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Guo, Junwen
Publications (6 of 6) Show all publications
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
Cherif, M., Faithfull, C., Guo, J., Meunier, C. L., Sitters, J., Uszko, W. & Rivera Vasconcelos, F. (2017). An operational framework for the advancement of a molecule-to-biosphere stoichiometry theory. Frontiers in Marine Science, 4, Article ID 286.
Open this publication in new window or tab >>An operational framework for the advancement of a molecule-to-biosphere stoichiometry theory
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2017 (English)In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 4, article id 286Article in journal (Refereed) Published
Abstract [en]

Biological stoichiometry is an approach that focuses on the balance of elements in biological interactions. It is a theory that has the potential to causally link material processes at all biological levels—from molecules to the biosphere. But the lack of a coherent operational framework has so far restricted progress in this direction. Here, we provide a framework to help infer how a stoichiometric imbalance observed at one level impacts all other biological levels. Our framework enables us to highlight the areas of the theory in need of completion, development and integration at all biological levels. Our hope is that this framework will contribute to the building of a more predictive theory of elemental transfers within the biosphere, and thus, to a better understanding of human-induced perturbations to the global biogeochemical cycles.

Place, publisher, year, edition, pages
Lausanne: Frontiers Media S.A., 2017
Keywords
biological organization, biological stoichiometry, consumer-driven nutrient recycling, ecological theory, theory integration, growth-rate hypothesis, light:nutrient hypothesis
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-139395 (URN)10.3389/fmars.2017.00286 (DOI)
Available from: 2017-09-15 Created: 2017-09-15 Last updated: 2018-11-28Bibliographically approved
Liess, A., Rowe, O., Francoeur, S. N., Guo, J., Lange, K., Schroeder, A., . . . Faithfull, C. L. (2016). Terrestrial runoff boosts phytoplankton in a Mediterranean coastal lagoon, but these effects do not propagate to higher trophic levels. Hydrobiologia, 766(1), 275-291
Open this publication in new window or tab >>Terrestrial runoff boosts phytoplankton in a Mediterranean coastal lagoon, but these effects do not propagate to higher trophic levels
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2016 (English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 766, no 1, p. 275-291Article in journal (Refereed) Published
Abstract [en]

Heavy rainfall events causing significant terrestrial runoff into coastal marine ecosystems are predicted to become more frequent with climate change in the Mediterranean. To simulate the effects of soil runoff on the pelagic food web of an oligotrophic Mediterranean coastal lagoon, we crossed soil extract addition (increasing nutrient availability and turbidity) and fish presence in a full factorial design to coastal mesocosms containing a natural pelagic community. Soil extract addition increased both bacteria and phytoplankton biomass. Diatoms however profited most from soil extract addition, especially in the absence of fish. In contrast zooplankton and fish did not profit from soil extract addition. Furthermore, our data indicate that nutrients (instead of light or carbon) limited basal production. Presumed changes in carbon availability are relatively unimportant to primary and secondary production in strongly nutrient limited systems like the Thau Lagoon. We conclude that in shallow Mediterranean coastal ecosystems, heavy rainfall events causing soil runoff will (1) increase the relative abundance of phytoplankton in relation to bacteria and zooplankton, especially in the absence of fish (2) not lead to higher biomass of zooplankton and fish, possibly due to the brevity of the phytoplankton bloom and the slow biomass response of higher trophic levels.

Keywords
Bacteria, Dissolved organic carbon (DOC), Mesocosm experiment, Phytoplankton, Nutrient subsidy, Terrestrial subsidy
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-120835 (URN)10.1007/s10750-015-2461-4 (DOI)000367196900021 ()
Available from: 2016-05-23 Created: 2016-05-23 Last updated: 2018-06-07Bibliographically approved
Liess, A., Guo, J., Lind, M. I. & Rowe, O. (2015). Cool tadpoles from Arctic environments waste fewer nutrients - high gross growth efficiencies lead to low consumer-mediated nutrient recycling in the North. Journal of Animal Ecology, 84(6), 1744-1756
Open this publication in new window or tab >>Cool tadpoles from Arctic environments waste fewer nutrients - high gross growth efficiencies lead to low consumer-mediated nutrient recycling in the North
2015 (English)In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 84, no 6, p. 1744-1756Article in journal (Refereed) Published
Abstract [en]

Endothermic organisms can adapt to short growing seasons, low temperatures and nutrient limitation by developing high growth rates and high gross growth efficiencies (GGEs). Animals with high GGEs are better at assimilating limiting nutrients and thus should recycle (or lose) fewer nutrients. Longer guts in relation to body mass may facilitate higher GGE under resource limitation. Within the context of ecological stoichiometry theory, this study combines ecology with evolution by relating latitudinal life-history adaptations in GGE, mediated by gut length, to its ecosystem consequences, such as consumer-mediated nutrient recycling. In common garden experiments, we raised Rana temporaria tadpoles from two regions (Arctic/Boreal) under two temperature regimes (18/23 degrees C) crossed with two food quality treatments (high/low-nitrogen content). We measured tadpole GGEs, total nutrient loss (excretion+egestion) rates and gut length during ontogeny. In order to maintain their elemental balance, tadpoles fed low-nitrogen (N) food had lower N excretion rates and higher total phosphorous (P) loss rates than tadpoles fed high-quality food. In accordance with expectations, Arctic tadpoles had higher GGEs and lower N loss rates than their low-latitude conspecifics, especially when fed low-N food, but only in ambient temperature treatments. Arctic tadpoles also had relatively longer guts than Boreal tadpoles during early development. That temperature and food quality interacted with tadpole region of origin in affecting tadpole GGEs, nutrient loss rates and relative gut length, suggests evolved adaptation to temperature and resource differences. With future climate change, mean annual temperatures will increase. Additionally, species and genotypes will migrate north. This will change the functioning of Boreal and Arctic ecosystems by affecting consumer-mediated nutrient recycling and thus affect nutrient dynamics in general. Our study shows that evolved latitudinal adaption can change key ecosystem functions.

Keywords
assimilation efficiency, consumer-mediated nutrient recycling, digestive efficiency, ecological oichiometry, latitudinal adaptation, Rana temporaria
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-110990 (URN)10.1111/1365-2656.12426 (DOI)000362741000029 ()26239271 (PubMedID)
Available from: 2015-11-18 Created: 2015-11-02 Last updated: 2018-06-07Bibliographically approved
Liess, A., Faithfull, C., Reichstein, B., Rowe, O., Guo, J., Pete, R., . . . Francoeur, S. N. (2015). Terrestrial runoff may reduce microbenthic net community productivity by increasing turbidity: a Mediterranean coastal lagoon mesocosm experiment. Hydrobiologia, 753(1), 205-218
Open this publication in new window or tab >>Terrestrial runoff may reduce microbenthic net community productivity by increasing turbidity: a Mediterranean coastal lagoon mesocosm experiment
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2015 (English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 753, no 1, p. 205-218Article in journal (Refereed) Published
Abstract [en]

Terrestrial runoff into aquatic ecosystems may have both stimulatory and inhibitory effects, due to nutrient subsidies and increased light attenuation. To disentangle the effects of runoff on microbenthos, we added soil to coastal mesocosms and manipulated substrate depth. To test if fish interacted with runoff effects, we manipulated fish presence. Soil decreased microphytobenthic chlorophyll-a per area and per carbon (C) unit, increased microbenthic phosphorous (P), and reduced microbenthic nitrogen (N) content. Depth had a strong effect on the microbenthos, with shallow substrates exhibiting greater microbenthic net ecosystem production, gross primary production, and community respiration than deep substrates. Over time, micobenthic algae compensated for deeper substrate depth through increased chlorophyll-a synthesis, but despite algal shade compensation, the soil treatment still appeared to reduce the depth where microbenthos switched from net autotrophy to net heterotrophy. Fish interacted with soil in affecting microbenthic nutrient composition. Fish presence reduced microbenthic C/P ratios only in the no soil treatment, probably since soil nutrients masked the positive effects of fish excreta on microbenthos. Soil reduced microbenthic N/P ratios only in the absence of fish. Our study demonstrates the importance of light for the composition and productivity of microbenthos but finds little evidence for positive runoff subsidy effects.

Keywords
Bacteria, Dissolved organic carbon (DOC), Enclosure experiment, Microbenthos, Nutrient subsidy, Terrestrial subsidy
National Category
Ecology Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-106254 (URN)10.1007/s10750-015-2207-3 (DOI)000354194600014 ()
Available from: 2015-07-13 Created: 2015-07-09 Last updated: 2018-06-07Bibliographically approved
Liess, A., Rowe, O., Guo, J., Thomsson, G. & Lind, M. I. (2013). Hot tadpoles from cold environments need more nutrients - life history and stoichiometry reflects latitudinal adaptation. Journal of Animal Ecology, 82(6), 1316-1325
Open this publication in new window or tab >>Hot tadpoles from cold environments need more nutrients - life history and stoichiometry reflects latitudinal adaptation
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2013 (English)In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 82, no 6, p. 1316-1325Article in journal (Refereed) Published
Abstract [en]

1. High-latitude species (and populations within species) are adapted to short and cold summers. They often have high growth and development rates to fully use the short growing season and mature before the onset of winter. Within the context of ecological stoichiometry theory, this study combines ecology with evolution by relating latitudinal life-history adaptations to their molecular consequences in body nutrient composition in Rana temporaria tadpoles. Temperature and food quality were manipulated during the development of tadpoles from Arctic and Boreal origins. We determined tadpole growth rate, development rate, body size and nutrient content, to test whether (i) Arctic tadpoles could realize higher growth rates and development rates with the help of higher-quality food even when food quantity was unchanged, (ii) Arctic and Boreal tadpoles differed in their stoichiometric (and life history) response to temperature changes, (iii) higher growth rates lead to higher tadpole P content (growth rate hypothesis) and (iv) allometric scaling affects tadpole nutrient allocation. We found that especially Arctic tadpoles grew and developed faster with the help of higher-quality food and that tadpoles differed in their stoichiometric (and life history) response to temperature changes depending on region of origin (probably due to different temperature optima). There was no evidence that higher growth rates mediated the positive effect of temperature on tadpole P content. On the contrary, the covariate growth rate was negatively connected with tadpole P content (refuting the growth rate hypothesis). Lastly, tadpole P content was not related to body size, but tadpole C content was higher in larger tadpoles, probably due to increased fat storage. We conclude that temperature had a strong effect on tadpole life history, nutrient demand and stoichiometry and that this effect depended on the evolved life history.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2013
Keywords
allometry, amphibian, C: nutrient ratio, common frog, development rate, growing season, northern Sweden, temperature adaptation, vertebrate stoichiometry
National Category
Zoology Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-83752 (URN)10.1111/1365-2656.12107 (DOI)000326036800020 ()
Funder
Swedish Research CouncilSwedish Research Council Formas
Available from: 2013-12-10 Created: 2013-12-06 Last updated: 2018-06-08Bibliographically approved
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