| 1. |
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| 2. |
- Tao, Lily S. R., et al.
(författare)
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Stable-isotope based trophic metrics reveal early recovery of tropical crustacean assemblages following a trawl ban
- 2020
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Ingår i: Ecological Indicators. - : Elsevier. - 1470-160X .- 1872-7034. ; 117
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Tidskriftsartikel (refereegranskat)abstract
- Trawl bans are relatively uncommon, particularly at the level of an entire coastal jurisdiction, and have seldom been studied in the tropics. A permanent territory-wide trawl ban has been implemented in Hong Kong coastal waters since the beginning of 2013. We used isotope-based metrics, in addition to traditional community measurements, to determine whether benthic crustacean assemblages had shown any signs of recovery three years after the trawl ban. We expected increases in species richness, abundance and biomass as well as shifts in trophic structure, including longer food-chain length (FCL) and greater trophic diversity after the ban. We further anticipated that carnivorous crustaceans would have higher mean trophic positions (MTPoC) at the assemblage level, and broader trophic niches at the species level. Sampling was undertaken at six sites in three regions (eastern, western and southern waters) before (in 2012) and after (in 2015) the ban. In general, there were no changes in assemblage total abundance or species richness after the trawl ban, but a decrease in biomass was observed. Isotope-based metrics showed that trophic niches of the crustacean assemblages were, however, broader at all sites after the ban. The FCLs at four sites in the eastern and western waters were longer after the ban, and three of them also showed increased MTPoC. In contrast, declines in FCL and other trophic metrics were recorded at the two southern sites. Among the five most abundant carnivorous crustaceans, all species at one eastern site, three at one western site, and four at three other sites expanded their trophic niches after the trawl ban; no changes were evident at the other eastern site where carnivores were scarce. By using isotope-based trophic metrics, we detected early functional recovery of the crustacean assemblages that cannot be revealed by traditional community analyses, implying that the effectiveness of the trawl ban would be underestimated if the assessment was based on community measurements only. We, therefore, advocate the use of isotope-based trophic metrics in tandem with the community measurements for more comprehensive assessments of ecosystem responses to anthropogenic disturbances and management interventions designed to alleviate them.
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| 3. |
- Brett, Michael T., et al.
(författare)
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How important are terrestrial organic carbon inputs for secondary production in freshwater ecosystems?
- 2017
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Ingår i: Freshwater Biology. - : WILEY. - 0046-5070 .- 1365-2427. ; 62:5, s. 833-853
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Forskningsöversikt (refereegranskat)abstract
- 1. Many freshwater systems receive substantial inputs of terrestrial organic matter. Terrestrially derived dissolved organic carbon (t-DOC) inputs can modify light availability, the spatial distribution of primary production, heat, and oxygen in aquatic systems, as well as inorganic nutrient bioavailability. It is also well-established that some terrestrial inputs (such as invertebrates and fruits) provide high-quality food resources for consumers in some systems. 2. In small to moderate-sized streams, leaf litter inputs average approximately three times greater than the autochthonous production. Conversely, in oligo/mesotrophic lakes algal production is typically five times greater than the available flux of allochthonous basal resources. 3. Terrestrial particulate organic carbon (t-POC) inputs to lakes and rivers are comprised of 80%-90% biochemically recalcitrant lignocellulose, which is highly resistant to enzymatic breakdown by animal consumers. Further, t-POC and heterotrophic bacteria lack essential biochemical compounds that are critical for rapid growth and reproduction in aquatic invertebrates and fishes. Several studies have directly shown that these resources have very low food quality for herbivorous zooplankton and benthic invertebrates 4. Much of the nitrogen assimilated by stream consumers is probably of algal origin, even in systems where there appears to be a significant terrestrial carbon contribution. Amino acid stable isotope analyses for large river food webs indicate that most upper trophic level essential amino acids are derived from algae. Similarly, profiles of essential fatty acids in consumers show a strong dependence on the algal food resources. 5. Primary production to respiration ratios are not a meaningful index to assess consumer allochthony because respiration represents an oxidised carbon flux that cannot be utilised by animal consumers. Rather, the relative importance of allochthonous subsidies for upper trophic level production should be addressed by considering the rates at which terrestrial and autochthonous resources are consumed and the growth efficiency supported by this food. 6. Ultimately, the biochemical composition of a particular basal resource, and not just its quantity or origin, determines how readily this material is incorporated into upper trophic level consumers. Because of its highly favourable biochemical composition and greater availability, we conclude that microalgal production supports most animal production in freshwater ecosystems.
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| 4. |
- Huser, Brian, et al.
(författare)
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Spatial and temporal variation in Arctic freshwater chemistry : Reflecting climate-induced landscape alterations and a changing template for biodiversity
- 2022
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Ingår i: Freshwater Biology. - : John Wiley & Sons. - 0046-5070 .- 1365-2427. ; 67:1, s. 14-29
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Tidskriftsartikel (refereegranskat)abstract
- 1. Freshwater chemistry across the circumpolar region was characterised using a pan-Arctic data set from 1,032 lake and 482 river stations. Temporal trends were estimated for Early (1970-1985), Middle (1986-2000), and Late (2001-2015) periods. Spatial patterns were assessed using data collected since 2001.2. Alkalinity, pH, conductivity, sulfate, chloride, sodium, calcium, and magnesium (major ions) were generally higher in the northern-most Arctic regions than in the Near Arctic (southern-most) region. In particular, spatial patterns in pH, alkalinity, calcium, and magnesium appeared to reflect underlying geology, with more alkaline waters in the High Arctic and Sub Arctic, where sedimentary bedrock dominated.3. Carbon and nutrients displayed latitudinal trends, with lower levels of dissolved organic carbon (DOC), total nitrogen, and (to a lesser extent) total phosphorus (TP) in the High and Low Arctic than at lower latitudes. Significantly higher nutrient levels were observed in systems impacted by permafrost thaw slumps.4. Bulk temporal trends indicated that TP was higher during the Late period in the High Arctic, whereas it was lower in the Near Arctic. In contrast, DOC and total nitrogen were both lower during the Late period in the High Arctic sites. Major ion concentrations were higher in the Near, Sub, and Low Arctic during the Late period, but the opposite bulk trend was found in the High Arctic.5. Significant pan-Arctic temporal trends were detected for all variables, with the most prevalent being negative TP trends in the Near and Sub Arctic, and positive trends in the High and Low Arctic (mean trends ranged from +0.57%/year in the High/Low Arctic to -2.2%/year in the Near Arctic), indicating widespread nutrient enrichment at higher latitudes and oligotrophication at lower latitudes.6. The divergent P trends across regions may be explained by changes in deposition and climate, causing decreased catchment transport of P in the south (e.g. increased soil binding and trapping in terrestrial vegetation) and increased P availability in the north (deepening of the active layer of the permafrost and soil/sediment sloughing). Other changes in concentrations of major ions and DOC were consistent with projected effects of ongoing climate change. Given the ongoing warming across the Arctic, these region-specific changes are likely to have even greater effects on Arctic water quality, biota, ecosystem function and services, and human well-being in the future.
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| 5. |
- Bergström, Ann-Kristin, 1968-, et al.
(författare)
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Biomass, community composition and N:P recycling ratios of zooplankton in northern high-latitude lakes with contrasting levels of N deposition and dissolved organic carbon
- 2022
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Ingår i: Freshwater Biology. - : John Wiley & Sons. - 0046-5070 .- 1365-2427. ; 67:9, s. 1508-1520
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Tidskriftsartikel (refereegranskat)abstract
- Global changes are causing decreases in inorganic nitrogen (N) concentrations, increases in coloured dissolved organic carbon (DOC) concentrations, and decreases in dissolved inorganic N to total phosphorus ratios (DIN:TP) in northern lakes. The effects of these changes on phytoplankton and zooplankton biomass and the N:P recycling ratio of zooplankton remain unresolved.In 33 Swedish headwater lakes across subarctic-to-boreal gradients with different levels of N deposition (low N in the north [Västerbotten, boreal; Abisko, subarctic] vs. high N in the south [Värmland, boreal; Jämtland, subarctic]), we measured water chemistry, phytoplankton biomass (chlorophyll-a [Chl-a], Chl-a:TP), seston mineral quality (C:P, N:P), as well as zooplankton biomass, community composition, and C:N:P stoichiometry. We estimated nutrient imbalances and the N:P recycling ratios of zooplankton using ecological stoichiometry models.There was a large-scale gradient from low lake DIN and DIN:TP in the north to high DIN and DIN:TP in the south, with lower DIN:TP in lakes coinciding with higher DOC within each region. Lower lake DIN was associated with lower phytoplankton biomass (lower Chl-a:TP). Lower lake DIN:TP was associated with richer seston mineral quality (lower seston C:P and N:P) and higher zooplankton biomass.Zooplankton community composition differed in the north vs. south, with a dominance of N-requiring calanoid copepods with high N:P in the north and P-requiring cladocerans with low N:P in the south. Also, greater differences in zooplankton community composition were found between subarctic regions (with lower DOC) than between boreal regions (with higher DOC), suggesting that increases in lake DOC and associated declines in lake DIN:TP reduce differences in zooplankton community composition.The combination of lower lake DIN, higher lake DOC, and lower lake DIN:TP led to reduced zooplankton N:P recycling ratios, possibly by reducing seston N:P and/or by enhancing calanoid copepod dominance in the zooplankton community.Our findings suggest that the combination of declining N deposition and increasing lake browning in northern high-latitude lakes will reduce phytoplankton biomass, but will concurrently enhance seston mineral quality and probably also zooplankton biomass and their recycling efficiency of P relative to N.
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| 6. |
- Bergström, Ann-Kristin, 1968-, et al.
(författare)
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Changes in nutritional quality and nutrient limitation regimes of phytoplankton in response to declining N deposition in mountain lakes
- 2020
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Ingår i: Aquatic Sciences. - : Springer. - 1015-1621 .- 1420-9055. ; 82:2
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton play a key role in supporting aquatic food webs. However, the effects of ongoing large-scale changes in the concentrations and stoichiometry of important biological compounds [dissolved inorganic N (DIN), total phosphorus (TP), dissolved organic carbon (DOC) and DIN:TP] on the development and nutritional quality of phytoplankton for higher trophic levels are unclear. We conducted lake studies and in situ bioassay experiments in two Swedish mountain regions [Abisko (north) and Jamtland (south)] with different N deposition and where lakes in each region were distributed along a similar gradient in lake DOC (2-7 mg L-1) to assess whether differences in nutrients, DOC and DIN:TP induced differences in phytoplankton quantity [chlorophyll a (Chl-a) and seston carbon (C)] and quality [seston C:N:P stoichiometry and fatty acid (FA) composition]. Using long-term monitoring data from lakes in these two mountain regions, we found declining long-term trends in N deposition and lake DIN and total TP concentrations, but not in lake DIN:TP. Lakes in Abisko received lower N deposition and had lower DIN:TP than those in Jamtland. Phytoplankton was N- to NP-limited in Abisko lakes but NP dual-limited in Jamtland lakes. The N fertilization effects induced by higher DIN:TP were weak on phytoplankton quantity but strong on phytoplankton quality. The phytoplankton had lower eicosapentaenoic acid (EPA) content and higher P content (lower seston C:P) in Abisko compared to in Jamtland. In addition, the quality of the DOC (as indicated by its aromaticity and SUVA) influenced not only the light conditions and the seston C:P ratios, but also the FA composition. We found higher bacteria FA concentrations in seston in Abisko than in Jamtland, despite lower amounts of FA of terrestrial origin in Abisko. Our findings suggest that declining N deposition and enhanced colored terrestrial C loadings leads to lower nutritional quality of basal resources for higher consumers in mountain lakes.
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| 7. |
- Bergström, Ann-Kristin, 1968-, et al.
(författare)
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Declining calcium concentration drives shifts toward smaller and less nutritious zooplankton in northern lakes
- 2024
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 30:3
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Tidskriftsartikel (refereegranskat)abstract
- Zooplankton community composition of northern lakes is changing due to the interactive effects of climate change and recovery from acidification, yet limited data are available to assess these changes combined. Here, we built a database using archives of temperature, water chemistry and zooplankton data from 60 Scandinavian lakes that represent broad spatial and temporal gradients in key parameters: temperature, calcium (Ca), total phosphorus (TP), total organic carbon (TOC), and pH. Using machine learning techniques, we found that Ca was the most important determinant of the relative abundance of all zooplankton groups studied, while pH was second, and TOC third in importance. Further, we found that Ca is declining in almost all lakes, and we detected a critical Ca threshold in lake water of 1.3 mg L−1, below which the relative abundance of zooplankton shifts toward dominance of Holopedium gibberum and small cladocerans at the expense of Daphnia and copepods. Our findings suggest that low Ca concentrations may shape zooplankton communities, and that current trajectories of Ca decline could promote widespread changes in pelagic food webs as zooplankton are important trophic links from phytoplankton to fish and different zooplankton species play different roles in this context.
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| 8. |
- Bidleman, Terry F., et al.
(författare)
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Bromoanisoles and Methoxylated Bromodiphenyl Ethers in Macroalgae from Nordic Coastal Regions
- 2019
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Ingår i: Environmental Science. - London : Royal Society of Chemistry. - 2050-7887 .- 2050-7895. ; , s. 881-892
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Tidskriftsartikel (refereegranskat)abstract
- Marine macroalgae are used worldwide for human consumption, animal feed, cosmetics and agriculture. In addition to beneficial nutrients, macroalgae contain halogenated natural products (HNPs), some of which have toxic properties similar to those of well-known anthropogenic contaminants. Sixteen species of red, green and brown macroalgae were collected in 2017–2018 from coastal waters of the northern Baltic Sea, Sweden Atlantic and Norway Atlantic, and analyzed for bromoanisoles (BAs) and methoxylated bromodiphenyl ethers (MeO-BDEs). Target compounds were quantified by gas chromatography-low resolution mass spectrometry (GC-LRMS), with qualitative confirmation in selected species by GC-high resolution mass spectrometry (GC-HRMS). Quantified compounds were 2,4-diBA, 2,4,6-triBA, 2′-MeO-BDE68, 6-MeO-BDE47, and two tribromo-MeO-BDEs and one tetrabromo-MeO-BDE with unknown bromine substituent positions. Semiquantitative results for pentabromo-MeO-BDEs were also obtained for a few species by GC-HRMS. Three extraction methods were compared; soaking in methanol, soaking in methanol–dichloromethane, and blending with mixed solvents. Extraction yields of BAs did not differ significantly (p > 0.05) with the three methods and the two soaking methods gave equivalent yields of MeO-BDEs. Extraction efficiencies of MeO-BDEs were significantly lower using the blend method (p < 0.05). For reasons of simplicity and efficiency, the soaking methods are preferred. Concentrations varied by orders of magnitude among species: ∑2BAs 57 to 57 700 and ∑5MeO-BDEs < 10 to 476 pg g−1 wet weight (ww). Macroalgae standing out with ∑2BAs >1000 pg g−1 ww were Ascophyllum nodosum, Ceramium tenuicorne, Ceramium virgatum, Fucus radicans, Fucus serratus, Fucus vesiculosus, Saccharina latissima, Laminaria digitata, and Acrosiphonia/Spongomorpha sp. Species A. nodosum, C. tenuicorne, Chara virgata, F. radicans and F. vesiculosus (Sweden Atlantic only) had ∑5MeO-BDEs >100 pg g−1ww. Profiles of individual compounds showed distinct differences among species and locations.
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| 9. |
- Chaguaceda, Fernando, et al.
(författare)
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Zooplankton in northern lakes show taxon-specific responses in fatty acids across climate-productivity and ecosystem size gradients
- 2024
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 69, s. 947-960
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Tidskriftsartikel (refereegranskat)abstract
- Northern lakes are facing rapid environmental alterations-including warming, browning, and/or changes in nutrient concentrations-driven by climate change. These environmental changes can have profound impacts on the synthesis and trophic transfer of polyunsaturated fatty acids (PUFA), which are important biochemical molecules for consumer growth and reproduction. Zooplankton are a key trophic link between phytoplankton and fish, but their biochemical responses to environmental change are not well understood. In this study, we assess the trends in fatty acid (FA) composition of zooplankton taxa among 32 subarctic and temperate lakes across broad climate-productivity and ecosystem size gradients. We found that genus-level taxonomy explained most FA variability in zooplankton (54%), suggesting that environmental changes that alter the taxonomic composition also affect the FA composition of zooplankton communities. Furthermore, the FA responses and their underlying environmental drivers differed between cladocerans and copepods. Cladocerans, including widespread Bosmina spp. and Daphnia spp., showed pronounced responses across the climate-productivity gradient, with abrupt declines in PUFA, particularly eicosapentaenoic acid and arachidonic acid in warmer, browner, and more eutrophic lakes. Conversely, calanoid copepods had high and relatively stable PUFA levels across the gradient. In addition, all zooplankton taxa increased in stearidonic acid levels in larger lakes where PUFA-rich cryptophytes were more abundant. Overall, our results suggest that climate-driven environmental alterations pose heterogeneous impacts on PUFA levels among zooplankton taxa, and that the negative impacts of climate warming are stronger for cladocerans, especially so in small lakes.
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| 10. |
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| 11. |
- Fölster, Jens, et al.
(författare)
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Responses of benthic invertebrates to chemical recovery from acidification
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The report provides an assessment of biological recovery from acidification in freshwater environments in Europe. The report consists of two parts, a regional data analysis based on an international dataset of biological and water chemical records, and a collection of national contributions on monitoring and assessment of biological recovery in different countries. The regional analysis showed that 47% of all included rivers (21 sites, for the period 1994-2018) and 35% percent of all lakes (34 sites, for the period 2000 to 2018) showed significant increases in species richness. Correlations between species diversity and water chemical components (ANC, pH, SO4) were found, supporting that the biological responses were related to chemical recovery. Additionally, the composition of functional traits in rivers underwent significant changes over time. Both parts of the report demonstrate ongoing biological recovery from acidification in European acid-sensitive freshwater environments.
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| 12. |
- Goedkoop, Willem, et al.
(författare)
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CAFF Circumpolar Biodiversity Monitoring Program State of Arctic Freshwater Biodiversity Report
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Arctic freshwater ecosystems (lakes, rivers, and associated wetlands) are threatened by climate change and human development that can affect freshwater biodiversity. Such effects will change not only the distributions and abundances of aquatic species, but also the lives of Arctic Peoples that are dependent on the ecosystem services supplied by lakes and rivers. Thus, the freshwater biodiversity program of the Circumpolar Biodiversity Monitoring Program (Freshwater-CBMP) focuses on lake and river ecosystems and has established a long-term monitoring framework for these Arctic freshwaters. Developed for the Conservation of Arctic Flora and Fauna (CAFF; the biodiversity Working Group of the Arctic Council), this framework facilitates more accurate and rapid detection, communication and response to significant trends in Arctic water quality and biodiversity. Freshwater-CBMP goals are addressed in the “Arctic Freshwater Biodiversity Monitoring Plan”, which describes an integrated, ecosystem-based approach for monitoring Arctic freshwaters.
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| 13. |
- Goedkoop, Willem, et al.
(författare)
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Inverting nutrient fluxes across the land-water interface - Exploring the potential of zebra mussel (Dreissena polymorpha) farming
- 2021
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Ingår i: Journal of Environmental Management. - : Elsevier. - 0301-4797 .- 1095-8630. ; 281, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- We studied the potential of zebra mussel farming for nutrient retention in a eutrophic lake. Duplicate experimental long-line cultivation units were deployed and mussel growth and nutrient retention were quantified after 28 months. Mussels grew well at shallow water depth (<3 m) and our 625 m(2) (lake area) experimental units produced 507 and 730 kg dry biomass, respectively, of which 94% were shells. These yields corresponded to an average retention of 92.7 +/- 23.1 kg C, 6.1 +/- 0.68 kg N, and 0.43 +/- 0.04 kg P retention, or 742 kg C, 49 kg N, and 3.5 kg P for a full-size (0.5 ha) mussel farm. We estimate that concentrating the long-lines to a depth of 2.5 m would probably have doubled these yields, based on the differences in mussel growth among depths. We further estimate that a full-size cultivation unit (0.5 ha) thus could compensate for the annual total-P run-off from 23 ha, or the biologically available P from approximately 49 ha of agricultural soils. As traditional measures have proven insufficient, decision-makers need to facilitate novel approaches to mitigate the negative effects of cultural eutrophication. We envision that zebra mussel farming, within their invaded range, provides a promising approach to invert nutrient losses in lakes and coastal lagoons.
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| 14. |
- Grieve, Adrian, et al.
(författare)
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Do autochthonous resources enhance trophic transfer of allochthonous organic matter to aquatic consumers, or vice versa?
- 2018
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Ingår i: Ecosphere. - : Wiley-Blackwell. - 2150-8925 .- 2150-8925. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- Autochthonous and allochthonous resources are known to differ in nutritional quality and trophic support for aquatic food webs, but it is less clear how these high- and low-quality resources interact to affect trophic transfer and consumer production. We conducted 30-d feeding trials to investigate the resource assimilation, somatic growth, and fatty-acid (FA) composition of the widespread benthic generalist isopod Asellus aquatints, in response to different ratios of low-quality allochthonous (leaf litter) to high-quality autochthonous diets (algae). Wet mass growth of Asellus was lowest when fed 100% leaf litter or algae (0.53 +/- 0.46 and 0.55 +/- 0.57 mg center dot g(-1)center dot d(-1), respectively; mean +/- SE) and highest (4.95 +/- 0.51 mg center dot g(-1)center dot d(-1)) with a diet of 90:10 leaf litter:algae ratio. Asellus tended to grow slower with increasing dietary algal proportions (10-100%), yet stable isotopes and Bayesian mixing models revealed consistently high algal assimilation (>= 94%) by Asellus. Therefore, among the mixed-diet treatments, Asellus biomass production using algal resources was optimized when terrestrial organic matter (OM) dominated over algae. Eicosapentaenoic acid (EPA):total FA, EPA:omega-3 FA, and arachidonic acid:total FA declined, but docosahexaenoic acid (DHA):omega-3 FA increased, with increasing growth of Asellus. Tissue EPA concentrations of Asellus were similar among treatments, so reductions in EPA:omega-3 and EPA:total FA were due to increases in DHA concentration. Overall, our results suggest synergistic effects between autochthonous and allochthonous resources on Asellus growth and that allochthonous OM particularly facilitates the trophic transfer of autochthonous resources. Asellus preferentially retains DHA at low algal availability. This may improve its neural tissue development and so its success in accessing algae. The growth and FA responses of the widespread Asellus can enhance resource and DHA transfer to visual predators that have greater DHA demands, particularly when brownification of boreal freshwaters likely intensifies upon global climate change.
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| 15. |
- Grosbois, Guillaume, et al.
(författare)
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Land and Freshwater Complex Interactions in Boreal Forests: A Neglected Topic in Forest Management
- 2023
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Ingår i: Boreal Forests in the Face of Climate Change. - Cham : Springer International Publishing. - 9783031159886 - 9783031159879 - 9783031159909 ; 74, s. 719-745
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Bokkapitel (refereegranskat)abstract
- Aquatic and terrestrial habitats are interdependent components of the boreal forest landscape involving multiple dynamic interactions; these are manifested particularly in riparian areas, which are key components in the forest landscape. However, this interdependence between aquatic and terrestrial habitats is not adequately accounted for in the current management of forest ecosystems. Here we review the impacts of land disturbances on the optical and physicochemical properties of water bodies, aquatic food web health, and the ecological functioning of these freshwaters. We also describe how freshwaters influence the adjacent terrestrial ecosystems. A better understanding of these dynamic biotic and abiotic interactions between land and freshwater of the boreal forest is a first step toward including these freshwaters in the sustainable management of the boreal forest.
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| 16. |
- Guo, Junwen, 1982-, et al.
(författare)
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Spatiotemporal carbon, nitrogen and phosphorus stoichiometry in planktonic food web in a northern coastal area
- 2022
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Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier. - 0272-7714 .- 1096-0015. ; 272
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Tidskriftsartikel (refereegranskat)abstract
- The concentrations of ambient nutrients and dissolved organic carbon (DOC) in northern coastal ecosystems often show large variations, due to the spatiotemporal differences in terrestrial inputs. How these variations affect the stoichiometry of coastal planktonic organisms is, however, poorly known. Here we assessed the spatiotemporal variability of C, nitrogen (N), and phosphorous (P) concentrations of the seawater on the elemental stoichiometry of seston and dominant mesozooplankton taxa in a coastal area of the northern Baltic Sea. The freshwater inflow peaked in spring following the snowmelt and brought a significant amount of DOC, but not N and P to the coastal system. DOC was the main environmental descriptor for seston C:N stoichiometry. The C:N ratio of seston from 0.7 to 50 μm and mesozooplankton followed the temporal pattern of water C:N ratio, while the temporal trend of bacteria C:N showed an opposite pattern. Our results also indicated that the C:N ratio of seawater controlled both seston and mesozooplankton C:N ratios. Our findings imply that inflows of terrestrial DOC alter the stoichiometry and reduce the nutritional quality of planktonic food webs in northern coastal ecosystems.
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| 17. |
- Guo, Junwen, et al.
(författare)
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Stoichiometric changes in planktonic food web upon environmental fluctuations in northern oligotrophic coastal ecosystem
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Climate-driven changes, e.g. increasing precipitation, will increase terrestrial runoff and freshwater inputs to coastal ecosystems in the future. Consequently, we expect that altered availability of inorganic and organic forms of carbon (C), nitrogen (N) and phosphorus (P) will lead to spatial and temporal variation in the elemental composition of coastal organisms. To identify the major spatiotemporal patterns in seston and zooplankton elemental (C, N and P) composition, we sampled four bays of northern Baltic Sea from May to September 2018. This sampling design covers spatial and temporal variation in freshwater input, as it includes the spring flood driven by snowmelt in May, and bays receiving varying catchment areas. We analyzed CNP composition for different size fractions of seston, and dominant zooplankton taxa. Our results showed that the stoichiometric composition of individual seston size fractions varied more through time than in space. The concentrations of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in water were the major explanatory variables for seston stoichiometry. We also found that zooplankton stoichiometry was relatively similar between taxa within specific months, although the dominant zooplankton taxa differed over time and among sites. This could partly be explained by the similar stoichiometric requirements and homeostasis among zooplankton taxa. Our findings imply that the spatiotemporal variation in physicochemical characteristics of coastal ecosystems will alter the quality of seston and zooplankton. Yet, further investigations on the role of zooplankton in stoichiometry related nutrient cycling in the Baltic Sea coastal ecosystems are needed.
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| 18. |
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| 19. |
- Hedberg, Per, 1978-, et al.
(författare)
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Variation in fatty acid content among benthic invertebrates in a seasonally driven system
- 2023
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Ingår i: Limnology and Oceanography Letters. - : John Wiley & Sons. - 2378-2242. ; 8:5, s. 751-759
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Tidskriftsartikel (refereegranskat)abstract
- At temperate latitudes where seasonal changing environmental conditions strongly affect the magnitude, duration and species composition of pelagic primary production, macrobenthic organisms living below the photic zone rely on the sedimentation of organic matter as their primary energy source. The succession from nutritious spring blooms to summer cyanobacteria is assumed to reduce food quality for benthic primary consumers and their fatty acid (FA) profiles. In contrast, we find low seasonal variability in FA content of five benthic macroinvertebrates spanning two trophic levels in the Baltic Sea, a system with high seasonal variation in phytoplankton species composition. However, levels of the major FA groups vary greatly between benthic species. The results suggest that benthic macroinvertebrates have evolved FA metabolism adapted to degraded sedimenting material. Moreover, our study shows that species composition of benthic macrofauna rather than seasonal changing conditions affect availability of essential nutrients to higher trophic levels.
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| 20. |
- Herath, Tharindu, et al.
(författare)
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Dataset on seston and zooplankton fatty-acid compositions, zooplankton and phytoplankton biomass, and environmental conditions of coastal and offshore waters of the northern Baltic Sea
- 2022
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Ingår i: Data in Brief. - : Elsevier. - 2352-3409. ; 42
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Tidskriftsartikel (refereegranskat)abstract
- We analyzed the taxonomic and fatty-acid (FA) compositions of phytoplankton and zooplankton, and the environmental conditions at three coastal and offshore stations of the northern Baltic Sea. Plankton samples for FA analyses were collected under the framework of sampling campaigns of the Swedish National Marine Monitoring program in September 2017. Monitoring data of phytoplankton and zooplankton biomass, and environmental variables at each station were extracted from the Swedish Meteorological and Hydrological Institute database (https://sharkweb.smhi.se/). Monthly phytoplankton biomass at each station in July-September 2017 was aggregated by class (i.e., chyrsophytes, cryptophytes, dinoflagellates, diatoms, euglenophytes, cyanobacteria, etc.). Zooplankton biomass in September 2017 was aggregated by major taxa (i.e., Acartia sp. [Calanoida], Eurytemora affinis [Calanoida], Cladocera, Limnocalanus macrurus and other copepods (i.e. excluding Eurytemora and Acartia)). Environmental variables monthly monitored in January-October 2017 included salinity, concentrations of dissolved organic carbon, humic substances, total nitrogen and total phosphorus. These variables were measured from 0 to 10 m depth below water surface, and the depth-integrated averages were used for data analyses. Seston and zooplankton (Eurytemora affinis, Acartia sp. and Cladocera) FA compositions were analyzed using gas chromatography and mass spectroscopy (GC–MS). Our dataset could provide new insights into how taxonomic composition and biochemical quality of the planktonic food chains change with the environmental conditions in subarctic marine ecosystems.
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| 21. |
- Herath, Tharindu, et al.
(författare)
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Seawater browning alters community composition and reduces nutritional quality of plankton in a subarctic marine ecosystem
- 2022
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - : Canadian Science Publishing. - 0706-652X .- 1205-7533. ; 79:8, s. 1291-1301
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Tidskriftsartikel (refereegranskat)abstract
- Inflows of coloured terrestrial organic matter cause seawater browning and reduced phytoplankton production in subarctic coastal ecosystems, potentially deteriorating the nutritional quality of marine food webs. We analyzed the fatty-acid (FA) compositions of seston and the zooplankton taxa Eurytemora affinis and cladocerans at three locations of the northern Baltic Sea. At the coastal and northerly locations, salinity and phosphorus concentrations were low, while concentrations of humic substances (i.e., terrestrial organic matter) were high. The southerly location showed the opposite trend. The ratio between alga-specific ?3 polyunsaturated FA and terrigenous monounsaturated FA (MUFA) in Eurytemora decreased from south to north, as did the ratio between the alga-specific docosahexaenoic acid (DHA) and terrigenous MUFA in cladocerans. With increasing humic substances, the biomass of DHA-rich phytoplankton decreased and the zooplankton MUFA content increased. Our results indicate that coloured terrestrial organic matter alters the phytoplankton composition, consequently affecting the zooplankton nutritional quality.
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| 22. |
- Lau, Danny C P, et al.
(författare)
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Autochthonous resources are the main driver of consumer production in dystrophic boreal lakes
- 2014
-
Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 95, s. 1506-1519
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Tidskriftsartikel (refereegranskat)abstract
- Dystrophic lakes are widespread in temperate regions and intimately interact with surrounding terrestrial ecosystems in energy and nutrient dynamics, yet the relative importance of autochthonous and allochthonous resources to consumer production in dystrophic lakes remains controversial. We argue that allochthonous organic matter quantitatively dominates over photosynthetic autotrophs in dystrophic lakes, but that autotrophs are higher in diet quality and more important for consumers as they contain essential polyunsaturated fatty acids (PUFA). In a field study, we tested the hypotheses that (1) autochthonous primary production is the main driver for consumer production, despite being limited by light availability and low nutrient supplies, and greater supply of allochthonous carbon, (2) the relative contribution of autotrophs to consumers is directly related to their tissue PUFA concentrations, and (3) methane-oxidizing bacteria (MOB) provide an energy alternative for consumers.Pelagic and benthic consumer taxa representing different trophic levels were sampled from five dystrophic lakes: isopod Asellus aquaticus, megalopteran Sialis lutaria, dipteran Chaoborus flavicans, and perch Perca fluviatilis. Based on carbon and nitrogen stable isotopes, the relative contributions of autochthonous (biofilms and seston) and allochthonous (coarse particulate and dissolved organic matter) resources and MOB to these taxa were 47-79%, 9-44% and 7-12% respectively. Results from fatty acid (FA) analyses show that the relative omega 3-FA and PUFA concentrations increased with trophic level (Asellus < Sialis and Chaoborus < Perca). Also, eicosapentaenoic-acid (EPA), omega 3-FA and PUFA concentrations increased with the autochthonous contribution in consumers, i.e., a 47-79% biofilm and/or seston diet resulted in tissue EPA of 4.2-18.4, omega 3 FAs of 11.6-37.0 and PUFA of 21.6-61.0 mg/g dry mass. The results indicate that consumers in dystrophic lakes predominantly rely on energy from autotrophs and that their PUFA concentrations are dependent on the relative contribution of these autochthonous resources. The limited energy support from MOB suggests they are not negligible and are potentially an integral part of the food webs. Our findings show that autochthonous resources are the main driver of secondary production even in dystrophic lakes and offer new insights into the functioning of these ecosystems.
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| 23. |
- Lau, Danny C P, et al.
(författare)
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Cross-ecosystem differences in lipid composition and growth limitation of a benthic generalist consumer
- 2013
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 58, s. 1149-1164
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Tidskriftsartikel (refereegranskat)abstract
- In a field study, we analyzed the fatty acid (FA) composition of the benthic generalist Asellus aquaticus collected from boreal lakes, ponds, and streams across gradients in ambient nutrient levels. In laboratory feeding experiments, we tested the diet-quality and seasonal effects on somatic growth and FAs of spring-and autumn-collected Asellus that were fed four different diets containing increasing concentrations of polyunsaturated FAs (PUFA): conditioned leaf litter, algal flakes, mixed litter and algal flakes (Mixed), or Mixed plus fish-food flakes. Ambient nutrients were strong determinants of FA variation of field Asellus, explaining > 44% in total. The ratios of eicosapentaenoic acid (EPA) to total FAs, EPA: omega 3, and omega 3 : omega 6 of Asellus increased up to four times with increasing trophic state and decreasing humic matter content, likely because dietary omega 3 FAs were more prevalent in benthic habitats of eutrophic than of oligotrophic systems. In the feeding trials, growth of Asellus collected in both seasons was markedly lower on leaf litter than on higher PUFA diets. However, autumn-collected Asellus fed a Mixed or Mixed+fish-food diet grew 3-10 times faster, but retained < 50% EPA and PUFA than spring counterparts. Asellus optimized PUFA accumulation in spring but somatic growth in autumn. Our field survey suggests ambient nutrient concentrations modify dietary PUFA supply from basal resources, while laboratory studies show that growth response and PUFA accumulation of Asellus differ between seasons, likely due to its season-specific physiological status and diet quality. An increase in nutrients will release benthic consumers from growth limitation and favor more efficient trophic transfer.
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| 24. |
- Lau, Danny C P
(författare)
-
Data for: Variation in fatty acid content among benthic invertebrates in a seasonally driven system
- 2023
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- At temperate latitudes where seasonal changing environmental conditions strongly affect the magnitude, duration and species composition of pelagic primary production, macrobenthic organisms living below the photic zone rely on the sedimentation of this organic matter as their primary energy source. The succession from nutritious spring blooms to summer cyanobacteria is assumed to reduce food quality for benthic primary consumers and their fatty acid profiles. In contrast, we find low seasonal variability in fatty acid content of five benthic macroinvertebrates spanning two trophic levels in the Baltic Sea, a system with high seasonal variation in phytoplankton species composition. However, levels of the major FA groups vary greatly between benthic species. The results suggest that benthic macroinvertebrates have evolved FA metabolism adapted to degraded sedimenting material. Moreover, our study shows that species composition of benthic macrofauna rather than seasonal changing conditions affect availability of essential nutrients to higher trophic levels.
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| 25. |
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| 26. |
- Lau, Danny C P, et al.
(författare)
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Fatty-acid based assessment of benthic food-web responses to multiple stressors in a large river system
- 2023
-
Ingår i: Environmental Pollution. - 0269-7491 .- 1873-6424. ; 337
-
Tidskriftsartikel (refereegranskat)abstract
- Rivers are often exposed to multiple stressors, such as nutrients and contaminants, whose impacts on the river food webs may not be distinguished by sole assessment of biological community structures. We examined the benthic algal assemblages and the fatty acids (FA) of benthic macroinvertebrates in the lower Athabasca River in Canada, aiming to assess the changes in algal support and nutritional quality of the benthic food web in response to cumulative exposure to natural bitumen, municipal sewage discharge (hereafter, "sewage"), and oil sands mining ("mining"). Data show that the decline in water quality (increases in nutrient concentrations and total suspended solids) was associated with decreases in benthic diatom abundance, and was driven mainly by sewageinduced nutrient enrichment. Responses in nutritional quality of benthic macroinvertebrates, indicated by their polyunsaturated FA (PUFA) concentrations, were taxon- and stressor-specific. Nutritional quality of the larval dragonfly predator, Ophiogomphus, decreased nonlinearly with decreasing benthic diatom abundance and was lowest at the sewage-affected sites, although exposure to natural bitumen also resulted in reduced Ophiogomphus PUFA concentrations. In contrast, the PUFA concentrations of mayfly grazers/collector-gatherers were not affected by natural bitumen exposure, and were higher at the sewage and sewage+mining sites. The PUFA concentrations of the shredder Pteronarcys larvae did not change with cumulative exposure to the stressors. Sediment metal and polycyclic aromatic compound concentrations were not associated with the macroinvertebrate FA changes. Overall, we provide evidence that sewage induced reduction in trophic support by PUFA-rich diatoms, and was the predominant driver of the observed changes in FA composition and nutritional quality of the benthic macroinvertebrates. Fatty-acid metrics are useful to untangle effects of concurrent stressors, but the assessment outcomes depend on the functional feeding guilds used. A food-web perspective using multiple trophic levels and feeding guilds supports a more holistic assessment of the stressor impacts.
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| 27. |
- Lau, Danny C P, et al.
(författare)
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Fatty acid composition of consumers in boreal lakes - variation across species, space and time
- 2012
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 57, s. 24-38
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Tidskriftsartikel (refereegranskat)abstract
- 1. Fatty acids (FAs) have been widely applied as trophic biomarkers in aquatic food web studies. However, current knowledge of inter- and intraspecific variation in consumer FA compositions across spatial and temporal scales is constrained to a few pelagic taxa.
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| 28. |
- Lau, Danny C P
(författare)
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Improvements of Population Fitness and Trophic Status of a Benthic Predatory Fish Following a Trawling Ban
- 2021
-
Ingår i: Frontiers in marine science. - : Frontiers Media SA. - 2296-7745. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Trawl fisheries have been shown to cause overfishing and destruction of benthic habitats in the seabed. To mitigate these impacts, a trawling ban has been enforced in Hong Kong waters since December 31, 2012 to rehabilitate the ecosystem and enhance fisheries resources. Previous studies demonstrated that reduced trawling activities would increase the heterogeneity of benthic habitats, thereby enhancing species richness and abundance of benthic fauna and providing more prey resources for predatory fishes. This study aimed to test a hypothesis that the population and trophic dynamics of the Bartail flathead Platycephalus indicus, a heavily fished benthic predatory fish, at inner and outer Tolo Channel of Hong Kong (i.e., EI and EO) improved with increases in their body size, abundance, biomass, trophic niche, and trophic position after the trawl ban. Samples were collected from trawl surveys before and after the trawl ban to compare the pre-ban and post-ban populations of P. indicus from EI and EO. Body size, abundance, and biomass were assessed in 2004, 2013–2014, and 2015–2016, whereas trophic niche and trophic position were analyzed based on stable isotopes of fish samples collected in dry season of 2012, 2015, and 2018. Following the trawl ban, the abundance and biomass of P. indicus increased in EO, with body size increased in EI. Furthermore, as indicated by the results of stable isotope analysis (SIA) on their tissues and prey items, trophic niche, and trophic position of P. indicus increased in EI and EO, respectively. Our study demonstrated that the trawl ban had promoted the recovery of a predatory fish population through restoring size structure and trophic dynamics.
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| 29. |
- Lau, Danny C. P., et al.
(författare)
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Lake responses to long-term disturbances and management practices
- 2017
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Ingår i: Freshwater Biology. - : WILEY. - 0046-5070 .- 1365-2427. ; 62:4, s. 792-806
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Tidskriftsartikel (refereegranskat)abstract
- 1. Long-term human-induced disturbances such as acidification and algal invasions, and management practices such as liming, are known to alter community structure and biodiversity of north temperate lakes. We assessed if they impacted on the trophic ecology and production of apex consumers (i.e. fish) and the overall food-chain length (FCL) of boreal lake ecosystems, and if these functional responses were consistent with the biodiversity changes. We hypothesise that fish production and FCL decrease with decreasing species biodiversity of lake communities, and that long-term environmental perturbations will alter the relative reliance of fish on littoral versus pelagic trophic pathways and their ontogenetic changes in trophic position (TP). 2. We analysed long-term data and stable isotopes of multiple organismal groups - phytoplankton, zooplankton, littoral and sub-littoral/profundal macroinvertebrates, and fish - collected from small boreal lakes that have been subjected to acidification, lime application and/or algal invasion by Gonyostomum semen. Species biodiversity, FCL and fish production (i.e. growth and catch-per-uniteffort) were compared among three lake categories, i.e. acidic, limed and circumneutral (reference) lakes, within each three lakes were selected. Fish TP and their relative littoral versus pelagic reliance were estimated based on stable nitrogen and carbon isotopes respectively. 3. Gonyostomum contributed to 77-98% phytoplankton biovolume in acidic lakes, <1-79% in limed lakes and 0-30% in circumneutral lakes. Its prevalence was correlated with total organic carbon concentration but not with lake pH, alkalinity or any other environmental variable. Diversity and evenness of phytoplankton, macroinvertebrates and fish generally decreased with increasing Gonyostomum biovolume, such that biodiversity was higher in circumneutral and limed lakes than in acidic lakes. 4. Isotopic data revealed that FCL was shortest in limed lakes (3.94 +/- 0.08; least- squares mean +/- SE), intermediate in acidic lakes (4.19 +/- 0.07) and longest in circumneutral lakes (4.38 +/- 0.08). Limed lakes also had the lowest fish growth and CPUE. Overall littoral reliance of fish was higher in acidic lakes (0.53 +/- 0.03) than in limed lakes (0.42 +/- 0.02) and circumneutral lakes (0.30 +/- 0.02), suggesting that fish production and FCL there could have been sustained by the increased littoral reliance when pelagic trophic pathways were hindered by Gonyostomum invasion. European perch (Perca fluviatilis), the most common fish in the lakes, showed faster TP increases in acidic and limed lakes, likely due to their earlier ontogenetic shift from zooplanktivory to zoobenthivory and/or piscivory. 5. Overall, our findings indicate that long-term disturbances (i.e. acidification and algal invasions) and management practices (i.e. liming) can (i) induce contrasting responses in biodiversity, FCL and fish production of boreal lakes; (ii) be the primary driver of FCL variation among small and similar-size ecosystems; and (iii) alter the trophic ecology (i.e. TP change during ontogeny and littoral reliance) of key fish species. The trophic ecology and production of apex consumers and FCL together can provide useful integrated proxies for ecosystem functioning, which can supplement traditional biodiversity measurements for more robust environmental assessments.
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| 30. |
- Lau, Danny C. P., et al.
(författare)
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Lowered nutritional quality of plankton caused by global environmental changes
- 2021
-
Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 27:23, s. 6294-6306
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Tidskriftsartikel (refereegranskat)abstract
- Global environmental changes are causing widespread nutrient depletion, declines in the ratio of dissolved inorganic nitrogen (N) to total phosphorus (DIN:TP), and increases in both water temperature and terrestrial colored dissolved organic carbon (DOC) concentration (browning) in high-latitude northern lakes. Declining lake DIN:TP, warming, and browning alter the nutrient limitation regime and biomass of phytoplankton, but how these stressors together affect the nutritional quality in terms of polyunsaturated fatty acid (PUFA) contents of the pelagic food web components remains unknown. We assessed the fatty acid compositions of seston and zooplankton in 33 lakes across south-to-north and boreal-to-subarctic gradients in Sweden. Data showed higher lake DIN:TP in the south than in the north, and that boreal lakes were warmer and browner than subarctic lakes. Lake DIN:TP strongly affected the PUFA contents—especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—in seston, calanoids, and copepods (as a group), but not in cladocerans. The EPA+DHA contents increased by 123% in seston, 197% in calanoids, and 230% in copepods across a lake molar DIN:TP gradient from 0.17 to 14.53, indicating lower seston and copepod nutritional quality in the more N-limited lakes (those with lower DIN:TP). Water temperature affected EPA+DHA contents of zooplankton, especially cladocerans, but not seston. Cladoceran EPA+DHA contents were reduced by ca. 6% for every 1°C increase in surface water. Also, the EPA, DHA, or EPA+DHA contents of Bosmina, cyclopoids, and copepods increased in lakes with higher DOC concentrations or aromaticity. Our findings indicate that zooplankton food quality for higher consumers will decrease with warming alone (for cladocerans) or in combination with declining lake DIN:TP (for copepods), but impacts of these stressors are moderated by lake browning. Global environmental changes that drive northern lakes toward more N-limited, warmer, and browner conditions will reduce PUFA availability and nutritional quality of the pelagic food web components.
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| 31. |
- Lau, Danny C P, et al.
(författare)
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Macroinvertebrate traits in Arctic streams reveal latitudinal patterns in physiology and habits that are strongly linked to climate
- 2023
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Ingår i: Frontiers in Ecology and Evolution. - 2296-701X. ; 11
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: Arctic freshwater ecosystems are undergoing rapid environmental transformation because of climate change, which is predicted to produce fundamental alterations in river community structure and function.Methods: We explored how climate change affects benthic invertebrate communities of Arctic streams by examining patterns of their biological traits along latitudinal and climatic gradients in eastern North America (Canada) and northwestern Europe (Sweden, Norway).Results: Despite differences in taxonomic composition between continents, we identified similarities in the functional trait niche (FTN) of predominant macroinvertebrate taxonomic groups. Trait composition differed by latitude in eastern Canada, with a predominance of cold-tolerant taxa, tubular body shape, and cased and attached habits at the highest latitudes. Differences in trait composition were evident among ecoregions in Europe, with trait dominance at the highest latitudes that was comparable to North America. There was a similar increase in the relative abundance of cold tolerance and tubular body shape and a decrease in obligate shredders and trait richness with decreasing temperatures across both continents.Discussion: These patterns are indicative of FTNs that include physiological traits and habits that are advantageous for the low temperatures, short ice-free period, and low riparian vegetation cover at the highest latitudes. We predict that climate change will lead to an increase in functional diversity at high latitudes, as organisms with trait modalities that are currently only found at lower latitudes move northward. However, this change in trait composition will be mediated by the effect of spatial connectivity on dispersal ability, with slower change occurring on Arctic islands. These findings can support modelling of future change in Arctic freshwater assemblages in response to ongoing climate change.
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| 32. |
- Lau, Danny C. P., et al.
(författare)
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Multitrophic biodiversity patterns and environmental descriptors of sub‐Arctic lakes in northern Europe
- 2022
-
Ingår i: Freshwater Biology. - : John Wiley & Sons. - 0046-5070 .- 1365-2427. ; 67:1, s. 30-48
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Tidskriftsartikel (refereegranskat)abstract
- 1. Arctic and sub‐Arctic lakes in northern Europe are increasingly threatened by climate change, which can affect their biodiversity directly by shifting thermal and hydrological regimes, and indirectly by altering landscape processes and catchment vegetation. Most previous studies of northern lake biodiversity responses to environmental changes have focused on only a single organismal group. Investigations at whole‐lake scales that integrate different habitats and trophic levels are currently rare, but highly necessary for future lake monitoring and management.2. We analysed spatial biodiversity patterns of 74 sub‐Arctic lakes in Norway, Sweden, Finland, and the Faroe Islands with monitoring data for at least three biological focal ecosystem components (FECs)—benthic diatoms, macrophytes, phytoplankton, littoral benthic macroinvertebrates, zooplankton, and fish—that covered both pelagic and benthic habitats and multiple trophic levels.3. We calculated the richnessrelative (i.e. taxon richness of a FEC in the lake divided by the total richness of that FEC in all 74 lakes) and the biodiversity metrics (i.e. taxon richness, inverse Simpson index (diversity), and taxon evenness) of individual FECs using presence–absence and abundance data, respectively. We then investigated whether the FEC richnessrelative and biodiversity metrics were correlated with lake abiotic and geospatial variables. We hypothesised that (1) individual FECs would be more diverse in a warmer and wetter climate (e.g. at lower latitudes and/or elevations), and in hydrobasins with greater forest cover that could enhance the supply of terrestrial organic matter and nutrients that stimulated lake productivity; and (2) patterns in FEC responses would be coupled among trophic levels.4. Results from redundancy analyses showed that the richnessrelative of phytoplankton, macrophytes, and fish decreased, but those of the intermediate trophic levels (i.e. macroinvertebrates and zooplankton) increased with decreasing latitude and/or elevation. Fish richnessrelative and diversity increased with increasing temporal variation in climate (temperature and/or precipitation), ambient nutrient concentrations (e.g. total nitrogen) in lakes, and woody vegetation (e.g. taiga forest) cover in hydrobasins, whereas taxon richness of macroinvertebrates and zooplankton decreased with increasing temporal variation in climate.5. The similar patterns detected for richnessrelative of fish, macrophytes, and phytoplankton could be caused by similar responses to the environmental descriptors, and/or the beneficial effects of macrophytes as habitat structure. By creating habitat, macrophytes may increase fish diversity and production, which in turn may promote higher densities and probably more diverse assemblages of phytoplankton through trophic cascades. Lakes with greater fish richnessrelative tended to have greater average richnessrelative among FECs, suggesting that fish are a potential indicator for overall lake biodiversity.6. Overall, the biodiversity patterns observed along the environmental gradients were trophic‐level specific, indicating that an integrated food‐web perspective may lead to a more holistic understanding of ecosystem biodiversity in future monitoring and management of high‐latitude lakes. In future, monitoring should also focus on collecting more abundance data for fish and lower trophic levels in both benthic and pelagic habitats. This may require more concentrated sampling effort on fewer lakes at smaller spatial scales, while continuing to sample lakes distributed along environmental gradients.
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| 33. |
- Lau, Danny C P
(författare)
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Preservation effects on C/N ratios and stable isotope signatures of freshwater fishes and benthic macroinvertebrates
- 2012
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Ingår i: Limnology and Oceanography: Methods. - : Wiley. - 1541-5856. ; 10, s. 75-89
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Tidskriftsartikel (refereegranskat)abstract
- This study examined the effects of fluid preservatives on carbon and nitrogen stable isotopes (δ13C and δ15N) and C/N ratios of freshwater animals. Brotia hainanensis snails, Caridina cantonensis and Macrobrachium hainanense shrimps, and Pseudogastromyzon myersi, Liniparhomaloptera disparis, and Ctenogobius duospilus fishes were collected from seven Hong Kong streams, so as to incorporate natural variations in isotopic signals among conspecifics. Samples were preserved with 10% formalin, 70% ethanol, or formalin-ethanol solution (fixation in formalin then storage in ethanol). We compared sample molar C/N, δ13C, and δ15N with frozen conspecifics after 30, 60, 90, 180, and 360 d. Increases in C/N were evident in formalin-fixed shrimps and fish only, whereas ΔC/N attributable to ethanol and formalin-ethanol preservation was insignificant in all species. Chemical preservation generally caused δ13C depletion in fishes and Δδ13C significantly declined over time in formalin-ethanol-preserved L. disparis. Formalin-induced δ13C shifts were observed in shrimps (C. cantonensis: -1.54‰; M. hainanense: -0.80‰) and snails (-0.25‰) and were relatively consistent when preservation was ≤ 60 d. The influence of formalin-ethanol on C/N and δ 13C was smaller than that of formalin for all species and more consistent than ethanol preservation. δ 15N of all species was unaffected (within ±1‰) by chemical preservation. Effects on isotopic signals were more predictable among fishes than shrimps or snails. Corrections of +1.11‰ and +1.24‰ should be applied to δ13C of fishes preserved with formalin and formalin-ethanol (respectively) during trophic analysis. We recommend using formalin-ethanol for macroinvertebrates to limit isotopic shifts, especially those preserved for > 60 d.
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| 34. |
- Lento, Jennifer, et al.
(författare)
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Temperature and spatial connectivity drive patterns in freshwater macroinvertebrate diversity across the Arctic
- 2022
-
Ingår i: Freshwater Biology. - : John Wiley & Sons. - 0046-5070 .- 1365-2427. ; 67:1, s. 159-175
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Tidskriftsartikel (refereegranskat)abstract
- Warming in the Arctic is predicted to change freshwater biodiversity through loss of unique taxa and northward range expansion of lower latitude taxa. Detecting such changes requires establishing circumpolar baselines for diversity, and understanding the primary drivers of diversity. We examined benthic macroinvertebrate diversity using a circumpolar dataset of >1,500 Arctic lake and river sites. Rarefied α diversity within catchments was assessed along latitude and temperature gradients. Community composition was assessed through region-scale analysis of β diversity and its components (nestedness and turnover), and analysis of biotic–abiotic relationships. Rarefied α diversity of lakes and rivers declined with increasing latitude, although more strongly across mainland regions than islands. Diversity was strongly related to air temperature, with the lowest diversity in the coldest catchments. Regional dissimilarity was highest when mainland regions were compared with islands, suggesting that connectivity limitations led to the strongest dissimilarity. High contributions of nestedness indicated that island regions contained a subset of the taxa found in mainland regions. High Arctic rivers and lakes were predominately occupied by Chironomidae and Oligochaeta, whereas Ephemeroptera, Plecoptera, and Trichoptera taxa were more abundant at lower latitudes. Community composition was strongly associated with temperature, although geology and precipitation were also important correlates. The strong association with temperature supports the prediction that warming will increase Arctic macroinvertebrate diversity, although low diversity on islands suggests that this increase will be limited by biogeographical constraints. Long-term harmonised monitoring across the circumpolar region is necessary to detect such changes to diversity and inform science-based management.
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| 35. |
- Olid, Carolina, 1981-, et al.
(författare)
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The Role of Methane Transport From the Active Layer in Sustaining Methane Emissions and Food Chains in Subarctic Ponds
- 2021
-
Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 126:3
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Tidskriftsartikel (refereegranskat)abstract
- Groundwater discharge from the seasonally thawed active layer is increasingly recognized as an important pathway for delivering methane (CH4) into Arctic lakes and streams, but its contribution to CH4 emissions from thaw ponds and its influence on the trophic support and nutritional quality of pond food chains remains unexplored. We quantified the transport of CH4 from the active layer through groundwater discharge into thaw ponds in a subarctic catchment in northern Sweden, using radon (222Rn) as groundwater tracer. We analyzed stable isotopes and fatty acids of pond macroinvertebrates to evaluate the potential effects of groundwater-mediated CH4 inputs on the aquatic food chains. Our results indicate that active layer groundwater discharge flows are nontrivial (range 6%–46% of pond volume per day) and the associated CH4 fluxes (median 339 mg C m−2day−1, interquartile range [IQR]: 179–419 mg C m−2 day−1) can sustain the diffusive CH4 emissions from most of the ponds (155 mg C m−2 day−1, IQR: 55–234 mg C m−2 day−1). Consumers in ponds receiving greater CH4 inputs from the active layer had lower stable carbon (C) isotope signatures that indicates a greater trophic reliance on methane oxidizing bacteria (MOB), and they had lower nutritional quality as indicated by their lower tissue concentrations of polyunsaturated fatty acids. Overall, this work links physical (CH4 transport from the active layer), biogeochemical (CH4 emission), and ecological (MOB-consumer interaction) processes to provide direct evidence for the role of active layer groundwater discharge in CH4 cycling of subarctic thaw ponds.
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| 36. |
- Palstev, Aleksey, et al.
(författare)
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Phytoplankton biomass in northern lakes reveals a complex response to global change
- 2024
-
Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 940
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Tidskriftsartikel (refereegranskat)abstract
- Global change may introduce fundamental alterations in phytoplankton biomass and community structure that can alter the productivity of northern lakes. In this study, we utilized Swedish and Finnish monitoring data from lakes that are spatially (135 lakes) and temporally (1995-2019, 110 lakes) extensive to assess how phytoplankton biomass (PB) of dominant phytoplankton groups related to changes in water temperature, pH and key nutrients [total phosphorus (TP), total nitrogen (TN), total organic carbon (TOC), iron (Fe)] along spatial (Fennoscandia) and temporal (25 years) gradients. Using a machine learning approach, we found that TP was the most important determinant of total PB and biomass of a specific species of Raphidophyceae - Gonyostomum semen - and Cyanobacteria (both typically with adverse impacts on food-webs and water quality) in spatial analyses, while Fe and pH were second in importance for G. semen and TN and pH were second and third in importance for Cyanobacteria. However, in temporal analyses, decreasing Fe and increasing pH and TOC were associated with a decrease in G. semen and an increase in Cyanobacteria. In addition, in many lakes increasing TOC seemed to have generated browning to an extent that significantly reduced PB. The identified discrepancy between the spatial and temporal results suggests that substitutions of data for space-for-time may not be adequate to characterize long-term effects of global change on phytoplankton. Further, we found that total PB exhibited contrasting temporal trends (increasing in northern- and decreasing in southern Fennoscandia), with the decline in total PB being more pronounced than the increase. Among phytoplankton, G. semen biomass showed the strongest decline, while cyanobacterial biomass showed the strongest increase over 25 years. Our findings suggest that progressing browning and changes in Fe and pH promote significant temporal changes in PB and shifts in phytoplankton community structures in northern lakes.
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| 37. |
- Ramberg, Ellinor, et al.
(författare)
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The Structure of Riparian Vegetation in Agricultural Landscapes Influences Spider Communities and Aquatic-Terrestrial Linkages
- 2020
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Ingår i: Water. - : MDPI. - 2073-4441. ; 12:10
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Tidskriftsartikel (refereegranskat)abstract
- Riparian habitats are important ecotones connecting aquatic and terrestrial ecosystems, but are often highly degraded by human activities. Riparian buffers might help support impacted riparian communities, and improve trophic connectivity. We sampled spider communities from riparian habitats in an agricultural catchment, and analyzed their polyunsaturated fatty acid (PUFA) content to quantify trophic connectivity. Specific PUFAs are exclusively produced by stream algae, and thus are used to track uptake of aquatic resources by terrestrial consumers. Riparian spiders were collected from 10 site pairs situated along agricultural streams, and from five forest sites (25 sites total). Each agricultural site pair comprised an unshaded site with predominantly herbaceous vegetation cover, and a second with a woody riparian buffer. Spider communities differed between site types, with web-building spiders dominating woody buffered sites and free-living spiders associated with more open habitats. PUFA concentrations were greatest overall in free-living spiders, but there was also evidence for increased PUFA uptake by some spider groups when a woody riparian buffer was present. Our results reveal the different roles of open and wooded riparian habitats in supporting terrestrial consumers and aquatic-terrestrial connectivity, and highlight the value of incorporating patches of woody vegetation within riparian networks in highly modified landscapes.
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| 38. |
- Wang, Teng-Wei, et al.
(författare)
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Autochthony and isotopic niches of benthic fauna at shallow-water hydrothermal vents
- 2022
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The food webs of shallow-water hydrothermal vents are supported by chemosynthetic and photosynthetic autotrophs. However, the relative importance of these two basal resources for benthic consumers and its changes along the physicochemical gradient caused by vent plumes are unknown. We used stable carbon and nitrogen isotopes (i.e., δ13C and δ15N) and Bayesian mixing models to quantify the dietary contribution of basal resources to the benthic fauna at the shallow-water vents around Kueishan Island, Taiwan. Our results indicated that the food chains and consumer production at the shallow-water vents were mainly driven by photoautotrophs (total algal contribution: 26–54%) and zooplankton (19–34%) rather than by chemosynthetic production (total contribution: 14–26%). Intraspecific differences in the trophic support and isotopic niche of the benthic consumers along the physicochemical gradient were also evident. For instance, sea anemone Anthopleura sp. exhibited the greatest reliance on chemosynthetic bacteria (26%) and photoautotrophs (66%) near the vent openings, but zooplankton was its main diet in regions 150–300 m (32–49%) and 300–700 m (32–78%) away from the vent mouths. The vent-induced physicochemical gradient structures not only the community but also the trophic support and isotopic niche of vent consumers.
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