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91.
Comparison of benthic foraminiferal and macrofaunal responses to organic pollution in the Firth of Clyde (Scotland) 总被引：1，自引：1，他引：0
By comparing benthic foraminiferal and macrofaunal responses to sewage sludge disposal in the Firth of Clyde (Scotland), we wanted to investigate the possibility of using foraminifera as bio-indicators of marine environmental degradation. Both groups present a similar distributional pattern, with poor faunas composed of species tolerant to strong oxygen depletion near to the disposal site, surrounded by high density of opportunistic species. Farther away, faunal density decreases and equilibrium taxa gradually replace opportunistic species. No more environmental impact is perceptible beyond 3 km. Nevertheless, some differences exist: foraminifera appear to be more impacted at the disposal site, probably as a consequence of the low pH, a supplementary stress factor for organisms provided with a calcareous test. At 3 km west of the disposal site, macrofauna is comparable to the reference station, whereas foraminifera still indicate environmental degradation, suggesting their higher sensitivity to this type of pollution. It appears that benthic foraminifera may add valuable information to open marine environmental monitoring. 相似文献
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93.
富营养化对海洋生态系统的影响及其围隔实验研究 总被引：17，自引：1，他引：16
陆源的营养盐输入引起海洋中的富营养化,提高了水体中营养盐含量,改变了水体中营养盐比例,引起浮游植物水华甚至赤潮。水华发生时由于沿传统食物链的能流在浮游植物环节阻塞,能量过多地分配到微生物环,细菌大量繁殖分解有机物,导致水体缺氧,造成鱼虾贝类窒息死亡。围隔系统是物质相对守恒的系统,围隔与自然海水没有水交换,利用现场围隔实验可以定量地、系统地研究海洋生态系统对富营养化的响应。围隔实验现已成为全球海洋生态系统动力学研究的重要手段。 相似文献
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96.
James G. Cooke 《水文研究》1988,2(2):123-133
The management of the riparian zone has been suggested as a technique for controlling the amounts of phosphorus (P) entering watercourses draining pasture catchments. A study was therefore made of P entering a stream from various sources (rainfall, surface and subsurface derived runoff, direct fallout from aerial topdressing), with the object of providing a rational basis for the design of effective riparian management schemes. P entrained in surface runoff could account for virtually all of the P entering the stream during storms. Approximately 20 per cent of the annual P export from the catchment could be accounted for by direct aerial input of P to the stream during autumn fertilizer topdressing. More than 85 per cent of the P was exported from the catchment as particulate P. Stream sediment had higher P sorption capacities, and were enriched with P relative to the soils from which they were derived. There was a pronounced seasonal variation in sediment enrichment which could be predicted (r2 = 0.92) by the logarithm of the rainfall since fertilizer topdressing (LNFERT) and flood intensity. The amount of P lost in streamflow during any flood event was predicted (r2 = 0.94) by peak flow, seven day antecedent peak flow and LNFERT. Approximately 40 per cent of the 1.3 kg P ha?1 exported during 1981 occurred in four storms with recurrence intervals of more than three months. From a P budget compiled from nine events it was hypothesized that the stream acted as a net sink for P at baseflow and low-medium intensity floods but was a source of P at higher flood intensities. It was concluded that P losses from hill pasture catchments could be reduced by avoidance of direct application of P fertilizer to the stream channel, and by fencing out stock from seasonally saturated areas during periods of saturation. The ultimate success of the latter technique would depend on whether buffer vegetation could retain accumulated P during extreme storm events. 相似文献
97.
Chau KW 《Marine pollution bulletin》2005,51(8-12):1078-1084
The eutrophication phenomenon often leads to undesirable water quality. This paper delineates an unsteady three-dimensional finite difference numerical model for eutrophication dynamics in the coastal waters of Tolo harbour, Hong Kong, employing the numerically generated, boundary-fitted, orthogonal curvilinear grid system as well as a grid “block” technique. It models the transport and interaction of nine water quality constituents. Adjustments of values of some kinetic coefficients in the model are effected through calibration with field data. It is demonstrated that the model can reasonably reproduce the interactions amongst all the water quality constituents, the eutrophication processes and, in particular, the featured bottom water anoxic condition during the summer in Tolo harbour. 相似文献
98.
E. G. Reinhardt M. Little S. Donato D. Findlay A. Krueger C. Clark J. Boyce 《Environmental Geology》2005,47(5):729-739
Frenchmans Bay, on the northern shore of Lake Ontario, has been negatively impacted by eutrophication in the last 50 years through urbanization and the use of chemical fertilizers. Eutrophication began with wholesale land clearance and agricultural practises beginning in the mid-nineteenth century and reached a peak with urbanization after World War II. Eutrophication and the effects of land-use changes on the watershed were investigated by a combined analysis of the sediment magnetic properties and arcellacean (thecamoebian) microfauna. Micropaleontological analyses were conducted on two 2-m-long cores (FMB1 and FMB2) every 10 cm (42 samples) and magnetic susceptibility was measured at 2-cm intervals. Both cores showed a distinct correlative transition at 60 cm and 110 cm that was marked by a rapid increase in thecamoebian concentrations (from approx. 10×103 to 30×103 specimens per cc) and a large increase in Cucurbitella tricuspis (from approx. 10–20% to 40–70%). This transition correlated with a marked increase in magnetic susceptibility (150–200×10–8 m3 Kg–1) at the same depth, which was attributed to elevated levels of detrital magnetic minerals derived from land clearance and soil erosion in the watershed. It was indicated by 210 Pb dates indicate that there was a gradual onset of eutrophication in the mid-nineteenth century (AD 1850±56) and a more rapid rise in the mid-1940s to late 1950s. The initial increase in eutrophication was due to land clearing, agricultural development and increased nutrient loadings. The major eutrophication increase in the 1950s was from urbanization and storm sewer discharge loaded with high yield chemical fertilizers from lawns and gardens. This high concentration of nutrients has led to an unprecedented level of eutrophication within the wetland. 相似文献
99.
A 1.2 m sediment core from Lake Forsyth, Canterbury, New Zealand, records the development of the catchment/lake system over the last 7000 years, and its response to anthropogenic disturbance following European settlement c. 1840 AD. Pollen was used to reconstruct catchment vegetation history, while foraminifera, chironomids, Trichoptera, and the abundance of Pediastrum simplex colonies were used to infer past environmental conditions within the lake. The basal 30 cm of core records the transition of the Lake Forsyth Basin from a tidal embayment to a brackish coastal lake. Timing of closure of the lake mouth could not be accurately determined, but it appears that Lake Forsyth had stabilised as a slightly brackish, oligo-mesotrophic shallow lake by about 500 years BP. Major deforestation occurred on Banks Peninsula between 1860 AD and 1890 AD. This deforestation is marked by the rapid decline in the main canopy trees (Prumnopitys taxifolia (matai) and Podocarpus totara/hallii (totara/mountain totara), an increase in charcoal, and the appearance of grasses. At around 1895 AD, pine appears in the record while a willow (Salix spp.) appears somewhat later. Redundancy analysis (RDA) of the pollen and aquatic species data revealed a significant relationship between regional vegetation and the abundance of aquatic taxa, with the percentage if disturbance pollen explaining most (14.8%) of the constrained variation in the aquatic species data. Principle components analysis (PCA) of aquatic species data revealed that the most significant period of rapid biological change in the lakes history corresponded to the main period of human disturbance in the catchment. Deforestation led to increased sediment and nutrient input into the lake which was accompanied by a major reduction in salinity. These changes are inferred from the appearance and proliferation of freshwater algae (Pediastrum simplex), an increase in abundance and diversity of chironomids, and the abundance of cases and remains from the larvae of the caddisfly, Oecetis unicolor. Eutrophication accompanied by increasing salinity of the lake is inferred from a significant peak and then decline of P. simplex, and a reduction in the abundance and diversity of aquatic invertebrates. The artificial opening of the lake to the Pacific Ocean, which began in the late 1800s, is the likely cause of the recent increase in salinity. An increase in salinity may have also encouraged blooms of the halotolerant and hepatotoxic cyanobacteria Nodularia spumigena. 相似文献
100.
Musky Bay in Lac Courte Oreilles, Wisconsin, USA, is currently eutrophic. This large, shallow bay of an oligotrophic lake possesses the densest aquatic plant growth and a floating algal mat. Paleoecological reconstructions encompassing the last 130 years, were based on multiproxy analyses of sediment cores from three coring sites, two within the bay and one in the lake itself. These data were compared to historical records of the construction and expansion of two commercial cranberry bogs and shoreline residential homes to identify temporal and causal relations of eutrophication. The proxies investigated included: minor and trace elements; biogenic silica; and the diatom community. Post-depositional diagenesis of organic carbon, nitrogen, and phosphorus in the upper 30 cm of the core obscured records of historical ambient nutrient concentrations in the bay obviating their usefulness for this purpose. In contrast, calcium, magnesium, and potassium concentration profiles appeared to reflect runoff of soil amendments applied to the cranberry bogs and aerial fertilizer spraying over the eastern bog adjacent to Musky Bay. The increase in aluminum content since about 1930 coincided with the historical trend in shoreland development and construction of the original commercial cranberry farm. The biogenic silica profile recorded a steady increase of nutrients to Musky Bay over the last several decades. Stratigraphic changes in the diatom community indicated that nutrient input began to increase in the 1940s and accelerated in the mid-1990s with the onset of a noxious floating algal mat. The diatom community indicates the bay has possessed a significant macrophyte community for at least the last 200 years, but increased nutrient input was manifested by a change in the composition, and an increase in the density of the epiphytic diatom community. Cranberry farming appeared to be the major source of nutrients because the diatom community changes occurred prior to the significant increase in residential housing. 相似文献