Greenland halibut diet in the Northwest Atlantic from 1978 to 2003 as an indicator of ecosystem change     

K.S. Dwyer  A. Buren  M. Koen-Alonso   《Journal of Sea Research》2010,64(4):436-445

The Northwest Atlantic marine community underwent dramatic changes during the last 30 years, including the collapse of many groundfish stocks and an increase in shrimp populations. Greenland halibut Reinhardtius hippoglossoides is an important commercial species and one of the top fish predators in this system. It is a large, wide-ranging flatfish that is found at depths up to 2200 m and it has an opportunistic diet which makes it a potential candidate for an ecosystem indicator. Analysis of stomach contents of Greenland halibut between 1978 and 2003 indicates that diet composition reflects the major changes in community structure. Over the entire period there was a clear increase in the importance of invertebrates, particularly after 1992. This change was associated with a higher importance of Pandalus shrimp and Gonatus squid and a protracted reliance on zooplankton by predators under 25 cm length. Capelin Mallotus villosus was the dominant prey between 1978 and 1992 for predators in the 12–63 cm range, but its importance dropped off drastically in the mid 1990s. Levels of main prey in the diet of Greenland halibut correlated well with fishery-independent surveys. Greenland halibut sample capelin well, compared to bottom trawl surveys and acoustic surveys. Greenland halibut consumed small shrimp which are not routinely caught by surveys and may be important in deriving information on year classes and growth of shrimp. Our results suggest that Greenland halibut's diet is a useful tracker of ecosystem change.  相似文献   

重力测量中地形改正新法     

黄元有  吕许朋  付彦平 《云南地质》2012,(1):77-79

重力近区地形改正采用激光测距测高仪,中区地形改正采用国家地理信息中心提供的1∶5万DEM高程数据使用软件,精度满足设计和规范要求,工作效率高,减少了人为误差的影响,是一种多快好省的方法。  相似文献   

干旱区绿洲型城市土地持续利用评价:以奎屯市为例   总被引：2，自引：0，他引：2  

王爱辉  张丹  戴新俊 《干旱区地理》2006,29(3):431-438

绿洲是干旱区城市发展的主要空间。干旱区绿洲城市土地的高效集约化利用不仅是城市可持续发展,同时是实现绿洲可持续发展的客观需要。从城市用地经济效益水平、城市用地规模合理性、城市内部用地合理性、城市土地生态系统以及城市对绿洲生态环境的影响五个方面,选择26个因素作为参评因子,利用层次分析法、模糊隶属函数及线性加权函数建立干旱区绿洲型城市土地利用评价指标体系数学模型。以奎屯市为例,对评价指标体系数学模型进行实证研究,并针对评价结果,提出可持续利用具体对策,为相关工作提供参考。  相似文献   

Seasonal variability of benthic indices: an approach to test the applicability of different indices for ecosystem quality assessment     

Reiss H  Kröncke I 《Marine pollution bulletin》2005,50(12):1490-1499

In recent studies, several benthic biological indices were developed or used to assess the ecological quality status of marine environments. In the present study the seasonal variability of several univariate and multimetric indices was studied on a monthly scale (September 2000 until May 2002) in different areas of the North Sea such as the German Bight, the Oyster Ground and the Dogger Bank. The stations were chosen to reflect a gradient in the hydrographic regime, temperature and organic matter supply. The seasonal variability was highest for the univariate indices such as the Shannon–Wiener Index and the Hurlbert Index. Thus, due to sensitivity to recruitment the corresponding ecological status ranged from ‘good’ to ‘poor’ depending on the season. For the multimetric indices such as the AMBI or the BQI the seasonal variability and the corresponding ecological status were low. The results are discussed concerning possible consequences for ecological quality assessment especially related to the Water Framework Directive (WFD).  相似文献   

Using Chlorine Dioxide for Drinking Water Disinfection by the Application of the Chlorite/Chlorine Process     

Wido Schmidt 《洁净——土壤、空气、水》2004,32(1):48-60

Chlorine dioxide stock solutions for the disinfection of drinking water are made by the application of chlorite/chlorine process in many waterworks. In such cases the stock solution is always characterised by a mixture of chlorine and chlorine dioxide. The disinfection of waters of different origin with a mixture of chlorine dioxide and chlorine showed the formation of odours of different intensity. The reasons are the re‐formation of chlorine dioxide and the formation of odorous disinfection by‐products. Applying the chlorine dioxide for disinfection, its re‐formation caused by the reaction of chlorite with chlorine is the dominant reason of odour formation. When chlorine is used, the formation of odorous by‐products becomes more relevant. In order to quantify the sensitivity of water concerning odour, the odour indicator coefficient OI was defined. The decreased demand of chlorine dioxide by applying chlorine and chlorine dioxide in combination is recognised to be the key in order to avoid the formation of odour after the disinfection of drinking water with chlorine dioxide.  相似文献   

红花沟金矿床地质特征及矿床成因研究   总被引：3，自引：0，他引：3  

张百胜 《矿产与地质》2001,15(5):311-314

通过矿物包裹体、硫同位素组成氢、氧、碳同位素的研究，认为红花沟金矿床为燕山期中低温热液型黄铁矿－石英脉型矿床，矿床具有多期改造的特征。  相似文献   

Increasing imposex in populations of Bolinus brandaris (Gastropoda: Muricidae) in the north-western Mediterranean     

M. Ramn  M. J. Amor 《Marine environmental research》2001,52(5)

The muricid gastropod Bolinus brandaris exhibited imposex, a phenomenon linked to the use of organotin biocides. Several stages of imposex development (1–5) could be distinguished and were documented with SEM-photographs for the first time in this species. Additional alterations of the genital tract in females (blocked vulva preventing copulation and deposition of egg capsules) and males (excrecences on the penis and vas deferens) were shown. Imposex intensity on the Catalan coast was very high. The frequency of imposex off Barcelona and Vilanova i la Geltrú was 100%, with all females showing stage 4. Imposex frequency off Sant Carles de la Ràpita was 99.7% and the VDS index scored 3.9. Despite regulations of TBT-containing antifouling paints in Spain since 1990, the present study revealed that frequency and intensity of imposex have increased on the Catalan coast, at least since 1997. However, at present, imposex does not apparently affect the population dynamics of B. brandaris in the studied area, since no serious consequences on female reproduction (only one case of female sterilization) were detected. Gonadal activity and oogenesis were not suppressed or supplanted by spermatogenesis. Sex ratios were not male-biased. Possible sources of organotin biocides are examined.  相似文献   

模糊集合理论在化学中的应用Ⅲ酸碱指示剂的研究     

李华祥  胡颜 《广东海洋大学学报》1990,(1)

本文根据模糊集合理论对9种酸碱指示剂作了研究,提出指示剂变色范围宽度和变色转折半宽度的新概念,测定了9种指示剂在不同浓度下的变色转折点和变色转折半宽度。实验结果说明,与经典指示剂理论不同,即使是双色指示剂其变色区间也受指示剂浓度的影响。  相似文献   

模糊集合理论在化学中的应用Ⅳ——百里酚酞-茜素黄R混合指示剂的研究     

胡颜  李华样 《广东海洋大学学报》1989,(Z1)

本文应用模糊集合理论和计算机研究百里酚酞-茜素黄R混合指示剂的变色现象。发现其变色存在滞后现象。讨论了产生滯后现象的原因。  相似文献   

地震应急救援能力评价指标与计算方法研究   总被引：1，自引：1，他引：0  

李亦纲  吴建春  张媛  张玮晶  丁璐 《震灾防御技术》2011,6(2):172-179

本文在地震应急与救援体系发展规划、地震应急能力评价指标框架体系研究的基础上,根据应急能力评估的现实需求、数据的可获取性和可计算性等因素,参考社会经济领域统计评价的思路,根据应急救援规划发展目标,给出了地震应急救援能力的评价指标体系,包括指标大类和具体的子指标.以省级行政单元的评估为例,给出了指标的具体含义和计算方法,以...  相似文献