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- Guo, Junwen, 1982-, et al.
(författare)
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Carbon-nitrogen association influences response of the microplankton food web to enrichment
- 2022
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 88, s. 187-199
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Tidskriftsartikel (refereegranskat)abstract
- In aquatic ecosystems, there are 2 major forms of N available at the base of the planktonic food web: dissolved organic N (DON) and dissolved inorganic N (DIN). In DON, N is associated with organic C, which may promote both heterotrophs and autotrophs. In environments where DIN nitrate is the prevailing N form and dissociated dissolved organic C (DOC) is available, heterotrophs may also be promoted, but they may compete with the autotrophs for DIN. The influence of associated or dissociated CN nutrient sources on the interaction between organisms and the food web function is poorly known and has not been studied before. To approach this question, we performed a microcosm experiment with a coastal microbial food web, where N and C nutrient sources were provided either associated in 1 molecular compound (DON), or dissociated in 2 separate molecular compounds (DIN and DOC). The results showed that association or dissociation of C and N input had marked effects on all trophic levels, most probably through its effect on bacteria-phytoplankton interaction, which switched between increased coupling and increased competition. The biomass of all components of the food web benefitted from the association of C and N in a single DON molecule. Our study indicated that the degree of association between C and N is an important factor affecting the productivity and efficiency of the microbial food web. Therefore, the C and N association should be considered when studying aquatic systems.
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| 3. |
- Guo, Junwen, 1982-
(författare)
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Consequences of consumer-resource stoichiometric imbalance in planktonic food webs
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Resource imbalance between consumers and their resources can come from inadequate resource quantity or quality. The ecological stoichiometry theory focuses on understanding the consequences of imbalance in elemental composition. In this thesis, I have used both resource quality (e.g., inorganic vs organic forms of nutrients) and resource quantity (e.g., terrestrial and freshwater nutrient loading to natural coastal systems) to address the consequences of consumer-resource imbalance in planktonic food webs. First, I provided a framework that summarizes how the stoichiometric imbalance is transferred from one biological level to another. The framework highlights the importance of the distribution of elements among different chemical forms and the distribution of elements among connected ecosystems. The framework then served as a guideline for the empirical work of my thesis. Second, I studied the response of bacterial community mineralization to the relative availability of different forms of nitrogen (inorganic vs. organic form) in a batch culture experiment. The study shows that different forms of nitrogen can significantly influence the growth of bacteria. More importantly, my results show that it is crucial to measure the actual bacterial carbon to nitrogen consumption ratio, rather than use classical theoretical models, to be able to make an accurate prediction of bacterial ammonium regeneration. Third, I tested the effect of different forms of nitrogen on microplankton food web dynamics in a microcosm experiment. I found that differences between nitrogen forms have a strong impact on food web dynamics that is channeled by the bacteria-phytoplankton interaction at the base of the food web. The whole microplankton food web benefits from organic forms of nitrogen as a result of increased mutualistic interactions between bacteria and phytoplankton. Hence, the form of nitrogen is an important factor to be considered in microplanktonic food web dynamics, at least on the short-term. In the final part of this thesis, I explored resource quality and quantity effects on the stoichiometric response of a natural coastal ecosystem in a field study. I expected that the relative availability of inorganic or organic forms of carbon, nitrogen and phosphorus in our sampling bays may affect organismal elemental composition both temporally and spatially. The results indicate that the stoichiometry among seston size fractions and zooplankton varied more through time than in space. However, zooplankton stoichiometry was relatively stable among species within specific months. Overall, the concentration of dissolved organic carbon and dissolved organic nitrogen in the water column were the major explanatory variables for the seston stoichiometry. In summary, this thesis uses multiple systems to elucidate how the form and input of nutrients shape the plankton food web dynamics and its stoichiometric responses.
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| 4. |
- Guo, Junwen, 1982-, et al.
(författare)
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Spatiotemporal carbon, nitrogen and phosphorus stoichiometry in planktonic food web in a northern coastal area
- 2022
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Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier. - 0272-7714 .- 1096-0015. ; 272
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Tidskriftsartikel (refereegranskat)abstract
- The concentrations of ambient nutrients and dissolved organic carbon (DOC) in northern coastal ecosystems often show large variations, due to the spatiotemporal differences in terrestrial inputs. How these variations affect the stoichiometry of coastal planktonic organisms is, however, poorly known. Here we assessed the spatiotemporal variability of C, nitrogen (N), and phosphorous (P) concentrations of the seawater on the elemental stoichiometry of seston and dominant mesozooplankton taxa in a coastal area of the northern Baltic Sea. The freshwater inflow peaked in spring following the snowmelt and brought a significant amount of DOC, but not N and P to the coastal system. DOC was the main environmental descriptor for seston C:N stoichiometry. The C:N ratio of seston from 0.7 to 50 μm and mesozooplankton followed the temporal pattern of water C:N ratio, while the temporal trend of bacteria C:N showed an opposite pattern. Our results also indicated that the C:N ratio of seawater controlled both seston and mesozooplankton C:N ratios. Our findings imply that inflows of terrestrial DOC alter the stoichiometry and reduce the nutritional quality of planktonic food webs in northern coastal ecosystems.
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| 5. |
- Rocklöv, Joacim, Professor, 1979-, et al.
(författare)
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Decision-support tools to build climate resilience against emerging infectious diseases in Europe and beyond
- 2023
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Ingår i: The Lancet Regional Health. - : Elsevier. - 2666-7762. ; 32
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Forskningsöversikt (refereegranskat)abstract
- Climate change is one of several drivers of recurrent outbreaks and geographical range expansion of infectious diseases in Europe. We propose a framework for the co-production of policy-relevant indicators and decision-support tools that track past, present, and future climate-induced disease risks across hazard, exposure, and vulnerability domains at the animal, human, and environmental interface. This entails the co-development of early warning and response systems and tools to assess the costs and benefits of climate change adaptation and mitigation measures across sectors, to increase health system resilience at regional and local levels and reveal novel policy entry points and opportunities. Our approach involves multi-level engagement, innovative methodologies, and novel data streams. We take advantage of intelligence generated locally and empirically to quantify effects in areas experiencing rapid urban transformation and heterogeneous climate-induced disease threats. Our goal is to reduce the knowledge-to-action gap by developing an integrated One Health—Climate Risk framework.
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