| 1. |
- Andersen Borg, Marc, 1967-
(författare)
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Non-indigenous zooplankton : the role of predatory cladocerans and of copepods in trophic dynamics
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human-mediated introductions of non-indigenous species now threaten to homogenize the biota of the Globe, causing huge economic and ecological damage. This thesis studies the ecological role of 3 invasive planktonic crustaceans, the omnivorous copepod Acartia tonsa (western Atlantic and Indo-Pacific) and the predatory cladocerans, Cercopagis pengoi (Ponto-Caspian) and Bythotrephes longimanus (Eurasian). B. longimanus invaded the North American Great Lakes in 1982, C. pengoi the Baltic in 1992 and the Great Lakes in 1999, while A. tonsa has an extensive invasion history that includes the Baltic.We review current knowledge on feeding biology of the predatory cladocerans. A study of stable C and N isotope ratios indicated mesozooplankton as the main food source of C. pengoi in the northern Baltic Sea proper, with young C. pengoi also eating microzooplankton, such as rotifers. Young-of-the-year herring did eat C. pengoi and herring trophic position shifted from 2.6 before the invasion to 3.4 after, indicating that C. pengoi had been “sandwiched” into the modified food web between mesozooplankton and fish.Salinity tolerance experiments on Acartia tonsa and co-occurring Acartia clausi showed the formers euryhaline character and high grazing potential. Energy partitioning between ingestion, production and respiration was rather constant over the tested salinity range of 2 to 33, with small differences in gross growth efficiency and cost of growth, but maximum ingestion at 10-20. Egg hatching in A. tonsa was only reduced at the lowest salinity. Extreme changes in salinity were needed to cause significant mortality of A. tonsa in the field, but its feeding activity could be severely reduced by salinity changes likely to occur in estuaries. A study of a hypertrophic estuary showed that A. tonsa can sustain a population despite very high mortality rates, caused by predation, high pH and low oxygen, helping explain the success of A. tonsa as an invader of estuaries.
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| 2. |
- Andersson, Agneta, et al.
(författare)
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The pelagic food web
- 2017
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Ingår i: Biological oceanography of the Baltic sea. - Dordrecht : Springer Netherlands. - 9789400706682 - 9789400706675 ; , s. 281-332
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Bokkapitel (refereegranskat)abstract
- Environmental drivers and food web structure in the pelagic zone vary from south to north in the Baltic Sea. While nitrogen is generally the limiting nutrient for primary production in the Baltic Sea, phosphorus is the limiting nutrient in the Bothnian Bay. In the Gulf of Bothnia the food web is to a large extent driven by terrestrial allochthonous material, while autochthonous production dominates in the other parts of the Baltic Sea. Changes in bacterioplankton, protist and zooplankton community composition from south to north are mainly driven by salinity. Bacteria are crucial constituents of the pelagic food web (microbial loop) and in oxygen-poor and anoxic bottom waters where they mediate element transformations. Diatoms and dinoflagellates are the major primary producers in the pelagic zone. Summer blooms of diazotrophic (nitrogen-fixing) filamentous cyanobacteria are typical of the Baltic Sea, especially in the Baltic Sea proper and the Gulf of Finland. The mesozooplankton (mainly copepods and cladocerans) channel energy from primary producers and the microbial food web to fish and finally to the top predators in the pelagic system (waterbirds and mammals). Herring and sprat populations are affected by the foraging intensity of their main predator (cod), and therefore the environmental conditions that affect cod may also influence mesozooplankton due to food web effects "cascading down the food web". Anthropogenic pressures, such as overexploitation of fish stocks, eutrophication, climate change, introduction of non-indigenous species and contamination of top predators by hazardous substances, cause changes in the pelagic food web that may have consequences for the balance and stability of the whole ecosystem.
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| 3. |
- Cristea, Alexander, et al.
(författare)
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Effects of combined strength and sprint training on regulation of muscle contraction at the whole-muscle and single fibre levels in elite master sprinters
- 2008
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Ingår i: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 193:3, s. 275-289
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Tidskriftsartikel (refereegranskat)abstract
- AIM: This study aims at examining the effects of progressive strength and sprint training on regulation of muscle contraction at the whole-muscle and single-fibre levels in older sprint-trained athletes. METHODS: Eleven men (52-78 years) were randomized to a training (EX, n = 7) or control (CTRL, n = 4) group. EX participated in a 20-week programme that combined sprint training with heavy and explosive strength exercises, while CTRL maintained their usual run-based training schedules. RESULTS: EX improved maximal isometric and dynamic leg strength, explosive jump performance and force production in running. Specific tension and maximum shortening velocity of single fibres from the vastus lateralis were not altered in EX or CTRL. Fibre type and myosin heavy chain isoform distributions remained unchanged in the two groups. There was a general increase in fibre areas in EX, but this was significant only in IIa fibres. The 10% increase in squat jump in EX was accompanied by a 9% increase in the integrated EMG (iEMG) of the leg extensors but the 21-40% increases in isometric and dynamic strength were not paralleled by changes in iEMG. CONCLUSION: Adding strength training stimulus to the training programme improved maximal, explosive and sport-specific force production in elite master sprinters. These improvements were primarily related to hypertrophic muscular adaptations.
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| 4. |
- Holopainen, Reetta, et al.
(författare)
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Impacts of changing climate on the non-indigenous invertebrates in the northern Baltic Sea by end of the twenty-first century
- 2016
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Ingår i: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 18:10, s. 3015-3032
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Tidskriftsartikel (refereegranskat)abstract
- Biological invasions coupled with climate change drive changes in marine biodiversity. Warming climate and changes in hydrology may either enable or hinder the spread of non-indigenous species (NIS) and little is known about how climate change modifies the richness and impacts of NIS in specific sea areas. We calculated from climate change simulations (RCO-SCOBI model) the changes in summer time conditions which northern Baltic Sea may to go through by the end of the twenty-first century, e.g., 2-5 A degrees C sea surface temperature rise and even up to 1.75 unit decrease in salinity. We reviewed the temperature and salinity tolerances (i.e., physiological tolerances and occurrence ranges in the field) of pelagic and benthic NIS established in-or with dispersal potential to-the northern Baltic Sea, and assessed how climate change will likely affect them. Our findings suggest a future decrease in barnacle larvae and an increase in Ponto-Caspian cladocerans in the pelagic community. In benthos, polychaetes, gastropods and decapods may become less abundant. By contrast, dreissenid bivalves, amphipods and mysids are expected to widen their distribution and increase in abundance in the coastal areas of the northern Baltic Sea. Potential salinity decrease acts as a major driver for NIS biogeography in the northern Baltic Sea, but temperature increase and extended summer season allow higher reproduction success in bivalves, zooplankton, amphipods and mysids. Successful NIS, i.e., coastal crustacean and bivalve species, pose a risk to native biota, as many of them have already demonstrated harmful effects in the Baltic Sea.
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| 5. |
- Häubner, Norbert
(författare)
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Dynamics of astaxanthin, tocopherol (Vitamin E) and thiamine (Vitamin B1) in the Baltic Sea ecosystem : Bottom-up effects in an aquatic food web
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis combines laboratory experiments and field expeditions to study production, transfer and consumption of non-enzymatic antioxidants and thiamine in an aquatic food web. In particular, I (1) documented spatial and seasonal variation of tocopherols and carotenoids in the Baltic Sea pelagic food web, and (2) examined the effects of abiotic and biotic factors on tocopherol, carotenoid and thiamine concentrations in phytoplankton, zooplankton and fish. Moderate differences in temperature and salinity affected α-tocopherol, β-carotene and thiamine production in microalgae. Furthermore, the results suggest that acute stress favors the expression of non-enzymatic antioxidants rather than enzymatic antioxidants. Because production of α-tocopherol, β-carotene and thiamine differ markedly between microalgae, the availability of non-enzymatic antioxidants and thiamine is likely to be highly variable in the Baltic Sea and is difficult to predict. The transfer of non-enzymatic antioxidants from phytoplankton to zooplankton was biomass dependent. The field expeditions revealed that phytoplankton biomass was negatively associated with α-tocopherol concentration in mesozooplankton. Thus, increased eutrophication of the Baltic Sea followed by an increase in phytoplankton biomass could decrease the transfer of essential biochemicals to higher levels in the pelagic food web. This could lead to deficiency syndromes, of the kind already observed in the Baltic Sea. Astaxanthin is synthesized from precursors provided by the phytoplankton community. Thus biomass dependent transfer of astaxanthin precursors from phytoplankton to zooplankton could be responsible for astaxanthin deficiency in zooplanktivorous herring. Astaxanthin in herring consists mostly of all-Z-isomers, which are characterized by low bioavailability. Therefore, astaxanthin deficiency in salmon could be explained by the low concentration of this substance and its isomeric composition in herring.
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| 6. |
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| 7. |
- Korhonen, Marko, et al.
(författare)
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Aging, muscle fiber type, and contractile function in sprint-trained athletes
- 2006
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 101:3, s. 906-917
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Tidskriftsartikel (refereegranskat)abstract
- Biopsy samples were taken from the vastus lateralis of 18- to 84-yr-old male sprinters (n = 91). Fiber-type distribution, cross-sectional area, and myosin heavy chain (MHC) isoform content were identified using ATPase histochemistry and SDS-PAGE. Specific tension and maximum shortening velocity (V-o) were determined in 144 single skinned fibers from younger (18-33 yr, n = 8) and older (53-77 yr, n = 9) runners. Force-time characteristics of the knee extensors were determined by using isometric contraction. The cross-sectional area of type I fibers was unchanged with age, whereas that of type II fibers was reduced (P < 0.001). With age there was an increased MHC I (P < 0.01) and reduced MHC IIx isoform content (P < 0.05) but no differences in MHC IIa. Specific tension of type I and IIa MHC fibers did not differ between younger and older subjects. V-o of fibers expressing type I MHC was lower (P < 0.05) in older than in younger subjects, but there was no difference in V-o of type IIa MHC fibers. An aging-related decline of maximal isometric force (P < 0.001) and normalized rate of force development (P < 0.05) of knee extensors was observed. Normalized rate of force development was positively associated with MHC II (P < 0.05). The sprint-trained athletes experienced the typical aging-related reduction in the size of fast fibers, a shift toward a slower MHC isoform profile, and a lower V-o of type I MHC fibers, which played a role in the decline in explosive force production. However, the muscle characteristics were preserved at a high level in the oldest runners, underlining the favorable impact of sprint exercise on aging muscle.
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| 8. |
- Kotta, Jonne, et al.
(författare)
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Integrating experimental and distribution data to predict future species patterns
- 2019
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Predictive species distribution models are mostly based on statistical dependence between environmental and distributional data and therefore may fail to account for physiological limits and biological interactions that are fundamental when modelling species distributions under future climate conditions. Here, we developed a state-of-the-art method integrating biological theory with survey and experimental data in a way that allows us to explicitly model both physical tolerance limits of species and inherent natural variability in regional conditions and thereby improve the reliability of species distribution predictions under future climate conditions. By using a macroalga-herbivore association (Fucus vesiculosus - Idotea balthica) as a case study, we illustrated how salinity reduction and temperature increase under future climate conditions may significantly reduce the occurrence and biomass of these important coastal species. Moreover, we showed that the reduction of herbivore occurrence is linked to reduction of their host macroalgae. Spatial predictive modelling and experimental biology have been traditionally seen as separate fields but stronger interlinkages between these disciplines can improve species distribution projections under climate change. Experiments enable qualitative prior knowledge to be defined and identify cause-effect relationships, and thereby better foresee alterations in ecosystem structure and functioning under future climate conditions that are not necessarily seen in projections based on non-causal statistical relationships alone.
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| 9. |
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| 10. |
- Persson, Karl-Johan, 1982-
(författare)
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Influence of cyanobacterial blooms on coastal fish recruitment
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cyanobacteria are the oldest oxygen-producing organisms on Earth and can be found in almost every terrestrial and aquatic habitat. Their long evolutionary history has enabled them to develop diverse adaptations in order to increase their survival in environments subjected to natural and anthropogenic changes. The frequency and intensity of cyanobacterial blooms in the Baltic Sea have increased during the last century. Summer blooms consisting of the filamentous cyanobacterial genera Nodularia, Aphanizomenon and Anabaena may cover up to 50 % of the Baltic Sea surface, which are the largest cyanobacterial blooms in the world. Simultaneously, recruitment of spring spawning fish such as perch (Perca fluviatilis) and pike (Esox Lucius) have decreased along the Baltic Sea coast. Temporal variations in adult fish abundance have been linked to recruitment success, which is dependent on growth of juvenile fish. Generally, low growth rates affect survival of juvenile fish by causing an increase in the time spent in stages prone to predation and by increasing winter mortality which is negatively size selective. Since growth is a crucial factor determining fish recruitment, all parameters that have the potential to influence fish growth could affect fish recruitment dynamics. Cyanobacteria negatively influence fish growth directly (toxicity, turbidity and changes in water quality) and indirectly (toxin transfer, changes in zooplankton community structure). Cyanobacterial toxins i.e. nodularin accumulate in common coastal fish species (flounders, perch and roach) resulting in an energetic cost associated with detoxification. Cyanobacteria, toxic or non-toxic, also affect the behavior of fish (prey capture) further increasing energetic costs. In nature, spatial variations of both cyanobacteria and salinity are a deadly combination for juvenile fish leading to increased detrimental effects of cyanobacteria on juvenile fish in brackish waters compared to freshwater. However, different fish populations react differently to cyanobacteria i.e. a marine population had higher tolerance to cyanobacteria compared to an oligotrophic population. At the coastal ecosystem level, cyanobacteria cannot explain the decline of juvenile fish. Nevertheless, at the local scale cyanobacteria certainly influence the recruitment of juvenile fish.
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