| 11. |
- Abreu, PC, et al.
(author)
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Eutrophication processes and trophic interactions in a shallow estuary: Preliminary results based on stable isotope analysis (delta C-13 and delta N-15)
- 2006
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In: Estuaries and Coasts. - 1559-2731. ; 29:2, s. 277-285
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Journal article (peer-reviewed)abstract
- Stable isotopes ratios (delta C-13 and delta N-15) were measured in primary producers and consumers of two bays with contrasting eutrophic conditions in the pains Lagoon estuary, southern Brazil: the Justino bay, a more pristine ecosystem, and the Mangueira bay, a heavily polluted region that receives the Rio Grande city sewage and effluents of several industries. delta C-13 values of organisms collected in both subsystems were not different, but delta N-15 values had significant statistical differences, ca. 3.5 parts per thousand higher in the Mangueira bay. It is likely that primary producers and consumers in this subsystem are greatly influenced by higher nitrogen input due to domestic and industrial sewages. The stable isotope analysis also corroborated several trophic interactions previously established by gut content analysis, and due to its higher sensitivity, it was possible to better determine the contributions of different primary producers and detrital fractions to the consumers' diets. It was confirmed that plant detritus represents the main food source for most organisms. The stable isotope analysis also demonstrated that detritivorous benthic organisms in the same habitat have distinct diet compositions, with differential consumption of C3 and C4 plants. This technique showed that some consumers that eat detritus do not have in their stable isotopic signature any relationship with that of plants. It is likely that these consumers assimilate their carbon and nitrogen from other sources like microalgae or microorganisms that colonize decaying plants.
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| 12. |
- Ackefors, Hans
(author)
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Global fisheries - threats and opportunities
- 2009
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In: Fisheries, sustainablity and development. - Stockholm : Kungl. Skogs- och lantbruksakademien. ; , s. 35-68-
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Book chapter (other academic/artistic)
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| 13. |
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| 14. |
- Adelsköld, Göran
(author)
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Basin characteristics and nutrient losses: the EUROHARP catchment network perspective
- 2009
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In: Journal of Environmental Monitoring. - : Royal Society of Chemistry (RSC). - 1464-0325 .- 1464-0333. ; 11, s. 515-525
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Journal article (peer-reviewed)abstract
- The EC-funded EUROHARP project studies the harmonisation of modelling tools to quantify nutrient losses from diffuse sources. This paper describes a set of study areas used in the project from geographical conditions, to land use and land management, geological and hydro-geological perspectives. The status of data availability throughout Europe in relation to the modelling requirements is presented. The relationships between the catchment characteristics and the nutrient export are investigated, using simple data available for all the catchments. In addition, this study also analyses the hydrological representativity of the time series utilised in the EUROHARP project.
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| 15. |
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| 16. |
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| 17. |
- Aerts, R, et al.
(author)
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Nutritional constraints on Sphagnum-growth and potential decay in northern peatlands
- 2001
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In: Journal of Ecology. - : Wiley. - 1365-2745 .- 0022-0477. ; 89:2, s. 292-299
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Journal article (peer-reviewed)abstract
- 1 In a 4-year fertilization experiment we studied the effects of increased nitrogen (N) or phosphorus (P) supply on productivity and potential decay in the acrotelm of Sphagnum-dominated Swedish peatlands at northern (low atmospheric N input: low-N site) and southern (high atmospheric N input: high-N site) sites. 2 During the experimental period, there was a severe summer drought at the high-N site which led to strong limitations on Sphagnum growth, especially in the fertilized treatments. There were no significant effects of the nutrient treatments on cumulative length growth and productivity at either site. There were, however, significant effects of site and nutrient treatment on nutritional variables of the Sphagnum species. 3 Nitrogen concentration in living capitula was lower, but P concentration was higher at the low-N site than at the high-N site. However, at both sites N and P concentration in the living capitula showed only minor responses to the nutrient additions. 4 Litter chemistry variables differed significantly among sites and treatments. Sphagnum litter had lower N concentration, higher P concentration, a higher C : N ratio, a lower C : P ratio and a lower N : P ratio at the low-N site. Litter chemistry was significantly affected by the nutrient treatments only at the high-N site, where litter P concentrations increased significantly in the P-fertilized treatment, whereas C : P and N : P ratios showed a significant reduction. 5 Although potential rates of decay of Sphagnum litter were higher at the high-N site than at the low-N site, they were not significantly affected by nutrient additions. Potential decay rates did, however, show significant relations with all the litter chemistry variables we had determined. 6 An increase in nitrogen input to Sphagnum-dominated bogs appears to lead to higher N concentrations in litter and, as a result of dilution, to lower P concentrations. This change in litter chemistry leads to a higher potential decay rate of the litter and this may seriously affect the carbon balance in the acrotelm of these systems. 7 Our results also show that carbon balance characteristics of Sphagnum bogs can be strongly affected by unpredictable extreme climatic conditions. This suggests that the occurrence and consequences of these events need more attention when long-term responses of ecosystems to global change are studied.
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| 18. |
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| 19. |
- Agrell, Cecilia, et al.
(author)
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PCB congeners in precipitation, wash out ratios and depositional fluxes within the Baltic Sea region, Europe
- 2002
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In: Atmospheric Environment. - 1352-2310. ; 36:2, s. 371-383
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Journal article (peer-reviewed)abstract
- Concentrations of PCB congeners were determined in precipitation and the annual and seasonal depositional fluxes were calculated for 16 (mostly rural) stations around the Baltic Sea during 1990-1993. The concentrations of individual congeners in precipitation were found to be influenced by atmospheric concentrations of PCBs, ambient temperature, precipitation volume and physico-chemical properties of the compounds. Median levels of PCBs in precipitation differed one order of magnitude between stations. When analyzing all data together to obtain regional trends, concentrations of PCBs in precipitation decreased with increasing temperature. This relationship was the same for all stations but differed in the magnitude of the slope for individual congeners. Low chlorinated PCB congeners showed steeper slopes for the temperature relationship than did high chlorinated congeners, a result explained by high atmospheric concentrations of the low chlorinated congeners during low temperatures. Annual wash out ratios were between 31 and 72 x 103 and tended to be higher for the high chlorinated congeners. Wash out ratios decreased with increasing temperature for all congeners except PCB-33. At snow scavenging events, the wash out ratio of PCBs increased with a factor of 2. Latitudinal trends for PCB concentrations in precipitation and deposition were generally not statistically significant. The calculated yearly deposition of PCBs to the Baltic Sea was 390 and 5-18 kg for individual congeners, with PCB-138 having the highest flux. Deposition of PCB congeners varied seasonally, with a factor between 2 and 3, and was generally highest during fall. Relatively higher deposition of low chlorinated congeners compared to high chlorinated congeners was found during winter. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 20. |
- Agrell, Jep, et al.
(author)
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CO2 and O-3 effects on host plant preferences of the forest tent caterpillar (Malacosoma disstria)
- 2005
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In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 11:4, s. 588-599
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Journal article (peer-reviewed)abstract
- Elevated levels of CO2 and O-3 affect plant growth and phytochemistry, which in turn can alter physiological performance of associated herbivores. Little is known, however, about how generalist insect herbivores respond behaviorally to CO2- and O-3-mediated changes in their host plants. This research examined the effects of elevated CO2 and O-3 levels on host plant preferences and consumption of forest tent caterpillar (FTC, Malacosoma disstria Hbn.) larvae. Dual choice feeding assays were performed with foliage from birch (Betula papyrifera Marsh.) and aspen (Populus tremuloides Michx., genotypes 216 and 259). Trees were grown at the Aspen Free Air CO2 Enrichment (FACE) facility near Rhinelander, WI, USA, and had been exposed to ambient or elevated concentrations of CO2 and/or O-3. Levels of nutritional and secondary compounds were quantified through phytochemical analyses. The results showed that elevated O-3 levels increased FTC larval preferences for birch compared with aspen, whereas elevated CO2 levels had the opposite effect. In assays with the two aspen genotypes, addition of both CO2 and O-3 caused a shift in feeding preferences from genotype 259 to genotype 216. Consumption was unaffected by experimental treatments in assays comparing aspen and birch, but were increased for larvae given high O-3 foliage in the aspen genotype assays. Elevated levels of CO2 and O-3 altered tree phytochemistry, but did not explain shifts in feeding preferences. The results demonstrate that increased levels of CO2 and O-3 can alter insect host plant preferences both between and within tree species. Also, consequences of altered host quality (e.g., compensatory consumption) may be buffered by partial host shifts in situations when alternative plant species are available. Environmentally induced changes in host plant preferences may have the potential to alter the distribution of herbivory across plant genotypes and species, as well as competitive interactions among them.
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