Sublittoral meiofauna with particular reference to nematodes in the southern Yellow Sea, China

Densities of major meiofaunal taxa were investigated at 34 sampling stations during six cruises by R/V Beidou to the southern Yellow Sea, China from 2000 to 2004, and the community structure of free-living marine nematodes was studied during one of the cruises in 2003. Meiofauna abundance ranged from 487.4 to 1655.3 individuals per 10 cm². Nematodes and harpacticoid copepods were the two most dominant groups, contributing 73.8–92.8% and 3.5–18.7%, respectively, to the total meiofauna abundance. One-way ANOVA showed no significant annual fluctuation of meiofauna and nematode abundances from 2000 to 2004 in the southern Yellow Sea. However, two-way ANOVA based on six stations sampled in 4 years (2001–2004) showed that there were significant differences among the six stations and the 4 sampling years for meiofauna, nematode and copepod abundance. Correlation analysis demonstrated that meiofauna abundance was mainly linked to chloroplastic pigments. Other environmental factors could not be ruled out, however. A total of 232 free-living marine nematode species, belonging to 149 genera, 35 families and 4 orders, were identified. The dominant species in the sampling area were the following: Dorylaimopsis rabalaisi, Microlaimus sp.1, Prochromadorella sp., Promonohystera sp., Cobbia sp.1, Daptonema sp.1, Leptolaimus sp.1, Halalaimus sp.2, Aegialoalaimus sp., Chromadorita sp., Parodontophora marina, Parasphaerolaimus paradoxus, Quadricoma sp.1, Campylaimus sp.1, Halalaimus gracilis, Paramesacanthion sp.1, Paramonohystera sp.1, and Metalinhomoeus longiseta. CLUSTER and SIMPROF analyses revealed three main types of nematode community (or station groups) in the sampling area, including I: coastal community, II: transitory community between coastal and YSCWM (Yellow Sea Cold Water Mass), and III: YSCWM community. Each community was indicated by a number of dominant nematode species. Bio-Env correlation analysis between the nematode community and environmental variables showed that water depth, sediment water content, organic matter, chlorophyll a (Chl-a) and phaeophorbide a (Pha-a) were the most important factors to determine the community structure.     

夏、秋季南黄海小型底栖动物空间分布格局及其环境影响因素

为研究南黄海小型底栖动物的空间分布格局及其环境影响因素,于2020年8月（夏季）和11月（秋季）对南黄海进行了两个航次的野外观测和采样,对小型底栖动物的类群组成、丰度、生物量、垂直分布、群落结构及其与环境因子的关系进行了研究。结果显示,共鉴定出小型底栖动物类群15个,其中自由生活海洋线虫为最优势类群,在两个航次中分别占小型底栖动物总丰度的75.6%和84.6%。其他较重要的类群还包括底栖桡足类、轮虫类和枝角类等。夏季和秋季小型底栖动物的平均丰度分别为（514.9±32.1）ind./(10 cm²) 和（350.8±30.7）ind./(10 cm²),平均生物量（干质量）分别为（651.7±98.0）μg/(10 cm²)和（589.2±37.1）μg/(10 cm²)。小型底栖动物在时空分布上存在差异。在季节分布上,小型底栖动物丰度和类群组成存在极显著差异。结合环境因子分析结果可知,沉积物中值粒径是引起差异的主要环境因子。在空间分布上,夏季小型底栖动物丰度和类群组成在不同水深间存在极显著差异,秋季小型底栖动物丰度和类群组成在不同水深间差异不显著。推测黄海冷水团是影响夏季小型底栖动物空间分布差异的主要因素。本研究中小型底栖动物的数量和类群多样性相较于国内其他对南黄海小型底栖动物的研究较低,其中沉积物叶绿素a含量及有机质含量是引起南黄海小型底栖动物丰度变化的重要因素。海洋线虫与桡足类的丰度比值（N/C比值）评估显示秋季该区域存在有机污染,这一结果与应用大型底栖动物对同一区域进行环境评价的结果不一致,对于应用N/C比值评价环境质量还需要进一步的研究。     

Biomass of meiobenthic in the Bohai Sea, China

IorasMeiOfauna is a vmp imprtant pep in benthic small bo web energetica1ly duo to theirarell aize and high turnovr rates. A nde Of meMauna op be the recireulaton of nutrient8*Marine nemathe mey keep the bacterial chnies on sand grains in active phase Of gorth byfeding on bacteria, thus enhancing the recirculation Of nutrients (McIntyre, l969; Feller andWrmick, l988; MOntagna et al., l995). But energetics studie8, no matter tfor conductedon the energybudgt level for individua sPeCies or a…     

南海北部自由生活海洋线虫的群落结构和生物多样性

A quantitative study on the community structure and biodiversity of free-living marine nematodes and their relationship with environmental factors in the northern South China Sea were carried out based...     

Potential map of gas hydrate formation in Caspian Sea based on physicochemical stability evaluation of methane hydrate

Preliminary studies of Caspian Sea have shown the possibility of gas hydrate accumulations, because of suitable physicochemical conditions, existence of clayey deposits, and high concentrations of organic matter. Studies have indicated that gas hydrates are mainly composed of methane. Therefore, based on physicochemical equations for methane hydrate stability in different pressure, temperature, and salinity, this study was designed to calculate the potential of gas hydrate formation in the Caspian Sea basin. For this, data of more than 600 locations were analyzed and in each location, upper and lower limits of methane hydrate formation zone were calculated. Then, the zoning maps of upper and lower limits were prepared which can be useful for exploring the gas hydrate as an energy source or predicting gas hydrate hazards. According to the calculations and maps, methane hydrate formation in Caspian Sea, theoretically, can take place from near the seabed to 4000 and 2500 m beneath the sea surface when low and high geothermal gradient are supposed, respectively. By comparing the results with gas hydrate zones revealed in geophysical profiles, it has been shown that, in Caspian Sea, gas hydrates probably accumulate near the lower limit when a high geothermal gradient is assumed.     

东海大陆架自由生活海洋线虫一新种:镰刀光皮线虫(线虫:色矛科)

于东海陆架沉积物中发现并描述一自由生活海洋线虫新种：镰刀光皮线虫Actinonema falciforme sp.nov.镰刀光皮线虫的主要鉴定特征为：六根外唇刚毛和四根头刚毛成一圈;表皮具复杂而前后不同的装饰和侧分化;大而明显的化感器椭圆形,中间具一横裂口;单前精巢,反折;前后双卵巢,反折;缺失交接刺和引带,仅具有镰刀形引带侧件。在光皮线虫属中,只有镰刀光皮线虫和长尾光皮线虫A.longicaudatum缺失交接刺和引带,而仅具有引带侧件。镰刀光皮线虫可根据较短的体长、镰刀形引带侧件和较短的尾部而区别于长尾光皮线虫。     

Gorgan Bay:a microcosm for study on macrobenthos species-environment relationships in the southeastern Caspian Sea

The relationship between spatial patterns of macrobenthos community characteristics and environmental conditions(salinity, temperature, dissolved oxygen, organic matter content, sand, silt and clay) was investigated throughout the Gorgan Bay in June 2010. Principal components analysis(PCA) based on environmental data separated eastern and western stations. The maximum(4500 ind./m²) and minimum(411 ind./m²) densities were observed at Stas 1 and 6, respectively. Polychaeta was the major group and Streblospio gynobranchiata was dominant species in the bay. According to Distance Based Linear Models results, macrofaunal total density was correlated with silt percentage and salinity and these two factors explaining 64% of the variability while macrofaunal community structure just correlated with salinity(22% total variation). In general, western part of the bay showed the highest number of species and biodiversity while, the highest density was found at Sta. 1 and in the middle part of the bay. Furthermore, relationship between diversity indices and macrobenthic species with measured factors is also discussed. Our results confirm the effect of salinity as an important factor on distribution of macrobenthic fauna in south Caspian brackish waters.     

Coastal Wave Height Prediction using Recurrent Neural Networks (RNNs) in the South Caspian Sea

The prediction of wave parameters has a great significance in the coastal and offshore engineering. For this purpose, several models and approaches have been proposed to predict wave parameters, such as empirical, soft computing, and numerical based approaches. Recently, soft computing techniques such as recurrent neural networks (RNN) have been used to develop sea wave prediction models. In this study, the RNN for wave prediction based on the data gathered and the measurement of the sea waves in the Caspian Sea, in the north of Iran is used for this study. The efficiency of RNNs for 3, 6, and 12 hourly and diurnal wave prediction using correlation coefficients is calculated to be 0.96, 0.90, 0.87, and 0.73, respectively. This indicates that wave prediction by using RNNs yields better results than the previous neural network approaches.     

Nematode community dynamics over an annual production cycle in the central North Sea

Nematode species composition, trophic structure and body size distributions were followed over an annual production cycle in the central North Sea; to test responses to temporally changing food quality and quantity in the sediment. Changes in the phytoplankton concentration in the water column were quantitatively reflected in the concentration of chlorophyll a and breakdown products in the sediment, with higher concentrations in spring and autumn following blooms, and lower concentrations in summer and winter. The taxonomic and trophic structure of nematode communities differed significantly among stations over relatively short distances, potentially masking some of the temporal dynamics. Spatio-temporal differences in nematode species composition were linked to changes in the quality and quantity of organic material reaching the seabed, reflecting a species-specific response to the nutritional quality of sedimenting organic material and the biochemical changes in the sediment associated with its decomposition. The size distributions of selected nematode species indicated that most species bred continuously throughout the sampling period, although one species, the epigrowth feeder Spilophorella paradoxa, had periods of increased growth following the deposition of the spring phytoplankton bloom. There was no consistent temporal relationship between the trophic composition of nematode communities and spring chlorophyll a or carbon sedimentation, most likely a result of the trophic plasticity of most feeding types and the capacity of the community to use both freshly sedimented material as well as the subsequent breakdown products and refractory organic matter. Community metrics implied that there were small responses to the seasonal production cycle, but these belied strong responses of a few species with life histories that allowed them to track the availability of suitable food resources.     

Characterization of natural hydrocarbon seepage in the South Caspian Sea off Iran using satellite SAR and geological data

Abstract

Two groups of oil slicks have been repeatedly detected in the Southern Caspian Sea, off Cape Sefidrud and close to the Iranian coast of the sea on the synthetic aperture radar (SAR) images acquired by the Sentinel-1A and Sentinel-1B satellites in April–June 2018. Analysis of the SAR images together with bathymetry, geological and geophysical data in geographic information system showed that these manifestations (oil slicks) visible on the sea surface have natural origin, related to the bottom seepage phenomenon and are associated with existing hydrocarbon system. Oil slicks are concentrated over the continental slope and related to local geological formations of the sedimentary cover having oil deposits related to paleo-delta of Sefidrud River. Our evidence shows that two seeps in this area are active and repeating. It is concluded that the SAR is an excellent tool for monitoring of seepage phenomenon. Moreover, results indicate that the use of remote methods to identify offshore natural oil seeps related to existing active petroleum system can be considered as a well-accepted approach to support oil and gas exploration in frontier areas such as the South Caspian Basin.     

黄海中南部头足类的群落结构与生物多样性

为掌握黄海中南部头足类的群落结构及数量分布,作者根据2010~2011年间春、秋、冬3个季节的底拖网调查资料,对黄海中南部头足类的种类组成、生物量分布及生物多样性进行了研究。结果显示:3个季节共捕获头足类13种,隶属3目6科6属。各季节的优势种及其生物量比重分别为:春季——双喙耳乌贼(Sepiola birostrata)50.07%、秋季——针乌贼(Sepia esculenta)40.88%、冬季——枪乌贼(Loligo spp.)68.20%。各季节头足类平均资源密度分别为春季4.85 kg/km2、秋季2.52 kg/km2、冬季12.72 kg/km2,春秋两季间差异性不显著(P0.05),冬季与其他两季差异性显著(P0.05)。黄海中南部不同季节头足类的生物量分布变化较大,春季以西南及东北部密度最高,秋季以西南部密度最高,冬季以中部及东北部密度最高。头足类在各水深的垂直分布随季节变化。无论根据生物量还是丰度,种类丰富度指数、均匀度指数及Shannon-Wiener指数等多样性指数均以冬季最高,其次是春季,秋季最低。春季与冬季群落结构相似性较高,秋季与其他两个季节的群落结构相似性均较低。与1998~2000年同期相比,头足类种类数增加5种,相对资源密度增长了12%,枪乌贼类的生物量比重仍最高,耳乌贼类的比重提高,太平洋褶柔鱼的比重则大幅下降。     

渤海自由生活海洋线虫多样性的研究

首先介绍Warwick和Clarke(1995)提出的等级生物多样性指数以及在自由生活海洋线虫中的应用,重点以1998年9～10月和1999年4～5月两个航次的沉积物样品,用物种数目(S)、Margalef物种丰富度指数(d)、优势度Simpson指数(λ)、多样性Shannon-Wiener指数(H')、Pielou的均匀度指数(J)、Hill多样性系列指数(N₁,N₂和N_+∞)、分类多样性指数(△)、分类差异指数(△*)、等级多样性指数(△+)对渤海自由生活海洋线虫的多样性进行了研究。结果表明,黄河输入的泥沙对渤海自由生活海洋线虫多样性的变化有一定的作用,距离黄河口越近的站位,群落具有的物种多样性和均匀性越低,优势度越高;距离黄河口越远的站位,群落具有的物种多样性和均匀性越高,优势度越低。     

2014年春季渤海浮游植物群落结构

基于2014年春季在渤海进行的水文、化学和生物方面的综合大面调查,研究了渤海浮游植物群落的结构特征,并结合文献资料,分析影响浮游植物群落结构形成的原因。结果显示：2014年渤海春季共鉴定浮游植物3门29属50种,以硅藻为主,还有少数甲藻和金藻。其中,硅藻门中圆筛藻属的种类最多,共12种,其次为角毛藻属,共5种。浮游植物总细胞丰度介于1.08×10⁴~181.09×10⁴个/m³,平均为25.47×10⁴个/m³。硅藻与甲藻细胞丰度比值为12：1,硅藻在物种数量和细胞丰度上均占有绝对优势,为渤海浮游植物的主要类群。浮游植物优势种主要为密联角毛藻（Chaetoceros densus）、斯氏几内亚藻（Guinardia striata）、具槽帕拉藻（Paralia sulcata）和夜光藻（Noctiluca scintillans）。渤海春季浮游植物群落多样性水平较低,且分布不均。渤海中部和渤海海峡海域由于单一优势种过量繁殖导致群落稳定性较差。与历史同期资料对比,渤海海域浮游植物群落出现明显的物种演替现象,角毛藻的优势地位显著性下降,斯氏几内亚藻首次在渤海大面调查中被记录为优势种。本研究为今后渤海环境生态系统和渔业资源变动的研究提供重要基础资料和参考依据。     

Studies on the species composition and biodiversity of free-living marine nematodes in the southern Huanghai Sea

1 IntroductionThe conservation, persistentuse and basic re-search ofbiodiversity are increasingly becom ing oneofthe centraltopics concerned by internationalaca-dem iccirclesandothergroupsdueto itshugevaluetom ankind living and suffered seriousthreats. Fr…     

The distribution of macrozoobenthos in the southern North Sea in relation to meso-scale bedforms

This study investigates the distribution of macrozoobenthos in relation to meso-scale bedforms in the southern North Sea. Three sites on the Dutch Continental Shelf were sampled that are representative of large areas of the North Sea and show diverse morphological settings. These sites are (i) part of a shoreface-connected ridge, (ii) the lower part of a concave shoreface and (iii) a sandwave area. Within these sites, two or three different morphological units were distinguished. Sampling was undertaken in two seasons for two consecutive years. The species composition was analysed for differences in benthic assemblage within sites, based on the meso-scale morphology, and between sites and seasons. In addition, the benthic assemblage was correlated to water depth, median grain size (D50) and sorting (D60/D10). Results show that significant differences in the benthic assemblage can be found related to meso-scale bedforms, but macro-scale morphological setting and seasonal effects are more important.     

Distribution of phytoplankton in the East China Sea and the southern Yellow Sea in spring in relation to environmental variables and dimethylsulfide compounds

The coastal ecosystems are highly sensitive to climate change and are usually influenced by variations in phytoplankton communities and water physiochemical factors. In the present study, the phytoplankton community, chlorophyll a（Chl a） and their relationships with environmental variables and dimethylsulfide（DMS） and dimethylsulfoniopropionate（DMSP） were investigated in spring 2017（March 24 to April 16） in the East China Sea（26.0°–33.0°N, 120.0°–128.0°E） and southern Yellow Sea（31.0°–36.0°N, 12...