| 1. |
- Beck, Lisa J., et al.
(författare)
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Differing Mechanisms of New Particle Formation at Two Arctic Sites
- 2021
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 48:4
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Tidskriftsartikel (refereegranskat)abstract
- New particle formation in the Arctic atmosphere is an important source of aerosol particles. Understanding the processes of Arctic secondary aerosol formation is crucial due to their significant impact on cloud properties and therefore Arctic amplification. We observed the molecular formation of new particles from low-volatility vapors at two Arctic sites with differing surroundings. In Svalbard, sulfuric acid (SA) and methane sulfonic acid (MSA) contribute to the formation of secondary aerosol and to some extent to cloud condensation nuclei (CCN). This occurs via ion-induced nucleation of SA and NH3 and subsequent growth by mainly SA and MSA condensation during springtime and highly oxygenated organic molecules during summertime. By contrast, in an ice-covered region around Villum, we observed new particle formation driven by iodic acid but its concentration was insufficient to grow nucleated particles to CCN sizes. Our results provide new insight about sources and precursors of Arctic secondary aerosol particles.
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| 2. |
- Brodersen, Jakob, et al.
(författare)
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Condition-dependent individual decision-making determines cyprinid partial migration
- 2008
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 89:5, s. 1195-1200
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Tidskriftsartikel (refereegranskat)abstract
- Partial migration is a common phenomenon among many animals and occurs in many types of ecosystems. Understanding the mechanisms behind partial migration is of major importance for the understanding of population dynamics and, eventually, ecosystem processes. We studied the effects of food availability on the seasonal partial migration of cyprinid fish from a lake to connected streams during winter by the use of passive telemetry. Fish with increased access to food were found to migrate in higher proportion, earlier in the season, and to reside in the streams for a longer period compared to fish with decreased access to food. Furthermore, fewer unfed migrants returned to the lake, indicating higher overwinter mortality. Our results suggest that individual fish trade off safety from predation and access to food differently depending on their body condition, which results in a condition-dependent partial migration. Hence, our main conclusion is that individual decision-making is based on assessment of own condition which offers a mechanistic explanation to partial migration. Moreover, this may be of high importance for understanding population responses to environmental variation as well as ecosystem dynamics and stability. Read More: http://www.esajournals.org/doi/abs/10.1890/07-1318.1
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Brodersen, Jakob, et al.
(författare)
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Variable individual consistency in timing and destination of winter migrating fish
- 2012
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Ingår i: Biology Letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 8, s. 21-23
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Tidskriftsartikel (refereegranskat)abstract
- Migration is an important event in the life history of many animals, but there is considerable variation within populations in the timing and final destination. Such differential migration at the population level can be strongly determined by individuals showing different consistencies in migratory traits. By tagging individual cyprinid fish with uniquely coded electronic tags, and recording their winter migrations from lakes to streams for 6 consecutive years, we obtained highly detailed long-term information on the differential migration patterns of individuals. We found that individual migrants showed consistent site fidelities for over-wintering streams over multiple migratory seasons and that they were also consistent in their seasonal timing of migration. Our data also suggest that consistency itself can be considered as an individual trait, with migrants that exhibit consistent site fidelity also showing consistency in migratory timing. The finding of a mixture of both consistent and inconsistent individuals within a population furthers our understanding of intrapopulation variability in migration strategies, and we hypothesize that environmental variation can maintain such different strategies.
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| 7. |
- Brönmark, Christer, et al.
(författare)
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Regime shifts in shallow lakes: the importance of seasonal fish migration
- 2010
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 646:1, s. 91-100
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Konferensbidrag (refereegranskat)abstract
- Shallow eutrophic lakes commonly exist in two alternative stable states: a clear-water state and a turbid water state. A number of mechanisms, including both abiotic and biotic processes, buffer the respective states against changes, whereas other mechanisms likely drive transitions between states. Our earlier research shows that a large proportion of zooplanktivorous fish populations in shallow lakes undertake seasonal migrations where they leave the lake during winter and migrate back to the lake in spring. Based on our past research, we propose a number of scenarios of how feedback processes between the individual and ecosystem levels may affect stability of alternative stable states in shallow lakes when mediated by fish migration. Migration effects on shallow lakes result from processes at different scales, from the individual to the ecosystem. Our earlier research has shown that ecosystem properties, including piscivore abundance and zooplankton productivity, affect the individual state of zooplanktivorous fish, such as growth rate or condition. Individual state, in turn, affects the relative proportion and timing of migrating zooplanktivorous fish. This change, in turn, may stabilize states or cause runaway processes that eventually lead to state shifts. Consequently, such knowledge of processes coupled to seasonal migration of planktivorous fish should increase our understanding of shallow lake dynamics.
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| 8. |
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| 9. |
- Brönmark, Christer, et al.
(författare)
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Seasonal migration determined by a trade-off between predator avoidance and growth
- 2008
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Migration is a common phenomenon in many organisms, terrestrial as well as aquatic, and considerable effort has been spent to understand the evolution of migratory behaviour and its consequences for population and community dynamics. In aquatic systems, studies on migration have mainly been focused on commercially important fish species, such as salmon and trout. However, seasonal mass-migrations may occur also among other freshwater fish, e.g. in cyprinids that leave lakes and migrate into streams and wetlands in the fall and return back to the lake in spring. In a conceptual model, we hypothesized that this is an adaptive behaviour in response to seasonal changes in predation (P) and growth (G) and that migrating fish change habitat so as to minimise the ratio between predation mortality and growth rate (P/G). Estimates from bioenergetic modelling showed that seasonal changes in the ratio between predator consumption rate and prey growth rate followed the predictions from the conceptual model and also gave more precise predictions for the timing of the habitat change. By quantifying the migration of more than 1800 individually marked fish, we showed that actual migration patterns followed predictions with a remarkable accuracy, suggesting that migration patterns have evolved in response to seasonally fluctuating trade-offs between predator avoidance and foraging gains. Thus, the conceptual model provides a mechanistic understanding to mass–migration in prey fish. Further, we also show that the dominant prey fish is actually absent from the lake during a major part of the year, which should have strong implications for the dynamics of the lake ecosystem through direct and indirect food-web interactions.
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| 10. |
- Chapman, Ben, et al.
(författare)
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A foraging cost of migration for a partially migratory cyprinid fish
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- Migration has evolved as a strategy to maximise individual fitness in response to seasonally changing ecological and environmental conditions. However, migration can also incur costs, and quantifying these costs can provide important clues to the ultimate ecological forces that underpin migratory behaviour. A key emerging model to explain migration in many systems posits that migration is driven by seasonal changes to a predation/growth potential (p/g) trade-off that a wide range of animals face. In this study we assess a key assumption of this model for a common cyprinid partial migrant, the roach Rutilus rutilus, which migrates from shallow lakes to streams during winter. By sampling fish from stream and lake habitats in the autumn and spring and measuring their stomach fullness and diet composition, we tested if migrating roach pay a cost of reduced foraging when migrating. Resident fish had fuller stomachs containing more high quality prey items than migrant fish. Hence, we document a feeding cost to migration in roach, which adds additional support for the validity of the p/g model of migration in freshwater systems.
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