| 1. |
- Engwall, Magnus, 1965-, et al.
(författare)
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Biological and chemical determination of contaminant levels in settling particulate matter and sediments : a Swedish river system before, during, and after dredging of PCB-contaminated lake sediments
- 1998
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Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 27:5, s. 403-410
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Tidskriftsartikel (refereegranskat)abstract
- A sensitive bioassay, based on EROD induction in cultured chicken embryo livers, was used together with chemical analysis to determine levels of dioxin-like contaminants in particulate matter in Eman. Extracts of sediment and settling particulate matter (SPM) collected in the river system before, during, and after dredging of a PCB contaminated lake, Lake Jarnsjon, were separated into three fractions containing a) monoaromatic/aliphatic; b) diaromatic (e.g., PCBs and polychlorinated dibenzodioxins and dibenzofurans); and c) polyaromatic compounds (e.g., polycyclic aromatic hydrocarbons). The samples from Lake Jarnsjon contained the highest PCB concentrations and the diaromatic extracts from Lake Jarnsjon samples showed the highest activities of EROD-inducing diaromatic compounds. The dioxin-like activity of the diaromatic fraction in sediment collected after the dredging of Jarnsjon had only around 1% of the activity of the pre-dredging sediment, showing that the remediation was successful in terms of removal of the PCB-contaminated sediment from the lake. In SPM collected immediately downstream from Jarnsjon, levels of diaromatic dioxin-like compounds were elevated during the dredging, and decreased after that. The post-dredging concentrations were however higher than in SPM from lakes upstream of Jarnsjon, showing that elevated levels of dioxin-like diaromatic compounds were still present in the water System downstream of Jarnsjon a couple of years after the dredging.
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| 2. |
- Kuparinen, Jorma, et al.
(författare)
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Food web structure and function in the Gulf of Bothnia, the Baltic Sea
- 1996
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Ingår i: Ambio. - Stockholm : Swedish Royal Academy of Sciences. - 0044-7447 .- 1654-7209. ; , s. 13-21
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Tidskriftsartikel (refereegranskat)abstract
- To improve the spatio-temporal information of ecological variables, a multidisciplinary joint study between Finnish and Swedish marine scientists was conducted in the Gulf of Bothnia, 1991. The study corroborated previous reports, suggesting a markedly lower phytoplankton production and biomass of benthic fauna in the Bothnian Bay than in the Bothnian Sea, However, contrary to the general view, the offshore carbon fixation in the Bothnian Sea exceeded that at the corresponding coastal station. The results further indicated a greater importance of bacterioplankton production to the food web in the Bothnian Bay than previously assumed. The total carbon requirement of bacteria and zooplankton was estimated to exceed carbon fixation by a factor of 1.7 in the northern basin, possibly a result of the discharge of riverine organic carbon. Diversity and biomass of both fish and benthic fauna were lower in the Bothnian Bay, with benthic meiofauna being of relatively greater importance than macrofauna in this basin.
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| 3. |
- Molau, U, et al.
(författare)
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Responses of subarctic-alpine plant communities to simulated environmental change : Biodiversity of bryophytes, lichens, and vascular plants
- 1998
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Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 27:4, s. 322-329
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Tidskriftsartikel (refereegranskat)abstract
- The predicted changes in climate over the next 50 years are expected to be most pronounced in arctic and subarctic regions. In the present study, we examine the responses of a subarctic-alpine rich meadow and poor heath community to factorial manipulations of temperature and nutrient treatments. Specifically, we address response to the treatments in terms of biodiversity and relative cover of the bryophyte, lichen and vascular plant communities. We point out that the responses differ among mosses, lichens, vascular plants, and communities, and this will probably cause shifts in the dominance of both bottom layer and canopy layer species. It is important to note that the decrease in cover and species number of the bottom layer mainly occurred due to a decline in mosses; in contrast, lichen cover increased in all treatments in both communities. Climate change may thus cause a shift in the bottom layer from being dominated by mosses, to become dominated by lichens.
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| 4. |
- Ndaro, Simon G. M., et al.
(författare)
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Small-Scale Variation in Major Meiofaunal Taxa and Sediment Chemistry in Tropical Sediments
- 1995
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Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 24:7/8, s. 470-474
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Tidskriftsartikel (refereegranskat)abstract
- Variations in sediment biochemistry and abundance of meiofauna were investigated in three tropical habitats: mangrove forest, intertidal lagoon, and subtidal reef area in eastern Africa. Both the biochemical components of the pore water and the meiofauna varied substantially over small distances in all three habitats. In the mangrove area, the color of the pore water was found to be positively correlated with the major meiofaunal taxa, especially the nematodes. In the coastal lagoon, polychaetes showed negative correlation with particulate organic matter while other groups showed no correlation with any of the chemical components analyzed. In the subtidal reef area no chemical components were found to correlate with the meiofauna. When data from the three habitats are taken together two clear associations emerge. First, grain size shows a highly significant relationship with both total fauna and nematode numbers. Second, there is clear association between the amount of particulate organic carbon and particulate organic nitrogen in the pore water.
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| 5. |
- Strömquist, L, et al.
(författare)
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Utilizing landscape information to analyze and predict environmental change : The extended baseline perspective - Two Tanzanian examples
- 1999
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Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 28:5, s. 436-443
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Tidskriftsartikel (refereegranskat)abstract
- This paper illustrates the need for a revival and renewal of landscape analysis in order to identify, evaluate and predict environmental change in environmental impact assessment (EIA) and development perspectives. An initial focus on the landscape, rather than on individual systems or processes, makes it possible to widen the scope of study, to assess change in different temporal and spatial perspectives and thereafter to converge on key issues of relevance for specific areas or development projects. This approach can be seen as a process rather than a method, which calls for intradisciplinary competence in data collection and evaluation as well as an interdisciplinary assessment capability. A combination of such scientific competence, local knowledge, and experiences of the local environment is used to widen the assessment perspectives and the prediction competence. The approach is illustrated by its application in two Tanzanian studies. The Southern Highland study emerged from two feasibility environmental impact assessments (EIAs) of proposed hydropower projects whilst the Babati study was initiated as a result of previous sectorial research on land management, which had to be analyzed in broader perspectives. In both cases, a need to define environmental baselines to assess land use and project related environmental change had been defined by different donor agencies. One conclusion from our study is, however, that there is no such thing as an environmental baseline, rather a baseline that has to be extended in different temporal and spatial perspectives to fully understand and predict environmental and related social change. This study can therefore be seen as a contribution to a new understanding of environmental change that is required for strategic environmental impact assessments and long-term natural resource-use planning.
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| 6. |
- Wiklund, Christer G., et al.
(författare)
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Lemming predators on the Siberian tundra
- 1999
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Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 28:3, s. 281-286
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Tidskriftsartikel (refereegranskat)abstract
- In the Eurasian Arctic, the most common lemming species are the Siberian lemming (Lemmus sibiricus) and the collared lemming (Dicrostonyx torquatus). Lemmings constitute the main food item for 5 common predators in the area: arctic fox; snowy owl; rough-legged buzzard; long-tailed skua; and pomarine skua. Hence, these predators form a foraging guild. We have studied factors influencing the structure of this guild. When comparing cooccurrence of the predators between 17 sites across Siberia, there were positive associations between the snowy owl and the two skuas, and a negative association between snowy owl and rough-legged buzzard. There was also a large variation in local population density among the predators, conceivably, due to the risk of intra-guild predation as well as the variation in food supply. There were significant relationships between lemming abundance and the abundance of each predator. An analysis of the predatory response by the arctic fox indicated a response pattern similar to that of a delayed numerical response to lemming abundance. For this and other reasons, we propose that the arctic fox is a resident specialist predator on microtine rodents. Further, the birds appeared to be nomadic specialist predators with, perhaps, one exception, the rough-legged buzzard.
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