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Diehl, Sebastian
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Publications (10 of 71) Show all publications
Vasconcelos, F. R., Diehl, S., Rodríguez, P., Hedström, P., Karlsson, J. & Byström, P. (2019). Bottom-up and top-down effects of browning and warming on shallow lake food webs. Global Change Biology, 25, 504-521
Open this publication in new window or tab >>Bottom-up and top-down effects of browning and warming on shallow lake food webs
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2019 (English)In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 25, p. 504-521Article in journal (Refereed) Published
Abstract [en]

The productivity and trophic structure of aquatic ecosystems is the result of an interplay between bottom-up and top-down forces that operate both within and across the benthic and pelagic compartments of lake food webs. Contemporary and projected climate changes urge the question how this interplay will be affected by increasing inputs of terrestrial derived, dissolved organic matter (‘browning’) and warming. We addressed this issue by exploring how browning and warming affect the behavior of a relatively simple, conceptual model of a shallow lake food web that is compartmentalized into, dynamically coupled, benthic and pelagic components (abiotic resources, primary producers, grazers, and carnivores). We compared model expectations with the results of a factorial manipulation of browning and warming in a replicated, large-scale field experiment. Both the model and the experiment suggest that browning affects the food web from the bottom-up by reducing light supply to the benthic habitat and increasing nutrient supply to the pelagic habitat, with concomitant decreases of benthic and increases of pelagic primary and secondary production. The model also predicts that warming effects should primarily operate via relaxed top-down control by top consumers in the more productive of the two habitats. The latter was only partially supported by the experimental data, possibly because the model still lacks one or two important trophic links, such as the one from pelagic producers to benthic deposit feeders. We propose that our coupled benthic-pelagic food web model provides a useful conceptual starting point for future theoretical and empirical studies of the impacts of environmental changes on shallow lakes.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
benthic and pelagic habitats, bottom-up and top-down control, browning, food webs, light and nutrients, shallow lake, top predator, warming
National Category
Ecology Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-133326 (URN)10.1111/gcb.14521 (DOI)000456028900011 ()30430702 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council, 621-2011-3908Swedish Research Council, 621-2014-5238Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGEThe Kempe Foundations
Note

Originally included in thesis in manuscript form.

Available from: 2017-04-05 Created: 2017-04-05 Last updated: 2019-03-26Bibliographically approved
Wickman, J., Diehl, S. & Brännström, Å. (2019). Evolution of resource specialisation in competitive metacommunities. Ecology Letters
Open this publication in new window or tab >>Evolution of resource specialisation in competitive metacommunities
2019 (English)In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248Article in journal (Refereed) Epub ahead of print
Abstract [en]

Spatial environmental heterogeneity coupled with dispersal can promote ecological persistence of diverse metacommunities. Does this premise hold when metacommunities evolve? Using a two-resource competition model, we studied the evolution of resource-uptake specialisation as a function of resource type (substitutable to essential) and shape of the trade-off between resource uptake affinities (generalist- to specialist-favouring). In spatially homogeneous environments, evolutionarily stable coexistence of consumers is only possible for sufficiently substitutable resources and specialist-favouring trade-offs. Remarkably, these same conditions yield comparatively low diversity in heterogeneous environments, because they promote sympatric evolution of two opposite resource specialists that, together, monopolise the two resources everywhere. Consumer diversity is instead maximised for intermediate trade-offs and clearly substitutable or clearly essential resources, where evolved metacommunities are characterised by contrasting selection regimes. Taken together, our results present new insights into resource-competition-mediated evolutionarily stable diversity in homogeneous and heterogeneous environments, which should be applicable to a wide range of systems.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
Adaptive dynamics, coexistence, consumer-resource interactions, ESS, spatial models
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-162861 (URN)10.1111/ele.13338 (DOI)000480204800001 ()31389134 (PubMedID)
Available from: 2019-09-06 Created: 2019-09-06 Last updated: 2019-09-06
Maier, D. B., Diehl, S. & Bigler, C. (2019). Interannual variation in seasonal diatom sedimentation reveals the importance of late winter processes and their timing for sediment signal formation. Limnology and Oceanography, 64(3), 1186-1199
Open this publication in new window or tab >>Interannual variation in seasonal diatom sedimentation reveals the importance of late winter processes and their timing for sediment signal formation
2019 (English)In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 64, no 3, p. 1186-1199Article in journal (Refereed) Published
Abstract [en]

Disentangling the process information contained in a diatom sediment signature is crucial for reliable future predictions based on paleolimnological records. In this study, we combine limnological and paleolimnological monitoring to address the fundamental question: Which environmental information is contained in a diatom sediment signal? We compared annual diatom sequential sediment trap records with the diatom record of the annually varved lake sediment of Nylandssjon (northern Sweden) from three meteorologically different years (2012-2014). The seasonal patterns in diatom sedimentation were strikingly different in varve years 2012 and 2014 compared to varve year 2013. In 2012 and 2014, up to 70% of the annual flux occurred in a single spring month and was dominated by Cyclotella glomerata. In contrast, in 2013, peak fluxes were much lower and more annually integrated. Next, we compared the full-year diatom trap results with year round in-lake physical, chemical, and biological monitored parameters, as well as meteorological variables. Annual averages of environmental conditions did not explain the interannual variability in diatom sedimentation. Instead, the seasonality of diatom sedimentation was determined by the timing of the spring diatom bloom relative to lake over-turn in winters with warm vs. cold air temperature. With our combined limnological and paleolimnological monitoring approach, we find that an annual diatom signal can either contain primarily seasonal climate information from a short time period or be annually integrated. We synthesize our results in a novel conceptual model, which describes the response of sediment diatom signals to two distinct sequences of late-winter conditions.

Place, publisher, year, edition, pages
Association for the Science of Limnology and Oceanography, 2019
National Category
Geology Climate Research
Identifiers
urn:nbn:se:umu:diva-159614 (URN)10.1002/lno.11106 (DOI)000467593600022 ()
Available from: 2019-06-17 Created: 2019-06-17 Last updated: 2019-06-17Bibliographically approved
Vasconcelos, R. F., Diehl, S., Rodríguez, P., Karlsson, J. & Byström, P. (2018). Effects of Terrestrial Organic Matter on Aquatic Primary Production as Mediated by Pelagic-Benthic Resource Fluxes. Ecosystems (New York. Print), 21(6), 1255-1268
Open this publication in new window or tab >>Effects of Terrestrial Organic Matter on Aquatic Primary Production as Mediated by Pelagic-Benthic Resource Fluxes
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2018 (English)In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, no 6, p. 1255-1268Article in journal (Refereed) Published
Abstract [en]

Flows of energy and matter across habitat boundaries can be major determinants of the functioning of recipient ecosystems. It is currently debated whether terrestrial dissolved organic matter (tDOM) is a resource subsidy or a resource subtraction in recipient lakes. We present data from a long-term field experiment in which pelagic phosphorus concentration and whole-ecosystem primary production increased with increasing tDOM input, suggesting that tDOM acted primarily as a direct nutrient subsidy. Piecewise structural equation modeling supports, however, a substantial contribution of a second mechanism: colored tDOM acted also as a resource subtraction by shading benthic algae, preventing them from intercepting nutrients released across the sediment-water interface. Inhibition of benthic algae by colored tDOM thus indirectly promoted pelagic algae and whole-ecosystem primary production. We conclude that cross-ecosystem terrestrial DOM inputs can modify light and nutrient flows between aquatic habitats and alter the relative contributions of benthic and pelagic habitats to total primary production. These results are particularly relevant for shallow northern lakes, which are projected to receive increased tDOM runoff.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
spatial subsidy, allochthonous input, dissolved organic matter, resource competition, nutrients, light, pelagic, benthic, warming, brownification, piecewise SEM
National Category
Ecology Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-152268 (URN)10.1007/s10021-017-0217-x (DOI)000444384400013 ()
Funder
Knut and Alice Wallenberg FoundationThe Kempe FoundationsSwedish Research Council, 621-2011-3908Swedish Research Council, 621-2014-5238
Available from: 2018-10-02 Created: 2018-10-02 Last updated: 2019-01-23Bibliographically approved
Diehl, S., Thomsson, G., Kahlert, M., Guo, J., Karlsson, J. & Liess, A. (2018). Inverse relationship of epilithic algae and pelagic phosphorus in unproductive lakes: Roles of N-2 fixers and light. Freshwater Biology, 63(7), 662-675
Open this publication in new window or tab >>Inverse relationship of epilithic algae and pelagic phosphorus in unproductive lakes: Roles of N-2 fixers and light
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2018 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 63, no 7, p. 662-675Article in journal (Refereed) Published
Abstract [en]

Phosphorus (P) often limits the biomass of primary producers in freshwater lakes. However, in unproductive northern lakes, where anthropogenic nitrogen (N) deposition is low, N instead of P can limit primary producers. In addition, light can be limiting to primary producers at high concentrations of coloured dissolved organic matter (cDOM), as cDOM is the major determinant of light penetration in these lakes.

To address resource limitation of epilithic algal biomass, we repeatedly sampled epilithon (periphyton on stony substrata) in 20 lakes covering a large, correlated cDOM and N‐deposition gradient across boreal and subarctic Sweden. Across these lakes, pelagic total N (TN) and total P (TP) were positively correlated, and benthic light supply was negatively correlated, with cDOM. Microscopically determined algal biovolume and epilithic carbon (C), N and P were subsequently regressed against benthic light supply and pelagic TN and TP.

Patterns in epilithic biovolume were driven by N2‐fixing cyanobacteria, which accounted for 2%–90% of total epilithic biovolume. Averaged over the growing season, epilithic algal biovolume, C and N were negatively related to TP and positively to TN, and were highest in the clearest, most phosphorus‐poor lakes, where epilithon was heavily dominated by potentially N2‐fixing cyanobacteria.

A structural equation model supports the hypothesis that cDOM had two counteracting effects on total epilithic algal biovolume: a positive one by providing N to algae that depend on dissolved N for growth, and a negative one by shading N2‐fixing cyanobacteria, with the negative effect being somewhat stronger.

Together, these findings suggest that (1) light and N are the main resources limiting epilithic algal biomass in boreal to subarctic Swedish lakes, (2) epilithic cyanobacteria are more competitive in high‐light and low‐nitrogen environments, where their N2‐fixing ability allows them to reach high biomass, and (3) epilithic N increases with N2 fixer biomass and is—seemingly paradoxically—highest in the most oligotrophic lakes.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
dissolved organic matter, light, nitrogen-fixing cyanobacteria, nutrients, periphyton
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-150170 (URN)10.1111/fwb.13103 (DOI)000434110200005 ()
Funder
Swedish Research Council, 621-2014-5238Swedish Research Council Formas
Available from: 2018-07-18 Created: 2018-07-18 Last updated: 2018-07-18Bibliographically approved
Wickman, J., Diehl, S., Blasius, B., Klausmeier, C. A., Ryabov, A. B. & Brännström, Å. (2017). Determining Selection across Heterogeneous Landscapes: A Perturbation-Based Method and Its Application to Modeling Evolution in Space. American Naturalist, 189(4), 381-395
Open this publication in new window or tab >>Determining Selection across Heterogeneous Landscapes: A Perturbation-Based Method and Its Application to Modeling Evolution in Space
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2017 (English)In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 189, no 4, p. 381-395Article in journal (Refereed) Published
Abstract [en]

Spatial structure can decisively influence the way evolutionary processes unfold. To date, several methods have been used to study evolution in spatial systems, including population genetics, quantitative genetics, moment-closure approximations, and individual-based models. Here we extend the study of spatial evolutionary dynamics to eco-evolutionary models based on reaction-diffusion equations and adaptive dynamics. Specifically, we derive expressions for the strength of directional and stabilizing/disruptive selection that apply both in continuous space and to metacommunities with symmetrical dispersal between patches. For directional selection on a quantitative trait, this yields a way to integrate local directional selection across space and determine whether the trait value will increase or decrease. The robustness of this prediction is validated against quantitative genetics. For stabilizing/disruptive selection, we show that spatial heterogeneity always contributes to disruptive selection and hence always promotes evolutionary branching. The expression for directional selection is numerically very efficient and hence lends itself to simulation studies of evolutionary community assembly. We illustrate the application and utility of the expressions for this purpose with two examples of the evolution of resource utilization. Finally, we outline the domain of applicability of reaction-diffusion equations as a modeling framework and discuss their limitations.

Place, publisher, year, edition, pages
UNIV CHICAGO PRESS, 2017
Keywords
evolution, spatial, reaction-diffusion models, adaptive dynamics, quantitative genetics, metacommunities
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-134209 (URN)10.1086/690908 (DOI)000398685600006 ()28350499 (PubMedID)
Available from: 2017-06-20 Created: 2017-06-20 Last updated: 2019-01-08Bibliographically approved
Uszko, W., Diehl, S., Englund, G. & Amarasekare, P. (2017). Effects of warming on predator-prey interactions - a resource-based approach and a theoretical synthesis. Ecology Letters, 20(4), 513-523
Open this publication in new window or tab >>Effects of warming on predator-prey interactions - a resource-based approach and a theoretical synthesis
2017 (English)In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 20, no 4, p. 513-523Article in journal (Refereed) Published
Abstract [en]

We theoretically explore consequences of warming for predator-prey dynamics, broadening previous approaches in three ways: we include beyond-optimal temperatures, predators may have a type III functional response, and prey carrying capacity depends on explicitly modelled resources. Several robust patterns arise. The relationship between prey carrying capacity and temperature can range from near-independence to monotonically declining/increasing to hump-shaped. Predators persist in a U-shaped region in resource supply (=enrichment)-temperature space. Type II responses yield stable persistence in a U-shaped band inside this region, giving way to limit cycles with enrichment at all temperatures. In contrast, type III responses convey stability at intermediate temperatures and confine cycles to low and high temperatures. Warming-induced state shifts can be predicted from system trajectories crossing stability and persistence boundaries in enrichment-temperature space. Results of earlier studies with more restricted assumptions map onto this graph as special cases. Our approach thus provides a unifying framework for understanding warming effects on trophic dynamics.

Keywords
Carrying capacity, consumer-resource interaction, Daphnia, enrichment, functional response, rsistence, predator-prey interaction, stability, temperature, warming
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-133190 (URN)10.1111/ele.12755 (DOI)000397100900013 ()
Available from: 2017-04-13 Created: 2017-04-13 Last updated: 2018-06-09Bibliographically approved
Vasconcelos, F. R., Diehl, S., Rodriguez, P., Hedström, P., Karlsson, J. & Byström, P. (2016). Asymmetrical competition between aquatic primary producers in a warmer and browner world. Ecology, 97(10), 2580-2592
Open this publication in new window or tab >>Asymmetrical competition between aquatic primary producers in a warmer and browner world
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2016 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 10, p. 2580-2592Article in journal (Refereed) Published
Abstract [en]

In shallow lakes, pelagic and benthic producers engage in spatially asymmetrical resource competition. Pelagic producers intercept the flux of light to the benthic habitat and benthic producers intercept the flux of sediment-derived nutrients to the pelagic habitat. In boreal and subarctic regions, climate change is affecting this interaction both directly through warming and indirectly through increased loading with colored dissolved organic matter (cDOM) from the catchment (brownification). We use a dynamical ecosystem model to explore the consequences of these changing environmental conditions for lake primary production and compare model predictions with the results of an experiment in which we manipulated water temperature and cDOM supply in a 2x2 factorial design. The experiment was performed in field mesocosms large enough to harbor reproducing fish populations and was run over an entire growing season. In agreement with model predictions, benthic algal production and biomass declined and pelagic algal production and biomass increased with browning. Pelagic nutrient concentrations diverged over time between low and high cDOM treatments, suggesting that browning alleviated pelagic algal nutrient limitation by shading benthic competitors and preventing them from intercepting the release of nutrients from the sediment. Warming considerably reduced benthic and pelagic algal production as well as pelagic algalbiomass and total phosphorus. The warming results are only in partial accordance with model expectations, but can be explained by an indirectly inferred, positive response of macrophyte production (which was not included in the model) to warming. Our study suggests that lake ecosystem responses to climate change are mediated by cross-habitat feedbacks between benthic and pelagic producers.

Keywords
asymmetry, benthic, boreal, brownification, pelagic, resource competition, shallow lake, warming
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-127720 (URN)10.1002/ecy.1487 (DOI)000386088000007 ()27859128 (PubMedID)
Available from: 2016-12-15 Created: 2016-11-18 Last updated: 2018-06-09Bibliographically approved
Henriksson, A., Wardle A., D., Trygg, J., Diehl, S. & Englund, G. (2016). Strong invaders are strong defenders: implications for the resistance of invaded communities. Ecology Letters, 19(4), 487-494
Open this publication in new window or tab >>Strong invaders are strong defenders: implications for the resistance of invaded communities
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2016 (English)In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 19, no 4, p. 487-494Article in journal (Refereed) Published
Abstract [en]

Many ecosystems receive a steady stream of non-native species. How biotic resistance develops over time in these ecosystems will depend on how established invaders contribute to subsequent resistance. If invasion success and defence capacity (i.e. contribution to resistance) are correlated, then community resistance should increase as species accumulate. If successful invaders also cause most impact (through replacing native species with low defence capacity) then the effect will be even stronger. If successful invaders instead have weak defence capacity or even facilitative attributes, then resistance should decrease with time, as proposed by the invasional meltdown hypothesis. We analysed 1157 introductions of freshwater fish in Swedish lakes and found that species' invasion success was positively correlated with their defence capacity and impact, suggesting that these communities will develop stronger resistance over time. These insights can be used to identify scenarios where invading species are expected to cause large impact.

Keywords
biotic resistance, freshwater fish, introductions, interaction hierarchies, strong invaders, strong defenders, invasions
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-110248 (URN)10.1111/ele.12586 (DOI)000372654800015 ()
Note

Originally included in thesis in manuscript form.

Available from: 2015-10-19 Created: 2015-10-19 Last updated: 2018-06-07Bibliographically approved
Diehl, S., Berger, S. A., Soissons, Q., Giling, D. P. & Stibor, H. (2015). An experimental demonstration of the critical depth principle. ICES Journal of Marine Science, 72(6), 2051-2060
Open this publication in new window or tab >>An experimental demonstration of the critical depth principle
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2015 (English)In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 72, no 6, p. 2051-2060Article in journal (Refereed) Published
Abstract [en]

Sverdrup's critical depth hypothesis, which has had an almost canonical status in biological oceanography, has recently been challenged as a universal explanation for the formation of oceanic spring blooms, and several alternative hypotheses have been proposed. Arguments pro and contra alternative explanations have so far relied on theoretical considerations and purely observational data. In this paper, we propose that mesocosm experiments with natural plankton communities could make important contributions to the resolution of the issue. We first briefly review the foundations of the critical depth concept and derive an approximate relationship that relates optically scaled critical depth (="critical optical depth", i.e. the product of the light attenuation coefficient and the critical depth) to light-dependent phytoplankton production in the mixed surface layer. We describe how this relationship can be used to scale experimental mesocosms such that they reproduce ambient light conditions of natural water columns from the surface down to the critical depth and beyond. We illustrate the power of the approach with a mesocosm study in which we experimentally controlled the onset of the spring bloom of a lake plankton community through the manipulation of optically scaled mixed-layer depth. This experiment may be the first experimental demonstration of the critical depth principle acting on a natural plankton community. Compensation light intensity (=minimum average mixed-layer light intensity required to trigger a bloom of the ambient plankton community) could be constrained to be somewhat above 3.2 moles PAR m(-2) d(-1), corresponding to a critical optical depth of 10.5. We compare these numbers to estimates from marine systems and end with a discussion of how experiments could be designed to (i) more accurately determine the critical depth in a given system and (ii) resolve among competing hypotheses for vernal bloom onset.

Keywords
compensation light intensity, critical optical depth, dimensional analysis, mesocosm experiment, phytoplankton spring bloom, scaling
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:umu:diva-108156 (URN)10.1093/icesjms/fsv032 (DOI)000359696500030 ()
Available from: 2015-09-16 Created: 2015-09-04 Last updated: 2018-06-07Bibliographically approved
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