| 1. |
- Huss, Magnus, et al.
(författare)
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Experimental evidence of gradual size-dependent shifts in body size and growth of fish in response to warming
- 2019
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 25, s. 2285-2295
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Tidskriftsartikel (refereegranskat)abstract
- A challenge facing ecologists trying to predict responses to climate change is the few recent analogous conditions to use for comparison. For example, negative relationships between ectotherm body size and temperature are common both across natural thermal gradients and in small-scale experiments. However, it is unknown if short-term body size responses are representative of long-term responses. Moreover, to understand population responses to warming, we must recognize that individual responses to temperature may vary over ontogeny. To enable predictions of how climate warming may affect natural populations, we therefore ask how body size and growth may shift in response to increased temperature over life history, and whether short-and long-term growth responses differ. We addressed these questions using a unique setup with multidecadal artificial heating of an enclosed coastal bay in the Baltic Sea and an adjacent reference area (both with unexploited populations), using before-after control-impact paired time-series analyses. We assembled individual growth trajectories of similar to 13,000 unique individuals of Eurasian perch and found that body growth increased substantially after warming, but the extent depended on body size: Only among small-bodied perch did growth increase with temperature. Moreover, the strength of this response gradually increased over the 24 year warming period. Our study offers a unique example of how warming can affect fish populations over multiple generations, resulting in gradual changes in body growth, varying as organisms develop. Although increased juvenile growth rates are in line with predictions of the temperature-size rule, the fact that a larger body size at age was maintained over life history contrasts to that same rule. Because the artificially heated area is a contemporary system mimicking a warmer sea, our findings can aid predictions of fish responses to further warming, taking into account that growth responses may vary both over an individual's life history and over time.
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| 2. |
- Huss, Magnus, et al.
(författare)
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Larval fish body growth responses to simultaneous browning and warming
- 2021
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 11, s. 15132-15140
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Tidskriftsartikel (refereegranskat)abstract
- Organisms are facing global climate change and other anthropogenic pressures, but most research on responses to such changes only considers effects of single drivers. Observational studies and physiological experiments suggest temperature increases will lead to faster growth of small fish. Whether this effect of warming holds in more natural food web settings with concurrent changes in other drivers, such as darkening water color ("browning") is, however, unknown. Here, we set up a pelagic mesocosm experiment with large bags in the Baltic Sea archipelago, inoculated with larval Eurasian perch (Perca fluviatilis) and zooplankton prey and varying in temperature and color, to answer the question how simultaneous warming and browning of coastal food webs impact body growth and survival of larval perch. We found that browning decreased body growth and survival of larval perch, whereas warming increased body growth but had no effect on survival. Based on daily fish body growth estimates based on otolith microstructure analysis, and size composition and abundance of available prey, we explain how these results may come about through a combination of physiological responses to warming and lower foraging efficiency in brown waters. We conclude that larval fish responses to climate change thus may depend on the relative rate and extent of both warming and browning, as they may even cancel each other out.
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| 3. |
- Van Dorst, Renee, et al.
(författare)
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Does browning-induced light limitation reduce fish body growth through shifts in prey composition or reduced foraging rates?
- 2020
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Ingår i: Freshwater Biology. - : WILEY. - 0046-5070 .- 1365-2427. ; 65:5, s. 947-959
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Tidskriftsartikel (refereegranskat)abstract
- Browning of waters, coupled to climate change and land use changes, can strongly affect aquatic ecosystems. Browning-induced light limitation may have negative effects on aquatic consumers via shifts in resource composition and availability and by negatively affecting foraging of consumers relying on vision. However, the extent to which light limitation caused by browning affects fish via either of these two pathways is largely unknown. Here we specifically test if fish growth responses to browning in a pelagic food web are best explained by changes in resource availability and composition due to light limitation, or by reduced foraging rates due to decreased visual conditions. To address this question, we set up a mesocosm experiment to study growth responses of two different fish species to browning and conducted an aquaria experiment to study species-specific fish foraging responses to browning. Furthermore, we used a space-for-time approach to analyse fish body length-at-age across >40 lakes with a large gradient in lake water colour to validate experimental findings on species-specific fish growth responses. With browning, we found an increase in chlorophyll a concentrations, shifts in zooplankton community composition, and a decrease in perch (Perca fluviatilis) but not roach (Rutilus rutilus) body growth. We conclude that fish growth responses are most likely to be linked to the observed shift in prey (zooplankton) composition. In contrast, we found limited evidence for reduced perch, but not roach, foraging rates in response to browning. This suggests that light limitation led to lower body growth of perch in brown waters mainly through shifts in resource composition and availability, perhaps in combination with decreased visibility. Finally, with the lake study we confirmed that perch but not roach body growth and length-at-age are negatively affected by brown waters in the wild. In conclusion, using a combination of experimental and observational data, we show that browning of lakes is likely to (continue to) result in reductions in fish body growth of perch, but not roach, as a consequence of shifts in prey availability and composition, and perhaps reduced foraging.
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| 4. |
- Van Dorst, Renee, et al.
(författare)
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Ecosystem heating experiment reveals sex-specific growth responses in fish
- 2024
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 0706-652X .- 1205-7533. ; 81, s. 90–96 -
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Tidskriftsartikel (refereegranskat)abstract
- Size-specific body growth responses to warming are common among animal taxa, but sex-specific responses are poorly known. Here we ask if body growth responses to warming are sex-dependent, and if such sex-specific responses vary with size and age. This was tested with sex-specific data of back-calculated individual growth trajectories, in European perch (Perca fluviatilis) from a long-term whole-ecosystem warming experiment (6.3 C above the surrounding sea). Warming led to both size- and sex-specific differences in growth responses. Warming had a consistent positive effect on body growth of females, but negative effects on male growth at size > 10 cm and age > 2 years. These sex-specific growth responses translate to an increased degree of female-biased sexual size dimorphism (in length-at-age) with warming. Although the exact temperature-mediated effects underlying differential growth responses could not be resolved, results imply global warming may have highly different effects during ontogeny of male and female perch. Such effects should be considered in climate warming scenarios concerning fish growth, population size-structure, and dynamics of aquatic food webs that include fish exhibiting sexual size dimorphism.
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| 5. |
- Van Dorst, Renee
(författare)
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How do warmer and darker waters influence population dynamics in size-structured fish communities?
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Changes associated with an increased water temperature due to global climate change have potentially large consequences for aquatic organisms. However, not only temperature but also the amount of precipitation is increasing. This increased precipitation leads to increased runoff from terrestrial ecosystems into lakes and coastal waters, introducing brown coloured humic substances containing dissolved organic carbon, leading to browner waters. This browning leads to a decrease of light in the water, which may reduce both primary production and visibility. The reduced visibility can, in turn, impact organisms dependent on light for e.g. feeding, mating, and predator evasion. Warmer and browner waters can influence aquatic ecosystems on several levels of biological organization: individuals, populations and communities. The impacts on fish populations and communities mostly arise from individual-level impacts and interactions. To understand how this works, knowledge of how food-dependent body growth and size-dependent food intake impact fish population and community dynamics is needed. Some of the separate impacts of warming and browning on fish are well studied on multiple organizational levels. It is known that both warming and browning can have considerable influences on both availability and uptake of resources in aquatic systems. This influence can have immediate impact on fish individuals and populations, but also shift competitive ability among individuals of different sizes. As a consequence, there may be changes in growth rates, mean body size, fish productivity and species composition in response to warming and browning. Climate change often results in both warmer and darker lakes. Still, the combination of warmer and darker water bodies on fish individuals, populations, and communities, have not been studied extensively. In combination, the various effects of warming and browning might even be more pronounced than individually. As fish populations and communities are important for both ecosystem function, and recreational and commercial fisheries, it is important to identify the knowledge gaps concerning the combined impact of an increase in temperature and browning. In this essay I identify big gaps in our current knowledge on the combined effects of temperature and browning on interacting fish individuals and populations. The knowledge arising from future studies on combined climate change effects on interacting fish species can, for example, be used to adapt current fisheries management strategies to a future climate characterized by warmer and darker lakes.
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| 6. |
- Van Dorst, Renee
(författare)
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Trophic Transfer Efficiency in Lakes
- 2022
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Ingår i: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 25, s. 1628–165-
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Forskningsöversikt (refereegranskat)abstract
- Trophic transfer efficiency (TTE) is usually calculated as the ratio of production rates between two consecutive trophic levels. Although seemingly simple, TTE estimates from lakes are rare. In our review, we explore the processes and structures that must be understood for a proper lake TTE estimate. We briefly discuss measurements of production rates and trophic positions and mention how ecological efficiencies, nutrients (N, P) and other compounds (fatty acids) affect energy transfer between trophic levels and hence TTE. Furthermore, we elucidate how TTE estimates are linked with size-based approaches according to the Metabolic Theory of Ecology, and how food-web models can be applied to study TTE in lakes. Subsequently, we explore temporal and spatial heterogeneity of production and TTE in lakes, with a particular focus on the links between benthic and pelagic habitats and between the lake and the terrestrial environment. We provide an overview of TTE estimates from lakes found in the published literature. Finally, we present two alternative approaches to estimating TTE. First, TTE can be seen as a mechanistic quantity informing about the energy and matter flow between producer and consumer groups. This approach is informative with respect to food-web structure, but requires enormous amounts of data. The greatest uncertainty comes from the proper consideration of basal production to estimate TTE of omnivorous organisms. An alternative approach is estimating food-chain and food-web efficiencies, by comparing the heterotrophic production of single consumer levels or the total sum of all heterotrophic production including that of heterotrophic bacteria to the total sum of primary production. We close the review by pointing to a few research questions that would benefit from more frequent and standardized estimates of TTE in lakes.
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| 7. |
- Van Dorst, Renee, et al.
(författare)
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Warmer and browner waters decrease fish biomass production
- 2019
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Ingår i: Global Change Biology. - : WILEY. - 1354-1013 .- 1365-2486. ; 25:4, s. 1395-1408
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Tidskriftsartikel (refereegranskat)abstract
- Climate change studies have long focused on effects of increasing temperatures, often without considering other simultaneously occurring environmental changes, such as browning of waters. Resolving how the combination of warming and browning of aquatic ecosystems affects fish biomass production is essential for future ecosystem functioning, fisheries, and food security. In this study, we analyzed individual- and population-level fish data from 52 temperate and boreal lakes in Northern Europe, covering large gradients in water temperature and color (absorbance, 420 nm). We show that fish (Eurasian perch, Perca fluviatilis) biomass production decreased with both high water temperatures and brown water color, being lowest in warm and brown lakes. However, while both high temperature and brown water decreased fish biomass production, the mechanisms behind the decrease differed: temperature affected the fish biomass production mainly through a decrease in population standing stock biomass, and through shifts in size- and age-distributions toward a higher proportion of young and small individuals in warm lakes; brown water color, on the other hand, mainly influenced fish biomass production through negative effects on individual body growth and length-at-age. In addition to these findings, we observed that the effects of temperature and brown water color on individual-level processes varied over ontogeny. Body growth only responded positively to higher temperatures among young perch, and brown water color had a stronger negative effect on body growth of old than on young individuals. Thus, to better understand and predict future fish biomass production, it is necessary to integrate both individual- and population-level responses and to acknowledge within-species variation. Our results suggest that global climate change, leading to browner and warmer waters, may negatively affect fish biomass production, and this effect may be stronger than caused by increased temperature or water color alone.
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| 8. |
- Van Dorst, Renee
(författare)
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Warmer and browner waters: fish responses vary with size, sex, and species
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Current understanding of fish population responses to climate change is often limited to studies on the effect of temperature, ignoring potential co-occurring changes in other environmental variables. However, next to getting warmer, temperate and boreal aquatic systems are getting browner due to increased concentrations of dissolved organic carbon. Studies also generally predict mean population responses to climate change, thereby ignoring the potential for size, sex, and also species-specific responses. In this thesis, I aim to study the effects of warmer and browner waters on individual and population level responses in fish, and investigate if these responses vary with size, sex, and between species (Eurasian perch, Perca fluviatilis or common roach, Rutilus rutilus). To do this I used multiple methods, including space-for-time analyses, a wholeecosystem warming experiment, and aquaria and mesocosm experiments. I found that both warming and browning of lakes will likely decrease fish biomass production. Warming may cause a shift in size-structure towards smaller perch individuals and a lower perch population biomass, while browning will likely affect perch biomass production through lower body growth. Body growth responses to warming likely depend on body size, as small but not large individuals in my study were positively affected by high temperatures, and also sex, as males were more negatively affected by warming than females. Responses to browning may vary with body size and between species, as I found browning had a stronger negative effect on body growth of larger individuals in perch, while in roach browning only affected very small individuals. Overall, my findings suggest that future warming and browning will negatively affect fish individuals and populations, but that responses will vary with size, sex, and species, with potential consequences for ecological interactions and ecosystem functioning. This thesis highlights the importance of considering multiple climate stressors, integrating responses across several levels of biological organization, and acknowledging withinand between species variation, in order to understand and predict fish population responses to further climate change.
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| 9. |
- Van Dorst, Renee, et al.
(författare)
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Zooplanktivore fish body growth responses to browning-induced light limitation vary over ontogeny, but not with fish density
- 2022
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Ingår i: Ecology of Freshwater Fish. - : John Wiley & Sons. - 0906-6691 .- 1600-0633. ; 31:1, s. 17-28
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Tidskriftsartikel (refereegranskat)abstract
- Ongoing climate change is leading to browning of many lakes and coastal areas, which can impair fish body growth and biomass production. However, whether and how effects of light limitation caused by browning on fish body growth vary over early ontogeny is unknown. In this study, we set up a mesocosm experiment to test whether roach (Rutilus rutilus) body growth responses to browning depend on body size, and if findings are robust over roach densities. We also studied a potential mechanism for size-specific responses by conducting an aquaria experiment to test if size-specific prey selectivity in roach changes with browning. We found that roach body growth responses to browning-induced light limitation vary over ontogeny (independent of roach density), negatively affecting body growth of young-of-the-year (YOY) but not of 1-year-old individuals. We also show that this difference in growth response is likely a consequence of browning-induced alterations in zooplankton community composition and variation in prey selectivity between YOY and 1-year-old fish. This suggests that we should account for the diverse effects of browning over fish ontogeny, mediated via altered prey composition and ontogenetic changes in prey preference, when assessing overall impacts of browning on aquatic ecosystems.
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