The Structure of a Free-living Nematode Community in Wrangel Bay of the Sea of Japan

The qualitative composition and distribution of the meiobenthos in Wrangel Bay (Nakhodka Bay of the Sea of Japan) depend on the bottom sediment grain composition and on the concentration of heavy metals in the ground. It was established that the meiobenthos in the bay was represented by 13 groups of animals (class, order) and was relatively evenly distributed. The nematodes dominated (50–80%), and their settlement density was slightly higher in silty ground than in silty–sandy ground. Forty-eight species of nematodes were found; Dorylaimopsis peculiaris, Viscosia stenostoma, Axonolaimus seticaudatus, Metasphaerolaimus japonicus, and Pseudosteineria inaequispiclata dominated in the silty–sandy sediments; Sabatieria pulchra, S. palmaris, Metalaimus pumilus, Sphaerolaimus limosus, and Oncholaimium ramosum dominated in the silty ground. A slightly expressed correlation of the settlement density with the ground type and lead concentration in the bottom sediments emerged for two species (S. pulchra and S. palmaris).     

长江口及东海夏季小型底栖动物丰度和生物量变化

2012年7月,对长江口及东海海域的小型底栖动物类群组成、丰度、生物量的空间分布及其与沉积环境的关系进行了调查研究。该研究海域夏季小型底栖动物的丰度和生物量总体上自北向南递减,在长江口以东的海域由近岸向外海增加,至约45 m等深线达到最高,然后向深水区减少。其小型底栖动物的丰度和生物量分别为(1203±191) 个/10 cm²和(723±171) μg 干重/10 cm²,略高于同一海域春季和秋冬季的数量,但明显低于以往夏季的数量,这可能与本年度该海域沉积物中叶绿素a含量明显偏低有关。在小型底栖动物11个主要类群中,自由生线虫在丰度上占绝对优势(94.1%),其次是桡足类(2.7%)和涡虫类(1.2%)。线虫在生物量上也是最优势类群(62.1%),其次是多毛类(18.8%)、桡足类(8.3%)和涡虫类(6.1%)。Spearman相关分析表明,小型底栖动物的生物量、桡足类和涡虫的丰度均与沉积物中有机氮含量呈负相关;多毛类的丰度与盐度、叶绿素a呈显著正相关;而线虫与所测环境因子未见任何相关关系。BIOENV分析显示,与小型底栖动物各类群的丰度相关性最高的环境因子组合为盐度、沉积物含水量和有机氮含量。研究发现,近10年该海域小型底栖动物的丰度呈总体下降趋势;而且,小型底栖动物的垂直分布随时间推移趋向于向沉积物表层聚集,一定程度上显示沉积环境趋于恶化。通过对近岸和外海两个站位的702条线虫生物体积的测算,获得两个站位线虫的平均个体干重分别为0.186 μg/个体和0.281 μg/个体,两站位平均为0.214 μg/个体,与2009年秋冬季相邻两站位的0.213 μg/个体非常接近,但各站位的线虫个体干重变化相对较大。该结果一方面反映了我国当前普遍采用的0.4 μg/个体系数高估了线虫的生物量,另一方面显示季节和站位差异影响了线虫个体的大小。     

Annual Changes in Meiobenthos Community Structure in Alekseev Bight, Sea of Japan

We performed a comparative analysis of the taxonomical composition and population density of the meiobenthos and substrate types of Alekseev Bight, Sea of Japan, throughout the period when a plantation for mariculture of Japanese scallop was exploited in the bight and for a decade after the plantation had been removed. We found that silting of substrates in the bight decreased and the number of taxonomical groups that constituted the meiobenthos increased. The nematodes that, earlier, dominated the meiobenthos in terms of population density were later exceeded by foraminiferans, the species diversity of which increased. Changes are revealed in the composition of the dominant species of these groups.     

Preliminary data on rotifers in the interstitial of the Ninnescah river, Kansas, USA

One-hundred five rotifer species were identified from a sandy, plains river in Kansas, USA (the Ninnescah river). Of those rotifers identified, eighty occurred only in the interstitial sand, fifty-six in only the flow as plankton, and thirty-one from both habitats. Most species can be characterized as being more commonly found in littoral habitats, and not the interstitial or plankton. Lecane inermis (Bryce, 1892) had the highest density in the hygropsammon interstitial with an average 401 ind. 10 cm⁻³ at 1–3 cm depth in September 1993. New records for the US include Encentrum wiszniewski Wulfert (1939), E. longidens Donner (1943) ant E. (Parencentrum) longipes Wulfert (1960). A small form of Lecane levistyla Olofsson (1917) is further examined and discussed.     

Spatial patterns and feeding of meiobenthic harpacticoid copepods in relation to resident microbial flora

Distributional and feeding relationships of harpacticoid copepods and their microbial prey were examined in a tidal channel at Great Sippewissett Marsh. A horizontal zonation of photosynthetic microorganisms was composed of: 1) a diatom area; 2) a purple sulfur bacterial (Thiocapsa sp.) area; and 3) a clear area. Four species of harpacticoid copepods were associated with given areas. Leptocaris brevicornis occurred in very high densities in the diatom area but in relatively low densities in other areas. Mesochra lilljeborgi occurred in significantly higher densities in the purple and clear areas.Feeding experiments, using resident microbial flora labelled with NaH¹⁴CO₃ and ³H-thymidine, were conducted to determine which foods are 1) ingested but simply pass through the gut and 2) ingested, and retained. These experiments indicated that L. brevicornis ingested diatoms and the heterotrophs associated with the diatoms, but only retained the heterotrophic portion. Microscopic examination indicated that diatoms were passed out intact in feces. Oscillatoria sp. (cyanobacterium) was not ingested. Mesochra lilljeborgi ingested Spirulina sp. (cyanobacterium), Thiocapsa sp., and the heterotrophs associated with Thiocapsa but only retained the Thiocapsa label.These data for harpacticoids suggest that spatial distributions of meiofauna may be closely coupled with microbial food organisms which they consume. Also, that while several microbial foods may be ingested, only certain microbes are digested and assimilated as a food resource, further indicating the complexity of feeding relationships among the meiofauna.     

Estuarine intertidal meiofauna and nematode communities as indicator of ecosystem's recovery following mitigation measures

The Mondego estuary (Portugal) has been under environmental pressure since the early 1990s due to different anthropogenic stresses. The system has been studied following benthic communities’ features from an impacted situation until the recovery phase, focusing mostly on macrobenthos. Following the application of mitigation measures in the estuary, this study is focused on the variability of the intertidal meiobenthic and nematode communities in a system that has recovered after different anthropogenic stresses. While at the spatial level (among areas along the eutrophication gradient) no significant differences were observed regarding the structure and function of the nematode communities, at the seasonal level some differences stood out. These results broadly suggest that the system has recovered from the early situations of pressures being, to the best of our knowledge, the first attempt to investigate the variability of intertidal meiobenthic and nematode communities in the scope of a system's recovery along an estuarine gradient of eutrophication. Even if performed in a short timeline, this study provides a good baseline analysis of conditions, being important for future comparisons.     

Towards a revision of the genus Halectinosoma (Copepoda, Harpacticoida, Ectinosomatidae): new species from the North Atlantic and Arctic regions

This paper contributes to a revision of the genus Halectinosoma . Four new species are described, based on examination of ectinosomatid material from localities in western Europe, eastern Canada and the Arctic. Halectinosoma mandibularis sp. nov. is distinguishable from other species by the reduced setation of the mouthparts and enlarged mandibular gnathobase. Halectinosoma latisetifera sp. nov. bears an affinity with H. cooperatum but is easily distinguished by the shape of the setae on the female fifth leg. A species previously erroneously ascribed to H. finmarchicum (Scott) by several authors is described here as Halectinosoma kliei sp. nov. Halectinosoma gothiceps (Giesbrecht) is redescribed and the closely related Halectinosoma paragothiceps sp. nov. is described and distinguished from H. gothiceps . It is considered likely that some previous records of H. gothiceps are in error.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 149 , 453–475.     

珠江口水域夏季小型底栖生物群落结构

于2010年8月在珠江口水域进行小型底栖生物取样分析,结果表明,该调查水域夏季小型底栖生物的平均丰度为(183±174)个/10 cm2,平均生物量为(345±334)μg干重/10 cm2,平均生产量为(3104±3008)μg干重/10 cm2。共鉴定出小型底栖生物16个类群,按丰度,自由生活海洋线虫和双壳类幼体为优势类群,其丰度分别占调查水域小型底栖生物总丰度的62.61%和22.62%。按生物量,优势类群由双壳类幼体(50.57%)、线虫(13.33%)和多毛类(12.47%)等组成。81.15%的小型底栖生物分布在0—5 cm的沉积物中。与环境因子相关分析表明:小型底栖生物丰度、线虫丰度与温度呈显著负相关,与盐度呈显著正相关。调查水域线虫与桡足类数量的比值(N/C)呈现出由河口上游向下游递增,且西岸明显高于东岸的趋势。     

Sand dwelling Turbellaria from the Netherlands Delta area

Sand dwelling Turbellaria from the Delta of the Rivers Rhine, Meuse and Scheldt have been investigated. Thirty-eight samples taken from littoral and sublittoral stations in the Grevelingen, Eastern and Western Scheldt have been analysed.Thirty-three species were recorded (Acoela were not considered); twenty-four of them are new for the area and seven new species are described.Density and diversity of Turbellaria were higher in the Eastern Scheldt than in the Western Scheldt or in the Lake Grevelingen. A maximum density of 82 ind./100 cm³ was noted. A tentative calculation on relative abundance of the representatives of the different Turbellaria orders is established. Proseriata seem to be dominant in the localities studied.Abbreviations acg : accessory glands - aco : accessory organ - ad : atrial diverticle - b : bursa - br : brain - cil : cilia - cm : circular muscle - cn : cnidosac - co : copulatory organ - cs : cuticular spines - css : cuticular stylet sheat - de : ejaculatory duct - di : ductus intervesicularis - ds : seminal duct - dsp : spermatic duct - en : enteron - fd : female duct - fp : femal pore - ga : genital atrium - gf : glands in female duct - gg : glands - gp : genital pore - hp : adhesive papillae - ivs : intra capsular seminal vesicle - lm : longitudinal muscle - m : mouth - mp : male pore - ov : ovary - p : proboscis - pg : proboscisglands - ph : pharynx - phg : pharyngial glands - r : retractor muscle - rh : rhabdites - rhg : rhabdite glands - rs : seminal receptacle - s : stylet - sta : statocyst - ut : uterus - t : testis - v : vagina - vg : prostate vesicle - vi : vitellary - vs : seminal vesicle     

长江口及邻近海域秋冬季小型底栖动物类群组成与分布

对2009年11-12月采自长江口及邻近的东海海域19个站位的小型底栖动物类群组成、丰度、生物量和空间分布及其与沉积环境的关系进行了研究.结果表明,该海域秋冬季小型底栖动物的平均丰度和生物量分别为(1081 ±700)个/10 cm2和(600±374) μg干重/10 cm2,均呈现由北往南、由近岸向外海递减的趋势,且在长江口冲淡水向东海的扩展区域内,小型底栖动物的丰度明显较东海外围海域高.该数量与同一海域春季的研究结果相近,但明显低于夏季.在分选出的12个主要类群中,海洋线虫在丰度上占绝对优势(94.4％),其次是涡虫类(2.3％)和桡足类(2.0％).线虫也是生物量上的最优势类群(占68.1％),其次是涡虫类(14.8％)、桡足类(6.8％)和多毛类(5.8％).在垂直分布上,占总量70.8％的小型底栖动物和69.9％的线虫分布于0-2 cm表层,均高于54％-65％的历史资料.Spearman相关分析表明,小型底栖动物丰度与叶绿素a含量呈显著正相关,与水深、底层水温和底层盐度呈显著负相关.BIOENV分析显示与小型底栖动物类群组成和丰度相关性最高的环境因子组合为水深和脱镁叶绿素a含量.海洋线虫与桡足类数量之比(N/C)可大致反映本海域沉积环境的质量状况,但沉积物类型等因素的影响可造成环境评价的偏差.通过对639条线虫生物体积的测算,获得两个站位的线虫平均个体干重分别为0.104μg/个和0.365 μg/个.研究表明,我国当前普遍采用的0.4 μg/个这一系数估计的线虫生物量将不同程度地高估其实际生物量.