| 1. |
- Andersson, Matilda L., et al.
(författare)
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Chasing away accurate results : exhaustive chase protocols underestimate maximum metabolic rate estimates in European perch Perca fluviatilis
- 2020
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 97:6, s. 1644-1650
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic rates are one of many measures that are used to explain species' response to environmental change. Static respirometry is used to calculate the standard metabolic rate (SMR) of fish, and when combined with exhaustive chase protocols it can be used to measure maximum metabolic rate (MMR) and aerobic scope (AS) as well. While these methods have been tested in comparison to swim tunnels and chambers with circular currents, they have not been tested in comparison with a no‐chase control. We used a repeated‐measures design to compare estimates of SMR, MMR and AS in European perch Perca fluviatilis following three protocols: (a) a no‐chase control; (b) a 3‐min exhaustive chase; and (c) a 3‐min exhaustive chase followed by 1‐min air exposure. We found that, contrary to expectations, exhaustive chase protocols underestimate MMR and AS at 18°C, compared to the no‐chase control. This suggests that metabolic rates of other species with similar locomotorty modes or lifestyles could be similarly underestimated using chase protocols. These underestimates have implications for studies examining metabolic performance and responses to climate change scenarios. To prevent underestimates, future experiments measuring metabolic rates should include a pilot with a no‐chase control or, when appropriate, an adjusted methodology in which trials end with the exhaustive chase instead of beginning with it.
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| 2. |
- Andersson, Matilda L.
(författare)
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Fish population responses to climate change : Causes and consequences
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lake environments are heterogeneous, and animals show a variety of adaptations to deal with this heterogeneity. Fish often show intraspecific variation in diet, metabolism, and behavior, corresponding to their habitat use. Studies on climate change often ignore this heterogeneity and its importance in determining population-level responses to climate change. This thesis can be broken into two interacting pieces. First, my goal was to assess how water color and temperature changes impact the size, number, and distribution of a common predator, Eurasian perch (Perca fluviatilis), in Swedish lakes. Second, I aimed to examine whether metabolism and resource use differed between lake habitats, corresponding with documented patterns of polymorphism and whether diet differences were maintained along a thermal and water color gradient. By combining the information gleaned from these studies, the overarching goal of my thesis is to better understand how climate change will impact fish populations and how intraspecific variance in these responses will impact ecosystem functioning. I found that warming and browning will likely decrease fish biomass but via different mechanisms. Warming reduces average fish size through its impact on metabolism and energy requirements. Browning decreases fish abundance likely due to its negative effects on resource abundance, increasing mortality, and decreasing reproductive effort. Though warming decreases biomass at the lake level, pelagic perch abundance increases. I found that these pelagic perch have higher metabolic rates and, especially in darker lakes, rely heavily on pelagic resources. As more fish shift into the pelagic habitat, this will increase top-down pressure on pelagic resources and decrease energy transfer from littoral to pelagic habitats altering energy flow within lakes. Variation in metabolic phenotype across habitats, combined with the positive scaling of metabolic rates with temperature, will likely determine which fish can persist under climate change scenarios. Studies that measure this variation rely heavily on respirometry to measure fish metabolism. I found that current respirometry methods underestimate maximum metabolic rate and suggest an updated method to improve the accuracy of future studies. Overall, I conclude that habitats should be examined separately to better understand population-level responses to climate change. Perch caught in different habitats have different energy requirements and respond differently to warming and browning. These differences will affect the distribution of top-down pressure and habitat coupling within lake ecosystems, with implications for broader ecosystem functioning in the future.
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| 3. |
- Andersson, Matilda L., et al.
(författare)
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Habitat coupling is modified by dissolved organic carbon but not temperature in lake ecosystems
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Generalist predators play an essential role in lake ecosystems by linking spatially distinct habitats, a process known as habitat coupling. By eating a wide array of resources and moving between littoral and pelagic habitats, they link food webs and provide critical habitat stability. As climate change is expected to affect ecosystem stability, our attention should focus on how habitat coupling in these predator-stabilized systems is altered by climate change.Expected climate change effects in boreal regions are increases in temperature and dissolved organic carbon (DOC) concentrations. Therefore, we used stable isotopes and a space-for-time approach to examine the impact of DOC and temperature on resource use in a generalist predator, European perch (Perca fluviatilis), in 17 lakes in Sweden and Germany. We found that the impact of DOC on habitat coupling depended on fish ecotype, while both ecotypes showed increases in pelagic resource use, this will increase coupling by littoral fish, while decreasing coupling by pelagic fish. Though we found no direct effect of temperature on resource use, we did find that fish size, which decreases with warming, has an impact. We show that in the future, as fish size decreases and DOC increases, generalist predators will couple habitats less and have a more narrow dietary niche width. This shows that while perch will respond flexibly to changes in resource availability, stability may decrease in the process.
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| 4. |
- Andersson, Matilda L., et al.
(författare)
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Habitat specific impacts of warming and browning on a generalist freshwater predator
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Mobile generalist predators are important components of community food webs because they can forage over a large spatial range and provide links that mediate ecosystem responses to climate change. However, many species show intraspecific variation in habitat and resource use. By evaluating the effects of increased temperature and water color on a predator fish living in two contiguous habitats, we can better understand how climate change effects can be mediated by specific ecotypes’ responses, and the implications for future ecosystem functioning.Using a space for time approach, our study examines the impact of increased temperature and water color of inland waters on European perch (Perca fluviatilis) populations, differentiating between the effects on perch inhabiting littoral and pelagic habitats. We found that littoral perch abundance decreased with increasing water color, likely as a result of decreased fecundity and prey availability. Average littoral perch size decreased with increasing temperatures reinforcing the negative effects of browning in reducing littoral perch biomass. In contrast, the biomass of pelagic perch increased with increasing temperature due to increased abundance and was not impacted by water color. Combined, this resulted in a shift towards a higher proportion of the perch population occupying the pelagic habitat in warmer lakes. These shifts in size and abundance at the lake level and between habitats are likely to impact ecosystem functioning and stability as the climate continues to change and will also affect fisheries and recreation.
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| 5. |
- Andersson, Matilda L., et al.
(författare)
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The interaction between metabolic rate, habitat choice, and resource use in a polymorphic freshwater species
- 2022
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 12:8
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Tidskriftsartikel (refereegranskat)abstract
- 1. Resource polymorphism is common across taxa and can result in alternate ecotypes with specific morphologies, feeding modes, and behaviours that increase performance in a specific habitat. This can result in high intraspecific variation in the expression of specific traits and the extent to which these traits are correlated within a single population. Although metabolic rate influences resource acquisition and the overall pace of life of individuals it is not clear how metabolic rate interact with the larger suite of traits to ultimately determine individual fitness.2. We examined the relationship between metabolic rates and the major differences (habitat use, morphology, and resource use) between littoral and pelagic ecotypes of European perch (Perca fluviatilis) from a single lake in Central Sweden.3. Standard metabolic rate (SMR) was significantly higher in pelagic perch but did not correlate with resource use or morphology. Maximum metabolic rate (MMR) was not correlated with any of our explanatory variables or with SMR. Aerobic scope (AS) showed the same pattern as SMR, differing across habitats, but contrary to expectations was lower in pelagic perch.4. This study helps to establish a framework for future experiments further exploring the drivers of intraspecific differences in metabolism. In addition, since metabolic rates scale with temperature and determine predator energy requirements, our observed differences in SMR across habitats will help determine ecotype-specific vulnerabilities to climate change and differences in top-down predation pressure across habitats.
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| 6. |
- Bartels, Pia, et al.
(författare)
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Dissolved Organic Carbon Reduces Habitat Coupling by Top Predators in Lake Ecosystems
- 2016
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Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 19, s. 955-967
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Tidskriftsartikel (refereegranskat)abstract
- Increasing input of terrestrial dissolved organic carbon (DOC) has been identified as a widespread environmental phenomenon in many aquatic ecosystems. Terrestrial DOC influences basal trophic levels: it can subsidize pelagic bacterial production and impede benthic primary production via light attenuation. However, little is known about the impacts of elevated DOC concentrations on higher trophic levels, especially on top consumers. Here, we used Eurasian perch (Perca fluviatilis) to investigate the effects of increasing DOC concentrations on top predator populations. We applied stable isotope analysis and geometric morphometrics to estimate long-term resource and habitat utilization of perch. Habitat coupling, the ability to exploit littoral and pelagic resources, strongly decreased with increasing DOC concentrations due to a shift toward feeding predominantly on pelagic resources. Simultaneously, resource use and body morphology became increasingly alike for littoral and pelagic perch populations with increasing DOC, suggesting more intense competition in lakes with high DOC. Eye size of perch increased with increasing DOC concentrations, likely as a result of deteriorating visual conditions, suggesting a sensory response to environmental change. Increasing input of DOC to aquatic ecosystems is a common result of environmental change and might affect top predator populations in multiple and complex ways.
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| 7. |
- Bartels, Pia
(författare)
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Ecology across Boundaries : Food web coupling among and within ecosystems
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 8. |
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| 9. |
- Bartels, Pia, et al.
(författare)
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Reciprocal subsidies between freshwater and terrestrial ecosystems structure consumer resource dynamics
- 2012
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 93:5, s. 1173-1182
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Bartels, Pia, et al.
(författare)
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Terrestrial subsidies to lake food webs : an experimental approach
- 2012
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Ingår i: Oecologia. - New York : Springer. - 0029-8549 .- 1432-1939. ; 168:3, s. 807-818
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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