| 1. |
- Greenberg, L A, et al.
(author)
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Effects of kinship on growth and movements of brown trout in field enclosures
- 2002
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In: Ecology of Freshwater Fish. - : Wiley. - 0906-6691 .- 1600-0633. ; 11:4, s. 251-259
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Journal article (peer-reviewed)abstract
- The effect of kinship on growth and use of space by individually PIT-tagged 1+ brown trout was studied for 11 weeks in eight stream enclosures. Each enclosure consisted of two sections, separated by a region containing PIT-detecting antennae, which enabled us to measure use of sections by all individuals. Two types of sibling groups were tested, a single sibling group, F1, consisting of four individuals that were reared together in hatchery tank 'a' (F1(a)) plus four additional siblings of the same family but raised in hatchery tank 'b' (F1(b)), and a mixed sibling group, consisting of four F1(a) individuals plus four siblings from a second family, F2. Based on kin theory and earlier laboratory studies, we expected that growth of the F1(a) individuals in the single sibling group to be greater than that of F1(a) individuals in the mixed family sibling group, but instead we found just the opposite. The variance of growth did not differ between treatments. Nor was there a difference in time F1(a) individuals spent together when they were in mixed versus single sibling groups. We did find that F1(a) individuals changed habitat more frequently than F2 individuals in the mixed sibling group but less frequently than F1(b) in the single sibling groups. Thus, our predictions based on kin theory for growth and behavior of brown trout were not supported by our data, and we suggest that the role of kin recognition for the ecology of salmonids deserves further attention.
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| 2. |
- Ahlberg, Erik, et al.
(author)
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"Vi klimatforskare stödjer Greta och skolungdomarna"
- 2019
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In: Dagens nyheter (DN debatt). - 1101-2447.
-
Journal article (pop. science, debate, etc.)abstract
- DN DEBATT 15/3. Sedan industrialiseringens början har vi använt omkring fyra femtedelar av den mängd fossilt kol som får förbrännas för att vi ska klara Parisavtalet. Vi har bara en femtedel kvar och det är bråttom att kraftigt reducera utsläppen. Det har Greta Thunberg och de strejkande ungdomarna förstått. Därför stödjer vi deras krav, skriver 270 klimatforskare.
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| 3. |
- Ahlgren, Johan, et al.
(author)
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Camouflaged or tanned: plasticity in freshwater snail pigmentation.
- 2013
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In: Biology letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 9:5, s. 4-20130464
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Journal article (peer-reviewed)abstract
- By having phenotypically plastic traits, many organisms optimize their fitness in response to fluctuating threats. Freshwater snails with translucent shells, e.g. snails from the Radix genus, differ considerably in their mantle pigmentation patterns, with snails from the same water body ranging from being completely dark pigmented to having only a few dark patterns. These pigmentation differences have previously been suggested to be genetically fixed, but we propose that this polymorphism is owing to phenotypic plasticity in response to a fluctuating environment. Hence, we here aimed to assess whether common stressors, including ultraviolet radiation (UVR) and predation, induce a plastic response in mantle pigmentation patterns of Radix balthica. We show, in contrast to previous studies, that snails are plastic in their expression of mantle pigmentation in response to changes in UVR and predator threats, i.e. differences among populations are not genetically fixed. When exposed to cues from visually hunting fish, R. balthica increased the proportion of their dark pigmentation, suggesting a crypsis strategy. Snails increased their pigmentation even further in response to UVR, but this also led to a reduction in pattern complexity. Furthermore, when exposed to UVR and fish simultaneously, snails responded in the same way as in the UVR treatment, suggesting a trade-off between photoprotection and crypsis.
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| 4. |
- Ahlgren, Johan, et al.
(author)
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Fleeing towards death - leech-induced behavioural defences increase freshwater snail susceptibility to predatory fish
- 2012
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In: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 121:9, s. 1501-1506
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Journal article (peer-reviewed)abstract
- Prey species are often exposed to multiple predators, which presents several difficulties to prey species. This is especially true when the response to one predator influences the preys susceptibility to other predators. Predator-induced defences have evolved in a wide range of prey species, and experiments involving predators with different hunting strategies allow researchers to evaluate how prey respond to multiple threats. Freshwater snails are known to respond to a variety of predators with both morphological and behavioural defences. Here we studied how freshwater snails Radix balthica responded behaviourally to fish and leech predators, both separately and together. Our aim was to explore whether conflicting predator-induced responses existed and, if so, what effect they had on snail survival when both predatory fish and leeches were present. We found that although R. balthica increased refuge use when exposed to predatory fish, they decreased refuge use when exposed to predatory leeches. When both predators were present, snails showed a stronger response towards leech than fish and responded by leaving the refuge. This response made the snails more susceptible to fish predation, which increased snail mortality when exposed to both fish and leech compared to fish only. We show that predators that have a relatively low predation rate can substantially increase mortality rates by indirect effects. By forcing snails out of refuges such as rock and macrophyte habitats, leeches can indirectly increase predation from molluscivorous fish and may thus affect snail densities.
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| 5. |
- Ahlgren, Johan, et al.
(author)
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Individual boldness is linked to protective shell shape in aquatic snails
- 2015
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In: Biology Letters. - London : Royal society. - 1744-9561 .- 1744-957X. ; 11:4
-
Journal article (peer-reviewed)abstract
- The existence of consistent individual differences in behaviour ('animal personality') has been well documented in recent years. However, how such individual variation in behaviour is maintained over evolutionary time is an ongoing conundrum. A well-studied axis of animal personality is individual variation along a bold-shy continuum, where individuals differ consistently in their propensity to take risks. A predation-risk cost to boldness is often assumed, but also that the reproductive benefits associated with boldness lead to equivalent fitness outcomes between bold and shy individuals over a lifetime. However, an alternative or complementary explanation may be that bold individuals phenotypically compensate for their risky lifestyle to reduce predation costs, for instance by investing in more pronounced morphological defences. Here, we investigate the 'phenotypic compensation' hypothesis, i.e. that bold individuals exhibit more pronounced anti-predator defences than shy individuals, by relating shell shape in the aquatic snail Radix balthica to an index of individual boldness. Our analyses find a strong relationship between risk-taking propensity and shell shape in this species, with bolder individuals exhibiting a more defended shell shape than shy individuals. We suggest that this supports the 'phenotypic compensation' hypothesis and sheds light on a previously poorly studied mechanism to promote the maintenance of personality variation among animals.
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| 6. |
- Ahlgren, Johan, et al.
(author)
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The influence of predator regime on the behaviour and mortality of a freshwater amphipod, Gammarus pulex
- 2011
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 671:1, s. 39-49
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Journal article (peer-reviewed)abstract
- In species with restricted dispersal, traits may become genetically fixed leading to local adaptations. Therefore, predator avoidance in a prey species may differ between populations experiencing different predator regimes, but also between sexes within a population due to different vulnerability to predators. In this study we used male and female Gammarus pulex from two different predator regimes: fishless ponds, where invertebrates are the dominant predators and ponds with predatory fish. In the laboratory we examined refuge use, mortality, leaf decomposition rate and pair-formation in G. pulex when exposed to predator cues from either invertebrate predators or fish. Individuals from fish ponds spent more time in refuge and had a higher mortality than those from fishless ponds independent of predator cues. There was no effect of pond predator regime or predator cues on leaf decomposition rates. Further, fewer individuals formed pairs in G. pulex from fish ponds than from fishless ponds. Male G. pulex had a higher mortality and a higher decomposition rate than females independent of predator cues. However, there was no difference in refuge use between sexes. Our study shows that there are general differences in behaviour traits, both between predator regimes and sexes in G. pulex.
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| 7. |
- Andersson, Matilda L., et al.
(author)
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Linking behavioural type with cannibalism in Eurasian perch
- 2021
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In: PLOS ONE. - : Public Library Science. - 1932-6203. ; 16:12
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Journal article (peer-reviewed)abstract
- The propensity to kill and consume conspecifics (cannibalism) varies greatly between and within species, but the underlying mechanisms behind this variation remain poorly understood. A rich literature has documented that consistent behavioural variation is ubiquitous across the animal kingdom. Such inter-individual behavioural differences, sometimes referred to as personality traits, may have far-reaching ecological consequences. However, the link between predator personality traits and the propensity to engage in cannibalistic interactions remains understudied. Here, we first quantified personality in Eurasian perch (Perca fluviatilis), measured as activity (time spent moving) and sociability (time spent near conspecifics). We then gave perch of contrasting behavioural types the option to consume either conspecific or heterospecific (roach, Rutilus rutilus) prey. Individual perch characterized by a social-active behavioural phenotype (n = 5) selected roach before being cannibalistic, while asocial-inactive perch (n = 17) consumed conspecific and heterospecific prey evenly. Thus, asocial-inactive perch expressed significantly higher rates of cannibalism as compared to social-active individuals. Individual variation in cannibalism, linked to behavioural type, adds important mechanistic understanding to complex population and community dynamics, and also provides insight into the diversity and maintenance of animal personality.
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| 8. |
- Berglund, Olof, et al.
(author)
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Factors influencing organochlorine uptake in age-0 brown trout (Salmo trutta) in lotic environments
- 1997
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In: Canadian Journal of Fisheries and Aquatic Sciences. - 1205-7533. ; 54:12, s. 2767-2774
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Journal article (peer-reviewed)abstract
- In 1994 and 1995, we investigated the relationship between stream morphology and water chemistry and levels of organochlorines (HCB, PCB, and DDT) in young-of-the-year brown trout (Salmo trutta) from 25 streams in southern Sweden. Contrary to earlier findings for lakes, we found a positive relationship between trophic status (total phosphorus) and uptake of persistent pollutants in stream biota (trout). This difference between benthic, stream environments and pelagic, lake environments may be related to processes affecting pollutant uptake, i.e., pollutant "spiralling" or the shift from heterotrophy to autotrophy in streams. Land use in the catchment area of the streams also affected pollutant levels in trout, with higher levels in agricultural landscapes and lower levels in forested areas. Size of catchment area, however, did not influence uptake of pollutants in trout. The results indicate that eutrophication of streams by agricultural activities and excessive nutrient loading may increase uptake of persistent pollutants in stream biota.
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| 9. |
- 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
-
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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| 10. |
- Blake, Chelsea A., et al.
(author)
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Conspecific boldness and predator species determine predation-risk consequences of prey personality
- 2018
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In: Behavioral Ecology and Sociobiology. - : Springer-Verlag New York. - 0340-5443 .- 1432-0762. ; 72:8, s. 1-7
-
Journal article (peer-reviewed)abstract
- Abstract: Individual variation in the behavior of prey can influence predation risk in complex ways. We ran individual roach (Rutilus rutilus), a common freshwater fish, through a standard refuge emergence protocol to characterize their boldness, a key animal personality trait. We then paired a bold and a shy roach and exposed the pair to one of two predator species that have contrasting hunting modes to ascertain how personality traits shaped their survival during predator encounters. When a paired bold and shy prey fish interacted with a perch predator (active foraging mode), bold and shy prey were consumed in almost equal numbers. However, pike predators (ambush foraging mode) selectively consumed more shy prey, and prey body size and boldness score both contributed significantly to which prey fish was eaten. Our findings support the idea that multiple predators with different foraging modes, and hence differential selection on prey personality, could contribute to maintaining variation in personality in prey populations. Furthermore, for social species, including shoaling fish, the ultimate consequences of an individual’s personality may depend upon the personality of its nearby conspecifics. Significance statement: Animals of the same species often look similar, but individuals show differences in their behavior that can have important consequences, for instance when these individuals interact with predators. The common roach is a freshwater fish that shows inter-individual variation in its propensity to take risks, a key personality trait often termed boldness. Variation in boldness may affect the outcome when roach interact with predators, i.e., if they get eaten or survive. However, we found the impact of roachs’ personality type depends on what species of predatory fish they face. When we put a shy and a bold roach together with predatory perch, the roachs’ personality did not significantly affect which individual was eaten. But when the predator was a pike, the predators selectively ate more shy roach, and the likelihood an individual would be eaten depended on their body size.
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| 11. |
- Bohan, A, et al.
(author)
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Networking our way to better Ecosystem Service provision
- 2016
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In: Trends in Ecology & Evolution. - : Elsevier BV. - 1872-8383 .- 0169-5347. ; 31:2, s. 105-115
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Journal article (peer-reviewed)abstract
- The ecosystem services (EcoS) concept is being used increasingly to attach values to natural systems and the multiple benefits they provide to human societies. Ecosystem processes or functions only become EcoS if they are shown to have social and/or economic value. This should assure an explicit connection between the natural and social sciences, but EcoS approaches have been criticized for retaining little natural science. Preserving the natural, ecological science context within EcoS research is challenging because the multiple disciplines involved have very different traditions and vocabularies (common-language challenge) and span many organizational levels and temporal and spatial scales (scale challenge) that define the relevant interacting entities (interaction challenge). We propose a network-based approach to transcend these discipline challenges and place the natural science context at the heart of EcoS research.
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| 12. |
- Bourdeau, P. E., et al.
(author)
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What can aquatic gastropods tell us about phenotypic plasticity? A review and meta-analysis
- 2015
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In: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 115:4, s. 312-321
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Journal article (peer-reviewed)abstract
- There have been few attempts to synthesise the growing body of literature on phenotypic plasticity to reveal patterns and generalities about the extent and magnitude of plastic responses. Here, we conduct a review and meta-analysis of published literature on phenotypic plasticity in aquatic (marine and freshwater) gastropods, a common system for studying plasticity. We identified 96 studies, using pre-determined search terms, published between 1985 and November 2013. The literature was dominated by studies of predator-induced shell form, snail growth rates and life history parameters of a few model taxa, accounting for 67% of all studies reviewed. Meta-analyses indicated average plastic responses in shell thickness, shell shape, and growth and fecundity of freshwater species was at least three times larger than in marine species. Within marine gastropods, species with planktonic development had similar average plastic responses to species with benthic development. We discuss these findings in the context of the role of costs and limits of phenotypic plasticity and environmental heterogeneity as important constraints on the evolution of plasticity. We also consider potential publication biases and discuss areas for future research, indicating well-studied areas and important knowledge gaps.
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| 13. |
- Brodersen, Jakob, et al.
(author)
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Condition-dependent individual decision-making determines cyprinid partial migration
- 2008
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In: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 89:5, s. 1195-1200
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Journal article (peer-reviewed)abstract
- Partial migration is a common phenomenon among many animals and occurs in many types of ecosystems. Understanding the mechanisms behind partial migration is of major importance for the understanding of population dynamics and, eventually, ecosystem processes. We studied the effects of food availability on the seasonal partial migration of cyprinid fish from a lake to connected streams during winter by the use of passive telemetry. Fish with increased access to food were found to migrate in higher proportion, earlier in the season, and to reside in the streams for a longer period compared to fish with decreased access to food. Furthermore, fewer unfed migrants returned to the lake, indicating higher overwinter mortality. Our results suggest that individual fish trade off safety from predation and access to food differently depending on their body condition, which results in a condition-dependent partial migration. Hence, our main conclusion is that individual decision-making is based on assessment of own condition which offers a mechanistic explanation to partial migration. Moreover, this may be of high importance for understanding population responses to environmental variation as well as ecosystem dynamics and stability. Read More: http://www.esajournals.org/doi/abs/10.1890/07-1318.1
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| 14. |
- Brodersen, Jakob, et al.
(author)
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Ecosystem effects of partial fish migration in lakes
- 2008
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In: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 117:1, s. 40-46
-
Journal article (peer-reviewed)abstract
- Migration is a widespread phenomenon in many ecosystems. Most often, studies on migration have focused on how migration strategies are dependent on ecological parameters, but little attention has been paid to the top-down effect of migration on ecosystem processes. Cyprinid fish in many European lakes undergo partial migration, where a part of the population leaves the lake and enters streams for the winter. In this study, we model the effect of partial migration by fish on lower trophic levels in a lake ecosystem. Our results suggest that spring phyto- and zooplankton dynamics, including occurrences of clear-water phases, can be related to the timing and magnitude of partial migration of planktivorous fish. From our results we conclude that partial migration can influence the dynamics of lower trophic levels in the ecosystem. Furthermore, we hypothesize that partial migration may affect the stability of alternative stable states and transitions between them.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Brodersen, Jakob, et al.
(author)
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Optimal Swimming Speed in Head Currents and Effects on Distance Movement of Winter-Migrating Fish.
- 2008
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 3:5
-
Journal article (peer-reviewed)abstract
- Migration is a commonly described phenomenon in nature that is often caused by spatial and temporal differences in habitat quality. However, as migration requires energy, the timing of migration may depend not only on differences in habitat quality, but also on temporal variation in migration costs. Such variation can, for instance, arise from changes in wind or current velocity for migrating birds and fish, respectively. Whereas behavioural responses of birds to such changing environmental conditions have been relatively well described, this is not the case for fish, although fish migrations are both ecologically and economically important. We here use passive and active telemetry to study how winter migrating roach regulate swimming speed and distance travelled per day in response to variations in head current velocity. Furthermore, we provide theoretical predictions on optimal swimming speeds in head currents and relate these to our empirical results. We show that fish migrate farther on days with low current velocity, but travel at a greater ground speed on days with high current velocity. The latter result agrees with our predictions on optimal swimming speed in head currents, but disagrees with previously reported predictions suggesting that fish ground speed should not change with head current velocity. We suggest that this difference is due to different assumptions on fish swimming energetics. We conclude that fish are able to adjust both swimming speed and timing of swimming activity during migration to changes in head current velocity in order to minimize energy use.
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| 19. |
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| 20. |
- Brodersen, Jakob, et al.
(author)
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Variable individual consistency in timing and destination of winter migrating fish
- 2012
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In: Biology Letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 8, s. 21-23
-
Journal article (peer-reviewed)abstract
- Migration is an important event in the life history of many animals, but there is considerable variation within populations in the timing and final destination. Such differential migration at the population level can be strongly determined by individuals showing different consistencies in migratory traits. By tagging individual cyprinid fish with uniquely coded electronic tags, and recording their winter migrations from lakes to streams for 6 consecutive years, we obtained highly detailed long-term information on the differential migration patterns of individuals. We found that individual migrants showed consistent site fidelities for over-wintering streams over multiple migratory seasons and that they were also consistent in their seasonal timing of migration. Our data also suggest that consistency itself can be considered as an individual trait, with migrants that exhibit consistent site fidelity also showing consistency in migratory timing. The finding of a mixture of both consistent and inconsistent individuals within a population furthers our understanding of intrapopulation variability in migration strategies, and we hypothesize that environmental variation can maintain such different strategies.
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| 21. |
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| 22. |
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| 23. |
- Brönmark, Christer, et al.
(author)
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Costs of inducible defence along a resource gradient.
- 2012
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In: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 7:1
-
Journal article (peer-reviewed)abstract
- In addition to having constitutive defence traits, many organisms also respond to predation by phenotypic plasticity. In order for plasticity to be adaptive, induced defences should incur a benefit to the organism in, for example, decreased risk of predation. However, the production of defence traits may include costs in fitness components such as growth, time to reproduction, or fecundity. To test the hypothesis that the expression of phenotypic plasticity incurs costs, we performed a common garden experiment with a freshwater snail, Radix balthica, a species known to change morphology in the presence of molluscivorous fish. We measured a number of predator-induced morphological and behavioural defence traits in snails that we reared in the presence or absence of chemical cues from fish. Further, we quantified the costs of plasticity in fitness characters related to fecundity and growth. Since plastic responses may be inhibited under limited resource conditions, we reared snails in different densities and thereby levels of competition. Snails exposed to predator cues grew rounder and thicker shells, traits confirmed to be adaptive in environments with fish. Defence traits were consistently expressed independent of density, suggesting strong selection from predatory molluscivorous fish. However, the expression of defence traits resulted in reduced growth rate and fecundity, particularly with limited resources. Our results suggest full defence in predator related traits regardless of resource availability, and costs of defence consequently paid in traits related to fitness.
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| 24. |
- Brönmark, Christer, et al.
(author)
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Decoupling of cascading trophic interactions in a freshwater, benthic food chain
- 1996
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In: Oecologia. - Heidelberg, Germany : Springer Berlin/Heidelberg. - 0029-8549 .- 1432-1939. ; 108:3, s. 534-541
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Journal article (peer-reviewed)abstract
- Food chain theory provides explicit predictions for equilibrium biomasses among trophic levels in food chains of different lengths. Empirical studies on freshwater benthic food chains have typically been performed on chains with up to three levels and in field experiments with limited spatial and temporal scale. Here we use a ‘’natural snapshot experiment” approach to study equilibrium biomass and abundance among trophic levels in natural ponds differing only with respect to fish assemblage structure. Forty-four ponds were surveyed for their density and biomass of fish, snails and periphyton. Ponds were divided into three categories based on fish assemblage: ponds with no fish (two trophic levels), ponds with molluscivorous fish (three trophic levels), ponds with molluscivorous fish (three trophic levels) and ponds that also had piscivorous fish (four trophic levels). Ponds without fish had a high density and biomass of snails and a low biomass of periphyton, whereas snails with molluscivorous fish. In the presence of piscivores, molluscivore populations consisted of low numbers of large individuals. Snail assemblages in piscivore ponds were characterised by relatively high densities of small-bodied detritivorous species and periphyton biomass was not significantly different from ponds with three trophic levels. Thus, predictions from classic food chain theory were upheld in ponds with up to three trophic levels. In ponds with four trophic levels, however, there was a decoupling of the trophic cascade at the piscivore-molluscivore level. Gape-limited piscivory, predation on snails by molluscivores that have reached an absolute size refuge from predation, and changes in food preferences of the dominant snails are suggested to explain the observed patterns.
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| 25. |
- Brönmark, Christer, et al.
(author)
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Environmental issues in lakes and ponds: current state and perspectives
- 2002
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In: Environmental Conservation. - 0376-8929. ; 29:3, s. 290-307
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Research review (peer-reviewed)abstract
- Lakes and ponds are habitats of great human importance as they provide water for domestic, industrial and agricultural use as well as providing food. In spite of their fundamental importance to humans, freshwater systems have been severely affected by a multitude of anthropogenic disturbances, which have led to serious negative effects on the structure and function of these ecosystems. The aim of the present study is to review the current state of lake and pond ecosystems and to present a likely scenario for threats against these ecosystems for the time horizon of the year 2025. Predictions are based on a review of the current state, projections of long-term trends, for example in population and global climate, and an analysis of the trends in publications in the scientific literature during the past 25 years (1975-2000). The biodiversity of lake and pond ecosystems is currently threatened by a number of human disturbances, of which the most important include increased nutrient load, contamination, acid rain and invasion of exotic species. Analysis of trends suggests that older, well known threats to biodiversity such as eutrophication, acidification and contamination by heavy metals and organochlorines may become less of a problem in developed countries in the future. New threats such as global warming, ultraviolet radiation, endocrine disruptors and, especially, invasion by exotic species including transgenic organisms will most likely increase in importance. However, in developing countries where priorities other than environmental conservation exist, the threat of eutrophication, acidification and contamination by toxic substances is predicted to continue to increase. Although the future of biodiversity in lakes and ponds is seriously threatened, growing concern for environmental problems, implementation of new environmental strategies and administrations, and international agreements, are positive signs of changes that should improve the ability to manage old as well as new, yet undiscovered, threats.
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| 26. |
- Brönmark, Christer, et al.
(author)
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Indirect effects of fish community structure on submerged vegetation in shallow, eutrophic lakes : an alternative mechanism
- 1992
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In: Hydrobiologia. - Dordrecht : Springer Netherlands. - 0018-8158 .- 1573-5117. ; 243/244:1, s. 293-301
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Journal article (peer-reviewed)abstract
- The loss of submerged macrophytes during eutrophication of shallow takes is a commonly observed phenomenon. The proximate reason for this decline is a reduction of available light due to increasing phytoplankton and/or epiphyton biomass. Here we argue that the ultimate cause for the transition from a macrophyte-dominated state to a phytoplankton-dominated state is a change in fish community structure. A catastrophic disturbance event (e.g. winterkill) acting selectively on piscivores, cascades down food chains, eventually reducing macrophyte growth through shading by epiphyton, an effect that is reinforced by increasing phytoplankton biomass. The transition back from the phytoplankton to the macrophyte state depends on an increase in piscivore standing stock and a reduction of planktivores. A conceptual model of these mechanisms is presented and supported by literature data and preliminary observations from a field experiment. © 1992 Kluwer Academic Publishers.
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| 27. |
- Brönmark, Christer, et al.
(author)
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Ponds as experimental arenas for studying animal movement : current research and future prospects
- 2023
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In: Movement Ecology. - 2051-3933. ; 11
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Research review (peer-reviewed)abstract
- Animal movement is a multifaceted process that occurs for multiple reasons with powerful consequences for food web and ecosystem dynamics. New paradigms and technical innovations have recently pervaded the field, providing increasingly powerful means to deliver fine-scale movement data, attracting renewed interest. Specifically in the aquatic environment, tracking with acoustic telemetry now provides integral spatiotemporal information to follow individual movements in the wild. Yet, this technology also holds great promise for experimental studies, enhancing our ability to truly establish cause-and-effect relationships. Here, we argue that ponds with well-defined borders (i.e. “islands in a sea of land”) are particularly well suited for this purpose. To support our argument, we also discuss recent experiences from studies conducted in an innovative experimental infrastructure, composed of replicated ponds equipped with modern aquatic telemetry systems that allow for unparalleled insights into the movement patterns of individual animals.
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| 28. |
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| 29. |
- Brönmark, Christer, et al.
(author)
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Predator induced morphological plasticity across local populations of a fresh water snail
- 2011
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:7
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Journal article (peer-reviewed)abstract
- The expression of anti-predator adaptations may vary on a spatial scale, favouring traits that are advantageous in a given predation regime. Besides, evolution of different developmental strategies depends to a large extent on the grain of the environment and may result in locally canalized adaptations or, alternatively, the evolution of phenotypic plasticity as different predation regimes may vary across habitats. We investigated the potential for predator-driven variability in shell morphology in a freshwater snail, Radix balthica, and whether found differences were a specialized ecotype adaptation or a result of phenotypic plasticity. Shell shape was quantified in snails from geographically separated pond populations with and without molluscivorous fish. Subsequently, in a common garden experiment we investigated reaction norms of snails from populations' with/without fish when exposed to chemical cues from tench (Tinca tinca), a molluscivorous fish. We found that snails from fish-free ponds had a narrow shell with a well developed spire, whereas snails that coexisted with fish had more rotund shells with a low spire, a shell morphology known to increase survival rate from shell-crushing predators. The common garden experiment mirrored the results from the field survey and showed that snails had similar reaction norms in response to chemical predator cues, i.e. the expression of shell shape was independent of population origin. Finally, we found significant differences for the trait means among populations, within each pond category (fish/fish free), suggesting a genetic component in the determination of shell morphology that has evolved independently across ponds.
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| 30. |
- Brönmark, Christer, et al.
(author)
-
Regime shifts in shallow lakes: the importance of seasonal fish migration
- 2010
-
In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 646:1, s. 91-100
-
Conference paper (peer-reviewed)abstract
- Shallow eutrophic lakes commonly exist in two alternative stable states: a clear-water state and a turbid water state. A number of mechanisms, including both abiotic and biotic processes, buffer the respective states against changes, whereas other mechanisms likely drive transitions between states. Our earlier research shows that a large proportion of zooplanktivorous fish populations in shallow lakes undertake seasonal migrations where they leave the lake during winter and migrate back to the lake in spring. Based on our past research, we propose a number of scenarios of how feedback processes between the individual and ecosystem levels may affect stability of alternative stable states in shallow lakes when mediated by fish migration. Migration effects on shallow lakes result from processes at different scales, from the individual to the ecosystem. Our earlier research has shown that ecosystem properties, including piscivore abundance and zooplankton productivity, affect the individual state of zooplanktivorous fish, such as growth rate or condition. Individual state, in turn, affects the relative proportion and timing of migrating zooplanktivorous fish. This change, in turn, may stabilize states or cause runaway processes that eventually lead to state shifts. Consequently, such knowledge of processes coupled to seasonal migration of planktivorous fish should increase our understanding of shallow lake dynamics.
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| 31. |
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| 32. |
- Brönmark, Christer, et al.
(author)
-
Seasonal migration determined by a trade-off between predator avoidance and growth
- 2008
-
In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 3
-
Journal article (peer-reviewed)abstract
- Migration is a common phenomenon in many organisms, terrestrial as well as aquatic, and considerable effort has been spent to understand the evolution of migratory behaviour and its consequences for population and community dynamics. In aquatic systems, studies on migration have mainly been focused on commercially important fish species, such as salmon and trout. However, seasonal mass-migrations may occur also among other freshwater fish, e.g. in cyprinids that leave lakes and migrate into streams and wetlands in the fall and return back to the lake in spring. In a conceptual model, we hypothesized that this is an adaptive behaviour in response to seasonal changes in predation (P) and growth (G) and that migrating fish change habitat so as to minimise the ratio between predation mortality and growth rate (P/G). Estimates from bioenergetic modelling showed that seasonal changes in the ratio between predator consumption rate and prey growth rate followed the predictions from the conceptual model and also gave more precise predictions for the timing of the habitat change. By quantifying the migration of more than 1800 individually marked fish, we showed that actual migration patterns followed predictions with a remarkable accuracy, suggesting that migration patterns have evolved in response to seasonally fluctuating trade-offs between predator avoidance and foraging gains. Thus, the conceptual model provides a mechanistic understanding to mass–migration in prey fish. Further, we also show that the dominant prey fish is actually absent from the lake during a major part of the year, which should have strong implications for the dynamics of the lake ecosystem through direct and indirect food-web interactions.
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| 33. |
- Brönmark, Christer, et al.
(author)
-
The biology of lakes and ponds
- 2017. - 3rd
-
Book (peer-reviewed)abstract
- This introduction to the biology of standing waters integrates the effects of abiotic constraints and biotic interactions at both the population and community level, and examines how the distribution and success of different organisms in this freshwater habitat can be explained and predicted
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| 34. |
- Brönmark, Christer, et al.
(author)
-
The biology of lakes and ponds (2nd edition)
- 2005
-
Book (other academic/artistic)abstract
- This introduction to the biology of standing waters integrates the effects of abiotic constraints and biotic interactions at both the population and community level, and examines how the distribution and success of different organisms in this freshwater habitat can be explained and predicted
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| 35. |
- Brönmark, Christer, et al.
(author)
-
There and back again : migration in freshwater fishes
- 2014
-
In: Canadian Journal of Zoology. - Ottawa : CANADIAN SCIENCE PUBLISHING. - 0008-4301 .- 1480-3283. ; 92:6, s. 467-479
-
Journal article (peer-reviewed)abstract
- Animal migration is an amazing phenomenon that has fascinated humans for long. Many freshwater fishes also show remarkable migrations, whereof the spectacular mass migrations of salmonids from the spawning streams are the most well known and well studied. However, recent studies have shown that migration occurs in a range of freshwater fish taxa from many different habitats. In this review we focus on the causes and consequences of migration in freshwater fishes. We start with an introduction of concepts and categories of migration, and then address the evolutionary causes that drive individuals to make these migratory journeys. The basis for the decision of an individual fish to migrate or stay resident is an evaluation of the costs and benefits of different strategies to maximize its lifetime reproductive effort. We provide examples by discussing our own work on the causes behind seasonal migration in a cyprinid fish, roach (Rutilus rutilus (L., 1758)), within this framework. We then highlight different adaptations that allow fish to migrate over sometimes vast journeys across space, including capacity for orientation, osmoregulation, and efficient energy expenditure. Following this we consider the consequences of migration in freshwater fish from ecological, evolutionary, and conservation perspectives, and finally, we detail some of the recent developments in the methodologies used to collect data on fish migration and how these could be used in future research.
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| 36. |
- Carlsson, Nils, et al.
(author)
-
Invading herbivory: The golden apple snail alters ecosystem functioning in Asian wetlands
- 2004
-
In: Ecology. - 0012-9658. ; 85:6, s. 1575-1580
-
Journal article (peer-reviewed)abstract
- We investigated the effects of an exotic snail, the golden apple snail (Pomacea canaliculata) on biodiversity and ecosystem functioning in tropical wetland ecosystems. This large snail (up to 80-mm shell height) has invaded large parts of Southeast Asia during recent decades. A survey of natural wetlands in Thailand showed that high densities of the snail were associated with almost complete absence of aquatic plants, high nutrient concentrations, and high phytoplankton biomass, that is, a complete shift in both ecosystem state and function. A field experiment demonstrated that grazing by the snail can cause the loss of aquatic plants, a change toward dominance of planktonic algae, and thereby a shift toward turbid water. Estimates of biologically fixed nutrients released through snails grazing on aquatic plants revealed that phosphorus releases were sufficient to explain the recorded increase in phytoplankton biomass. Hence, our study demonstrates how an herbivore may trigger a shift from clear water and macrophyte dominance to a turbid state dominated by planktonic algae. This shift and the continuing aggressive invasion of this exotic species are detrimental to the integrity and functioning of wetland ecosystems, and to the services these provide in Southeast Asia.
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| 37. |
- Carlsson, Nils, et al.
(author)
-
Size-dependent effects of an invasive herbivorous snail (Pomacea canaliculata) on macrophytes and periphyton in Asian wetlands
- 2006
-
In: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 51:4, s. 695-704
-
Journal article (peer-reviewed)abstract
- 1. The invasive golden apple snail (Pomacea canaliculata), native to South America, is a serious pest on rice seedlings in south-east Asia and has also been shown to consume large amounts of macrophytes in natural wetlands, with large effects on ecosystem functioning. Earlier studies suggest that the snail undergoes an ontogenetic diet shift, feeding on algae and detritus as juveniles and shifting to aquatic macrophytes as adults. 2. Here, we study the effects of snail populations with a size-structure typical of either populations at an invasive front or the size-structure of established populations. In an enclosure experiment performed in a wetland in Laos, we compared treatments with small snails only (3 mm; invasive treatment) to treatments with small, medium sized (10 mm) and adult (> 25 mm) snails (established treatment). The effects of snail grazing on three aquatic macrophyte species and periphytic algae were quantified. 3. We found that snails of all sizes had a strong negative effect on the biomass of all macrophyte species and periphytic algae. There was no evidence of an ontogenetic diet change, i.e. snails in both the invasive and established treatments affected macrophyte biomass. Foraging was size-dependent in that small snails had higher relative foraging capacity (g plant consumed per g of snail) compared with medium and adult snails. Small snails, therefore, depressed growth of medium snails at increasing densities through exploitative competition for preferred resources, while adult snails did not grow at all in the presence of small snails. 4. Density dependence is common in freshwater invertebrates, including gastropod populations, but differences in size dependent foraging- and competitive-ability have rarely been demonstrated in this group of organisms. Knowledge about intra-specific differences in ecological performance may, however, both deepen our understanding of the processes that underlie population dynamics in invertebrates such as gastropods, and help develop control strategies for invasive golden apple snails.
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| 38. |
- Chapman, Ben, et al.
(author)
-
A foraging cost of migration for a partially migratory cyprinid fish
- 2013
-
In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:5
-
Journal article (peer-reviewed)abstract
- Migration has evolved as a strategy to maximise individual fitness in response to seasonally changing ecological and environmental conditions. However, migration can also incur costs, and quantifying these costs can provide important clues to the ultimate ecological forces that underpin migratory behaviour. A key emerging model to explain migration in many systems posits that migration is driven by seasonal changes to a predation/growth potential (p/g) trade-off that a wide range of animals face. In this study we assess a key assumption of this model for a common cyprinid partial migrant, the roach Rutilus rutilus, which migrates from shallow lakes to streams during winter. By sampling fish from stream and lake habitats in the autumn and spring and measuring their stomach fullness and diet composition, we tested if migrating roach pay a cost of reduced foraging when migrating. Resident fish had fuller stomachs containing more high quality prey items than migrant fish. Hence, we document a feeding cost to migration in roach, which adds additional support for the validity of the p/g model of migration in freshwater systems.
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| 39. |
- Chapman, Ben B, et al.
(author)
-
Patterns of Animal Migration
- 2014
-
In: Animal movement across scales. - : Oxford University Press. - 9780199677184 ; , s. 11-35
-
Book chapter (peer-reviewed)
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| 40. |
- Chapman, Ben, et al.
(author)
-
Partial migration: an introduction
- 2011
-
In: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 120:12, s. 1761-1763
-
Journal article (other academic/artistic)
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| 41. |
- Chapman, Ben, et al.
(author)
-
Partial migration in fishes: causes and consequences.
- 2012
-
In: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 81:2, s. 456-478
-
Journal article (peer-reviewed)abstract
- Partial migration, where only some individuals from a population migrate, has been widely reported in a diverse range of animals. In this paper, what is known about the causes and consequences of partial migration in fishes is reviewed. Firstly, the ultimate and proximate drivers of partial migration are reflected upon: what ecological factors can shape the evolution of migratory dimorphism? How is partial migration maintained over evolutionary timescales? What proximate mechanisms determine whether an individual is migratory or remains resident? Following this, the consequences of partial migration are considered, in an ecological and evolutionary context, and also in an applied sense. Here it is argued that understanding the concept of partial migration is crucial for fisheries and ecosystem managers, and can provide information for conservation strategies. The review concludes with a reflection on the future opportunities in this field, and the avenues of research that are likely to be fruitful to shed light on the enduring puzzle of partial migration in fishes.
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| 42. |
- Chapman, Ben, et al.
(author)
-
Partial migration in fishes: definitions, methodologies and taxonomic distribution.
- 2012
-
In: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 81:2, s. 479-499
-
Journal article (peer-reviewed)abstract
- Partial migration, where populations are composed of both migratory and resident individuals, is extremely widespread across the animal kingdom. Researchers studying fish movements have long recognized that many fishes are partial migrants, however, no detailed taxonomic review has ever been published. In addition, previous work and synthesis has been hampered by a varied lexicon associated with this phenomenon in fishes. In this review, definitions and important concepts in partial migration research are discussed, and a classification system of the different forms of partial migration in fishes introduced. Next, a detailed taxonomic overview of partial migration in this group is considered. Finally, methodological approaches that ichthyologists can use to study this fascinating phenomenon are reviewed. Partial migration is more widespread amongst fishes than previously thought, and given the array of techniques available to fish biologists to study migratory variation the future of the field looks promising.
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| 43. |
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| 44. |
- Chapman, Ben, et al.
(author)
-
The ecology and evolution of partial migration
- 2011
-
In: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 120:12, s. 1764-1775
-
Journal article (peer-reviewed)abstract
- Partial migration, where populations of animals are composed of a mixture of resident and migratory individuals, is a widespread phenomenon in nature. It has been reported to occur in all major vertebrate groups, and can have significant ecological consequences. Here we give an overview of the ecology and evolution of partial migration in animals. We firstly review the different types of partial migration, and assess the ecological drivers responsible for driving individual differences in migratory tendency within populations. A variety of factors can be important in promoting the evolution of partial migration, including competition for resources or breeding opportunities, predation risk and intraspecific niche diversity. Often various factors act synergistically to create complex patterns of movement polymorphism within populations. The question of how partial migration is maintained over evolutionary timescales is also addressed. Whilst many theoretical considerations of partial migration utilise an evolutionary stable state (ESS) paradigm, empirical evidence for this is lacking. Rather the evidence suggests that partial migration is mostly condition dependent, and the optimum outcome for an individual is dependent upon its phenotype. What determines whether an individual follows a migratory or resident strategy is discussed in light of new theory and empirical data which supports the idea that environmentally responsive genetic thresholds are important across a range of species, from birds to fish, in proximately shaping migratory tendency. Finally we espouse our vision of how partial migration research will develop in the future, and suggest a number of exciting directions that studies into migratory dimorphism may take in the coming years.
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| 45. |
- Chapman, Ben, et al.
(author)
-
To boldly go: individual differences in boldness influence migratory tendency.
- 2011
-
In: Ecology Letters. - : Wiley. - 1461-023X. ; 14, s. 871-876
-
Journal article (peer-reviewed)abstract
- Ecology Letters (2011) ABSTRACT: Partial migration, whereby only a fraction of the population migrates, is thought to be the most common type of migration in the animal kingdom, and can have important ecological and evolutionary consequences. Despite this, the factors that influence which individuals migrate and which remain resident are poorly understood. Recent work has shown that consistent individual differences in personality traits in animals can be ecologically important, but field studies integrating personality traits with migratory behaviour are extremely rare. In this study, we investigate the influence of individual boldness, an important personality trait, upon the migratory propensity of roach, a freshwater fish, over two consecutive migration seasons. We assay and individually tag 460 roach and show that boldness influences migratory propensity, with bold individuals being more likely to migrate than shy fish. Our data suggest that an extremely widespread personality trait in animals can have significant ecological consequences via influencing individual-level migratory behaviour.
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| 46. |
-
Chemical Ecology in Aquatic Systems
- 2012
-
Editorial collection (other academic/artistic)abstract
- In recent years it has become increasingly clear that chemical interactions play a fundamental role in aquatic habitats and have far-reaching evolutionary and ecological consequences. A plethora of studies have shown that aquatic organisms from most taxa and functional groups respond to minute concentrations of chemical substances released by other organisms. However, our knowledge of this “chemical network” is still relatively undeveloped. Chemical interactions can be divided into two larger sub-areas based on the function of the chemical substance. Firstly there are those interactions where chemical substances are toxic to other organisms and are used as a defence against consumers (including both herbivores and predators), a weapon against competitors (allelopathy), or as a means of reducing overgrowth (anti-fouling). Secondly, chemical substances may be used in communication among aquatic organisms. This is particularly advantageous in aquatic environments where the use of visual signals may be reduced due to poor optical conditions, whereas chemical cues can be carried over considerable distances. Chemical Ecology of Aquatic Systems covers a wide range of studies, both plant and animal, from different geographic regions and habitats - pelagic as well as benthic. Most of the chemical interactions are similar in freshwater and marine habitats and this book therefore strives at integrating work on marine and freshwater systems.. This accessible, research level text is aimed at graduate students and professional researchers in the fields of limnology, marine ecology, evolutionary biology, behavioural ecology, and chemical ecology.
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| 47. |
- Domenici, Paolo, et al.
(author)
-
Predator-induced morphology enhances escape locomotion in crucian carp
- 2008
-
In: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 275:1631, s. 195-201
-
Journal article (peer-reviewed)abstract
- Fishes show a remarkable diversity of shapes which have been associated with their swimming abilities and anti-predator adaptations. The crucian carp (Carassius carassius) provides an extreme example of phenotypic plasticity in body shape which makes it a unique model organism for evaluating the relationship between body form and function in fishes. In crucian carp, a deep body is induced by the presence of pike (Esox lucius), and this results in lower vulnerability to gape-limited predators, such as pike itself. Here, we demonstrate that deep-bodied crucian carp attain higher speed, acceleration and turning rate during anti-predator responses than shallow-bodied crucian carp. Therefore, a predator-induced morphology in crucian carp enhances their escape locomotor performance. The deep-bodied carp also show higher percentage of muscle mass. Therefore, their superior performance in escape swimming may be due to a combination of higher muscle power and higher thrust.
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| 48. |
- Dänhardt, Juliana, et al.
(author)
-
Ekosystemtjänster i det skånska jordbrukslandskapet
- 2013
-
Reports (pop. science, debate, etc.)abstract
- Jordbrukslandskapet tillhandahåller ekosystemtjänster som utgör förutsättningen för en uthållig jordbruksproduktion och är till nytta för samhället i stort. Bakom dessa finns ekologiska processer som beror av samspel mellan en mångfald av organismer. Skånes jordbruk har genomgått betydande förändringar som förändrat landskapet och livsmiljön för många av dessa. För att bevara och förvalta ekosystemtjänsterna krävs en förståelse för sambanden mellan jordbruk, landskap och ekosystemprocesser. Rapporten beskriver ekologiska processer som ligger till grund för några viktiga ekosystemtjänster i Skånes jordbrukslandskap och visar betydelsen av biologisk mångfald för deras funktion. Där så är möjligt beskrivs hur de kan värderas. Slutligen redovisas praktiska åtgärder som gynnar dem. Rapporten visar att ekosystemtjänster inte enkelt går att ersätta med teknologiska lösningar, utan att förvaltning av dessa tjänster lönar sig. Detta kräver ökad ekologisk kunskap och anpassade styrmedel vilket kräver ökat samråd och regelbunden återkoppling mellan lantbrukare, myndigheter och forskare. Förhoppningen är att rapporten, framtagen av Lunds universitet och Region Skåne, inspirerar till detta!
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| 49. |
- Gyllström, Mikael, et al.
(author)
-
Bioturbation as Driver of Zooplankton Recruitment, Biodiversity and Community Composition in Aquatic Ecosystems
- 2008
-
In: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 11:7, s. 1120-1132
-
Journal article (peer-reviewed)abstract
- In an experimental study we assessed if benthic bioturbating invertebrates affect the recruitment (hatching) of zooplankton from the sediment, and if this effect persists as differences in the zooplankton community in the water column, that is, if bioturbation quantitatively stimulates benthic-pelagic coupling. We investigated the effects of four different benthic invertebrates (Asellus aquaticus, Chironomus plumosus, Tubifex tubifex in the presence or absence of the predator Sialis lutaria). In total, 45 zooplankton taxa hatched from the sediment and the hatching success of some of these was dependent on the species identity of the bioturbating invertebrate. The predator Sialis reduced the abundance of all three invertebrate species, but tended to positively influence the zooplankton recruitment rates, possibly through increasing the activity of the bioturbating invertebrates. The most striking effect of bioturbation on the hatching and pelagic zooplankton community properties was that, on average, 11% more species hatched in the Asellus treatment than in any other treatment. This was also mirrored in the zooplankton water column community where, on average, 7% more species established a viable population in treatments with Asellus as bioturbator. In a complementary field survey, Asellus was more common in littoral than in profundal sediments. Because Asellus strongly affected recruitment of zooplankton in our experiment, we argue that bioturbation may partly explain why recruitment of resting stages of both phyto- and zooplankton is generally higher in littoral than in profundal areas.
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| 50. |
- Hallgren, Per, et al.
(author)
-
Synthetic estrogen directly affects fish biomass and may indirectly disrupt aquatic food webs
- 2014
-
In: Environmental Toxicology and Chemistry. - : Wiley. - 0730-7268. ; 33:4, s. 930-936
-
Journal article (peer-reviewed)abstract
- Endocrine-disrupting chemicals are known to alter the fitness of individual organisms via changes in growth, behavior, and reproduction. It is largely unknown, however, whether these effects cascade through the food web and indirectly affect other, less sensitive organisms. The authors present results from a mesocosm experiment whereby the effects of the synthetic estrogen 17α-ethinylestradiol (EE2) were quantified in pelagic communities. Treatment with EE2 at a concentration of 28 ng/L had no large effects on the pelagic communities composed only of phytoplankton and zooplankton. In communities where planktivorous roach (Rutilus rutilus) were also present, however, EE2 caused a significant reduction in fish biomass. Moreover, zooplankton biomass was higher in the EE2 treatments, suggesting that zooplankton may have been released from fish predation. Hence, the direct effect of EE2 on roach may have cascaded down the food web to produce positive indirect effects on zooplankton. This result was supported in complementary foraging experiments with roach, showing reduced foraging performance after exposure to EE2. Despite the observed negative effect of EE2 on roach and the positive indirect effect on zooplankton, these effects did not cascade to phytoplankton, possibly because only copepods, but not cladocerans—the major grazers in these systems—were released from fish predation. The authors conclude that the known reproductive impairment in fish by EE2 in combination with the disturbed foraging performance observed in the present study may be a disadvantage to fish that may result in increasing abundance or biomass of prey such as zooplankton. Hence, EE2 may have consequences for both the structure and function of freshwater communities.
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