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  • 1
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    Online Resource
    The exponentially fed batch culture as a reliable alternative to conventional chemostats
    Wiley ; 2014
    In:  Limnology and Oceanography: Methods Vol. 12, No. 7 ( 2014-07), p. 432-440
    Details
    In: Limnology and Oceanography: Methods, Wiley, Vol. 12, No. 7 ( 2014-07), p. 432-440
    Abstract: Chemostats and their common alternative, semicontinuous cultures, play a pivotal role as model systems in aquatic ecology. Despite the theoretical and conceptual advantages chemostat systems offer, they can be challenging to set up and operate. One such challenge is to obtain a representative sample volume without changing the dilution rate, another is to ensure that the outflow constitutes an unbiased loss of the chemostat contents. Here, we present a specific system, the exponentially fed‐batch culture (EFB), as an economic, simply operable albeit reliable alternative to conventional chemostats. The EFB is well‐known in biotechnological research and in industrial bioengineering. Like a conventional chemostat, the EFB culture is a continuous culture method. In contrast to a conventional chemostat, there is no outflow. To ensure a constant dilution rate and therefore steady state, fresh medium is continuously supplied proportional to the current culture volume. Hence culture volume and medium supply rate both increase exponentially with time until sampling, when the volume is set back to the initial state. This allows taking large sample volumes without disturbing the steady state of the experimental unit. Here we compare the performance of the exponentially fed‐batch culture with a conventional chemostat and a semicontinuous system by growing a green algae until steady state is reached. Most pronounced differences were found between semicontinuous system and the two continuous methods. Results from the EFB and chemostat were very similar. However, a bias in the sampling of the chemostat resulted in accumulation of biomass relative to the EFB.
    Type of Medium: Online Resource
    ISSN: 1541-5856 , 1541-5856
    URL: Article
    DOI: 10.4319/lom.2014.12.432
    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 2161715-6
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  • 2
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    From adverse to beneficial: Contrasting dietary effects of freshwater mixotrophs on zooplankton
    Wiley ; 2021
    In:  Freshwater Biology Vol. 66, No. 12 ( 2021-12), p. 2272-2282
    Details
    In: Freshwater Biology, Wiley, Vol. 66, No. 12 ( 2021-12), p. 2272-2282
    Abstract: The importance of mixotrophic algae as key bacterivores in microbial food webs is increasingly acknowledged, but their effects on the next trophic level remain poorly understood. Their high stoichiometric food quality is contrasted by anti‐grazing strategies. We tested the quality of freshwater mixotrophs as prey for zooplankton, using four non‐colonial chrysophyte species and a cryptophyte as a high quality reference food. We (1) analyzed the stoichiometric and biochemical (fatty acid) composition of the mixotrophs, and (2) quantified their dietary effects on Daphnia longispina survival. Survival of D . longispina significantly depended on the identity of species provided as food, ranging from higher to lower as compared to starvation. This was not reflected in differences in cellular stoichiometry or fatty acid profiles of the mixotrophs. We suggest that toxicity may be the driver for the observed differences. Generalization of the dietary effects of mixotrophic chrysophytes does not appear straightforward. Besides fundamental species‐specific differences, potential toxic effects may vary depending on environmental cues or physiological strategies. Notably in our study, Ochromonas tuberculata , a species previously reported to be deleterious, turned out to be a beneficial food source in terms of enabling high survival of D . longispina . We challenge the generality of the assumption that chrysophytes are of low value as food for zooplankton. We recommend that future studies test how environmental conditions and physiological strategies shape the quality of mixotrophs as food for consumers at higher trophic levels, specifically focusing on effects of dietary toxicity.
    Type of Medium: Online Resource
    ISSN: 0046-5070 , 1365-2427
    URL: Issue
    URL: Article
    DOI: 10.1111/fwb.v66.12
    DOI: 10.1111/fwb.13832
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2020306-8
    detail.hit.zdb_id: 121180-8
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  • 3
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    Light‐dependent niche differentiation in two mixotrophic bacterivores
    Wiley ; 2022
    In:  Environmental Microbiology Reports Vol. 14, No. 4 ( 2022-08), p. 530-537
    Details
    In: Environmental Microbiology Reports, Wiley, Vol. 14, No. 4 ( 2022-08), p. 530-537
    Abstract: Mixotrophy usually is considered with respect to the advantages gained and the associated trade‐offs of this form of nutrition, compared to specialized competitors, strict photoautotrophs and heterotrophs. However, we currently have an incomplete understanding of the functional diversity of mixotrophs and the factors controlling niche differentiation in different mixotrophic species. Here we experimentally studied the light‐dependent niche differentiation in two chrysophyte species. We show that the newly isolated Ochromonas sp. is an obligate phototroph and possibly an obligate mixotroph. In contrast, Poterioochromonas malhamensis is a facultative mixotroph; photosynthesis and heterotrophy in this species represent substitutable routes of resource acquisition. We further hypothesize that the variable plasticity in the considered traits of the here tested species may result in different niche differentiation with regard to a vertical light gradient. Ochromonas sp. should perform better in stable stratified surface water layers, where light is available, but prey abundances might be low. However, P . malhamensis should be able to also successfully grow in deeper water layers, benefiting from higher bacterial production. This study represents a first step towards understanding competition between mixotrophs engaging in different physiological strategies, and consequently their potential co‐occurrence due to niche differentiation.
    Type of Medium: Online Resource
    ISSN: 1758-2229 , 1758-2229
    URL: Issue
    URL: Article
    DOI: 10.1111/emi4.v14.4
    DOI: 10.1111/1758-2229.13071
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2485218-1
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  • 4
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    Importance of mixotrophic bacterivory can be predicted by light and loss rates
    Wiley ; 2017
    In:  Oikos Vol. 126, No. 5 ( 2017-05), p. 713-722
    Details
    In: Oikos, Wiley, Vol. 126, No. 5 ( 2017-05), p. 713-722
    Abstract: Recent observational studies form oligotrophic waters provide ample evidence that mixotrophic flagellates often account for the bulk of bacterivory. However, we lack a general framework that allows a mechanistic understanding of success of mixotrophs in the competition with heterotrophic bacterivores. This is especially needed for integrating mixotrophy in models of the microbial loop. Based on general tradeoffs linked to the combined resource use in mixotrophs (generalist versus specialist), we propose a concept where mixotrophs are favored by conditions of high light – low losses, corresponding to the situation found in the surface waters of oligotrophic oceans. Under such conditions, they can achieve positive net growth at very low resource levels, allowing simultaneous competition with specialized protists. Conversely, heterotrophic bacterivores and photoautotrophs should be especially favored in more productive and low‐light conditions. We show experimentally that the combined effect of light and loss rates (dilution) predicts the success of mixotrophic bacterivorous flagellates. Moreover, our results suggest that total bacterivory, contrary as seen in the traditional microbial loop concept, has a more intricate coupling to light.
    Type of Medium: Online Resource
    ISSN: 0030-1299 , 1600-0706
    URL: Issue
    URL: Article
    DOI: 10.1111/oik.2017.v126.i5
    DOI: 10.1111/oik.03539
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2025658-9
    detail.hit.zdb_id: 207359-6
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  • 5
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    Functional and structural stability are linked in phytoplankton metacommunities of different connectivity
    Wiley ; 2017
    In:  Ecography Vol. 40, No. 6 ( 2017-06), p. 719-732
    Details
    In: Ecography, Wiley, Vol. 40, No. 6 ( 2017-06), p. 719-732
    Abstract: The diversity–stability debate is a long‐standing issue in ecology, asking whether more diverse communities show higher stability over time and more rapid recovery from disturbances. Connection to undisturbed habitats is thought to affect compositional and functional stability after disturbances. Therefore, we established marine phytoplankton metacommunities consisting of three microcosms (local patches), which were connected by tubes opened for different time intervals to create 5 levels of connectivity. We performed two experiments differing by homogeneous (HOM) or heterogeneous (HET) supply of irradiance across patches. As disturbance we either removed 75% of the algal biomass locally from one randomly chosen patch, or 25 or 75% regionally from each local patch. By comparing these treatments to an undisturbed control, we analyzed resilience (rate of recovery) and final recovery (recovery ratio) with regard to biomass (functional stability) and species composition (structural stability). In both experiments (HET, HOM), functional and structural aspects of stability responded significantly to connectivity and disturbance treatments. Functional resilience was enhanced by increasing connectivity (HET and HOM), which partially also increased functional recovery (HET) and structural resilience (HOM). By contrast, the treatment‐induced gradients in diversity (species richness and evenness) had no clear effect on functional resilience or recovery. Instead, structural and functional resilience were strongly correlated regardless of patch quality, indicating that only a full recovery in community composition ensured functional stability. Our findings suggest that connectivity plays a pivotal role in maintaining ecosystem stability under pulse disturbance such that a more complete understanding of stability requires spatially explicit approaches.
    Type of Medium: Online Resource
    ISSN: 0906-7590 , 1600-0587
    URL: Issue
    URL: Article
    DOI: 10.1111/ecog.2017.v40.i6
    DOI: 10.1111/ecog.02458
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2024917-2
    detail.hit.zdb_id: 1112659-0
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  • 6
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    Chytrids enhance Daphnia fitness by selectively retained chytrid‐synthesised stearidonic acid and conversion of short‐chain to long‐chain polyunsaturated fatty acids
    Wiley ; 2023
    In:  Freshwater Biology Vol. 68, No. 1 ( 2023-01), p. 77-90
    Details
    In: Freshwater Biology, Wiley, Vol. 68, No. 1 ( 2023-01), p. 77-90
    Abstract: Chytrid fungal parasites convert dietary energy and essential dietary molecules, such as long‐chain (LC) polyunsaturated fatty acids (PUFA), from inedible algal/cyanobacteria hosts into edible zoospores. How the improved biochemical PUFA composition of chytrid‐infected diet may extend to zooplankton, linking diet quality to consumer fitness, remains unexplored. Here, we assessed the trophic role of chytrids in supporting dietary energy and PUFA requirements of the crustacean zooplankton Daphnia , when feeding on the filamentous cyanobacterium Planktothrix . Only Daphnia feeding on chytrid‐infected Planktothrix reproduced successfully and had significantly higher survival and growth rates compared with Daphnia feeding on the sole Planktothrix diet. While the presence of chytrids resulted in a two‐fold increase of carbon ingested by Daphnia , carbon assimilation increased by a factor of four, clearly indicating enhanced carbon transfer efficiency with chytrid presence. Bulk carbon ( δ 13 C) and nitrogen ( δ 15 N) stable isotopes did not indicate any treatment‐specific dietary effects on Daphnia , nor differences in trophic position among diet sources and the consumer. Compound‐specific carbon isotopes of fatty acids ( δ 13 C FA ), however, revealed that chytrids bioconverted short‐chain to LC‐PUFA, making it available for Daphnia. Chytrids synthesised the ω‐3 PUFA stearidonic acid de novo , which was selectively retained by Daphnia . Values of δ 13 C FA demonstrated that Daphnia also bioconverted short‐chain to LC‐PUFA. We provide isotopic evidence that chytrids improved the dietary provision of LC‐PUFA for Daphnia and enhanced their fitness. We argue for the existence of a positive feedback loop between enhanced Daphnia growth and herbivory in response to chytrid‐mediated improved diet quality. Chytrids upgrade carbon from the primary producer and facilitate energy and PUFA transfer to primary consumers, potentially also benefitting upper trophic levels of pelagic food webs.
    Type of Medium: Online Resource
    ISSN: 0046-5070 , 1365-2427
    URL: Issue
    URL: Article
    DOI: 10.1111/fwb.v68.1
    DOI: 10.1111/fwb.14010
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2020306-8
    detail.hit.zdb_id: 121180-8
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  • 7
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    Accounting for temporal change in multiple biodiversity patterns improves the inference of metacommunity processes
    Wiley ; 2022
    In:  Ecology Vol. 103, No. 6 ( 2022-06)
    Details
    In: Ecology, Wiley, Vol. 103, No. 6 ( 2022-06)
    Abstract: In metacommunity ecology, a major focus has been on combining observational and analytical approaches to identify the role of critical assembly processes, such as dispersal limitation and environmental filtering, but this work has largely ignored temporal community dynamics. Here, we develop a “virtual ecologist” approach to evaluate assembly processes by simulating metacommunities varying in three main processes: density‐independent responses to abiotic conditions, density‐dependent biotic interactions, and dispersal. We then calculate a number of commonly used summary statistics of community structure in space and time and use random forests to evaluate their utility for inferring the strength of these three processes. We find that (i) both spatial and temporal data are necessary to disentangle metacommunity processes based on the summary statistics we test, and including statistics that are measured through time increases the explanatory power of random forests by up to 59% compared to cases where only spatial variation is considered; (ii) the three studied processes can be distinguished with different descriptors; and (iii) each summary statistic is differently sensitive to temporal and spatial sampling effort. Including repeated observations of metacommunities over time was essential for inferring the metacommunity processes, particularly dispersal. Some of the most useful statistics include the coefficient of variation of species abundances through time and metrics that incorporate variation in the relative abundances (evenness) of species. We conclude that a combination of methods and summary statistics is probably necessary to understand the processes that underlie metacommunity assembly through space and time, but we recognize that these results will be modified when other processes or summary statistics are used.
    Type of Medium: Online Resource
    ISSN: 0012-9658 , 1939-9170
    URL: Issue
    URL: Article
    DOI: 10.1002/ecy.v103.6
    DOI: 10.1002/ecy.3683
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 1797-8
    detail.hit.zdb_id: 2010140-5
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  • 8
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    A compendium of cell and natural unit biovolumes for 〉1200 freshwater phytoplankton species : Ecological Archives E095‐257
    Wiley ; 2014
    In:  Ecology Vol. 95, No. 10 ( 2014-10), p. 2984-2984
    Details
    In: Ecology, Wiley, Vol. 95, No. 10 ( 2014-10), p. 2984-2984
    Abstract: Cell size determination is a critical part of sampling phytoplankton communities, as size is both a fundamental trait determining species' ecological niches and a quantity necessary for generating unbiased estimates of community composition. The sizes of algal cells span orders of magnitude, driving variation in growth parameters, sinking rates, herbivore defense, and biogeochemical roles. Size variation occurs at both intra‐ and interspecific levels. Many central questions in community and ecosystem ecology require estimating and comparing the relative abundances of species. Cell counts provide insufficient estimates, due to interspecific variation in cell size, as they over‐estimate the importance of abundant, small species. While cell size (or biovolume) estimation has become standard practice in limnology, many older data sets lack this information, limiting their interpretation and utility. To address these challenges, and advance the study of freshwater phytoplankton communities, we have compiled a database of 〉 260 000 algal biovolume estimates, spanning ∼400 genera and ∼1200 species. This represents the most extensive, standardized, and taxonomically diverse data set of its kind, drawing on both publicly and privately held sources. Estimates of the sizes of colonies or filaments are included, where applicable. With these data researchers will be able to account for intra‐ and interspecific variation in cell size, enabling new and improved analyses of classic data sets.
    Type of Medium: Online Resource
    ISSN: 0012-9658 , 1939-9170
    URL: Article
    DOI: 10.1890/14-0603.1
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 1797-8
    detail.hit.zdb_id: 2010140-5
    SSG: 12
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  • 9
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    Environmental variability in aquatic ecosystems: Avenues for future multifactorial experiments
    Wiley ; 2023
    In:  Limnology and Oceanography Letters Vol. 8, No. 2 ( 2023-04), p. 247-266
    Details
    In: Limnology and Oceanography Letters, Wiley, Vol. 8, No. 2 ( 2023-04), p. 247-266
    Abstract: The relevance of considering environmental variability for understanding and predicting biological responses to environmental changes has resulted in a recent surge in variability‐focused ecological research. However, integration of findings that emerge across studies and identification of remaining knowledge gaps in aquatic ecosystems remain critical. Here, we address these aspects by: (1) summarizing relevant terms of variability research including the components (characteristics) of variability and key interactions when considering multiple environmental factors; (2) identifying conceptual frameworks for understanding the consequences of environmental variability in single and multifactorial scenarios; (3) highlighting challenges for bridging theoretical and experimental studies involving transitioning from simple to more complex scenarios; (4) proposing improved approaches to overcome current mismatches between theoretical predictions and experimental observations; and (5) providing a guide for designing integrated experiments across multiple scales, degrees of control, and complexity in light of their specific strengths and limitations.
    Type of Medium: Online Resource
    ISSN: 2378-2242 , 2378-2242
    URL: Issue
    URL: Article
    DOI: 10.1002/lol2.v8.2
    DOI: 10.1002/lol2.10286
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2876718-4
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  • 10
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    Environmental constraint of intraguild predation: Inorganic turbidity modulates omnivory in fairy shrimps
    Wiley ; 2020
    In:  Freshwater Biology Vol. 65, No. 2 ( 2020-02), p. 226-239
    Details
    In: Freshwater Biology, Wiley, Vol. 65, No. 2 ( 2020-02), p. 226-239
    Abstract: Omnivory is widespread in food webs, with an important stabilising effect. The strength of omnivorous trophic interactions may change considerably with changes in the local environment. Shallow temporary waters are often characterised by high levels of inorganic turbidity that may directly limit the food uptake of filter‐feeding organisms, but there is little evidence on how it might affect omnivorous species. Anostracans are key species of temporary waters and recent evidence suggests that these organisms are omnivorous consumers of both phyto‐ and zooplankton. Using Branchinecta orientalis as a model species, our aim was to test how turbidity affects the feeding of an omnivorous anostracan. To do this, we used short‐term feeding experiments and stable isotope analyses, with animals collected from soda pans in eastern Austria. In the feeding experiments, algae and zooplankton were offered as food either separately or in combination. The prey type treatments were crossed with turbidity levels in a factorial design. There was a pronounced decrease in the ingested algal biomass with increasing turbidity. Conversely, ingestion rates on zooplankton were less affected by turbidity. Stable isotope analyses from field material supported our experimental results by showing a positive relationship of the trophic position of anostracans and the trophic niche of the communities with turbidity. Our results show that turbidity modulates the intraguild trophic relationship between anostracans and their prey by shifting the diet of anostracans from more herbivorous in transparent to more carnivorous in turbid waters. Thus, inorganic turbidity might also have a community‐shaping role in plankton communities of temporary waters through altering trophic relationships.
    Type of Medium: Online Resource
    ISSN: 0046-5070 , 1365-2427
    URL: Issue
    URL: Article
    DOI: 10.1111/fwb.v65.2
    DOI: 10.1111/fwb.13416
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2020306-8
    detail.hit.zdb_id: 121180-8
    SSG: 12
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