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Temperature mediated effects on top consumer populations in subarctic lakes
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The effects of temperature on top consumer populations in subarctic lake communities were studied by contrasting two lake pairs in different climate regimes: one pair on the low alpine tundra and one pair in the subalpine birch forest. We measured zooplankton and macroinvertebrate biomasses over the season and estimated population density and size structure of the top consumer Arctic char (Salvelinus alpinus). Furthermore, we modelled char growth using literature data on temperature dependent search rate, handling time and metabolic demands. The forest lakes were warmer than the tundra lakes. Char in the forest lakes were larger and had a higher individual growth compared to char in the tundra lakes, while population density and biomasses of char were not different between the forest and the tundra lakes. There were no differences in macroinvertebrate and zooplankton resource levels available for char between lake pairs. Our modeling of char growth revealed that higher temperature increased growth of char at the observed resource densities, suggesting that the higher temperature in the forest lakes was primarily the cause of the higher growth of char in these lakes. We suggest that cannibalism in char may regulate char recruitment and thereby population density and biomass of char leading to effects of increasing temperature on consumer biomass and consumer individual growth different from what is expected in pure consumer-resource systems. Our results emphasize the importance of feedbacks within ecosystems when addressing effects of climate change and increasing temperature on lake communities.

Keyword [en]
Arctic char, temperature, cannibalism, ecological feedbacks, climate
National Category
Ecology
Research subject
biology
Identifiers
URN: urn:nbn:se:umu:diva-37989OAI: oai:DiVA.org:umu-37989DiVA: diva2:371632
Available from: 2010-11-22 Created: 2010-11-22 Last updated: 2010-11-26Bibliographically approved
In thesis
1. Invasion of top and intermediate consumers in a size structured fish community
Open this publication in new window or tab >>Invasion of top and intermediate consumers in a size structured fish community
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Invasion av toppredatorer och intermediära konsumenter i ett storleksstrukturerat fisksamhälle
Abstract [en]

In this thesis I have investigated the effects of invading top and intermediate consumers in a size-structured fish community, using a combination of field studies, a lake invasion experiment and smaller scale pond and aquaria experiments.

The lake invasion experiment was based on introductions of an intermediate consumer, ninespine stickleback (Pungitius pungitius L.), in to allopatric populations of an omnivorous top predator, Arctic char (Salvelinus alpinus L.). The invasion experiment was performed in two tundra lakes and in two birch forest lakes to investigate the effect of climate on the invasion success. I found that the effect of sticklebacks on char was size dependent. Small char suffered reduced growth from resource competition with sticklebacks whereas the maximum size of adult char increased from the addition of a larger prey resource, stickleback. The negative effect of sticklebacks on the growth of small char suggests that sticklebacks may be a better resource competitor than char, which was also supported by the pond and aquaria experiments. The pond experiments also suggested that char were more efficient cannibals than interspecific predators on sticklebacks. Cannibalism in char may limit the recruitment of char and decrease both their predatory and competitive effect on coexisting species and thereby also promote the coexistence of char and sticklebacks. The successful invasion by sticklebacks and their subsequent increases in density suggest that the absence of sticklebacks in char lakes in this region is not caused by biotic interactions with char. Instead, it may be suggested that co-occurrence of sticklebacks and char in the region is limited by dispersal.

The char – stickleback system resembles an intraguild predation system with char as the top consumer and stickleback as the intermediate consumer. The effects of the stickleback invasion is also contrasted with a field study of a northern pike (Esox lucius L.) invasion into a system with coexisting char and stickleback, where pike can be viewed as the top consumer and char as the intermediate consumer both feeding on sticklebacks. In this case pike excluded char. The identity of the invading species and the relative strength of the predatory and competitive interactions in the two contrasting systems are discussed in relation to coexistence in intraguild predation systems. I found that the identity of the invading species is of crucial importance for the response at the ecosystem level, and that the inherent size dependency of competitive and predatory interactions in fish communities is important for attaining a mechanistical understanding of the effects of invasive species in lake ecosystems.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2010. 27 p.
Keyword
Invasion, intraguild predation, size-structure, cannibalism, climate, temperature, Arctic char, ninespine stickleback
National Category
Ecology
Research subject
biology
Identifiers
urn:nbn:se:umu:diva-37995 (URN)978-91-7459-119-4 (ISBN)
Public defence
2010-12-17, KBC-huset, KB3B1, Umeå Universitet, Umeå, 11:03 (English)
Opponent
Supervisors
Available from: 2010-11-26 Created: 2010-11-22 Last updated: 2010-11-26Bibliographically approved

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