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Ecology across Boundaries: Food web coupling among and within ecosystems
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cross-boundary movements of energy and material are ubiquitous. Freshwater ecosystems receive nutrients, dissolved, and particulate organic matter from adjacent terrestrial ecosystems, whereas terrestrial ecosystems mainly receive prey organisms and detritus deposited by physical processes such as floods from freshwater ecosystems. Within lakes, fish are considered as integrators between habitats due to their high mobility, although they often occupy either near-shore littoral or open-water pelagic habitats and develop habitat-specific morphologies. Such intra-population divergence in morphological traits might limit the use of multiple habitats.

In this thesis, I first focused on quantity and quality of reciprocal fluxes of particulate organic matter between freshwater and terrestrial ecosystems and responses of recipient consumers. Freshwater ecosystems generally received higher amounts of externally-produced resources than terrestrial ecosystems. Despite this discrepancy, aquatic and terrestrial consumer responses were similar, likely due to the differences in resource quality. Second, I investigated the potential of particulate organic carbon (POC) supporting benthic food webs in lakes; a pathway that has largely been neglected in previous studies. I found that POC can substantially subsidize the benthic food web and that the effects on the benthic food web were transferred to the pelagic habitat, thus emphasizing the importance of benthic pathways for pelagic production. Third, I examined how water transparency can affect intra-population divergence in perch (Perca fluviatilis). I observed that increased water transparency can considerably increase morphological divergence between littoral and pelagic populations likely due to its effects on foraging. Finally, I investigated the effects of such intra-population divergence on littoral-pelagic food web coupling. I found that low morphological divergence corresponded with high overlap in resource use, whereas strong morphological divergence resulted in low overlap in resource use. Here littoral populations mainly utilized littoral resources and pelagic populations primarily utilized pelagic resources, indicating that habitat coupling might be strongly limited when intra-population divergence is high.

In conclusion, although different ecosystems seem separated by distinct physical boundaries, these boundaries are often crossed. However, the development of habitat-specific adaptive traits might limit movement between apparently contiguous habitats.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2011. , 48 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 881
Keyword [en]
cross-ecosystem, food web, habitat coupling, terrestrial-aquatic linkages, subsidy, allochthonous, lake ecosystem, population divergence, trait variation
National Category
Biological Sciences Ecology
Research subject
Biology with specialization in Limnology
URN: urn:nbn:se:uu:diva-160783ISBN: 978-91-554-8222-0OAI: diva2:453147
Public defence
2011-12-16, Friessalen, Evolutionary Biology Centre (EBC), Norbyvägen 18, Uppsala, 09:00 (English)
Available from: 2011-11-24 Created: 2011-10-31 Last updated: 2012-01-03
List of papers
1. Reciprocal subsidies between freshwater and terrestrial ecosystems structure consumer-resource dynamics
Open this publication in new window or tab >>Reciprocal subsidies between freshwater and terrestrial ecosystems structure consumer-resource dynamics
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2012 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 93, no 5, 1173-1182 p.Article in journal (Refereed) Published
Abstract [en]

Cross-ecosystem movements of material and energy, particularly reciprocal resource fluxes across the freshwater-land interface, have received major attention. Freshwater ecosystems may receive higher amounts of subsidies (i.e., resources produced outside the focal ecosystem) than terrestrial ecosystems, potentially leading to increased secondary production in freshwaters. Here we used a meta-analytic approach to quantify the magnitude and direction of subsidy inputs across the freshwater-land interface and to determine subsequent responses in recipient animals. Terrestrial and freshwater ecosystems differed in the magnitude of subsidies they received, with aquatic ecosystems generally receiving higher subsidies than terrestrial ecosystems. Surprisingly, and despite the large discrepancy in magnitude, the contribution of these subsidies to animal carbon inferred from stable isotope composition did not differ between freshwater and terrestrial ecosystems, likely due to the differences in subsidy quality. The contribution of allochthonous subsidies was highest to primary consumers and predators, suggesting that bottom-up and top-down effects may be affected considerably by the input of allochthonous resources. Future work on subsidies will profit from a food web dynamic approach including indirect trophic interactions and propagating effects.

National Category
urn:nbn:se:uu:diva-160772 (URN)10.1890/11-1210.1 (DOI)000304368100022 ()
Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2012-06-19Bibliographically approved
2. Terrestrial subsidies to lake food webs: An experimental approach
Open this publication in new window or tab >>Terrestrial subsidies to lake food webs: An experimental approach
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2012 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 168, no 3, 807-818 p.Article in journal (Refereed) Published
Abstract [en]

Cross-ecosystem movements of material and energy are ubiquitous. Aquatic ecosystems typically receive material that also includes organic matter from the surrounding catchment. Terrestrial-derived (allochthonous) organic matter can enter aquatic ecosystems in dissolved or particulate form. Several studies have highlighted the importance of dissolved organic carbon to aquatic consumers, but less is known about allochthonous particulate organic carbon (POC). Similarly, most studies showing the effects of allochthonous organic carbon (OC) on aquatic consumers have investigated pelagic habitats; the effects of allochthonous OC on benthic communities are less well studied. Allochthonous inputs might further decrease primary production through light reduction, thereby potentially affecting autotrophic resource availability to consumers. Here, an enclosure experiment was carried out to test the importance of POC input and light availability on the resource use in a benthic food web of a clear-water lake. Corn starch (a C-4 plant) was used as a POC source due to its insoluble nature and its distinct carbon stable isotope value (delta C-13). The starch carbon was closely dispersed over the bottom of the enclosures to study the fate of a POC source exclusively available to sediment biota. The addition of starch carbon resulted in a clear shift in the isotopic signature of surface-dwelling herbivorous and predatory invertebrates. Although the starch carbon was added solely to the sediment surface, the carbon originating from the starch reached zooplankton. We suggest that allochthonous POC can subsidize benthic food webs directly and can be further transferred to pelagic systems, thereby highlighting the importance of benthic pathways for pelagic habitats.

Allochthonous, Cross-ecosystem, Autochthonous, Aquatic-terrestrial linkage, Benthic
National Category
urn:nbn:se:uu:diva-160774 (URN)10.1007/s00442-011-2141-7 (DOI)000301706800020 ()
Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2012-05-15Bibliographically approved
3. Water transparency drives intra-population divergence in Eurasian perch (Perca fluviatilis)
Open this publication in new window or tab >>Water transparency drives intra-population divergence in Eurasian perch (Perca fluviatilis)
2012 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 7, no 8, e43641- p.Article in journal (Refereed) Published
Abstract [en]

Trait combinations that lead to a higher efficiency in resource utilization are important drivers of divergent natural selection and adaptive radiation. However, variation in environmental features might constrain foraging in complex ways and therefore impede the exploitation of critical resources. We tested the effect of water transparency on intra-population divergence in morphology of Eurasian perch (Perca fluviatilis) across seven lakes in central Sweden. Morphological divergence between near-shore littoral and open-water pelagic perch substantially increased with increasing water transparency. Reliance on littoral resources increased strongly with increasing water transparency in littoral populations, whereas littoral reliance was not affected by water transparency in pelagic populations. Despite the similar reliance on pelagic resources in pelagic populations along the water transparency gradient, the utilization of particular pelagic prey items differed with variation in water transparency in pelagic populations. Pelagic perch utilized cladocerans in lakes with high water transparency and copepods in lakes with low water transparency. We suggest that under impaired visual conditions low utilization of littoral resources by littoral perch and utilization of evasive copepods by pelagic perch may lead to changes in morphology. Our findings indicate that visual conditions can affect population divergence in predator populations through their effects on resource utilization.

National Category
Biological Sciences
urn:nbn:se:uu:diva-158689 (URN)10.1371/journal.pone.0043641 (DOI)000308063700123 ()
Available from: 2011-09-13 Created: 2011-09-13 Last updated: 2012-11-07Bibliographically approved
4. Intra-population niche separation mediated by water transparency limits habitat coupling
Open this publication in new window or tab >>Intra-population niche separation mediated by water transparency limits habitat coupling
(English)Manuscript (preprint) (Other academic)
National Category
urn:nbn:se:uu:diva-160776 (URN)
Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2013-02-11

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