中国对虾幼体和仔虾消化酶活力及氨基酸组成的研究

于1987年5月初在山东日照市涛雒对虾育苗场采集中国对虾虾苗;成虾于1986年春、秋两季取自青岛胶州湾水域的网捕成虾。以酶学分析方法作试验。结果表明,1.虾苗酶活力结果为:类胰蛋白酶及胃蛋白酶的活性有差异,溞状幼体期<糠虾幼体期<仔虾期;酶活性随着生长发育而增高,类咦蛋白酶活性比胃蛋白酶高4倍左右。淀粉酶的活性是溞状幼体期>糠虾幼体期>仔虾期;纤维素酶活力极微;淀粉酶活性是纤维素酶的6—13倍左右。育苗期几种消化酶的活性均远远低于成虾。2,育苗期幼虾的氨基酸含量,随着生长发育而增高,在各期,氨基酸总和的差别是:溞状幼体期<糠虾幼体期<仔虾期。     

凡纳滨对虾幼体不同生长发育时期应答氨氮胁迫的敏感性研究

凡纳滨对虾(Litopenaeus vannamei)是世界上最重要的对虾养殖品种之一。为比较凡纳滨对虾不同生长发育时期应答氨氮胁迫的敏感性差异,作者对其不同生长发育时期24 h半数致死浓度(LC_(50))进行测定,并分析其胁迫效应。结果表明,24 h LC_(50)值在虾的不同生长发育时期差异显著(P0.05),不同时期凡纳滨对虾的LC90与LC_(50)变化趋势相同。在溞状幼体Ⅱ期(Z2)LC_(50)值最低,为17.811 mg/L,在仔虾第V期(P5)时,LC_(50)值最高,为44.808 mg/L。根据LC_(50)和LC90的变化趋势可以看出,仔虾比幼体期的耐受性强。本试验结果不仅为凡纳滨对虾不同生长发育时期的苗种培育提供了重要的基础数据,而且为凡纳滨对虾耐氨氮品系选育提供了重要指导。     

中国对虾幼体期视觉器官的发育

于１９９４年３－５月，以中国对虾无节幼体６个亚期，蚤状幼体３个亚期，糖虾幼体３个亚期及仔虾各时期的幼体为材料，用日产Ｏｌｙｍｐｕｓ万能研究显微镜观察研究各期幼体单眼及复眼的发育。结果表明：在中国对虾无节幼体Ｎ１－Ｎ６６个亚期，单眼的两侧均有复眼的原基组织。     

坚强芽孢杆菌对凡纳滨对虾幼体变态的影响

研究比较了坚强芽孢杆菌Bacillus firmusZOU4菌株对数期细胞和孢子在不同加菌量、次数及不同幼体期加菌对凡纳滨对虾Litopenaeus vannam ei幼体无节Ⅲ期到溞状Ⅱ期变态的影响。结果表明,多次加入高数量对数期细胞或孢子对无节Ⅲ期到溞状Ⅱ期幼体变态具有极显著(p<0.01)促进作用,且对数期细胞效果明显高于孢子,溞状Ⅰ期之前比其后加菌效果更显著(p<0.05),但对无节Ⅲ期变态到溞状Ⅰ期影响不明显(p>0.05)。     

重金属离子对中国对虾幼体的影响及其消除方法比较

为了建立新的防治重金属离子对中国对虾(Penaeus chinensis)人工育苗阶段危害的方法和进一步明确防治时机,本文研究了铜、锌、铅、镉离子对中国对虾各期幼体变态的影响,并比较了两种消除方法的效果.结果表明,与原海水对照,铜、锌、铅、镉4种离子的加入浓度各为15μg/dm3时,无节幼体的变态率显著(0.0250.1);糠虾幼体的变态率反而显著提高(P<0.005).幼体对重金属离子的敏感性为无节幼体>溞状幼体>糠虾幼体>仔虾.植物饵料对重金属离子有络合作用,可降低其毒性.采用EDTA螯合法和高分子吸附剂去除法均可消除其影响,两者之间无显著差异.高浓度的EDTA有害于幼体,10μg/cm3以下为安全浓度.初步观察到低浓度的铜、锌离子似乎对溞状幼体阶段有益.建议在一般海域进行对虾育苗,在溞状幼体以后阶段,不必采取消除重金属离子影响的措施.     

凡纳滨对虾幼体胃蛋白酶和类胰蛋白酶活力的研究

以酶学分析方法测定了凡纳滨对虾(LitopenaeusvannameiBoone)状幼体(Z2)、糠虾幼体(M2)和仔虾(P1)胃蛋白酶和类胰蛋白酶活力的变化。结果表明,在凡纳滨对虾幼体发育过程中,胃蛋白酶和类胰蛋白酶活力逐渐增大,表现为Z2相似文献   

光照对凡纳滨对虾幼体变态发育的影响

为了解光照对凡纳滨对虾(Litopenaeus vannamei)幼体发育和存活率的影响,作者在研究中设定了4种单色光(红、黄、蓝、绿光)及不同光照强度(0、1 500、5 500、12 000 lx)进行实验并就光照对幼体产生的影响进行分析。实验表明:4种单色光对幼体发育变态时间和成活率都有较大影响。幼体从ZⅠ变态发育至仔虾P1,蓝光的幼体发育时间最长,为262.83 h,比对照组多28 h;黄光存活率最低,只有14.49%,比对照组低25.00%,差异显著(P0.05)。同时,凡纳滨对虾幼体在不同的发育阶段对不同光色的敏感度不同,红光和黄光只对溞状幼体变态有较明显的抑制作用,但对糠虾幼体的发育却有促进作用;蓝光和绿光对整个发育阶段都有影响。光照强度对幼体的存活和变态影响差异显著(P0.05)。幼体从ZⅠ发育至P1,12 000 lx光照下幼体变态发育耗时最长(257.33 h),存活率最低(1.63%)。在溞状幼体期,光照大于1 500 lx时,幼体的变态时间增加,存活率下降。糠虾幼体期可适应光照在5 500 lx以下的环境,而仔虾期则可适应120 000 lx的光照。建议根据不同发育阶段调整光照强度,当幼体在ZⅠ时,光强应控制在1 500 lx以下,之后可逐渐增强。本实验结果可为凡纳滨对虾育苗期间的光照管理提供基础数据和理论依据。     

中国对虾幼虫眼发育的细胞学研究

从显微和超微水平研究了中国对虾幼虫眼的发育。结果表明,幼虫眼在膜内无节体期已具备。发育成熟的幼虫眼至少由３个眼单位组成。电镜下,每个眼单位由晶体细胞、网虫眼的最外围。至糠虾体第１期幼虫眼开始退化,表现在网膜细胞内的细胞器减少,色素颗粒致密度降低。糠虾幼体第２,３期,仅可见色素颗料存在;至仔虾期单眼完全消失。     

日本沼虾幼体摄食量及生长的研究

于1990年6月—7月,用南京丰年虫无节幼体作饵料,在培养皿中对日本沼虾溞状幼体作单只培养,测定了各期溞状幼体(Z_1—Z_9)的日摄食量及总摄食量,并观察了饥饿条件下溞状幼体的生长与成活情况。实验表明,Z_1,Z_2阶段,不投饵并不影响其变态和成活率;但自Z_1孵出连续饥饿5d后,即使投饵,溞状幼体也不能正常蜕壳和成活;Z_3阶段是摄食量增加的突变期。南京丰年虫无节幼体是日本沼虾幼体的适口饵料,P_1育成率可达70％。     

刀额新对虾幼体的培育及特点

在水温26～28℃,pH8.1～8.3,海水盐度27.6～29.7的条件下,刀额新对虾幼体从无节幼体第一期(N_1)培育至仔虾幼体第一期(P_1),历时10d,成活率81.9%;至仔虾幼体第8～10天(P_(8～10)),成活率为80%。刀额新对虾幼体发育具有许多不同于其他对虾类幼体的发育特点,其糠虾期身体仅稍倾斜而不呈倒悬状态,极少摄食丰年虫无节幼体,直至P_(3～4)摄食丰年虫幼体现象才较多见。     

Sea Levels and Coastal Inundation Due to Tropical Cyclones in Indian Coastal Regions of Andhra and Orissa

Coastal inundation associated with extreme sea levels is the main factor which leads to the loss of life and property whenever a severe tropical cyclonic storm hits the Indian coasts. The Andhra and Orissa coasts are most vulnerable for coastal inundation due to extreme rise in sea levels associated with tropical cyclones. Loss of life may be minimized if extreme sea levels and associated coastal flooding is predicted well in advance. Keeping this in view, location specific coastal inundation models are developed and applied for the Andhra and Orissa coasts of India. Several numerical experiments are carried out using the data of past severe cyclones that struck these regions. The simulated inland inundation distances are found to be in general agreement with the reported flooding.     

Sea Levels and Western Boundary Flow Near a Tectonic Zone in the Northern Pacific

This article concerns an interrelation between the sea levels and the western boundary flow near a tectonic boundary in a local zone in the Northwestern Pacific. In this zone, sea level variations at stations located on the coast facing the Pacific are studied to find the interrelation between variations of the Kurosio flow as an index of the distance of the flow axis off a specific coast. The result is discussed after data processing of the monthly means of the sea levels, and a notice is taken of variations caused by active crustal upheavals during a seismic event, a local earthquake.     

Role of Siliceous Fossil Dissolution in Downcore Variations of Grain Size and Water Content: Western Margin of Clarion-Clipperton Fracture Zone, NE Equatorial Pacific

Grain size and water content in box-core sediments from the Clarion-Clipperton fracture zone (C-C zone) in the northeast equatorial Pacific were analyzed in detail to understand the downcore variations across a hiatus between Quaternary and Tertiary layers. Grain-size distributions in the topmost core sediments show two modes: a coarse mode (peaked at 50 μm) and a fine mode (at 2-25 μm). The coarse mode disappears gradually with depth accompanied by the dissolution of siliceous fossil tests, whereas the fine mode coarsens due to the formation of authigenic minerals. Water content increases abruptly across a color boundary between an upper pale brown layer and a lower dark brown layer that is the hiatus between Quaternary and Tertiary layers. Abundant smectites and microvoid molds, which are created by the prolonged fossil dissolution in the underlying sediment, are attributed for the abrupt downcore variation of water content. Overall variations in grain size and water content in the topmost core sediments in the western C-C zone are possibly constrained by the dissolution of biogenic siliceous fossils. Variations in geotechnical properties related to these changes must be considered in the design of nodule collectors.     

A Nondestructive Technique for Predicting the In Situ Void Ratio for Marine Sediments

This study tests the hypothesis that the in situ void ratio of surficial marine sediments may be predicted from shear wave velocity-depth data with a reliability equal to that of other methods currently available. Shear wave velocity is fundamentally controlled by the number of grain-to-grain contacts per unit volume of material and by the effective stress across those contacts. In this study, three previously established empirical formulae are used to predict void ratio from velocity-depth data. Field data were acquired along a transect off the northern Californian coast across which water depth increased from 35 to 70 m and seafloor sediment type varied from sand to silty-sand, respectively. A towed seafloor sled device was used to collect shear wave refraction data, and a marked, systematic decrease in velocity was observed along the line, ranging from 35-70 m/s for the coarse, near-shore material to 25-40 m/s for the finer, offshore deposits. Void ratios predicted from these velocities were compared with data measured directly from box-core samples. Of the formulae used for prediction, two agree remarkably well with the control data. Both predicted and control values increase from 0.6-0.8 for the sandy material to 1.1-1.5 for the silty-sand. Thus, this study does not disprove the hypothesis set and demonstrates the potential of field shear wave velocity-depth data as a means of delineating spatial variation in void ratio for surficial marine sediments in a remote, nondestructive manner.     

Particulate n-alkanes and fatty acids in the Changjiang river system

Particulate samples were collected from the Changjiang river system during a flood period, in May 1997, and POC, stable isotope and lipids associated with particles were examined. Results showed the decrease (0.84% ～ 1.88%) of organic carbon content from the upper reaches to the estuary.δ13C values of particulate organic carbon was in the range of -24.9×10-3 to -26.6×10-3, which were close to the isotopic signature of continental C3 vegetation. Total particulate n-alkanes concentrations varied from 1.4 to 10.1μg/dm3,or from 23.7 to 107μg/g of total suspended matter. Fatty acids were present in all the samples, from 1.4 to 5.4μg/dm3, with saturated and unsaturated straight-chain and branched compounds in the carbon number range from C12 to C30. Both δ13C and the ratio of carbon content to nitrogen content indicate the predominance of terrestrial inputs (soil organic matter) among the particles. The biomarker approach has been used to identify the relative portion of terrigenous and autochthonous fraction in the particulate samples. The distribution of fatty acids suggests a striking phytoplanktonic and microbial signal in most particle samples. The terrestrial alkanes are used to estimate the contribution of terrestrial inputs along the mainstream.     

Three-Dimensional Geographically Weighted Inverse Regression (3GWR) Model for Satellite Derived Bathymetry Using Sentinel-2 Observations

Current trends of development of satellite derived bathymetry (SDB) models rely on applying calibration techniques including analytical approaches, neuro-fuzzy systems, regression optimization and others. In most of the cases, the SDB models are calibrated and verified for test sites, that provide favorable conditions for the remote derivation of bathymetry such as high water clarity, homogenous bottom type, low amount of sediment in the water and other factors. In this paper, a novel 3-dimensional geographical weighted regression (3GWR) SDB technique is presented, it binds together methods already presented in other studies, the geographically weighted local regression (GWR) model, with depth dependent inverse optimization. The proposed SDB model was calibrated and verified on a relatively difficult test site of the South Baltic near-shore areas with the use of multispectral observations acquired by a recently launched Sentinel-2 satellite observation system. By conducted experiments, it was shown that the proposed SDB model is capable of obtaining satisfactory results of RMSE ranging from 0.88 to 1.23[m] depending on the observation and can derive bathymetry for depths up to 12m. It was also shown, that the proposed approach may be used operationally, for instance, in the continuous assessment of temporal bathymetry changes, for areas important in the context of ensuring local maritime safety.     

Geotechnical Properties of Surface Sediments in the INDEX Area

As a part of the environmental impact assessment studies, geotechnical properties of sediments were determined in the Central Indian Basin. The undrained shear strength and index properties of the siliceous sediments were determined on 20 box cores of uniform dimension collected from various locations in five preselected sites. The maximum core length encountered was 41 cm and most of the sediments were siliceous oozes consisting of radiolarian or diatomaceous tests. The shear strength measurements revealed that surface sediments deposited in recent times (0-10 cm) have a shear strength of 0-1 kPa; this value increases with depth, reaching 10 kPa at 40 cm deep. Older sediments have greater strength because of compaction. Water content varies in the wide range of 312-577% and decreases with depth. The clay minerals such as smectite and illite are dominant and show some control over water content. Wet density, specific gravity, and porosity do not indicate any notable variation with depth, thereby indicating a uniform, slow rate of sedimentation. The average porosity of sediments is 90.2%, specific gravity 2.18, and wet bulk density 1.12 g/cm 3 . Sediments exhibit medium to high plasticity characteristics, with the average plasticity index varying between 105% and 136%. Preliminary studies on postdisturbance samples showed an increase in natural water content and a decrease in undrained shear strength of sediments in the top 10- to 15-cm layer.     

Ferromanganese Nodules and their Associated Sediments from the Central Indian Ocean Basin: Rare Earth Element Geochemistry

The rare earth element (REE) distribution in nine deep-sea ferromanganese nodules and their associated siliceous sediments from the Central Indian Ocean Basin (CIOB) have been studied to elucidate the REE relationship among them. Total REE concentration varies from 398-928 ppm in the nodules and 137-235 ppm in the associated sediments, suggesting two- to four-fold enrichment in the nodules compared to associated sediments. REE of nodules and their associated sediments show a positive correlation, suggesting REE are supplied from a common source such as seawater. The positive correlation between REE of nodules and sediments from the CIOB is contrary to the competitive scavenging of REE between nodules and sediment in the equatorial Pacific Ocean. REEs in the nodules are carried by Fe, P, and Ti, whereas in the sediment they are carried by P and Mn phases. A similar REE fractionation pattern with middle REE enrichment over heavy and light REE in both the nodules and their associated sediment suggest fractionation is independent of REE abundance and their carrier phases.     

Marine Minerals in the Mexican Pacific: Toward Efficient Resource Management

Vast reserves of marine minerals are known to occur within the Mexican Exclusive Economic Zone. These reserves include: (1) heavy mineral placers rich in titanium and iron along the coast of San Antonio del Mar, Baja California and the southern States of Oaxaca and Guerrero; (2) phosphorites, which represent the only source for superphosphate fertilizers along the Pacific coast off the Baja California peninsula and the Gulf of Tehuantepec; and (3) manganese oxide deposits in nodule and crusts located adjacent to the Clarion-Clipperton Zone and containing high concentrations of Cu + Ni + Co (up to 1.9%), which are essential for the steel and super-alloy industries. Few but important efforts toward surveying these deposits have been carried out by Mexican and international researchers. Relevant data generated by these investigations are reviewed here and put together in a single document. Adequate knowledge of Mexican mineral resources is essential for the development of management strategies when offshore mining starts during this century. Thus, the review discusses the economics inherent to ocean mining in Mexico, setting baselines for future exploration and development activities in the Mexican Exclusive Economic Zone.     

Enhanced Acoustic Backscatter Due to High Abundance of Sand Dollars, Dendraster excentricus

Detailed acoustic surveys of benthic sediments were conducted in July 1995 and September 1998 in the vicinity of Humboldt Bay, California. During these surveys, a band of enhanced acoustic backscatter was observed offshore from the bay entrance, approximately parallel to the isobaths, in water depths ranging from 16-24 m. In order to assess the cause of the increase in backscatter levels, a more comprehensive study was conducted in August and September 1999 using 100 kHz side-scan sonar, bottom grab sampling and underwater video recording. New observations indicated that a dense population of sand dollars ( Dendraster excentricus ) coincided with the enhanced backscatter band. Compared to the two previous acoustic studies, the central section of the band expanded westward by 180 m and the southern section of the band shifted eastward by 160 m, possibly resulting from a change in the biological or physical factors which influence the location and breadth of sand dollars. The relationship between high sand dollar abundance and enhanced acoustic backscatter was further verified in the nearshore region off Samoa Beach California, where a dense, banded population of sand dollars was previously observed. Video footage confirmed the presence of a band of sand dollars, also nominally parallel to the isobaths, in water depths of 8-15 m. A band of enhanced backscatter coincided with the dense sand dollar population. The identification of dense aggregations of sand dollars through enhanced acoustic backscatter could lead to the use of acoustic techniques to study sand dollar distributions and abundance.