排序方式: 共有2条查询结果,搜索用时 15 毫秒
1
1.
Energy (carbon) flows and element cycling are fundamental, interlinked principles explaining ecosystem processes. The element
balance in components, interactions and processes in ecosystems (ecological stoichiometry; ES) has been used to study trophic
dynamics and element cycling. This study extends ES beyond its usual limits of C, N, and P and examines the distribution and
transfer of 48 elements in 16 components of a coastal ecosystem, using empirical and modeling approaches. Major differences
in elemental composition were demonstrated between abiotic and biotic compartments and trophic levels due to differences in
taxonomy and ecological function. Mass balance modeling for each element, based on carbon fluxes and element:C ratios, was
satisfactory for 92.5% of all element–compartment combinations despite the complexity of the ecosystem model. Model imbalances
could mostly be explained by ecological processes, such as increased element uptake during the spring algal bloom. Energy
flows in ecosystems can thus realistically estimate element transfer in the environment, as modeled uptake is constrained
by metabolic rates and elements available. The dataset also allowed us to examine one of the key concepts of ES, homeostasis,
for more elements than is normally possible. The relative concentrations of elements in organisms compared to their resources
did not provide support for the theory that autotrophs show weak homeostasis and showed that the strength of homeostasis by
consumers depends on the type of element (for example, macroelement, trace element). Large-scale, multi-element ecosystem
studies are essential to evaluate and advance the framework of ES and the importance of ecological processes. 相似文献
2.
Due to the long half-lives of many radionuclides, safety assessments of nuclear waste facilities often need to consider the potential fate of radionuclides discharged to the environment in the future. In this study we explored the environmental fate of a hypothetical 14C release from a nuclear waste repository to a Baltic Sea bay in 2000 years. This was accomplished by connecting spatially linked biomasses and metabolic rates from a carbon flow model of the ecosystem at the site today to predicted changes in geomorphology and water exchange regimes. The employed extrapolation method was selected as shoreline displacement due to land-rise and sea level changes is the main process that affects the development of the coastal ecosystem around the repository in the coming 10 000 years. The modelling results indicate that the ecosystem will go through changes in several ecosystem properties in the coming 2000-year period, e.g. a decreased rate of primary production and changed feeding preferences of the fish community. Also, a decreased total biomass is expected and an ecosystem change altering the balance between producers and consumers towards a dominance of benthic plants. The changes of the ecosystem structure and carbon dynamics will also influence the potential fate of future discharges of 14C. We estimated an up to 1000 times higher 14C concentrations in biota compared to today. However, due to radioactive decay and reduced total biomass in the receiving ecosystem, the proportion of accumulated radionuclides is expected to decrease. Although the modelling approach used in this study is associated with several sources of uncertainty, it provides a way to both qualitatively and quantitatively assess likely effects of future discharges of contaminants. 相似文献
1