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排序方式: 共有1099条查询结果,搜索用时 328 毫秒
901.
The paper reviews the data of 10 yr of following up sewage (waste water) inflows of anthropological origin into the sea from all the coastal settlements in Croatia. In particular, we report the sea loading by biochemical oxygen demand (BOD5), expressed by the inhabitant equivalent (I.E.), for seven littoral counties. We estimated the loading of a coastal sea area for each county separately. The objective was to avoid any over- or underestimation of amounts and significance of sewage inflows into the seawater. For this purpose, a precisely determined sea volume up to the 10 m isobath has been chosen. Because of the inadequate treatment of wastewater, the total loading of that maritime territory expressed in terms of i.e. was found to be 26% higher than expected from the actual number of inhabitants. However, daily input represents only 12‰ of the considered volume of the sea. Recipient spent only 0.7% of the disposable oxygen quantity in the sea.  相似文献   
902.
Polychlorinated biphenyls (PCBs). DDT-related substances, hexachlorocyclohexane (HCH) and hexachlorobenzene (HCB) were analysed in female perch ( Perca fluviatilis ) collected in August and September 1999 in Matsalu Bay (Baltic Sea). Concentrations of all halogenated compounds were very low and notably lower than threshold values reported by FAO/WHO guidelines.  相似文献   
903.
Between 1980 and 1984, plankton was collected for metal analysis during four expeditions in the Baltic Sea. for comparison, samples from adjacent areas of the northeastern Atlantic Ocean were also taken. the mixed net-plankton samples were analyzed by AAS for metals (Al, Cd, Co, Cr, Cu. Fe, Mn, Ni, Pb, and Zn). the results are discussed with regard to spatial and temporal trends and for comparison with data from other authors. Correlations among the contents of the different metals and between the metal contents and 'external factors' including salinity, season, percentage of co-collected phytoplankton, and concentration of dissolved and particulate metals in the water are considered.

There is a tendency for higher metal contents in plankton from the brackish Baltic Sea (Al, Mn and Hg), while other metals (e.g. Cd) show higher levels in samples taken from the marine environment. Except for mercury, no clear correlations could be found between the metal content in plankton and the dissolved concentration of the same metal in the ambient water. Otherwise, the contents of aluminium, iron, manganese and zinc in the suspended particulate matter and in the plankton seem to be partly related to each other.  相似文献   
904.
采用走航连续观测系统分别在2011年5月和2015年5月对南海北部表层水体温度、盐度、溶解氧、叶绿素a和pCO_2进行了现场观测.在El Nio影响下,2015年5月华南地区及广东省降雨量偏多,大量冲淡水入海,南海北部冲淡水区域海表盐度显著降低,2015年5月冲淡水区域海表盐度平均值为(28.05±6.18),低于2011年5月的海表盐度平均值(29.65±2.58),同时实测冲淡水区域海表温度平均升高约2.10℃.冲淡水携带的营养物质和适度升高的海表温度共同促进了冲淡水区域浮游植物的繁殖.浮游植物光合作用不断地将海水中的游离CO2转化为有机碳,同时释放出氧气,使得水体pCO_2降低,2015年5月冲淡水区域pCO_2平均值为(286±95)μatm,低于2011年5月的pCO_2平均值(300±42)μatm.2015年5月实测获得离岸海域pCO_2平均值为(421±9)μatm,高于2011年5月pCO_2平均值(386±13)μatm,二者差值为35μatm,海表温度是离岸海域pCO_2的主要影响因子,2015年5月El Nio期间离岸海域SST升高1.96℃.El Nio影响下冲淡水区域的碳汇作用增加,离岸海域的碳源作用增强,冲淡水区域碳汇增加与离岸海域碳源增强基本抵消,2015年5月南海北部整体仍是CO_2弱汇区,约为-0.40 mmol·m~(-2)·d~(-1),与2011年5月通量值-0.58 mmol·m~(-2)·d~(-1)差别不明显.  相似文献   
905.
划定生态保护红线,是生态文明建设的一项重要任务,对维护国家和区域生态安全及经济社会可持续发展具有重要的战略意义。目前,城市化发展中面临着突出生态环境问题,在城市层面开展生态保护红线的划定工作显得更加紧迫。但现阶段生态保护红线的划分技术上仍处于不断探索与完善阶段。基于此,文章以湖北省宜昌市为例,利用RS和GIS技术,采用"识-评-落-融-分"的技术流程,提出了一套城市生态保护红线体系与划分方法。结果表明:宜昌市生态保护红线体系划分为3个层级:生态保护红线区、生态保护黄线区和生态保护绿线区;生态保护红线区、黄线区和绿线区分别占全市面积的48.83%、31.50%和19.67%。  相似文献   
906.
在生物多样性受到严重威胁前提下,为评估中国生物多样性保护的成效,引入了世界自然保护联盟(IUCN)开发设计的红色名录指数(Red List Index,RLI),结合我国实际情况修订后,计算脊椎动物和维管植物的红色名录指数。结果显示,以均值法(Equal-steps method)计算的脊椎动物RLI有所上升,脊椎动物整体多样性丧失速率下降;而以灭绝风险法(Extinction risk method)计算的脊椎动物RLI有所下降,表明有部分高濒危等级的脊椎动物物种进一步丧失;两种方法计算的维管植物RLI均有所下降,说明维管植物多样性丧失速率加快;而基于均值法计算的维管植物RLI下降速率更快,说明数量较多的物种丧失速率加快,亟需加强保护。这是RLI在国家水平上进行应用,也是在国家水平上对RLI指数进行验证,计算结果将为我国生物多样性保护提供参考。  相似文献   
907.
Concentrations and areal distribution of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn were determined in the surficial sea bottom sediments along the coastal areas of Istanbul at the southern exit of the Bosphorus Strait, ?stanbul, Turkey. The pollution status of shelf sediments was evaluated by employing pollution indicators (enrichment factors, geo-accumulation, and ecological risk indexes) and sediment quality guidelines (threshold effect level/probable effect level, effect range median (ERM)/effect range low). The results demonstrated that Cd, Cr, Zn, Cu, and Pb were enriched minor to moderate. The net sediment transport patterns show terrestrial inputs in front of the short streams. Another polluted region is at the western margin of the southern Bosphorus exit, where sediment transport is mainly controlled by the secondary currents driven by the Bosphorus jet, and depending on a sand ridge extending offshore. Based on the sediment quality guidelines, Cu, Pb, As, and Cr were likely the most dangerous chemicals to pose environmental risk, and may show toxic biological results. The areal distribution of ecotoxicological index (m-ERM-Q) suggested that 20% of the sediment sample sites fall in the medium–high priority zone and scattered at some specific areas along the coast.  相似文献   
908.
Nest site selection in the open-nesting honeybee Apis florea   总被引:1,自引:0,他引:1  
We studied nest site selection by swarms of the red dwarf honeybee, Apis florea. By video recording and decoding all dances of four swarms, we were able to determine the direction and distances indicated by 1,239 dances performed by the bees. The bees also performed a total of 715 nondirectional dances; dances that were so brief that no directional information could be extracted. Even though dances converged over time to a smaller number of areas, in none of the swarms did dances converge to one site. As a result, even prior to lift off, bees performed dances indicating nest sites in several different directions. Two of four swarms traveled directly in what seemed to be the general direction indicated by the majority of dances in the half hour prior to swarm lift off. The other two traveled along circuitous routes in the general direction indicated by the dances. We suggest that nest site selection in A. florea has similar elements to nest site selection in the better-studied Apis mellifera. However, the observation that many more locations are indicated by dances prior to lift off also shows that there are fundamental differences between the two species.  相似文献   
909.
Abstract: Populations of large brown algae of the Laminariales and Fucales (Phaeophyta) have declined or been extirpated from many locations on temperate coasts worldwide. We conducted field surveys and a literature review, and examined herbarium specimens, through which we discovered previously unreported extirpations of large brown algal species from a tropical and subtropical coastline. Sargassum amaliae, S. aquifolium, S. carpophyllum, S. polycystum, and S. spinifex were common habitat‐forming macroalgae that supported diverse assemblages of invertebrates and smaller algae before urbanization began in 1970 along the 45‐km length of Sunshine Coast in Queensland, Australia. Causes of these extirpations are not known, but are consistent with losses of other large brown algal species from coastal areas undergoing urbanization or eutrophication. Sargassum spp. do not have the characteristics thought to protect marine species from extinction (large geographical ranges, occurrence on many different substrata, long‐distance dispersal). Some local Sargassum spp. are endemic to eastern Australia. Abundance of Sargassum is limited by suitable substrata on the sandy southern Queensland coast (370 km). These substrata are 12 rocky headlands separated by long (5–105 km) sandy beaches. Most multicellular propagules (the only motile stage in Sargassum) settle within 1–3 m of parental thalli, which restricts long‐distance dispersal needed to maintain connectivity among populations and to recolonize areas of the headlands from which populations have been extirpated. Local Sargassum spp. could be categorized as data deficient by the International Union for Conservation of Nature (IUCN), but the IUCN vulnerable category is more accurate given extirpations, limited habitat, and the lack of connectivity among populations.  相似文献   
910.
Abstract: Globally, ecosystems are under increasing anthropogenic pressure; thus, many are at risk of elimination. This situation has led the International Union for Conservation of Nature (IUCN) to propose a quantitative approach to ecosystem‐risk assessment. However, there is a need for their proposed criteria to be evaluated through practical examples spanning a diverse range of ecosystems and scales. We applied the IUCN's ecosystem red‐list criteria, which are based on changes in extent of ecosystems and reductions in ecosystem processes, to New Zealand's 72 naturally uncommon ecosystems. We aimed to test the applicability of the proposed criteria to ecosystems that are naturally uncommon (i.e., those that would naturally occur over a small area in the absence of human activity) and to provide information on the probability of ecosystem elimination so that conservation priorities might be set. We also tested the hypothesis that naturally uncommon ecosystems classified as threatened on the basis of IUCN Red List criteria contain more threatened plant species than those classified as nonthreatened. We identified 18 critically endangered, 17 endangered, and 10 vulnerable ecosystems. We estimated that naturally uncommon ecosystems contained 145 (85%) of mainland New Zealand's taxonomically distinct nationally critical, nationally endangered, and nationally vulnerable plant species, 66 (46%) of which were endemic to naturally uncommon ecosystems. We estimated there was a greater number of threatened plant species (per unit area) in critically endangered ecosystems than in ecosystems classified as nonthreatened. With their high levels of endemism and rapid and relatively well‐documented history of anthropogenic change, New Zealand's naturally uncommon ecosystems provide an excellent case‐study for the ongoing development of international criteria for threatened ecosystems. We suggest that interactions and synergies among decline in area, decline in function, and the scale of application of the criteria be used to improve the IUCN criteria for threatened ecosystems.  相似文献   
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