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- Cunillera-Montcusí, David, et al.
(author)
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Freshwater salinisation : a research agenda for a saltier world
- 2022
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In: Trends in Ecology and Evolution. - : Elsevier BV. - 0169-5347 .- 1872-8383. ; 37:5, s. 440-453
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Research review (peer-reviewed)abstract
- The widespread salinisation of freshwater ecosystems poses a major threat to the biodiversity, functioning, and services that they provide. Human activities promote freshwater salinisation through multiple drivers (e.g., agriculture, resource extraction, urbanisation) that are amplified by climate change. Due to its complexity, we are still far from fully understanding the ecological and evolutionary consequences of freshwater salinisation. Here, we assess current research gaps and present a research agenda to guide future studies. We identified different gaps in taxonomic groups, levels of biological organisation, and geographic regions. We suggest focusing on global- and landscape-scale processes, functional approaches, genetic and molecular levels, and eco-evolutionary dynamics as key future avenues to predict the consequences of freshwater salinisation for ecosystems and human societies.
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- Lövgren, Johan, et al.
(author)
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Allochtonous input and trophic level heterogeneity: impact on an aquatic food web
- 2006
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In: Oikos. - : John Wiley & Sons. - 0030-1299 .- 1600-0706. ; 115:1, s. 141-147
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Journal article (peer-reviewed)abstract
- The impact of food web complexity in open and closed food webs was explored experimentally under controlled laboratory conditions. We used an aquatic model community consisting of two forms of primary producers, phytoplankton (Scenedesmus obtusiuscusculus) and periphyton (Nitzschia perminuta) and two types of consumers, Daphnia pulex feeding on phytoplankton and Chydorous sphaericus feeding on both periphyton and phytoplankton. Three different food webs all having the phytoplankton and periphyton, but having either one of the consumers or both were set up. These food webs were studied in an open and closed treatment. In the open treatment, phytoplankton was continuously flowing through the aquaria whereas in the closed system all the phytoplankton was delivered at the start of the experiment.D. pulex had a positive effect on the density of C. sphaericus in both the open and closed treatments. In the open treatment C. sphaericus increased to very high numbers and was able to depress phytoplankton and thereby negatively affect D. pulex. Our study shows that the explicit handling of the population dynamics of both grazers allowed us to show how a compensatory increase in one primary producer due to increased grazing on another primary producer creates a negative feedback between consumers: C. sphaericus increased and negatively affected D. pulex.
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- Oresic, Matej, 1967-, et al.
(author)
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Dysregulation of lipid and amino acid metabolism precedes islet autoimmunity in children who later progress to type 1 diabetes
- 2008
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In: Journal of Experimental Medicine. - New York, USA : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 205:13, s. 2975-2984
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Journal article (peer-reviewed)abstract
- The risk determinants of type 1 diabetes, initiators of autoimmune response, mechanisms regulating progress toward beta cell failure, and factors determining time of presentation of clinical diabetes are poorly understood. We investigated changes in the serum metabolome prospectively in children who later progressed to type 1 diabetes. Serum metabolite profiles were compared between sample series drawn from 56 children who progressed to type 1 diabetes and 73 controls who remained nondiabetic and permanently autoantibody negative. Individuals who developed diabetes had reduced serum levels of succinic acid and phosphatidylcholine (PC) at birth, reduced levels of triglycerides and antioxidant ether phospholipids throughout the follow up, and increased levels of proinflammatory lysoPCs several months before seroconversion to autoantibody positivity. The lipid changes were not attributable to HLA-associated genetic risk. The appearance of insulin and glutamic acid decarboxylase autoantibodies was preceded by diminished ketoleucine and elevated glutamic acid. The metabolic profile was partially normalized after the seroconversion. Autoimmunity may thus be a relatively late response to the early metabolic disturbances. Recognition of these preautoimmune alterations may aid in studies of disease pathogenesis and may open a time window for novel type 1 diabetes prevention strategies.
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- Reinikainen, Marko, et al.
(author)
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Resurrected Ceriodaphnia quadrangula highlight differences between pheno- and genotypic expressions
- 2012
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In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 2:12, s. 2989-2998
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Journal article (peer-reviewed)abstract
- The hatching of cladoceran ephippia from a 15-cm long sediment core was investigated, and Ceriodaphnia quadrangula clones were isolated from different sediment layers. Bosmina microfossil data were also analyzed, and compared with the corresponding data from a Pb210 dated core, which allowed us to infer the age of the sediment layers. Using changes in Bosmina microfossil morphologies, we were, furthermore, able to infer the presence of different regimes of fish predation. C. quadrangula was found to hatch in layers with an inferred age of approximately a century. Newly hatched individuals had smaller eye-size in sediment layers corresponding to high predation by young-of-the-year perch. Newly hatched individuals also generally had a marked neck-spine. In contrast, morphological characters of C. quadrangula clones reared in the laboratory over several generations showed no variation in relation to predation regime, indicating the absence of fixed genotype level changes. Furthermore, the laboratory grown clones only rarely produced a neck-spine. The results suggest phenotypic variation in response to the regime under which ephippia were produced.
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| 8. |
- Reinikainen, Marko, et al.
(author)
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Resurrected past-century Ceriodaphnia quadrangula highlight differences between pheno- and genotypic expressions
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Other publication (other academic/artistic)abstract
- The hatching of cladoceran ephippia from a 15 cm long sediment core was investigated, and Ceriodaphnia quadrangula -clones were isolated from different sediment layers. Bosmina-microfossil data were also analyzed, and compared with the corresponding data from a Pb210-dated core, which allowed us to infer the age of the sediment-layers. Using changes in Bosmina-microfossil morphologies, we were furthermore able to infer the presence of different regimes of fish-predation. C. quadrangula was found to hatch in layers with an inferred age of approximately a century. Newly hatched individuals had smaller eye-size in sediment layers corresponding to high predation by young-of-the-year perch. Newly hatched individuals also generally had a marked neck-spine. In contrast, morphological characters of C. quadrangula -clones reared in the laboratory over several generations showed no variation in relation to predation regime, indicating the absence of fixed genotype-level changes. Furthermore, the laboratory-grown clones only rarely produced a neck-spine. The results suggest phenotypic variation in response to the regime under which ephippia were produced.
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- Vehmaa, Anu, et al.
(author)
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How will increased dinoflagellate:diatom ratios affect copepod egg production? : a case study from the Baltic Sea
- 2011
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In: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 401:1-2, s. 134-140
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Journal article (peer-reviewed)abstract
- Mild winters are modifying the plankton spring bloom composition so that diatoms are decreasing and dinoflagellates increasing. We used two common spring bloom phytoplankton species, a diatom and a dinoflagellate to study the effects of changing bloom composition on the reproduction of the calanoid copepod Acartia bifilosa Giesbrecht, a dominant species in the northern Baltic Sea. Egg production was significantly higher when copepods were fed with Scrippsiella hangoei (Schiller) Larsen dinoflagellates or a mixture of Scrippsiella and Skeletonema marinoi Sarno and Zingone diatoms than when they were provided with Skeletonema only. This effect was observed despite the fact that the Skeletonema strain did not produce polyunsaturated aldehydes (PUAs) and its nutritional quality was high according to polyunsaturated fatty acid (PUFAs) and sterol measurements, and moderate according to mineral (C:N and C:P) measurements. When offered mixtures of Skeletonema and Scrippsiella, copepods ingested both, even when the other one was rare. This indicates potential positive effect of multispecies diets not verified in this study. Here we show that increasing dinoflagellate:diatom ratio might have a positive effect on copepod reproduction.
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| 10. |
- Åhlén, Emma, 1975-
(author)
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Fingerprints of planktivory : paleolimnological evidence of past fish community structure and dynamics
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Planktivorous fish affect the species composition, size and morphology of their zooplankton prey by size selective predation. Remains of cladocerans are deposited in the lake sediments and this microfossil community hence reflects the historical changes in the planktivore fish community. Most earlier work on quantitatively inferring past planktivory deals with ephippia (resting eggs) of Daphnia, however these remains are very scarce in northern Swedish lakes. In these lakes, often dominated by fish that are not obligate planktivores, such as perch (Perca fluviatilis), the individual size to a large degree determines the type of resource consumed. Therefore, in these lakes, the size distribution as well as the density of the fish community determines the overall planktivoryThis thesis deals with evaluating the use of Bosmina remains in the sediment as indicators of past planktivory. I developed a transfer function based on Bosmina remains to be used in oligotrophic lakes with omnivorous species to reconstruct past planktivory. I test the transfer function in a lake where the history is to a large extent known. Furthermore, in this thesis a novel quantitative measure of planktivore pressure, the PCC (Planktivore Community Capacity) was developed. It was also possible to compare the morphology measurements of carapace length and mucro length of contemporary Bosmina sampled in the lake, with the same measurements on microfossils of Bosmina sedimented during the corresponding time period. By using the resurrection approach this thesis also evaluates the use of Ceriodaphnia clones as indicators of micro-evolutionary responses to past planktivory.From the studies in this thesis I can draw some major conclusions; the morphological measurements carapace length and mucro length of Bosmina can be used to infer past planktivory in northern Swedish lakes. PCC has a higher explanatory power than CPUE in these lakes dominated by omnivorous fish. The morphology of the contemporary Bosmina corresponds well with the remains found in the sediment dating from the same time period. Both the contemporary and microfossil Bosmina changes in body size characteristics was in turn strongly related to PPC. Finally, the hatching of Ceriodaphnia ephippia is promising for studying past planktivory, both because of the high viability of the ephippia and the relationship between eye area and inferred PCC.
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