| 241. |
- Herath, Tharindu, et al.
(author)
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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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In: Canadian Journal of Fisheries and Aquatic Sciences. - : Canadian Science Publishing. - 0706-652X .- 1205-7533. ; 79:8, s. 1291-1301
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Journal article (peer-reviewed)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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| 242. |
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| 243. |
- Karlsson, Magnus, et al.
(author)
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International and ethnic variability of falls in older men
- 2014
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In: Scandinavian journal of public health. - : SAGE Publications. - 1651-1905 .- 1403-4948. ; 42:2, s. 194-200
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Journal article (peer-reviewed)abstract
- Aims: Fallers and especially recurrent fallers are at high risk for injuries. The aim of this study was to evaluate fall epidemiology in older men with special attention to the influence of age, ethnicity and country of residence. Methods: 10,998 men aged 65 years or above recruited in Hong Kong, the United States (US) and Sweden were evaluated in a cross-sectional retrospective study design. Self-reported falls and fractures for the preceding 12 months were registered through questionnaires. Group comparisons were done by chi-square test or logistic regression. Results: The proportion of fallers among the total population was 16.5% in ages 65-69, 24.8% in ages 80-84 and 43.2% in ages above 90 (P <0.001). The corresponding proportions of recurrent fallers in the same age groups were 6.3%, 10.1% and 18.2%, respectively (P <0.001), and fallers with fractures 1.0%, 2.3% and 9.1%, respectively (P <0.001). The proportion of fallers was highest in the US, intermediate in Sweden and lowest in Hong Kong (in most age groups P <0.05). The proportion of fallers among white men in the US was higher than in white men in Sweden (all comparable age groups P <0.01) but there were no differences in the proportion of fallers in US men with different ethnicity. Conclusions: The proportion of fallers in older men is different in different countries, and data in this study corroborate with the view that society of residence influences fall prevalence more than ethnicity.
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| 244. |
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| 245. |
- Lau, Danny C P, et al.
(author)
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Autochthonous resources are the main driver of consumer production in dystrophic boreal lakes
- 2014
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In: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 95, s. 1506-1519
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Journal article (peer-reviewed)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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| 246. |
- Lau, Danny C P, et al.
(author)
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Cross-ecosystem differences in lipid composition and growth limitation of a benthic generalist consumer
- 2013
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In: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 58, s. 1149-1164
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Journal article (peer-reviewed)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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| 247. |
- Lau, Danny C P
(author)
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Data for: Variation in fatty acid content among benthic invertebrates in a seasonally driven system
- 2023
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Other publication (other academic/artistic)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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| 248. |
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| 249. |
- Lau, Danny C P, et al.
(author)
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Fatty-acid based assessment of benthic food-web responses to multiple stressors in a large river system
- 2023
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In: Environmental Pollution. - 0269-7491 .- 1873-6424. ; 337
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Journal article (peer-reviewed)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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| 250. |
- Lau, Danny C P, et al.
(author)
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Fatty acid composition of consumers in boreal lakes - variation across species, space and time
- 2012
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In: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 57, s. 24-38
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Journal article (peer-reviewed)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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