| 31. |
- Lischke, Betty, et al.
(författare)
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Large biomass of small feeders : Ciliates may dominate herbivory in eutrophic lakes
- 2016
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 38:1, s. 2-15
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Tidskriftsartikel (refereegranskat)abstract
- The importance of ciliates as herbivores and in biogeochemical cycles is increasingly recognized. An opportunity to observe the potential consequences of zooplankton dominated by ciliates arose when winter fish kills resulted in strong suppression of crustaceans by young planktivorous fish in two shallow lakes. On an annual average, ciliates made up 38-76% of the total zooplankton biomass in both lakes during two subsequent years. Consequently, ciliate biomass and their estimated grazing potential were extremely high compared with other lakes of various trophic states and depths. Grazing estimates based on abundance and size suggest that ciliates should have cleared the water column of small (<5 mu m) and intermediate (5-50 mu m) sized phytoplankton more than once a day. Especially, small feeders within the ciliates were important, likely exerting a strong top-down control on small phytoplankton. Particle-attached bacteria were presumably strongly suppressed by intermediate-sized ciliate feeders. In contrast to other lakes, large phytoplankton was proportionately very abundant. The phytoplankton community had a high evenness, which may be attributed to the feeding by numerous fast growing and selective ciliate species. Our study highlights ciliates as an important trophic link and adds to the growing awareness of the role of winter processes for plankton dynamics.
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| 32. |
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| 33. |
- Mehner, Thomas, et al.
(författare)
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Weak response of animal allochthony and production to enhanced supply of terrestrial leaf litter in nutrient-rich lakes
- 2016
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Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 19:2, s. 311-325
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Tidskriftsartikel (refereegranskat)abstract
- Ecosystems are generally linked via fluxes of nutrients and energy across their boundaries. For example, freshwater ecosystems in temperate regions may receive significant inputs of terrestrially derived carbon via autumnal leaf litter. This terrestrial particulate organic carbon (POC) is hypothesized to subsidize animal production in lakes, but direct evidence is still lacking. We divided two small eutrophic lakes each into two sections and added isotopically distinct maize litter to the treatment sections to simulate increased terrestrial POC inputs via leaf litter in autumn. We quantified the reliance of aquatic consumers on terrestrial resources (allochthony) in the year subsequent to POC additions by applying mixing models of stable isotopes. We also estimated lake-wide carbon (C) balances to calculate the C flow to the production of the major aquatic consumer groups: benthic macroinvertebrates, crustacean zooplankton, and fish. The sum of secondary production of crustaceans and benthic macroinvertebrates supported by terrestrial POC was higher in the treatment sections of both lakes. In contrast, total secondary and tertiary production (supported by both autochthonous and allochthonous C) was higher in the reference than in the treatment sections of both lakes. Average aquatic consumer allochthony per lake section was 27–40%, although terrestrial POC contributed less than about 10% to total organic C supply to the lakes. The production of aquatic consumers incorporated less than 5% of the total organic C supply in both lakes, indicating a low ecological efficiency. We suggest that the consumption of terrestrial POC by aquatic consumers facilitates a strong coupling with the terrestrial environment. However, the high autochthonous production and the large pool of autochthonous detritus in these nutrient-rich lakes make terrestrial POC quantitatively unimportant for the C flows within food webs.
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| 34. |
- Menden-Deuer, Susanne, et al.
(författare)
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Cascading, interactive, and indirect effects of climate change on aquatic communities, habitats, and ecosystems
- 2023
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 68:S1, s. S1-S7
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Tidskriftsartikel (refereegranskat)abstract
- Climate-change is rapidly and intensively altering aquatic communities and habitats. While previous work has focused on direct effects of potential drivers, indirect and interactive effects on organisms and ecosystems have received less attention. Here, we give an overview of contributions to a special issue in Limnology and Oceanography that addresses this knowledge gap. Contributions covered diverse habitats, from polar to tropical regions, alpine streams to coral reefs. Several studies relied on time-series to identify indirect effects, thus emphasizing our need to maintain high-quality time-series data. Time-series are particularly crucial now that the pace of climate-change on aquatic-ecosystems is accelerating. Another common theme is the role of species-specific characteristics in physiology, behavior or genetics in aquatic ecosystem function. The addition of inter- and intra-specific variability to investigations of climate-change may be challenging particularly since ecosystem studies typically involve a large parameter space of environmental and biological variables across spatial and temporal scales. However, the results demonstrate that inclusion of species-specific dynamics, although challenging, can deliver mechanistic insights into aquatic ecosystem patterns and processes. Some contributions leverage habitat changes from disturbances or climate shifts to document capacity for resilience or recovery of pelagic and benthic communities. Jointly, the results in this special issue document fruitful approaches and provide urgent information needed for deciphering aquatic ecosystem responses to climate forcings. This information is foundational if we wish to tackle the combined effects of climate change and other human impacts with maximum efficacy and minimize unintended consequences for biodiversity and ecosystem functioning.
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| 35. |
- Moradi, Nasrollah, et al.
(författare)
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A Novel Measurement-Based Model for Calculating Diffusive Fluxes Across Substrate-Water Interfaces of Marine Aggregates, Sediments and Biofilms
- 2021
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Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Our understanding of the small-scale processes that drive global biogeochemical cycles and the Earth’s climate is dependent on accurate estimations of interfacial diffusive fluxes to and from biologically-active substrates in aquatic environments. In this study, we present a novel model approach for accurate calculations of diffusive fluxes of dissolved gases, nutrients, and solutes from concentration profiles measured across the substrate-water interfaces using microsensors. The model offers a robust computational scheme for automatized determination of the interface position and enables precise calculations of the interfacial diffusive fluxes simultaneously. In contrast to other methods, the new approach is not restricted to any particular substrate geometry, does not require a priori determination of the interface position for the flux calculation, and, thus, reduces the uncertainties in calculated fluxes arising from partly subjective identification of the interface position. In addition, it is robust when applied to measured profiles containing scattered data points and insensitive to reasonable decreases of the spatial resolution of the data points. The latter feature allows for significantly reducing measurement time which is a crucial factor for in situ experiments.
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| 36. |
- Nava, Veronica, et al.
(författare)
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Plastic debris in lakes and reservoirs
- 2023
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 619:7969, s. 317-322
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Tidskriftsartikel (refereegranskat)abstract
- Plastic debris is thought to be widespread in freshwater ecosystems globally(1). However, a lack of comprehensive and comparable data makes rigorous assessment of its distribution challenging(2,3). Here we present a standardized cross-national survey that assesses the abundance and type of plastic debris (>250 mu m) in freshwater ecosystems. We sample surface waters of 38 lakes and reservoirs, distributed across gradients of geographical position and limnological attributes, with the aim to identify factors associated with an increased observation of plastics. We find plastic debris in all studied lakes and reservoirs, suggesting that these ecosystems play a key role in the plastic-pollution cycle. Our results indicate that two types of lakes are particularly vulnerable to plastic contamination: lakes and reservoirs in densely populated and urbanized areas and large lakes and reservoirs with elevated deposition areas, long water-retention times and high levels of anthropogenic influence. Plastic concentrations vary widely among lakes; in the most polluted, concentrations reach or even exceed those reported in the subtropical oceanic gyres, marine areas collecting large amounts of debris(4). Our findings highlight the importance of including lakes and reservoirs when addressing plastic pollution, in the context of pollution management and for the continued provision of lake ecosystem services.
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| 37. |
- Paranaiba, Jose R., et al.
(författare)
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Cross-continental importance of CH4 emissions from dry inland-waters
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 814
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Tidskriftsartikel (refereegranskat)abstract
- Despite substantial advances in quantifying greenhouse gas (GHG) emissions from dry inland waters, existing estimates mainly consist of carbon dioxide (CO2) emissions. However, methane (CH4) may also be relevant due to its higher Global Warming Potential (GWP). We report CH4 emissions from dry inland water sediments to i) provide a cross-continental estimate of such emissions for different types of aquatic systems (i.e., lakes, ponds, reservoirs, and streams) and climate zones (i.e., tropical, continental, and temperate); and ii) determine the environmental factors that control these emissions. CH4 emissions from dry inland waters were consistently higher than emissions observed in adjacent uphill soils, across climate zones and in all aquatic systems except for streams. However, the CH4 contribution (normalized to CO2 equivalents; CO2-eq) to the total GHG emissions of dry inland waters was similar for all types of aquatic systems and varied from 10 to 21%. Although we discuss multiple controlling factors, dry inland water CH4 emissions were most strongly related to sediment organic matter content and moisture. Summing CO2 and CH4 emissions revealed a cross-continental average emission of 9.6 +/- 17.4 g CO2-eqm(-2) d(-1) from dry inland waters. We argue that increasing droughts likely expand the worldwide surface area of atmosphere-exposed aquatic sediments, thereby increasing global dry inland water CH4 emissions. Hence, CH4 cannot be ignored if we want to fully understand the carbon (C) cycle of dry sediments.
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| 38. |
- Reinl, Kaitlin L., et al.
(författare)
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Blooms also like it cold
- 2023
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Ingår i: Limnology and Oceanography Letters. - : John Wiley & Sons. - 2378-2242. ; 8:4, s. 546-564
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Forskningsöversikt (refereegranskat)abstract
- Cyanobacterial blooms have substantial direct and indirect negative impacts on freshwater ecosystems including releasing toxins, blocking light needed by other organisms, and depleting oxygen. There is growing concern over the potential for climate change to promote cyanobacterial blooms, as the positive effects of increasing lake surface temperature on cyanobacterial growth are well documented in the literature; however, there is increasing evidence that cyanobacterial blooms are also being initiated and persisting in relatively cold-water temperatures (< 15 °C), including ice-covered conditions. In this work, we provide evidence of freshwater cold-water cyanobacterial blooms, review abiotic drivers and physiological adaptations leading to these blooms, offer a typology of these lesser-studied cold-water cyanobacterial blooms, and discuss their occurrence under changing climate conditions.
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| 39. |
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| 40. |
- Salka, Ivette, et al.
(författare)
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Distribution of acI-Actinorhodopsin genes in Baltic Sea salinity gradients indicates adaptation of facultative freshwater photoheterotrophs to brackish waters
- 2014
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 16:2, s. 586-597
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge onActinobacteriarhodopsin gene (actR)diversity and spatial distribution is scarce. The BalticSea is characterized by strong salinity gradientsleading to the coexistence of marine and freshwaterbacteria and hence is an ideal study area to elucidatethe dispersion and phylogenetic affiliation ofactRindependence on salinity. ActRDGGE fingerprints insummer 2008 revealed between 3 and 19 distinctbands within a salinity range of 2.4–27 PSU. Environ-mentalactRclone sequences were obtained from sta-tions distributed along the whole salinity gradient.Overall, 20 differentactRsequence groups (opera-tional taxonomic units) were found, with up to 11different ones per station. Phylogenetically, theactRsequences were predominantly (80%) affiliated with freshwater acI-Actinobacteriawhose 16S rRNA geneaccounted for 2–33% of total 16S rRNA genes in both the Bothnian Sea and central Baltic Sea. However, atsalinities above 14 PSU, acI-16S rRNA gene accounted for less than 1%. In contrast, the diversity of actRremained high. Changes in actRgene diversity were significantly correlated with salinity, oxygen, silica orabundance of Synechococcussp. Our results demonstrate a wide distribution of freshwater actRalong theBaltic Sea salinity gradient indicating that some fresh-water Actinobacteriamight have adapted to higher salinities.
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