenthos and fish. We expected higher transfer efficiencies in the lake with macrophytes, because these provide shelter and food for macrozoobenthos and may thus enable a more efficient conversion of basal production to consumer production. 3. In both lakes, the majority of the whole-lake autotrophic and bacterial produc- tion was provided by benthic organisms, but whole-lake primary consumer pro- duction mostly relied on pelagic autotrophic and bacterial production. Consequently, transfer efficiency of benthic autotrophic and bacterial production to macrozoobenthos production was an order of magnitude lower than the transfer efficiency of pelagic autotrophic and bacterial production to rotifer and crustacean production. Between-lake differences in transfer efficiencies were minor. 4. We discuss several aspects potentially causing the unexpectedly low benthic transfer efficiencies, such as the food quality of producers, pelagic–benthic links, oxygen concentrations in the deeper lake areas and additional unaccounted con- sumer production by pelagic and benthic protozoa and meiobenthos at interme- diate or top trophic levels. None of these processes convincingly explain the large differences between benthic and pelagic transfer efficiencies. 5. Our data indicate that shallow eutrophic lakes, even with a major share of auto- trophic and bacterial production in the benthic zone, can function as pelagic sys- tems with respect to primary consumer production. We suggest that the benthic autotrophic production was mostly transferred to benthic bacterial production, which remained in the sediments, potentially cycling internally in a similar way to what has previously been described for the microbial loop in pelagic habitats. Understanding the energetics of whole-lake food webs, including the fate of the substantial benthic bacterial production, which is either mineralised at the sedi- ment surface or permanently buried, has important implications for regional and global carbon cycling

Keywords
bacterial production, benthic food chain, pelagic food chain, quantitative food webs, trophic transfer efficiency
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-334883 (URN)10.1111/fwb.12979 (DOI)000410094000003 ()
Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2018-05-17Bibliographically approved
Wurzbacher, C., Attermeyer, K., Kettner, M. T., Flintrop, C., Warthmann, N., Hilt, S., . . . Monaghan, M. T. (2017). DNA metabarcoding of unfractionated water samples relates phyto-, zoo- and bacterioplankton dynamics and reveals a single-taxon bacterial bloom. Environmental Microbiology Reports, 9(4), 383-388
Open this publication in new window or tab >>DNA metabarcoding of unfractionated water samples relates phyto-, zoo- and bacterioplankton dynamics and reveals a single-taxon bacterial bloom
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2017 (English)In: Environmental Microbiology Reports, ISSN 1758-2229, E-ISSN 1758-2229, Vol. 9, no 4, p. 383-388Article in journal (Refereed) Published
Abstract [en]

Most studies of aquatic plankton focus on either macroscopic or microbial communities, and on either eukaryotes or prokaryotes. This separation is primarily for methodological reasons, but can overlook potential interactions among groups. We tested whether DNA metabarcoding of unfractionated water samples with universal primers could be used to qualitatively and quantitatively study the temporal dynamics of the total plankton community in a shallow temperate lake. We found significant changes in the relative proportions of normalized sequence reads of eukaryotic and prokaryotic plankton communities over a three-month period in spring. Patterns followed the same trend as plankton estimates measured using traditional microscopic methods. We characterized the bloom of a conditionally rare bacterial taxon belonging to Arcicella, which rapidly came to dominate the whole lake ecosystem and would have remained unnoticed without metabarcoding. Our data demonstrate the potential of universal DNA metabarcoding applied to unfractionated samples for providing a more holistic view of plankton communities.

National Category
Microbiology Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-323620 (URN)10.1111/1758-2229.12540 (DOI)000405931900005 ()28429584 (PubMedID)
Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2018-01-13Bibliographically approved
Wurzbacher, C., Fuchs, A., Attermeyer, K., Frindte, K., Grossart, H.-P., Hupfer, M., . . . Monaghan, M. T. (2017). Shifts among Eukaryota, Bacteria, and Archaea define the vertical organization of a lake sediment. Microbiome, 5, Article ID 41.
Open this publication in new window or tab >>Shifts among Eukaryota, Bacteria, and Archaea define the vertical organization of a lake sediment
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2017 (English)In: Microbiome, ISSN 0026-2633, E-ISSN 2049-2618, Vol. 5, article id 41Article in journal (Refereed) Published
Abstract [en]

Background: Lake sediments harbor diverse microbial communities that cycle carbon and nutrients while being constantly colonized and potentially buried by organic matter sinking from the water column. The interaction of activity and burial remained largely unexplored in aquatic sediments. We aimed to relate taxonomic composition to sediment biogeochemical parameters, test whether community turnover with depth resulted from taxonomic replacement or from richness effects, and to provide a basic model for the vertical community structure in sediments.

Methods: We analyzed four replicate sediment cores taken from 30-m depth in oligo-mesotrophic Lake Stechlin in northern Germany. Each 30-cm core spanned ca. 170 years of sediment accumulation according to 137Cs dating and was sectioned into layers 1–4 cm thick. We examined a full suite of biogeochemical parameters and used DNA metabarcoding to examine community composition of microbial Archaea, Bacteria, and Eukaryota.

Results: Community β-diversity indicated nearly complete turnover within the uppermost 30 cm. We observed a pronounced shift from Eukaryota- and Bacteria-dominated upper layers (<5 cm) to Bacteria-dominated intermediate layers (5–14 cm) and to deep layers (>14 cm) dominated by enigmatic Archaea that typically occur in deep-sea sediments. Taxonomic replacement was the prevalent mechanism in structuring the community composition and was linked to parameters indicative of microbial activity (e.g., CO2 and CH4 concentration, bacterial protein production). Richness loss played a lesser role but was linked to conservative parameters (e.g., C, N, P) indicative of past conditions.

Conclusions: By including all three domains, we were able to directly link the exponential decay of eukaryotes with the active sediment microbial community. The dominance of Archaea in deeper layers confirms earlier findings from marine systems and establishes freshwater sediments as a potential low-energy environment, similar to deep sea sediments. We propose a general model of sediment structure and function based on microbial characteristics and burial processes. An upper “replacement horizon” is dominated by rapid taxonomic turnover with depth, high microbial activity, and biotic interactions. A lower “depauperate horizon” is characterized by low taxonomic richness, more stable “low-energy” conditions, and a dominance of enigmatic Archaea.

Keywords
Archaea, Eukaryota, Bacteria, Community, Freshwater, Lake, DNA metabarcoding, Beta-diversity, Sediment, Turnover
National Category
Microbiology Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-323607 (URN)10.1186/s40168-017-0255-9 (DOI)000398528500001 ()28388930 (PubMedID)
Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2018-01-13Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6503-9497

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