Alkaline phosphatase activity and its relationship to inorganic phosphorus in the transition zone of the North-western African upwelling system     

Marta Sebastin  Javier Arístegui  María F. Montero  Jose Escanez  F. Xavier Niell 《Progress in Oceanography》2004,62(2-4):131

The enzymatic activity of alkaline phosphatase (APA) was studied in the transition zone between the African upwelling system and the open ocean waters of the Canary Islands region. This region is recurrently dominated by the presence of upwelling filaments that may transport nutrient-enriched waters out into the open ocean before nutrients become exhausted by plankton. Turnover rates by APA were generally low in the whole region, but detectable in all the measurements carried out. On average, turnover rates were higher in the upwelling stations, and APA in those waters seemed to be mainly generated by heterotrophic bacteria to supply easily assimilable organic C. APA outside the upwelling area showed an inverse hyperbolic relationship with increasing phosphate, suggesting the presence of both constitutive and Pi-inducible APA. In these offshore waters, a threshold of 0.1 μM of phosphate could be defined for the regulatory function of Pi on APA. Thus, APA in nutrient-poor waters seemed to be induced to compensate for Pi-deficiency. Turnover rates in the filaments showed basal (probably constitutive) levels, whereas they increased in the surrounding waters, where phosphate concentration presumably did not satisfy plankton P-demands. The fertilising effect of the filaments and associated cyclonic eddies extended to at least 175 km offshore, where basal alkaline phosphatase activities were still found. The magnitude of this effect depends probably on the intensity of upwelling events and the degree of recirculation of filament water back to the coastal jet.  相似文献   

Management of the commons for biodiversity: lessons from the North Pacific   总被引：1，自引：0，他引：1  

Jerry McBeath   《Marine Policy》2004,28(6):580

The North Pacific has the world's largest groundfish fisheries, with a value in excess of $1 billion annually. The North Pacific also is home to the largest population of Steller sea lions (SSL), an ancient species that is now endangered. Decline of the western stock of SSL in the 1970–1990s coincided with the US nationalization and exponential growth in the Gulf of Alaska and Bering Sea/Aleutian Islands groundfish fishery.The article treats five aspects of the competition between the fishery and protection of the endangered species. First, we analyze competition of interests in the use, management, and preservation of the North Pacific commons, including offshore and near-shore fisheries, environmental organizations, governments (federal, state, and local), and the scientific community. Second, the article compares and contrasts provisions of the National Environmental Policy Act, the Marine Mammal Protection Act, the Endangered Species Act, and the Magnuson–Stevens Act (as amended in 1996 by the Sustainable Fisheries Act).Third, we examine the regulatory environment with a focus on the National Marine Fisheries Service (NMFS) and its relationship to the North Pacific Fishery Management Council. We illustrate how NMFS establishes fishery management plans and the methods, such as crafting biological opinions and environmental-impact-statements, it uses to resolve conflicts. Fourth, we investigate how the dual pressures on the agency—to increase fisheries production for the benefit of the industry and to preserve endangered marine species—have affected its culture (behavioral norms and operational codes). Then, the article explains agency changes in terms of crises, competition among affected interests, and development of new scientific knowledge.The article concludes by drawing lessons from the SSL controversy in the North Pacific which may pertain to national and global biodiversity conflicts. These concern the role of law in biodiversity protection, the role of science, and agency capacity for change.  相似文献   

现代黄河三角洲土地利用变化分析   总被引：3，自引：1，他引：3  

周良勇  李广雪  邓声贵  李安龙  温国义  赵东波 《海洋地质前沿》2003,19(10):1-4

人类对海岸带的开发利用影响着海岸的变迁。土地利用和土地覆被变化可以说是自然与人文过程交叉最为密切的问题，是人地关系的具体体现。通过对黄河三角洲土地利用变化的研究，可了解人为因素对三角洲海岸带的开发利用状况及其对海岸侵蚀的影响。根据1987年和2001年两期卫星遥感图像和2001年野外调查数据，运用地理信息系统方法及数理统计方法，分析了现代黄河三角洲地区1987年至2001年土地利用／覆被的数量变化和空间变化特征；揭示了该地区各类土地利用数量变化的幅度、速度和土地利用空间变化的主要类型；阐明了该区各类土地利用变化的区域特点。该地区土地利用变化速度比整个环渤海地区速度快，草地、滩地和不明地类这3种类型大量减少，其他类型增多。从变化率来看，养殖区、库塘、油田用地增长最快。库塘、海滩养殖区等类型的增加，滨海草地的减少，使海岸侵蚀加剧。  相似文献   

黄河河口演变(Ⅰ) --(一)河口水文特征   总被引：6，自引：0，他引：6  

庞家珍  姜明星 《海洋湖沼通报》2003,(3):1-13

本文利用20世纪后半个世纪的完整实测资料，研究了河口径流量与输沙量的变化，自50年代至90年代呈明显递减。对黄河口的水文特征：水情、沙情、断流、离子流量、滨海潮汐、潮流、余流、温、盐度分布、风暴潮、拦门沙与盐水楔等作出定性和定量的论述。对断流的危害、成因及缓解对策作出分析。河口淤积、延伸、改道对黄河下游的影响也作出时空上的定量分析。对1855年以来近代黄河三角洲海岸线变化，作出了定量研究。  相似文献   

长江冲淡水区细菌生产力研究   总被引：11，自引：3，他引：11  

刘子琳  越川海  宁修仁  史君贤  蔡昱明 《海洋学报》2001,23(4):93-99

为了解细菌在长江口冲淡水区生态系营养动力学过程中的重要作用,笔者于1997年10月10日至20日,1998年5月14日至6月1日在观测海区以及在绿华山海域设置大水体围隔生态系实验装置进行细菌生产力的现场观测研究.结果表明,秋季观测海区平均细菌生产力(C)为(1.44±1.30)μg/(dm3·h),高值出现在测区中部的A₃,B₃和C₃站.春季测区表层细菌生产力(2.43±1.22)μg/(dm3·h)高于底层(1.01±0.43)μg/(dm3·h),高值出现在测区中部的A₃和B断面诸站.秋、春季平均细菌生产力相当于浮游植物初级生产力的23%.秋季和春季表层细菌数量分别为(5.22×108±0.88×108)个/dm3和(1.97×108±1.10×108)个/dm3.1998年5月18日至6月1日在围隔实验点的自然海区中细菌生产力变幅范围为0.13～5.79μg/(dm3·h),平均值为(2.47±1.60)μg/(dm3·h).围隔装置内加可溶性磷(PO₄3-)实验,春季细菌生产力由1.28μg/(dm3·h)增长至32.20μg/(dm3·h),其增长幅度低于秋季1.43～43.47μg/(dm3·h).油污染实验中细菌生产力由6.61μg/(dm3·h)增长至37.97μg/(dm3·h),呈逐日上升趋势.  相似文献   

北太平洋亚热带环流区表层水中226Ra和228Ra的分布与变化     

李艳平  陈敏  黄奕普  蔡毅华 《台湾海峡》2004,23(3):261-267

对1999年9～10月采自北太平洋亚热带环流区的19份表层海水样品的Ra同位素分析表明。研究海域表层水中的^226Ra、^228Ra放射性比度分别介于0．67～0．92、0．08～0．30Bq／m^3之间，平均值分别为0．74、0．11Bq/m^3．^226Ra/^228Ra)A．R．活度比的变化范围为0．11～0．44，平均值为0．19．上述数值明显低于近岸海域水体的相应值，表现为典型的开阔大洋水的特征．从空间分布的特征看，研究海域Ra同位素含量与^226Ra/^228Ra)A.R.值均呈均匀分布态势．将本研究结果与历史数据进行对比后发现，本研究获得的^226Ra、^228Ra放射性比度比20世纪60～80年代得到的数据来得低，可能与水体层化作用加强导致的Ra补充量的减少以及生物生产力升高导致的Ra迁出量的增加有关．北太平洋亚热带环流区表层水中Ra同位素的时间变化与文献报道的该海域叶绿素a、硅酸盐、磷酸盐含量与初级生产力的历史变化趋势相吻合．  相似文献   

Upstream dams and downstream clams: growth rates of bivalve mollusks unveil impact of river management on estuarine ecosystems (Colorado River Delta, Mexico)     

B. R. Schne  K. W. Flessa  D. L. Dettman  D. H. Goodwin 《Estuarine, Coastal and Shelf Science》2003,58(4):715-726

We studied how the extensive diversion of Colorado River water, induced by dams and agricultural activities of the last 70 years, affected the growth rates of two abundant bivalve mollusk species (Chione cortezi and Chione fluctifraga) in the northern Gulf of California. Shells alive on the delta today (‘Post-dam’ shells) grow 5.8–27.9% faster than shells alive prior to the construction of dams (‘Pre-dam’ shells). This increase in annual shell production is linked to the currently sharply reduced freshwater influx to the Colorado River estuary. Before the upstream river management, lower salinity retarded growth rates in these bivalves. Intra-annual growth rates were 50% lower during spring and early summer, when river flow was at its maximum. Growth rates in Chione today are largely controlled by temperature and nutrients; prior to the construction of dams and the diversion of the Colorado River flow, seasonal changes in salinity played an important role in regulating calcification rates.Our study employs sclerochronological (growth increment analysis) and geochemical techniques to assess the impact of reduced freshwater influx on bivalve growth rates in the Colorado River estuary. A combination of both techniques provides an excellent tool to evaluate the impact of river management in areas where no pre-impact studies were made.  相似文献   

珠江口和琼东南盆地天然气水合物形成和稳定分布的地球化学边界条件及其分布区   总被引：22，自引：0，他引：22  

陈多福  姚伯初  赵振华  徐文新 《海洋地质与第四纪地质》2001,21(4):73-78

通过对南海北部陆缘珠江口和琼东南盆地气田的天然气形成水合物的地球化学计算模拟及地质地球化学条件分析，对珠江口和琼东南盆地天然气形成水合物的地球化学边界条件及分布区进行了研究。认识到南海北部陆缘琼东南和珠江口盆地内的断裂构造是天然气向海底渗漏的通道，为天然气水合物在海底的形成提供了物源；盆地内巨厚的第四纪富有机质沉积也为天然气水合物形成提供了充足的细菌成因生物气源。在海底温度2－16℃范围内，琼东南盆地气田10种天然气和珠江口盆地气田18种天然气形成水合物的压力有比较大的范围，随温度增高，天然气水合物形成的压力增高；盆地间和各天然气样品之间形成水合物的压力均是不一致的。在南海海水平均盐度3．4％条件下，结合海底温度与水深变化资料，珠江口和琼东南盆地天然气水合物形成和稳定分布的海区是不同的，珠江口盆地小于230m水深的海区没有天然气水合物的形成，在230－760m水深的海区可能有天然气水合物的存在，天然气水合物的稳定分布区应该在大于860m水深的深水区；在琼东南盆地水深小于320m的海区不可能有天然气水合物的形成，在320－650m水深的海区可能有天然气水合物的存在，大于650m水深的海区是天然气水合物的稳定分布区。  相似文献   

黄河口附近海域化学需氧量和石油烃分布及其关键控制环境因子分析   总被引：1，自引：0，他引：1  

曲良 《海洋通报》2020,39(3):335-341

于2009年12月、2010年5月、2011年9月、2013年5月和2014年10月,在黄河口附近海域进行了5个航次调查,研究了该海域的化学需氧量(COD)和石油烃的分布情况以及季节变化。结果表明,COD整体呈冬季低、春季高的趋势,而石油烃无明显季节变化趋势。平面分布上,春季和秋季COD高值主要分布在靠近黄河口海域。春季和冬季石油烃高值主要位于调查海域的东北部区域。相关分析结果表明盐度、温度、pH、悬浮物、溶解氧及磷酸盐是影响COD的主要环境因素,而石油烃主要受盐度、温度、pH、无机氮、磷酸盐的影响。进一步多元回归分析结果表明,p H、盐度和溶解氧是影响COD的关键因子,温度是影响石油烃的关键因子。  相似文献   

Validating management simulation models and implications for communicating results to stakeholders     

Pastoors  Martin A.; Poos  Jan Jaap; Kraak  Sarah B. M.; Machiels  Marcel A. M. 《ICES Journal of Marine Science》2007,64(4):818-824

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