Effects of wild fish and motile epibenthic invertebrates on the benthos below an open water fish farm

A manipulative caging experiment was carried out to evaluate the role of wild fish and motile epibenthic invertebrates on the benthic system influenced by an open water fish farm. Chemical and biological parameters of the sediment were measured as indicators of the ecological benthic status. The combination of wild fish and currents notably lowered aquaculture waste sedimentation below the fish farm. The limited waste sedimentation rate could have limited the scavenger and predation activity of wild fish on the benthos, whose role may be taken over by motile epibenthic invertebrates. The interaction of these motile epibenthic invertebrates with the sediment differed from that observed with fish. The motile epibenthic invertebrates led to more reduced conditions with lower redox values, significantly decreased the number of species of macrofaunal benthic assemblages and significantly modified macrofaunal benthic assemblages. Therefore, epibenthic invertebrates do not seem to have an ameliorative effect on the benthic status produced by fish farming. Since the effects of epibenthic species on the benthic system can greatly vary according to their identity, further experiments should be performed to better understand the drivers that influence the epibenthic species identity that modulate the benthic system affected by fish farming.     

Phylogeography of the pelagic fish Seriola lalandi at different scales: confirmation of inter-ocean population structure and evaluation of southern African genetic diversity

The study investigated the global and regional phylogeography of the yellowtail kingfish Seriola lalandi by examining genetic diversity and population genetic structure of this species at inter-and intra-ocean level and on a regional scale. DNA fragments of two mitochondrial genes, cytochrome b (Cytb) and cytochrome c oxidase subunit I (COI) and one nuclear gene, recombination activating gene 1 (RAG1), were sequenced to investigate the global-scale phylogeography of this species. The population genetic structure within the South Pacific, as well as along the South African coastline, was examined further using six microsatellite markers. Three distinct clades were identified for S. lalandi, which correspond with previously described subspecies of the North-East Pacific, North-West Pacific and the Southern Hemisphere. Within the latter, additional divergence was observed between the South Pacific and the South-East Atlantic regions. Divergence estimates were indicative of a Pacific origin for S. lalandi populations, because of Pleistocene vicariant events. Microsatellite analyses revealed overall significant genetic differentiation between South African and South Pacific samples. This corroborates recent findings on the global phylogeography of the species. No population differentiation was observed within South Africa, indicating high levels of gene flow.     

Spectral analyses of offshore magnetic data for computing depths to the basement rocks

This paper deals with the computation of the depth to the magnetic interface from the total magnetic field intensity values obtained along profiles in the offshore area between Vengurla and Rajapur bay off the West Coast of India, by the application of one dimensional spectral analysis method.From the response characteristics of the total field magnetic values it is surmised that the magnetic interface may be identified with the Deccan trap series of rocks which are likely to form the magnetic basement rocks in this area.The plot of depths to the basement rocks as obtained from spectral analysis indicates that the basement is sloping towards outer edge of the Continental Shelf though not uniformly.     

Tectonics related to the North Anatolian Fault in the Sea of Marmara: evidence from seismic reflection data

The North Anatolian Fault crosses the Sea of Marmara from east to west. Tectonic features of the Sea of Marmara were studied using multi-channel deep seismic reflection data. The northern branch of the North Anatolian Fault is active as a right lateral strike-slip fault zone and indicates both negative and positive flower structures. The North Anatolian Fault splays into two faults at the Sea of Marmara as a northern branch and north segment of the southern branch. The northern branch named the Main Marmara Fault extends in a complicated manner from the north of the Kapıdağı Peninsula to westward in the Sea of Marmara. The north segment of southern branch extends between the Gemlik and Bandırma gulfs in the south of the Sea of Marmara. In addition, uplift areas arose by compression and a push-up style in between the Kapıdağı Peninsula and the Main Marmara Fault. The North Anatolian Fault is characterized by a negative flower structure in basins and push-up style in uplift areas in the Sea of Marmara. An uplift area arose between the north segment of the southern branch and the northern branch of the North Anatolian Fault. The north segment of the southern branch of the North Anatolian Fault is a strike-slip fault and displays a pull-apart style in the seismic reflection data.     

Variations in the quantity and composition of seston from an estuary in southern Chile on different temporal scales

Estuaries are characterised by highly variable environmental conditions largely driven by tidal and atmospheric forces. This study investigates variation in the physical environment and the composition of the seston on various temporal scales in the Quempillén estuary, southern Chile. The water column was sampled throughout the tidal cycle at various times of the year. Total particulate matter, particulate inorganic matter, particulate organic matter, particle numbers, total particle volume, proximate biochemical composition and energy content of the seston, chlorophyll a and chloropigments were routinely measured. In each of the months in which sampling took place, two or three tidal cycles were examined. The information not only helps to explain the dynamics of the estuary, but is essential for an understanding of the physiology and ecology of the suspension-feeders which exploit the seston as a food source, the most dominant being the gastropod Crepipatella dilatata. Temperature and salinity were generally highest during summer, but seston quality, defined by energy content and biochemical composition (lipid, protein and carbohydrate) was higher at the end of winter and during spring. Chlorophyll a values were greatest in late spring (November). Many of the variables studied changed frequently according to the phase of the tidal cycle, and in several cases significant differences were observed among tidal cycles from the same month of the same year. In general the variables measured did not exhibit consistent patterns linked to the tidal cycle, possibly because any such patterns were masked by atmospheric conditions (wind and rain) that dominate the region and greatly influence the estuary. The quantity and quality of the seston available to suspension-feeders is largely determined by these atmospheric forces, which cause an influx of terrigenous material from adjacent areas and also resuspend bottom sediment. These effects are magnified by the shallowness of the estuary (<2 m depth). The food supply for C. dilatata and other suspension-feeders therefore varies on temporal scales varying from hourly (tidal cycle) to daily/weekly (atmospheric forces) to monthly (seasonal influences), but inhibition of feeding by low salinity sometimes limits the ability of C. dilatata to exploit fully the available organic matter.     

Suspended sediment transport of the Hangzhou Bay and its related hydrodynamic analyses

The 25-h measurements of current speed, flow direction, water depth, suspended sediment concentration and salinity were carried out at six anchored stations in the study area during spring and neap tides in winter of 1987 and summer of 1989. Caculations and analyses of the data obtained show that large amounts of suspended sediments are moved back and forth under the action of tidal current, and the net transport of sediment is small, with its predominance upstream in winter and downstream in summer. These calculations and analyses also suggest that the advective transport of sediment is dominant, while the vertical gravitational circulation of the suspended sediment comes next. Meantime, it is indicated that tidal currents play a major role in the suspended sediment transport, and residual flows have effect on the net transport of the suspended sediment, which is more remarkable during neap tide than during spring tide.     

Phase-reversed seabed reflections in seismic data: examples related to mud volcanoes from the South Caspian Sea

The sediment–water interface is usually marked by an increase in acoustic impedance and is therefore displayed in a seismic section as a positive polarity reflection. Here, we use the term “seabed phase reversal” to describe areas of seafloor which are instead expressed as a negative polarity reflection in seismic data. We describe in detail a number of examples of seafloor phase reversals and use a simple one-dimensional geophysical model to test the hypothesis that they are the result of the presence of gas within the seafloor sediment. Our examples are all related to seismically imaged mud volcanoes located within the South Caspian Sea. Sections of phase-reversed seafloor at the summit area of these volcanoes have been mapped to reveal the existence of seafloor mud pools (salses) and recently erupted mud flows which show a strong similarity to smaller-scale features at onshore volcanoes in Azerbaijan. Synthetic geophysical modelling indicates that under the physical conditions likely to occur when the seabed sediment is gas-bearing, the seafloor will be expressed as a strong negative polarity reflection. Unlike other indicators of seafloor gas, such as pockmarks, which merely record the transient expulsion of fluids from sedimentary basins, seafloor phase reversals indicate the presence of gas in marine sediment at the time of survey acquisition. They therefore are of significance to engineering and site survey operations as well as the identification of biological communities and gas flux calculations.     

中草药防治鱼病研究进展

中草药(traditional Chinese herb medicine)是中药和草药的总称,是中国医药的愧宝。它具有毒副作用小、价格低廉、不易产生抗药性等优点,且其中的某些药物成分不仅有抗菌作用,还具免疫作用,能改善机体的免疫状态,提高机体自身的抗菌防病能力。另外由于近年来,集约化、工厂化水产养殖方式的迅速发展,养殖产量的提高及抗生素等抗菌药物的使用,使养殖用水体日益恶化,水产品药物残留居高不下,这不仅威胁到水产养殖本身,水产养殖动物病害越来越严重,同时还威胁到人们的身心健康,所以进一步开展中草药在水产养殖上的应用研究成为必然趋势。1体外…     

Active tectonic morphology and submarine deformation of the northern Gulf of Eilat/Aqaba from analyses of multibeam data

A high-resolution marine geophysical study was conducted during October-November 2006 in the northern Gulf of Aqaba/Eilat, providing the first multibeam imaging of the seafloor across the entire gulf head spanning both Israeli and Jordanian territorial waters. Analyses of the seafloor morphology show that the gulf head can be subdivided into the Eilat and Aqaba subbasins separated by the north-south-trending Ayla high. The Aqaba submarine basin appears starved of sediment supply, apparently causing erosion and a landward retreat of the shelf edge. Along the eastern border of this subbasin, the shelf is largely absent and its margin is influenced by the Aqaba Fault zone that forms a steep slope partially covered by sedimentary fan deltas from the adjacent ephemeral drainages. The Eilat subbasin, west of the Ayla high, receives a large amount of sediment derived from the extensive drainage basins of the Arava Valley (Wadi ’Arabah) and Yutim River to the north–northeast. These sediments and those entering from canyons on the south-western border of this subbasin are transported to the deep basin by turbidity currents and gravity slides, forming the Arava submarine fan. Large detached blocks and collapsed walls of submarine canyons and the western gulf margin indicate that mass wasting may be triggered by seismic activity. Seafloor lineaments defined by slope gradient analyses suggest that the Eilat Canyon and the boundaries of the Ayla high align along north- to northwest-striking fault systems—the Evrona Fault zone to the west and the Ayla Fault zone to the east. The shelf–slope break that lies along the 100 m isobath in the Eilat subbasin, and shallower (70–80 m isobaths) in the Aqaba subbasin, is offset by approx. 150 m along the eastern edge of the Ayla high. This offset might be the result of horizontal and vertical movements along what we call the Ayla Fault on the east side of the structure. Remnants of two marine terraces at 100 m and approx. 150 m water depths line the southwest margin of the gulf. These terraces are truncated by faulting along their northern end. Fossil coral reefs, which have a similar morphological appearance to the present-day, basin margin reefs, crop out along these deeper submarine terraces and along the shelf–slope break. One fossil reef is exposed on the shelf across the Ayla high at about 60–63 m water depth but is either covered or eroded in the adjacent subbasins. The offshore extension of the Evrona Fault offsets a fossil reef along the shelf and extends south of the canyon to linear fractures on the deep basin floor.     

基于多源数据的福建东山岛海岸侵蚀及其不同时空尺度成因分析

海岸侵蚀对海岛紧缺的陆地资源及旅游价值较大的沙滩危害巨大。基于卫星遥感、有人航空摄影、无人机航测、GPS和现场调查等多源数据,利用GIS分析了东山岛海岸线类型、位置与长度变化及滩面冲蚀演变。研究表明,东山岛多处曲折自然岸线转化为较为平直的人工岸线致使整体岸线长度减少,无人机高程反演满足滩面排水冲蚀监测精度要求,乌礁湾和山南湾不同养殖排水方式形成不同特征的滩面冲沟,改变了沙滩微地貌形态。海平面上升和台风风暴潮是长期趋势性和短期突发性侵蚀因素的代表,当前短时间尺度的人类活动已成为滩面冲蚀的最主要因素,且有可能转变为长期趋势性因素。     

捕食者不同目标策略下的鱼群结构变化仿真与研究

在海洋生态环境中,食物链上层捕食者对下层鱼群的捕猎行为可以被普遍地观察到,捕食者攻击的策略以及鱼群的防御机制是海洋捕猎行为的关键。本文构建了鱼群行为模型并对捕食者目标选择策略进行模拟,3种策略分别是选择“最近”“最中心”和“最外围”的个体。在虚拟环境中模拟单个捕食者攻击鱼群这一过程,对3种目标选择策略做比较分析,以鱼群结构变化程度的3个关键参数做评判标准。首先发现采用选择“最外围”个体的策略对于中等规模鱼群造成的结构变化程度最大,其次拓展到不同大小规模的鱼群,此策略仍是最有效的,其中小规模鱼群因应对风险能力低,无法体现三种策略的区别。     

Oceanic response to atmospheric forcing derived from different climatic data sets. Intercomparison study for the Black Sea

Available climatic and atmospheric analysis data have been used to prepare forcing functions for the Black Sea numerical model, based on the Bryan-Semtner-Cox Modular Ocean Model and including parameterizations for the atmosphere-ocean exchange, inflow through the strait of Bosphorus and the Mediterranean plume. Atmospheric data from different sources are compared and the drawbacks of some of them illustrated. A new wind stress data set, based on ship observations, is prepared. Compared to the existing wind stress estimates, the present ones use additional data and more accurate parameterization of the boundary layer physics. The intercomparison between forcing data sets is focused on the heat flux and freshwater flux at the sea surface.The model simulates adequately vertical stratification, seasonal variability and horizontal patterns. Five data sets for heat flux, freshwater flux and wind stress are used in different combinations to study the model response. The large differences between the simulations, forced by different wind stress and identical thermohaline forcing, justify the computation of the new wind stress. Though the forcing data used are perhaps close to the best available at the moment for the Black Sea, the model simulations range in large intervals and some of them are very poor. The model responses to forcing functions of different origin give rough estimates on the possible errors in present-day simulations. Some inconsistencies give clear indications that further verifications, improvements of the forcing functions, and intercomparisons between the responses simulated by the ocean circulation models are needed.     

Validation of growth zone deposition rate in otoliths and scales of flathead mullet Mugil cephalus and freshwater mullet Myxus capensis from fish of known age

Flathead mullet Mugil cephalus and freshwater mullet Myxus capensis are important components in South African estuarine fish communities and fisheries, but there is little information on their age and growth or age validation. This study validated the periodicity of growth zone formation in sectioned sagittal otoliths and scales of fish of known age that had been at liberty for 10 years. For both M. cephalus and M. capensis, the number of growth zones counted on otolith sections did not differ significantly from the known age of the fish. There were significantly fewer growth zones on scales than the known age of both M. cephalus and M. capensis. Growth zone deposition rate could therefore be validated as annual for otoliths but not for scales of the two species. It is recommended that future ageing studies focus on otoliths rather than scales.     

Identifying anthropogenic sources of nitrogen oxide emissions from calculations of Lagrangian trajectories and the observational data from a tall tower in Siberia during the spring-summer period of 2007

The task of identifying climatically significant regional anthropogenic emissions and estimating their contribution to the variability of nitrogen oxides observed at a monitoring station is considered on the basis of NO and NO₂ surface concentrations measured at the Zotino background observation station (60°26′ N, 89°24′ E, Krasnoyarsk Territory). The approach used is based on an estimation of the conditional probability of polluted air arriving from individual regions by using the results of calculating backward Lagrangian trajectories in the lower troposphere. It is established that the contribution of air masses supplied from industrial regions in the south of the Krasnoyarsk Territory to episodes of high concentrations of nitrogen oxides (>0.7 ppb) is larger than the contribution from cities and towns located in the south of Western Siberia. The results indicate that anthropogenic sources of pollution substantially affect the balance of minor gases in the lower troposphere on a regional scale and that this factor must be taken into account when observational data from the Zotino background station are analyzed and interpreted.     

基于mtDNA ND1基因序列研究不同地理群体波纹唇鱼的遗传多样性和遗传分化

以海南陵水、马来西亚、西沙、南沙4个海域共101尾波纹唇鱼(Cheilinus undulatus)作为研究对象,利用线粒体DNA ND1基因序列对波纹唇鱼进行了遗传多样性分析。通过PCR扩增、克隆与序列测定技术,获得ND1基因序列长度为975 bp,其多态性遗传参数统计显示,101个个体存在13个变异位点,14个单倍型,总群体单倍型多样性(Hd)为0.292,平均核苷酸差异数(K)为0.335,核苷酸多样性指数(Pi)为0.000 35,表现出遗传多样性处于较低水平。Tajima′s D中性检验结果为-1.768 09(P=0.031)表明波纹唇鱼在历史上经历过近期群体扩张或瓶颈效应。分子方差分析(AMOVA)表明遗传变异来自群体内。该结果可为今后波纹唇鱼的种质资源保护工作提供必要的科学依据。     

网箱养殖对海南新村澙湖海菖蒲生物学与生态学特征的影响

以海南新村澙湖海草床优势种之一的海菖蒲（Enhalus acoroides）为研究对象,于2005年4月至2006年1月间,分4个季节对海菖蒲的茎枝生物量、叶长、叶宽、叶单位面积附着藻类生物量、茎枝密度及生物量等进行了研究,初步探讨了网箱养殖对海菖蒲生物学和生态学特征的影响.其结果表明：（1）在春、夏、秋3个季节里,海菖蒲叶长、叶宽和茎枝生物量等均显示了与其所在样区海水和沉积物间隙水D IN含量呈负相关关系.（2）随着水体N负荷的增加,海菖蒲叶单位面积附着藻类生物量剧增.（3）网箱养殖区海菖蒲较小的地上生物量、茎枝密度及地上生物量与地下生物量比,均表明网箱养殖区海菖蒲受人为干扰的影响明显大于其他2个样区.     

Measuring information content from observations for data assimilations: connection between different measures and application to radar scan design

The previously derived formulations for using the relative entropy and Shannon entropy difference ( SD ) to measure information content from observations are revisited in connection with another known information measure—degrees of freedom for signal, which is defined as the statistical average of the signal part of the relative entropy. For a linear assimilation system, the statistical average of the relative entropy reduces to the SD . The formulations are extended for four-dimensional variational data assimilation (4DVar). The extended formulations reveal that the information content increases (or decreases) as the model error increase (or decrease) and/or become strongly (or weakly) correlated in 4-D space. These properties are also highlighted by illustrative examples, and the extended formulations are shown to be potential useful for designing optimum phased-array radar scan configurations to maximize the extractable information contents from radar observations by a 4DVar analysis system.