| 1. |
- Ask, Jenny, et al.
(författare)
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Importance of coastal primary production in the northern Baltic Sea
- 2016
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 45:6, s. 635-648
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we measured depth-dependent benthic microalgal primary production in a Bothnian Bay estuary to estimate the benthic contribution to total primary production. In addition, we compiled data on benthic microalgal primary production in the entire Baltic Sea. In the estuary, the benthic habitat contributed 17 % to the total annual primary production, and when upscaling our data to the entire Bothnian Bay, the corresponding value was 31 %. This estimated benthic share (31 %) is three times higher compared to past estimates of 10 %. The main reason for this discrepancy is the lack of data regarding benthic primary production in the northern Baltic Sea, but also that past studies overestimated the importance of pelagic primary production by not correcting for system-specific bathymetric variation. Our study thus highlights the importance of benthic communities for the northern Baltic Sea ecosystem in general and for future management strategies and ecosystem studies in particular.
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| 2. |
- Byström, Mikael, et al.
(författare)
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Invandringens historia : från "folkhemmet" till dagens Sverige
- 2017
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Med denna kunskapsöversikt, som sträcker sig från folkhemsbygget under 1930-talet fram till dags dato, vill Delmi bidra till att ge en överskådlig bild av migrationen och dess betydelse. Översikten baserar sig på ett rikt urval av befintlig forskning på olika områden och den behandlar tre större frågekomplex: Hur utformades invandrings- och invandrarpolitiken? Vilka bakomliggande föreställningar styrde debatter, media och beslutsfattare? Hur såg praktiken ut när det gäller mottagande, försörjning, bemötande och deltagande i samhälls- och arbetsliv?
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| 3. |
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| 4. |
- Byström, Pär, et al.
(författare)
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Declining coastal piscivore populations in the Baltic Sea : where and when do sticklebacks matter?
- 2015
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 44:Suppl 3, s. S462-S471
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Tidskriftsartikel (refereegranskat)abstract
- Intraguild predation interactions make fish communities prone to exhibit alternative stable states with either piscivore or prey fish dominance. In the Baltic Sea, local declines of coastal piscivores like perch (Perca fluviatilis) have been observed to coincide with high densities of sticklebacks (Gasterosteus aculeatus). Mechanisms behind this shift between piscivore and stickleback dominance were studied both experimentally and in field. Results showed that predation by sticklebacks has a strong negative effect on perch larvae survival, but this effect rapidly decreases with increasing perch size, likely due to gape limitations and digestion constraints in sticklebacks. Large spatial and temporal variations in patterns of stickleback migration into perch spawning sites were observed. Whether or not high density of sticklebacks will cause declines in coastal piscivore populations is suggested to depend on the availability of spawning sites in which sticklebacks do not migrate into or arrive late in the reproduction season of coastal piscivores.
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| 5. |
- Calboli, Federico C. F., et al.
(författare)
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A test for within-lake niche differentiation in the nine-spined sticklebacks (Pungitius pungitius)
- 2016
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 6:14, s. 4753-4760
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Tidskriftsartikel (refereegranskat)abstract
- Specialization for the use of different resources can lead to ecological speciation. Accordingly, there are numerous examples of ecologically specialized pairs of fish species in postglacial lakes. Using a polymorphic panel of single nucleotide variants, we tested for genetic footprints of within-lake population stratification in nine-spined sticklebacks (Pungitius pungitius) collected from three habitats (viz. littoral, benthic, and pelagic) within a northern Swedish lake. Analyses of admixture, population structure, and relatedness all supported the conclusion that the fish from this lake form a single interbreeding unit.
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| 6. |
- Capo, Eric, et al.
(författare)
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Droplet digital PCR assays for the quantification of brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) from environmental DNA collected in the water of mountain lakes
- 2019
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- Classical methods for estimating the abundance of fish populations are often both expensive, time-consuming and destructive. Analyses of the environmental DNA (eDNA) present in water samples could alleviate such constraints. Here, we developed protocols to detect and quantify brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) populations by applying the droplet digital PCR (ddPCR) method to eDNA molecules extracted from water samples collected in 28 Swedish mountain lakes. Overall, contemporary fish CPUE (catch per unit effort) estimates from standardized survey gill nettings were not correlated to eDNA concentrations for either of the species. In addition, the measured environmental variables (e.g. dissolved organic carbon concentrations, temperature, and pH) appear to not influence water eDNA concentrations of the studied fish species. Detection probabilities via eDNA analysis showed moderate success (less than 70% for both species) while the presence of eDNA from Arctic char (in six lakes) and brown trout (in one lake) was also indicated in lakes where the species were not detected with the gillnetting method. Such findings highlight the limits of one or both methods to reliably detect fish species presence in natural systems. Additional analysis showed that the filtration of water samples through 1.2 mu m glass fiber filters and 0.45 mu m mixed cellulose ester filters was more efficient in recovering DNA than using 0.22 mu m enclosed polyethersulfone filters, probably due to differential efficiencies of DNA extraction. Altogether, this work showed the potentials and limits of the approach for the detection and the quantification of fish abundance in natural systems while providing new insights in the application of the ddPCR method applied to environmental DNA.
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| 7. |
- Degerman, Rickard, et al.
(författare)
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Food web interactions determine energy transfer efficiency and top consumer responses to inputs of dissolved organic carbon
- 2018
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 805:1, s. 131-146
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Tidskriftsartikel (refereegranskat)abstract
- Climate change projections indicate increased precipitation in northern Europe, leading to increased inflow of allochthonous organic matter to aquatic systems. The food web responses are poorly known, and may differ depending on the trophic structure. We performed an experimental mesocosm study where effects of labile dissolved organic carbon (DOC) on two different pelagic food webs were investigated, one having zooplankton as highest trophic level and the other with planktivorous fish as top consumer. In both food webs, DOC caused higher bacterial production and lower food web efficiency, i.e., energy transfer efficiency from the base to the top of the food web. However, the top-level response to DOC addition differed in the zooplankton and the fish systems. The zooplankton production increased due to efficient channeling of energy via both the bacteria land the phytoplankton pathway, while the fish production decreased due to channeling of energy mainly via the longer and less efficient bacterial pathway. We conclude that the added DOC either acted as a subsidy by increasing the production of the top trophic level (mesozooplankton), or as a sink causing decreased top consumer production (planktivorous fish).
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| 8. |
- Hamdan, Mohammed, et al.
(författare)
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Carbon dioxide stimulates lake primary production
- 2018
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Gross primary production (GPP) is a fundamental ecosystem process that sequesters carbon dioxide (CO2) and forms the resource base for higher trophic levels. Still, the relative contribution of different controls on GPP at the whole-ecosystem scale is far from resolved. Here we show, by manipulating CO2 concentrations in large-scale experimental pond ecosystems, that CO2 availability is a key driver of whole-ecosystem GPP. This result suggests we need to reformulate past conceptual models describing controls of lake ecosystem productivity and include our findings when developing models used to predict future lake ecosystem responses to environmental change.
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| 9. |
- Hedström, Per, 1974-, et al.
(författare)
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Brownification increases winter mortality in fish
- 2017
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 183:2, s. 587-595
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Tidskriftsartikel (refereegranskat)abstract
- In northernclimateswinter is a bottleneck for many organisms. Low light and resource availability constrain individual foraging rates,potentially leading tostarvation and increasedmortality.Increasinginput of humic substances to aquatic ecosystems causesbrownification of water and hence a further decreaseof light availability,which may lead tofurther decreased foraging ratesand starvation mortality during winter.To test this hypothesis, we measured the effectsof experimentally increased humicwaterinput on consumption and survival of young-of-the-year (YOY) three-spined stickleback (Gasterosteus aculeatus) over winterin largeoutdoor enclosures. Population densitieswereestimated in autumn andthefollowing springand food availabilityand consumptionwere monitoredoverwinter. As hypothesized,mortality washigher underhumic(76%)as compared to ambientconditions (64%).Also, body condition and ingested prey biomass werelower under humic conditionseven thoughresource availability wasnotlower under humic conditions. Light conditions were significantly poorer under humic conditions. This suggeststhat increased mortality and decreased body condition and ingested prey biomasswasnot due to decreased resource availability but due todecreasedsearch efficiencyin this visual feeding consumer. Increased future brownification of aquatic systems may therefore negatively affect both recruitment and densities of fish.
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| 10. |
- Hedström, Per, 1974-
(författare)
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Climate change impacts on production and dynamics of fish populations
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ongoing climate change is predicted to increase water temperatures and export of terrestrial dissolved matter (TDOM) to aquatic ecosystems influencing ecosystem productivity, food web dynamics and production of top consumers. Ecosystem productivity is mainly determined by the rates of primary production (GPP) in turn controlled by nutrients, light availability and temperature, while temperature alone affect vital rates like consumption and metabolic rates and maintenance requirements of consumers. Increased level of TDOM causes brownification of water which may cause light limitation in algae and decrease GPP and especially so in the benthic habitat. Temperature increase has a been suggested to increase metabolic rates of consumers to larger extent than the corresponding effect on GPP, which suggest reduced top consumer biomass and production with warming.The aim of this thesis was to experimentally study the effects of increased temperature and TDOM on habitat specific and whole ecosystem GPP and fish densities and production. In a replicated large-scale pond experiment encompassing natural food webs of lotic ecosystems I studied population level responses to warming and brownification in the three- spined stickleback (Gasterosteus aculeatus).Results showed overall that warming had no effect on whole ecosystem GPP, likely due to nutrient limitation, while TDOM input decreased benthic GPP but stimulated pelagic GPP. In fish, results first of all suggested that recruitment in sticklebacks over summer was negatively affected by warming as maintenance requirements in relation to GPP increased and thereby increased starvation mortality of young-of-the-year (YOY) sticklebacks. Secondly, brownification increased mortality over winter in YOY as the negative effect on light conditions likely decreased search efficiency and caused lower consumption rates and starvation over winter in sticklebacks. Third, seasonal production of YOY, older, and total stickleback production was negatively affected by warming, while increased TDOM caused decreased YOY and total fish production. The combined effect of the two was intermediate but still negative. Temperature effects on fish production were likely a result of increased energy requirements of fish in relation to resource production and intake rates whereas the negative effect of TDOM likely was a result of decreased benthic resource production. Finally, effects of warming over a three-year period caused total fish density and biomass and abundance of both mature and old fish to decrease, while proportion of young fish increased. The main cause behind the strong negative effects of warming on fish population biomass and changes in population demographic parameters were likely the temperature driven increased energy requirements relative to resource production and cohort competition.The results from this thesis suggest that predicted climate change impacts on lentic aquatic ecosystems will decrease future densities and biomass of fish and negatively affect fish production and especially so in systems dominated by benthic resource production.
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| 11. |
- Jonsson, Micael, et al.
(författare)
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Climate change modifies the size structure of assemblages of emerging aquatic insects
- 2015
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Ingår i: Freshwater Biology. - : Wiley-Blackwell. - 0046-5070 .- 1365-2427. ; 60:1, s. 78-88
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to not only raise water temperatures, but also to cause brownification of aquatic ecosystems via increased inputs of terrestrial dissolved organic matter. While efforts have been made to understand how increased temperature and brownification separately influence aquatic food webs, their interactive effects have been less investigated. Further, although climate change effects on aquatic ecosystems likely will propagate to terrestrial consumers via changes in aquatic insect emergence, this has rarely been studied. We investigated the effect of climate change on aquatic insect emergence, in a large-scale outdoor pond facility where 16 sections - each containing natural food webs including a fish top-consumer population - were subjected to warming (3 degrees C above ambient temperatures) and/or brownification (by adding naturally humic stream water). Aquatic insect emergence was measured biweekly over 18weeks. We found no effect of warming or brownification on total emergent insect dry mass. However, warming significantly reduced the number of emergent Chironomidae, while numbers of larger taxa, Trichoptera and Ephemeroptera, remained unchanged. On average, 57% and 58% fewer Chironomidae emerged from the warmed clear and humic pond sections, respectively. This substantial decrease in emergent Chironomidae resulted in a changed community structure and on average larger individuals emerging from warm sections as well as from humic sections under ambient conditions. There was also a weak influence of fish biomass on the size structure of emergent aquatic insects, with a positive relationship between individual insect size and total fish biomass, but effects of fish were clearly subordinate to those of warming. Climate change impacts on aquatic systems can have widespread consequences also for terrestrial systems, as aquatic insects are ubiquitous and their emergence represents an important resource flow from aquatic to terrestrial environments. While we found that neither warming nor brownification quantitatively changed total aquatic insect emergence biomass, the warming-induced decrease in number of emergent Chironomidae and the subsequent increase in average body size will likely impact terrestrial consumers relying on emergent aquatic insect as prey.
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| 12. |
- Karlsson, Jan, et al.
(författare)
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Terrestrial organic matter input suppresses biomass production in lake ecosystems
- 2015
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Ingår i: Ecology. - : Ecological Society of America. - 0012-9658 .- 1939-9170. ; 96:11, s. 2870-2876
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Tidskriftsartikel (refereegranskat)abstract
- Terrestrial ecosystems export large amounts of organic carbon (t-OC) but the net effect of this OC on the productivity of recipient aquatic ecosystems is largely unknown. In this study of boreal lakes, we show that the relative contribution of t-OC to individual top consumer (fish) biomass production, and to most of their potential prey organisms, increased with the concentration of dissolved organic carbon (DOC; dominated by t-OC sources) in water. However, the biomass and production of top consumers decreased with increasing concentration of DOC, despite their substantial use (up to 60%) of t-OC. Thus, the results suggest that although t-OC supports individual consumer growth in lakes to a large extent, t-OC input suppresses rather than subsidizes population biomass production.
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| 13. |
- Lagesson, Annelie, et al.
(författare)
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Bioaccumulation of five pharmaceuticals at multiple trophic levels in an aquatic food web : Insights from a field experiment
- 2016
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 568, s. 208-215
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Tidskriftsartikel (refereegranskat)abstract
- Pharmaceuticals derived from manufacturing and human consumption contaminate surface waters worldwide. To what extent such pharmaceutical contamination accumulates and disperses over time in different compartments of aquatic food webs is not well known. In this study we assess to what extent five pharmaceuticals (diphenhydramine, oxazepam, trimethoprim, diclofenac, and hydroxyzine) are taken up by fish (European perch) and four aquatic invertebrate taxa (damselfly larvae, mayfly larvae, waterlouse, and ramshorn snail), by tracing their bioconcentrations over several months in a semi-natural large-scale (pond) system. The results suggest both significant differences among drugs in their capacity to bioaccumulate and differences among species in uptake. While no support for in situ uptake of diclofenac and trimethoprim was found, oxazepam, diphenhydramine, and hydroxyzine were detected in all analyzed species. Here, the highest bioaccumulation factor (tissue:water ratio) was found for hydroxyzine. In the food web, the highest concentrations were found in the benthic species ramshorn snail and waterlouse, indicating that bottom-living organism at lower trophic positions are the prime receivers of the pharmaceuticals. In general, concentrations in the biota decreased over time in response to decreasing water concentrations. However, two interesting exceptions to this trend were noted. First, mayfly larvae (primarily grazers) showed peak concentrations (a fourfold increase) of oxazepam, diphenhydramine, and hydroxyzine about 30 days after initial addition of pharmaceuticals. Second, perch (top-predator) showed an increase in concentrations of oxazepam throughout the study period. Our results show that drugs can remain bioavailable for aquatic organism for long time periods (weeks to months) and even re-enter the food web at a later time. As such, for an understanding of accumulation and dispersion of pharmaceuticals in aquatic food webs, detailed ecological knowledge is required.
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| 14. |
- Lagesson, Annelie, et al.
(författare)
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No evidence of increased growth or mortality in fish exposed to oxazepam in semi-natural ecosystems
- 2018
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 615, s. 608-614
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Tidskriftsartikel (refereegranskat)abstract
- An increasing number of short-term laboratory studies on fish reports behavioral effects from exposure to aquatic contaminants or raised carbon dioxide levels affecting the GABAAreceptor. However, how such GABAergic behavioral modifications (GBMs) impact populations in more complex natural systems is not known. In this study, we induced GBMs in European perch (Perca fluviatilis) via exposure to a GABA agonist (oxazepam) and followed the effects on growth and survival over one summer (70 days) in replicated pond ecosystems. We hypothesized that anticipated GBMs, expressed as anti-anxiety like behaviors (higher activity and boldness levels), that increase feeding rates in laboratory assays, would; i) increase growth and ii) increase mortality from predation. To test our hypotheses, 480 PIT tagged perch of known individual weights, and 12 predators (northern pike, Esox lucius) were evenly distributed in 12 ponds; six control (no oxazepam) and six spiked (15.5 ± 4 μg l− 1 oxazepam [mean ± 1 S.E.]) ponds. Contrary to our hypotheses, even though perch grew on average 16% more when exposed to oxazepam, we found no significant difference between exposed and control fish in growth (exposed: 3.9 ± 1.2 g, control: 2.9 ± 1 g [mean ± 1 S.E.], respectively) or mortality (exposed: 26.5 ± 1.8 individuals pond− 1, control: 24.5 ± 2.6 individuals pond− 1, respectively). In addition, we show that reduced prey capture efficiency in exposed pike may explain the lack of significant differences in predation. Hence, our results suggest that GBMs, which in laboratory studies impact fish behavior, and subsequently also feeding rates, do not seem to generate strong effects on growth and predation-risk in more complex and resource limited natural environments.
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| 15. |
- Macura, Biljana, et al.
(författare)
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Impact of structural habitat modifications in coastal temperate systems on fish recruitment : a systematic review
- 2019
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Ingår i: Environmental Evidence. - : BioMed Central. - 2047-2382. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. As a result, an increasing number of structural modifications occur in coastal nursery and spawning habitats of fish. Concomitant to this increase, there have been declines in many coastal fish populations and changes in the composition of fish communities. As requested by Swedish stakeholders, this review aimed to synthesise scientific evidence of the impact on fish recruitment of structural modifications in temperate coastal areas.Methods: We searched for peer-reviewed and grey literature on such impacts in English, Dutch, Danish, Finnish, German, Swedish and Spanish. Searches were performed in bibliographic databases, specialist websites, bibliographies of review articles. We also contacted stakeholder to find relevant literature. Eligible studies included small- and large-scale field studies in marine systems and large lakes (> 10,000 km(2)) in temperate regions of the Northern and Southern Hemispheres. Included replicated comparisons of fish recruitment between altered and unaltered control areas, comparisons before and after an alteration, or both. Relevant outcomes (response variables) included measures of recruitment defined as abundance of juvenile fish in coastal habitats. All fish species were considered. Articles were screened for eligibility by title, abstract and full text. Eligible studies were critically appraised based on their external and internal validity. From each eligible study of sufficient validity, we extracted information on study design, measured outcomes, exposure, type of comparator, effect modifiers and study findings. Study findings were synthesised narratively.Results: We searched for eligible studies in 15 databases, 24 specialist websites, Google Scholar, and bibliographies of 11 review articles. The review finally included 37 studies that were eligible and of sufficient validity to be considered for final synthesis. Most studies (23 of 37) were from the Northern Hemisphere. Studies varied in design, spatial resolution, target fish species, and type of structural habitat change. This high level of variation did not allow for a quantitative synthesis and prevented us from drawing general conclusions on the impact of structures or structural modifications on fish recruitment. In this review we provide a narrative synthesis of the evidence base and classify eligible studies into six categories (based on type of exposure and comparator). The categories are as follows: the impacts on fish recruitment of: (1) artificial structures in coastal areas, (2) structures designed as fish attractors, (3) large scale urban sprawl, (4) 'novel' habitats, (5) habitat loss, and (6) restoration.Conclusions: This review revealed a very limited evidence base for how structural modifications and marine urban sprawl can affect fish recruitment. Thus, there is a substantial mismatch between stakeholder needs and research evidence. Further, the impact and ecological performance of artificial structures depend both on context and species. Clearly, there is a need for more research on the subject, especially on long-term consequences at larger spatial scales.
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| 16. |
- Macura, Biljana, et al.
(författare)
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What is the impact on fish recruitment of anthropogenic physical and structural habitat change in shallow nearshore areas in temperate systems? : A systematic review protocol
- 2016
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Ingår i: Environmental Evidence. - : Springer Science and Business Media LLC. - 2047-2382. ; 5:1
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Forskningsöversikt (refereegranskat)abstract
- Background:Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. The growing numbers of constructions and other physical and structural alterations of the shoreline often take place in nursery and spawning habitats of many fish and other aquatic species. Several coastal fish populations have seen marked declines in abundance and diversity during the past two decades. A systematic review on the topic would clarify if anthropogenic physical and structural changes of near-shore areas have effects on fish recruitment and which these effects are.Methods:The review will examine how various physical and structural anthropogenic changes of nearshore fish habitats affect fish recruitment. Relevant studies include small- and large-scale field studies in marine and brackish systems or large lakes in temperate regions of the Northern and Southern hemispheres. Relevant studies may be based on comparisons between undisturbed and disturbed areas, before and after disturbance, or both. Relevant outcomes include measures of recruitment defined as abundance of juveniles of nearshore fish communities. Searches will be made for peer-reviewed and grey literature in English, Dutch, Danish, Finnish, German, Swedish and Spanish. All fish species and species groups will be considered in this review. Included relevant studies will be subject to a critical appraisal that will assess study validity. From relevant included studies, we will extract information on study characteristics, measured outcomes, exposure, comparators, effect modifiers and critical appraisal. Data synthesis will contain narrative and summary findings of each included study of sufficient quality. Meta-analysis may be possible in cases where studies report similar types of outcomes.
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| 17. |
- Norlin, Linnea, et al.
(författare)
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Climate change will alter amphibian-mediated nutrient pathways : evidence from Rana temporaria tadpoles in experimental ponds
- 2016
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 61:4, s. 472-485
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Tidskriftsartikel (refereegranskat)abstract
- 1. With global warming, mean temperatures and brownification of many waterbodies are predicted to increase. This may have unknown consequences on aquatic consumer life histories and nutrient content, consumer-mediated nutrient recycling, and nutrient transport between water and land.2. Using a large-scale experimental pond facility, we altered temperature (ambient/+ 4 degrees C) and brownification (clear/humic) in a 2 x 2 factorial design (n = 16 pond sections) to test two aspects of climate change on Rana temporaria tadpole life-history traits and on tadpole-mediated nutrient pathways. On day 16 after hatching, we examined tadpole-mediated nutrient recycling by measuring tadpole nutrient excretion and egestion rates and tadpole body nutrient content. We estimated tadpole growth and development rates from hatching to emergence and measured emergent frog body size and body nutrient content.3. Brownification increased total pond water nutrient availability and total pond water nitrogen (N) : phosphorous (P) ratios. Warming positively affected tadpole growth and development rates, whereas browning increased tadpole growth rate only under ambient temperatures. Emergent frog body P content decreased with warming, but only in the clear treatments. But despite these variations in body nutrient content, body stoichiometry remained within a relatively narrow stoichiometric range for both emergent frogs (P content: 1.4-1.8%, N content: 11.4-11.8% and carbon [C] content: 46.9-51.3%) and tadpoles (P content: 1.1-1.2%, N content: 10.1-11.7% and C content: 48.0-50.5%). Warming increased tadpole body P content and browning had a positive effect on tadpole body N content and tadpole N excretion rates, probably mediated by the increased pond water total N availability.4. We conclude that warming and brownification will interact in changing aquatic consumer growth and body nutrient stoichiometry. In addition, warming has the potential to affect emergent frog body nutrient content and may thus affect nutrient transport from water to land. Last, by increasing pond water N availability, brownification appears to intensify consumer P limitation and thus amplify consumer-meditated N recycling.
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| 18. |
- Olsson, Jens, et al.
(författare)
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The first large-scale assessment of three-spined stickleback (Gasterosteus aculeatus) biomass and spatial distribution in the Baltic Sea
- 2019
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press. - 1054-3139 .- 1095-9289. ; 76:6, s. 1653-1665
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Tidskriftsartikel (refereegranskat)abstract
- Declines in predatory fish in combination with the impact of climate change and eutrophication have caused planktivores, including three-spined stickleback (Gasterosteus aculeatus), to increase dramatically in parts of the Baltic Sea. Resulting impacts of stickleback on coastal and offshore foodwebs have been observed, highlighting the need for increased knowledge on its population characteristics. In this article, we quantify abundance, biomass, size structure, and spatial distribution of stickleback using data from the Swedish and Finnish parts of the Baltic International Acoustic Survey (BIAS) during 2001-2014. Two alternative methods for biomass estimation suggest an increase in biomass of stickleback in the Baltic Proper, stable or increasing mean size over time, and larger individuals toward the north. The highest abundance was found in the central parts of the Baltic Proper and Bothnian Sea. The proportion of stickleback biomass in the total planktivore biomass increased from 4 to 10% in the Baltic Proper and averaged 6% of the total planktivore biomass in the Bothnian Sea. In some years, however, stickleback biomass has ranged from half to almost twice that of sprat (Sprattus sprattus) in both basins. Given the recent population expansion of stickleback and its potential role in the ecosystem, we recommend that stickleback should be considered in future monitoring programmes and in fisheries and environmental management of the Baltic Sea.
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| 19. |
- Rodriguez, Patricia, et al.
(författare)
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Do warming and humic river runoff alter the metabolic balance of lake ecosystems?
- 2016
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Ingår i: Aquatic Sciences. - : Springer Science and Business Media LLC. - 1015-1621 .- 1420-9055. ; 78:4, s. 717-725
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Tidskriftsartikel (refereegranskat)abstract
- Global warming is expected to influence lake gross primary production (GPP) and ecosystem respiration (R) by increasing water temperature and terrestrial export of organic material and inorganic nutrients from the catchment. We experimentally tested the effects of warming (3 A degrees C) and natural humic river runoff, separately and in combination, on habitat-specific and whole ecosystem net ecosystem production (NEP = GPP - R) in replicated large scale (136 m(3)) experimental pond ecosystems over one open water season. Pelagic NEP was reduced by warming and increased with humic river water addition. Littoral NEP (benthos, macrophytes, periphyton) showed an opposite pattern with increasing NEP following warming and decreasing NEP following humic river water addition. These changes were a result of changes in GPP with warming (negative in pelagic, positive in littoral) and with humic water addition (positive in pelagic, negative in littoral), while no effects were observed on pelagic respiration. As a result of the counteracting effects on NEP in pelagic and littoral habitats, whole ecosystem NEP was not affected by the treatments. The study suggests that climate mediated changes in temperature and river runoff have relatively small effects on the overall metabolic balance of shallow aquatic ecosystems but there may be large habitat-specific effects.
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| 20. |
- Rowe, Owen F., et al.
(författare)
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A potential barrier to the spread of the invasive cladoceran Cercopagis pengoi (Ostroumov 1891) in the Northern Baltic Sea
- 2016
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Ingår i: Regional Studies in Marine Science. - : Elsevier BV. - 2352-4855. ; 3, s. 8-17
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Tidskriftsartikel (refereegranskat)abstract
- The spread of the invasive cladoceran Cercopagis pengoi has been well documented in southern areas of the Baltic Sea, however, little research on this invasive species (nor the zooplankton community) has focused on the Gulf of Bothnia (Bothnian Sea and Bay). We analysed data collected over a 12–13 year period at two main stations, one coastal and one offshore, to examine the occurrence of C. pengoi, invasion dynamics, effects on natural zooplankton communities and associated environmental factors. Nine other stations in the Gulf of Bothnia were also examined and the contribution to three-spined stickleback (Gasterosteus aculeatus) diet was quantified. The zooplankton community response apparently differed between coastal and offshore stations with Bosmina, Eurytemora, and Acartia populations being influenced during peak abundances of C. pengoi. It appears that the native zooplankton community has some resilience, returning to its prior structure outside of peak invasion periods. C. pengoi, where present, contributed significantly to stickleback diet. We explored possible barriers for C. pengoi in the Bothnian Bay, suggesting that the low productive Bothnian Bay ecosystem may be incapable of supporting such a predator. This highlights the need for further studies, especially in the light of global climate change.
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| 21. |
- Seekell, David A., et al.
(författare)
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Lake morphometry moderates the relationship between water color and fish biomass in small boreal lakes
- 2018
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Ingår i: Limnology and Oceanography. - : Wiley-Blackwell. - 0024-3590 .- 1939-5590. ; 63:5, s. 2171-2178
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Tidskriftsartikel (refereegranskat)abstract
- Lake morphometry may moderate the effects of water color on fish biomass in boreal lakes, but empirical evidence is scarce because there are a limited number of lakes for which both water color and bathymetry have been measured. We evaluated variations in catch-per-unit-effort (CPUE), an indicator of fish biomass, across orthogonal gradients of light extinction and mean depth in 16 small Swedish lakes (mean depth 1.7-4.8 m, surface area 1-10 ha). Multiple regression coefficients indicated that the effect of light extinction on CPUE was negative, and that the relationship was more negative for deeper lakes than it was for shallower lakes. The pattern was strongest for lakes with mean depths between 2.1 m and 3.5 m. We estimated that 26% of small lakes in boreal Sweden fall within this mean depth range. These results contribute to the growing understanding of how variations in water color and lake morphometry influence patterns of fish biomass across the boreal landscape.
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| 22. |
- Vasconcelos, Francisco Rivera, et al.
(författare)
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Asymmetrical competition between aquatic primary producers in a warmer and browner world
- 2016
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 97:10, s. 2580-2592
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Tidskriftsartikel (refereegranskat)abstract
- In shallow lakes, pelagic and benthic producers engage in spatially asymmetrical resource competition. Pelagic producers intercept the flux of light to the benthic habitat and benthic producers intercept the flux of sediment-derived nutrients to the pelagic habitat. In boreal and subarctic regions, climate change is affecting this interaction both directly through warming and indirectly through increased loading with colored dissolved organic matter (cDOM) from the catchment (brownification). We use a dynamical ecosystem model to explore the consequences of these changing environmental conditions for lake primary production and compare model predictions with the results of an experiment in which we manipulated water temperature and cDOM supply in a 2x2 factorial design. The experiment was performed in field mesocosms large enough to harbor reproducing fish populations and was run over an entire growing season. In agreement with model predictions, benthic algal production and biomass declined and pelagic algal production and biomass increased with browning. Pelagic nutrient concentrations diverged over time between low and high cDOM treatments, suggesting that browning alleviated pelagic algal nutrient limitation by shading benthic competitors and preventing them from intercepting the release of nutrients from the sediment. Warming considerably reduced benthic and pelagic algal production as well as pelagic algalbiomass and total phosphorus. The warming results are only in partial accordance with model expectations, but can be explained by an indirectly inferred, positive response of macrophyte production (which was not included in the model) to warming. Our study suggests that lake ecosystem responses to climate change are mediated by cross-habitat feedbacks between benthic and pelagic producers.
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| 23. |
- Vasconcelos, Francisco Rivera, 1984-, et al.
(författare)
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Bottom-up and top-down effects of browning and warming on shallow lake food webs
- 2019
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 25, s. 504-521
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Tidskriftsartikel (refereegranskat)abstract
- The productivity and trophic structure of aquatic ecosystems is the result of an interplay between bottom-up and top-down forces that operate both within and across the benthic and pelagic compartments of lake food webs. Contemporary and projected climate changes urge the question how this interplay will be affected by increasing inputs of terrestrial derived, dissolved organic matter (‘browning’) and warming. We addressed this issue by exploring how browning and warming affect the behavior of a relatively simple, conceptual model of a shallow lake food web that is compartmentalized into, dynamically coupled, benthic and pelagic components (abiotic resources, primary producers, grazers, and carnivores). We compared model expectations with the results of a factorial manipulation of browning and warming in a replicated, large-scale field experiment. Both the model and the experiment suggest that browning affects the food web from the bottom-up by reducing light supply to the benthic habitat and increasing nutrient supply to the pelagic habitat, with concomitant decreases of benthic and increases of pelagic primary and secondary production. The model also predicts that warming effects should primarily operate via relaxed top-down control by top consumers in the more productive of the two habitats. The latter was only partially supported by the experimental data, possibly because the model still lacks one or two important trophic links, such as the one from pelagic producers to benthic deposit feeders. We propose that our coupled benthic-pelagic food web model provides a useful conceptual starting point for future theoretical and empirical studies of the impacts of environmental changes on shallow lakes.
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| 24. |
- Vasconcelos, Rivera Francisco, et al.
(författare)
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Effects of Terrestrial Organic Matter on Aquatic Primary Production as Mediated by Pelagic-Benthic Resource Fluxes
- 2018
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Ingår i: Ecosystems (New York. Print). - : Springer. - 1432-9840 .- 1435-0629. ; 21:6, s. 1255-1268
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Tidskriftsartikel (refereegranskat)abstract
- Flows of energy and matter across habitat boundaries can be major determinants of the functioning of recipient ecosystems. It is currently debated whether terrestrial dissolved organic matter (tDOM) is a resource subsidy or a resource subtraction in recipient lakes. We present data from a long-term field experiment in which pelagic phosphorus concentration and whole-ecosystem primary production increased with increasing tDOM input, suggesting that tDOM acted primarily as a direct nutrient subsidy. Piecewise structural equation modeling supports, however, a substantial contribution of a second mechanism: colored tDOM acted also as a resource subtraction by shading benthic algae, preventing them from intercepting nutrients released across the sediment-water interface. Inhibition of benthic algae by colored tDOM thus indirectly promoted pelagic algae and whole-ecosystem primary production. We conclude that cross-ecosystem terrestrial DOM inputs can modify light and nutrient flows between aquatic habitats and alter the relative contributions of benthic and pelagic habitats to total primary production. These results are particularly relevant for shallow northern lakes, which are projected to receive increased tDOM runoff.
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