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| 2. |
- Hansson, Lars-Anders, et al.
(author)
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Consumption patterns, complexity and enrichment in aquatic food chains
- 1998
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In: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 265:1399, s. 901-906
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Journal article (peer-reviewed)abstract
- The interactions between consumers and prey, and their impact on biomass distribution among trophic levels, are central issues in both empirical and theoretical ecology. In a long-term experiment, where all organisms, including the top predator, were allowed to respond to environmental conditions by reproduction, we tested predictions from `prey-dependent' and `ratio-dependent' models. Prey-dependent models made correct predictions only in the presence of strong interactors in simple food chains, but failed to predict patterns in more complex situations. Processes such as omnivory, consumer excretion, and unsuitable prey-size windows (invulnerable prey) increased the complexity and created patterns resembling ratio-dependent consumption. However, whereas the prey-dependent patterns were created by the mechanisms predicted by the model, ratio-dependent patterns were not, suggesting that they may be right for the wrong reason'. We show here that despite the enormous complexity of ecosystems, it is possible to identify and disentangle mechanisms responsible for observed patterns in community structure, as well as in biomass development of organisms ranging in size from bacteria to fish.
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| 3. |
- Persson, Anders, et al.
(author)
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Effects of enrichment on simple aquatic food webs
- 2001
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In: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 157:6, s. 654-669
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Journal article (peer-reviewed)abstract
- Simple models, based on Lotka-Volterra types of interactions between predator and prey, predict that enrichment will have a destabilizing effect on populations and that equilibrium population densities will change at the top trophic level and every second level below. We experimentally tested these predictions in three aquatic food web configurations subjected to either high or low nutrient additions. The results were structured by viewing the systems as either food chains or webs and showed that trophic level biomass increased with enrichment, which contradicts food chain theory. However, within each trophic level, food web configuration affected the extent to which different functional groups responded to enrichment. By dividing trophic levels into functional groups, based on vulnerability to consumption, we were able to identify significant effects that were obscured when systems were viewed as food chains. The results support the prediction that invulnerable prey may stabilize trophic-level dynamics by replacing other, more vulnerable prey. Furthermore, the vulnerable prey, such as Daphnia and edible algae, responded as predicted by the paradox of enrichment hypothesis; that is, variability in population density increased with enrichment. Hence, by describing ecosystems as a matrix of food web interactions, and by recognizing the interplay between interspecific competition and predation, a more complete description of the ecosystem function was obtained compared to when species were placed into distinct trophic levels.
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| 4. |
- Persson, Anders, et al.
(author)
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Effects of enrichment on simple aquatic food webs
- 2001
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In: The American Naturalist. ; 157:6, s. 654-669
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Journal article (peer-reviewed)abstract
- Simple models, based on Lotka-Volterra types of interactions between predator and prey, predict that enrichment will have a destabilizing effect on
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| 5. |
- Björnerås, Caroline, et al.
(author)
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Inland blue holes of The Bahamas - chemistry and biology in a unique aquatic environment
- 2020
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In: Fundamental and Applied Limnology. - : Schweizerbart science publishers. - 1863-9135. ; 194:2, s. 95-106
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Journal article (peer-reviewed)abstract
- While lake systems in temperate regions have been extensively studied, tropical and subtropical systems have received less attention. Here, we describe the water chemistry and biota of ten inland blue holes on Andros Island, The Bahamas, representative of the morphological, abiotic, and biotic variation among Androsian inland blue holes. The majority of the studied blue holes were vertically stratified with oxic freshwater overlying anoxic saline groundwater of marine origin. Water chemistry (e.g. total phosphorus and nitrogen) in shallow waters was similar among blue holes, while turbidity and water color varied. Presence of hydrogen sulfide and reduced iron in and below the halocline indicate reducing conditions in all stratified blue holes. The biota above the halocline was also similar among blue holes with a few taxa dominating the phytoplankton community, and the zooplankton community consisting of copepods and rotifers. The Bahamas mosquitofish (Gambusia hubbsi) was present in all investigated blue holes, often accompanied by other small planktivorous fish, while the piscivorous bigmouth sleeper (Gobiomorus donnitor) was only present in some of the blue holes. Our field study reinforces that inland blue holes are highly interesting for biogeochemical research, and provide naturally replicated systems for evolutionary studies.
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| 6. |
- Hansen, Joan H., et al.
(author)
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Ecological consequences of animal migration : Prey partial migration affects predator ecology and prey communities
- 2019
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In: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; , s. 1-15
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Journal article (peer-reviewed)abstract
- Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with negative controls, that is, ecosystems without migration. In this study, we tested whether partial migration of certain species within the overall prey community affects foraging ecology of top predators and thereby alters energy pathways in food webs. We carried out the study in independent replicated freshwater lake systems, four with and four without opportunity for prey migration. Specifically, we compared predator foraging mode in lakes where cyprinid prey fish perform seasonal partial migrations into connected streams with lakes lacking migratory opportunities for prey fish. We found clear seasonal bottom-up effects of prey migration on predators, including changes in size structure and total biomass of ingested prey, size-specific changes in littoral versus pelagic origin of diet, and a higher degree of feast-and-famine for predators in systems with migratory prey. Our analyses further showed that partially migratory prey species constitute a larger part of the prey community in systems that allow migration. Hence, prey migrations have important implications for predator foraging ecology and may cause seasonal shifts in the importance of their supporting energy pathways. We suggest that such bottom-up effects of partial migration may be a widespread phenomenon both in aquatic and in terrestrial ecosystems. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
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| 7. |
- Hansson, Lars-Anders, et al.
(author)
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Food-chain length alters community responses to global change in aquatic systems
- 2013
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In: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 3, s. 228-233
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Journal article (peer-reviewed)abstract
- Synergies between large-scale environmental changes, such as climate change1 and increased humic content (brownification)2, will have a considerable impact on future aquatic ecosystems. On the basis of modelling, monitoring and experimental data, we demonstrate that community responses to global change are determined by food-chain length and that the top trophic level, and every second level below, will benefit from climate change, whereas the levels in between will suffer. Hence, phytoplankton, and thereby algal blooms, will benefit from climate change in three-, but not in two-trophic-level systems. Moreover, we show that both phytoplankton (resource) and zooplankton (consumer) advance their spring peak abundances similarly in response to a 3 °C temperature increase; that is, there is no support for a consumer/resource mismatch in a future climate scenario. However, in contrast to other taxa, cyanobacteria—known as toxin-producing nuisance phytoplankton3—benefit from a higher temperature and humic content irrespective of the food-chain composition. Our results are mirrored in natural ecosystems. By mechanistically merging present food-chain theory with large-scale environmental and climate changes, we provide a powerful framework for predicting and understanding future aquatic ecosystems and their provision of ecosystem services and water resources.
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| 8. |
- Hansson, Lars-Anders, et al.
(author)
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Food-chain length alters community responses to global change in aquatic systems
- 2013
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In: Nature Climate Change. - 1758-6798. ; 3:3, s. 228-233
-
Journal article (peer-reviewed)abstract
- Synergies between large-scale environmental changes, such as climate change(1) and increased humic content (brownification)(2), will have a considerable impact on future aquatic ecosystems. On the basis of modelling, monitoring and experimental data, we demonstrate that community responses to global change are determined by food-chain length and that the top trophic level, and every second level below, will benefit from climate change, whereas the levels in between will suffer. Hence, phytoplankton, and thereby algal blooms, will benefit from climate change in three-, but not in two-trophic-level systems. Moreover, we show that both phytoplankton (resource) and zooplankton (consumer) advance their spring peak abundances similarly in response to a 3 degrees C temperature increase; that is, there is no support for a consumer/resource mismatch in a future climate scenario. However, in contrast to other taxa, cyanobacteria-known as toxin-producing nuisance phytoplankton(3)-benefit from a higher temperature and humic content irrespective of the food-chain composition. Our results are mirrored in natural ecosystems. By mechanistically merging present food-chain theory with large-scale environmental and climate changes, we provide a powerful framework for predicting and understanding future aquatic ecosystems and their provision of ecosystem services and water resources.
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| 9. |
- Hulthén, Kaj, et al.
(author)
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A predation cost to bold fish in the wild
- 2017
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In: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
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Journal article (peer-reviewed)abstract
- Studies of predator-mediated selection on behaviour are critical for our understanding of the evolution and maintenance of behavioural diversity in natural populations. Consistent individual differences in prey behaviour, especially in the propensity to take risks (“boldness”), are widespread in the animal kingdom. Theory predicts that individual behavioural types differ in a cost-benefit trade-off where bolder individuals benefit from greater access to resources while paying higher predation-risk costs. However, explicitly linking predation events to individual behaviour under natural conditions is challenging and there is currently little data from the wild. We assayed individual behaviour and electronically tagged hundreds of fish (roach, Rutilus rutilus) before releasing them into their lake of origin, thereby exposing them to predation risk from avian apex predators (cormorants, Phalacrocorax carbo). Scanning for regurgitated tags at the cormorant roosting site provided data on individual predation events. We found that fish with higher boldness have a greater susceptibility to cormorant predation compared to relatively shy, risk-averse individuals. Our findings hereby provide unique and direct evidence of behavioural type-dependent predation vulnerability in the wild, i.e. that there is a predation cost to boldness, which is critical for our understanding of the evolution and maintenance of behavioural diversity in natural populations.
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| 10. |
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