Impact of Two "El Niño" Events of Different Intensity on the Hypoxic Soft Bottom Macrobenthos off the Central Peruvian wast     

Juan  Tarazona  Wolf E.  Arntz Elba  Canahuire 《Marine Ecology》1996,17(1-3):425-446

Abstract. Monthly changes in the community structure of hypoxic soft-bottom macrobenthos have been studied at a station at 34 m depth in Ancón Bay (Peru) before and during two El Niño (EN) events. Of these events, 1982-83 is considered the strongest, and 1991–93 one of the most prolonged in the 20th century. On the oceanographic scale, EN 1982–83 ranges as "very strong", whereas EN 1991–93 ranges as "moderate".
The thermal anomalies at the station during EN 1982–83 (+ 7.8 °C) were almost twice those of EN 1991–93 (+ 4.1 °C). However, the community changes were not in all cases proportional to the extent of warming. Species numbers increased in a similar way (up to 24 species from near zero in each of the two events), but maximum faunal density was five times higher, and mean biomass was twice as high in 1982–83 compared with the event a decade later. Species diversity was slightly higher during EN 1982–83, whereas successional and trophic changes occurred on a broader scale during EN 1991–93. On the whole, the impact of the long-lasting event on the small soft-bottom macrofauna was not much weaker than that of the exceptionally strong event.
The authors discuss the mechanisms which may be responsible for the differences and similarities encountered in the benthic community dynamics during these two events. Both in the unusually strong and the unusually long EN, the community revealed a pattern of early biological response several months ahead of the onset of local warming which marks the official begin of EN. The question is addressed to what extent the increase of certain parameters in the benthic community could be used for predictive purposes.  相似文献   

Determination of technical efficiency of fisheries by stochastic frontier models: a case on the Gulf of Cadiz (Spain)     

Garcia del Hoyo  Juan Jose; Castilla Espino  David; Jimenez Toribio  Ramon 《ICES Journal of Marine Science》2004,61(3):416-421

  相似文献   

唐山市滨海湿地动态演变特征及其机制分析     

邱若峰  杨燕雄  刘松涛  周振祥  孙娟 《海洋湖沼通报》2006,(4):25-31

利用历史资料和Landsat TM卫星遥感图像,研究了唐山市滨海湿地自建国以来的演变特征,着重对1987~2004年陡河———滦河之间的滨海平原湿地类型进行了识别,绘制了不同时期的景观面解译图。利用Mapinfo制图软件计算出两个时期的面积(比例)转化矩阵,显示该区滨海湿地破碎化加重,其动态演变特征呈明显退化趋势,进而提出引起其退化的原因和发展趋势预测。  相似文献   

Seasonal and inter-annual variation of mesozooplankton in the coastal upwelling zone off central-southern Chile   总被引：1，自引：0，他引：1  

Ruben Escribano  Pamela Hidalgo  Humberto González  Ricardo Giesecke  Ramiro Riquelme-Bugueño  Karen Manríquez 《Progress in Oceanography》2007,75(3):470-485

Zooplankton sampling at Station 18 off Concepción (36°30′S and 73°07′W), on an average frequency of 30 days (August 2002 to December 2005), allowed the assessment of seasonal and inter-annual variation in zooplankton biomass, its C and N content, and the community structure in relation to upwelling variability. Copepods contributed 79% of the total zooplankton community and were mostly represented by Paracalanus parvus, Oithona similis, Oithona nana, Calanus chilensis, and Rhincalanus nasutus. Other copepod species, euphausiids (mainly Euphausia mucronata), gelatinous zooplankton, and crustacean larvae comprised the rest of the community. Changes in the depth of the upper boundary of the oxygen minimum zone indicated the strongly seasonal upwelling pattern. The bulk of zooplankton biomass and total copepod abundance were both strongly and positively associated with a shallow (<20 m) oxygen minimum zone; these values increased in spring/summer, when upwelling prevailed. Gelatinous zooplankton showed positive abundance anomalies in the spring and winter, whereas euphausiids had no seasonal pattern and a positive anomaly in the fall. The C content and the C/N ratio of zooplankton biomass significantly increased during the spring when chlorophyll-a was high (>5 mg m⁻³). No major changes in zooplankton biomass and species were found from one year to the next. We concluded that upwelling is the key process modulating variability in zooplankton biomass and its community structure in this zone. The spring/summer increase in zooplankton may be largely the result of the aggregation of dominant copepods within the upwelling region; these may reproduce throughout the year, increasing their C content and C/N ratios given high diatom concentrations.  相似文献   

Short-Term Benthic Recolonization after Dredging in the Harbour of Ceuta, North Africa   总被引：2，自引：0，他引：2  

José M. Guerra-García  Juan Corzo  & J. Carlos García-Gómez 《Marine Ecology》2003,24(3):217-229

Abstract. The benthic recovery after dredging (area: 2625 m²) was studied in a polluted and enclosed area of the harbour of Ceuta, in which the recolonization through the water column (larvae and adult bedload transport) could be limited by the lack of renewal. The benthos was sampled at two sites (control and dredged) using a van Veen grab and adopting a BACI (Before, After, Control, Impacted) approach. Five samplings were conducted after dredging (3, 15, 30, 90, 180 days). The proportion of gravel in the sediment of the dredged site increased after dredging, while the organic matter decreased. The impact on the community was estimated at species level, using both univariate and multivariate analyses. The maximum negative effect on benthic macrofauna was a reduction by 65% for species richness (15 days after dredging) and by 75% for abundance (3 days after dredging). Between 15 and 30 days after dredging, the abundance of some species such as the molluscs Parvicardium exiguum and Retusa obtusa and the polychaete Pseudomalacoceros tridentata increased considerably in the dredged site, while typical ‘opportunistic’ species such as Capitella capitata were disfavoured by the disturbance. For this small‐scale dredging, about 6 months are required for the disturbed area to re‐establish a sediment structure and a macrobenthic community similar to the undisturbed area. Small‐patch dredging operations are proposed in harbour management whenever possible, since they allow a quick re‐adjustment of the initial sediment structure and benthic communities.  相似文献   

Gas hydrate disturbance fabrics of southern Hydrate Ridge sediments (ODP Leg 204): Relationship with texture and physical properties   总被引：1，自引：0，他引：1  

Elena Piñero  Eulàlia Gràcia  Francisca Martínez-Ruiz  Juan Cruz Larrasoaña  Alexis Vizcaino  Gemma Ercilla 《Geo-Marine Letters》2007,27(2-4):279-288

Soupy and mousse-like fabrics are disturbance sedimentary features that result from the dissociation of gas hydrate, a process that releases water. During the core retrieval process, soupy and mousse-like fabrics are produced in the gas hydrate-bearing sediments due to changes in pressure and temperature conditions. Therefore, the identification of soupy and mousse-like fabrics can be used as a proxy for the presence of gas hydrate in addition to other evidence, such as pore water freshening or anomalously cool temperature. We present here grain-size results, mineralogical composition and magnetic susceptibility data of soupy and mousse-like samples from the southern Hydrate Ridge (Cascadia accretionary complex) acquired during Leg 204 of the Ocean Drilling Program. In order to study the relationship between sedimentary texture and the presence of gas hydrates, we have compared these results with the main textural and compositional data available from the same area. Most of the disturbed analyzed samples from the summit and the western flank of southern Hydrate Ridge show a mean grain size coarser than the average mean grain size of the hemipelagic samples from the same area. The depositional features of the sediments are not recognised due to disturbance. However, their granulometric statistical parameters and distribution curves, and magnetic susceptibility logs indicate that they correspond to a turbidite facies. These results suggest that gas hydrates in the southern Hydrate Ridge could form preferentially in coarser grain-size layers that could act as conduits feeding gas from below the BSR. Two samples from the uppermost metres near the seafloor at the summit of the southern Hydrate Ridge show a finer mean grain-size value than the average of hemipelagic samples. They were located where the highest amount of gas hydrates was detected, suggesting that in this area the availability of methane gas was high enough to generate gas hydrates, even within low-permeability layers. The mineralogical composition of the soupy and mousse-like sediments does not show any specific characteristic with respect to the other samples from the southern Hydrate Ridge.  相似文献   

蒽胁迫对2种海洋微藻的毒性效应     

田继远  唐学玺  于娟  王晨  刘文明 《中国海洋大学学报(自然科学版)》2002,32(6):919-925

采用水生毒理学方法以及通过分析蒽对 2种海洋微藻的几种生理生化指标的影响 ,初步研究了蒽胁迫对 2种海洋微藻的毒性效应。结果表明 :随着蒽浓度的不断增大 ,1 2种海洋微藻的相对增长率逐渐降低 ,叶绿素 a和类胡萝卜素含量稍有下降 ,蒽对小新月菱形藻生长的 72 h· EC50为 2 51μg· L-1 ,蒽对亚心形扁藻生长的 72 h· EC50 为 387μg· L-1 ;2还原型谷胱甘肽 (GSH)含量逐渐降低 ;3加入外源性抗氧化剂 (GSH和甘露醇 )可缓解蒽胁迫所造成的 2种海洋微藻的细胞密度的降低 ,即可缓解蒽胁迫对微藻的毒害作用  相似文献   

Distribution of dissolved species and suspended particulate copper in an intertidal ecosystem affected by copper mine tailings in Northern Chile   总被引：1，自引：0，他引：1  

Santiago Andrade  James Moffett  Juan A. Correa   《Marine Chemistry》2006,101(3-4):203-212

The coastline near Chañaral in Northern Chile is one of the most highly Cu-contaminated zones in the world due to discharges from mining activities for more than 60 years. The speciation of Cu has been studied to determine the importance of organic complexation in highly contaminated areas, and to assess the likely physiological impacts of Cu on marine organisms. Dissolved Cu concentrations of up to 500 nM were measured, completely saturating organic ligands and leading to free Cu²⁺ concentrations in excess of 10^− 8 M. These values are higher than those reported in any other marine environment, and because they occur over an extensive area, provide a unique opportunity to study the effects of Cu on marine ecosystems and to see how Cu behaves when its speciation is predominantly inorganic. We found strong gradients in free Cu²⁺ between Chañaral and adjacent areas with lower Cu, where speciation is dominated by organic complexation. There is also a significant increase in the partitioning of Cu onto suspended particles in the contaminated areas, consistent with previous studies that showed that organic ligands stabilize Cu in the dissolved phase, whilst “excess” Cu is rapidly scavenged. Those high dissolved Cu concentrations persist in spite of solid phase partitioning and advective processes along this open-ocean coastline, suggesting that Cu inputs into the system are still very large. Measurements were made using anodic stripping voltammetry with a thin mercury film coated with Nafion, which previous workers have shown can mitigate ambiguity in the data arising from inadvertent reduction of organic complexes. Our findings suggest that this is a useful methodology for contaminated systems.  相似文献   

养殖杂色鲍暴发病超微病理学研究   总被引：5，自引：0，他引：5       下载免费PDF全文

王江勇  郭志勋  冯娟  刘广锋  徐力文  陈毕生  潘金培 《海洋科学》2007,31(3):28-32

从1999年至2002年在中国南方沿海许多养殖场的杂色鲍(Haliotis diversicolor Reeve)出现了严重的疾病,该病可感染各种规格的鲍,死亡很快,死亡率高。病鲍的外观症状表现为外套膜收缩,腹足表面变黑,肌肉变得僵硬。通过电镜观察,在肝胰腺、外套膜、肾、鳃及肠等组织中发现了一种球状病毒。病毒粒子大小为100～130nm。该病毒一般存在于间质细胞的细胞质中,为双层质膜所包裹。染病鲍细胞器如滑面内质网扩张、线粒体崩解,糖原粒、核糖体减少,核膜松疏、溶解、消失,核质边缘化。病毒的病原性通过对健康鲍的感染试验得到证实。  相似文献   

东北区生态旅游资源的开发与保护   总被引：1，自引：0，他引：1  

陈娟  李煜华  陶永波 《海岸工程》2002,21(1):51-56

生态旅游作为一种新兴的旅游型式正显示出强大的发展势头,东北区作为我国生态旅游资源十分丰富的地区,以其分布的广泛性、类型的多样性、资源的独特性在旅游开发中具有一定的地位.该区应该从本身的资源特点出发,以保护为基础进行合理的开发.  相似文献