Holocene hydrographical changes of the eastern Laptev Sea (Siberian Arctic) recorded in δO profiles of bivalve shells

Oxygen isotope profiles along the growth axis of fossil bivalve shells of Macoma calcarea were established to reconstruct hydrographical changes in the eastern Laptev Sea since 8400 cal yr B.P.. The variability of the oxygen isotopes (δ¹⁸O) in the individual records is mainly attributed to variations in the salinity of bottom waters in the Laptev Sea with a modern ratio of 0.50‰/salinity. The high-resolution δ¹⁸O profiles exhibit distinct and annual cycles from which the seasonal and annual salinity variations at the investigated site can be reconstructed. Based on the modern analogue approach oxygen isotope profiles of radiocarbon-dated bivalve shells from a sediment core located northeast of the Lena Delta provide seasonal and subdecadal insights into past hydrological conditions and their relation to the Holocene transgressional history of the Laptev Sea shelf. Under the assumption that the modern relationship between δ¹⁸O_w and salinity has been constant throughout the time, the δ¹⁸O of an 8400-cal-yr-old bivalves would suggest that bottom-water salinity was reduced and the temperature was slightly warmer, both suggesting a stronger mixture of riverine water to the bottom water. Reconstruction of the inundation history of the Laptev Sea shelf indicates local sea level ∼27 m below present at this time and a closer proximity of the site to the coastline and the Lena River mouth. Due to continuing sea level rise and a southward retreat of the river mouth, bottom-water salinity increased at 7200 cal yr B.P. along with an increase in seasonal variability. Conditions comparable to the modern hydrography were achieved by 3800 cal yr B.P.     

蛤蜊岗滩涂贝类分布及其与环境因子的关系

为探明辽东湾蛤蜊岗潮间带滩涂贝类的物种组成、分布密度和生物量的变化状况,于2011年5月对蛤蜊岗滩涂贝类资源进行了现场调查,采集共获得滩涂贝类16种,其中文蛤、泥螺、四角蛤蜊、托氏琩螺为蛤蜊岗滩涂贝类优势种,青蛤和光滑河蓝蛤为常见种。托氏琩螺的分布密度最高,为83个/m2,四角蛤蜊的平均生物量最大,为178.51 g/m2。蛤蜊岗滩涂贝类的分布呈现从滩涂北部向南部逐渐减少的趋势,滩涂四周的分布密度大于滩涂中间区域。对滩涂贝类分布密度和生物量与底质粒度、有机物含量等环境因子进行相关分析的结果显示:文蛤分布与底质中值粒径呈极显著的负相关性;托氏琩螺分布与底质中有机质含量呈显著的正相关性,而泥螺、四角蛤蜊则与环境因子的关系不显著。调查结果表明,蛤蜊岗滩涂贝类资源丰富,但应加强文蛤自然资源的保护和恢复,同时应加强对托氏琩螺资源的合理开发利用。     

四十里湾几种双壳贝类及污损动物的氮、磷排泄及其生态效应

对多种经济双壳贝类和养殖中的污损动物的N和P排泄进行了测定 ,包括排泄成分和排泄速率。在这些动物的N排泄中 ,NH4 N占主要部分 ,如笼式养殖的双壳贝类NH4 N占总N排泄的平均值范围为 70 8%— 80 1 % ;氨基酸是第二大排泄成分 ,平均占总N排泄的 1 0 %—2 5 %。其他形态的N ,如尿素、亚硝酸盐和硝酸盐也有检出。在P排泄中 ,有机磷 (DOP)约占总溶解磷 (TDP)排泄的 1 5 %— 2 7%。据估算 ,整个四十里湾所养殖的双壳贝类在夏季每天将排泄4 5 4t总溶解氮 ,其中NH4 N 3 36t、Amino N 0 69t、Urea N 0 2t。同时每天磷的排泄为 0 5 7tTDP ,其中DOP 0 1 5t。对面积为 1 3× 1 0 4 hm2 的海区而言 ,贝类的N、P排泄分别能满足浮游植物生产所需N、P的 44%和 40 %。高密度的贝类养殖对养殖生态系统营养循环的影响是很显著的。附着动物 (柄海鞘等 )的N、P排泄及其对营养循环的影响也不容忽视。     

DIETARY PHOSPHORUS REQUIREMENT OF YOUNG ABALONE, HALIOTIS DISCUS HANNAI INO.

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Threshold of motion of bivalve and gastropod shells under oscillatory flow in flume experiments

The threshold of motion of non-fragmented mollusc shells was studied for the first time under oscillatory flow. In this regard, flume experiments were used to investigate the threshold of motion of three bivalve and three gastropod species, two typical mollusc classes of coastal coquina deposits. The sieve diameters ranged from 2·0 to 15·9 mm. These experiments were performed on a flat-bottom setup under regular non-breaking waves (swell) produced by a flap-type wave generator. The critical Shields values for each species of mollusc were plotted against the sieve and nominal diameter. Moreover, the dimensionless Corey shape factor of the shells was evaluated in order to investigate the effect of mollusc shell shapes on the threshold of motion. According to their critical Shields parameter, the mollusc threshold data under oscillatory flow present smaller values than the siliciclastic sediments when considering their sieve diameter. In addition, the mollusc datasets are below the empirical curves built from siliciclastic grain data under current and waves. When considering the nominal diameter, the critical Shields parameter increases and the mollusc data are closer to siliciclastic sediments. Bivalves, which have a flat-concave shape (form factor: 0·27 to 0·37), have a higher critical Shields parameter for smaller particles and more uniform datasets than the gastropod scattered data, which have a rounded shape (form factor: 0·58 to 0·62) and have varied morphologies (ellipsoidal, conical and cubic). The comparison between previous current-driven threshold data of bioclastic sediment motion and the data of mollusc whole shells under oscillatory flow shows a fair correlation on the Shields diagram, in which all datasets are below the mean empirical curves for siliciclastic sediments. These findings indicate that the shape effect on the transport initiation is predominant for smaller shells. The use of the nominal diameter is satisfactory to improve the bioclastic and siliciclastic data correlation.     

Early Cambrian Mollusc Watsonella crosbyi: A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2

The mollusc Watsonella crosbyi was studied on the basis of material from the lower Cambrian Dahai Member of the Zhujiaqing Formation in eastern Yunnan, China and the Pestrotsvet Formation of the Aldan River region in the Siberian Platform. This fossil had been excessively described under different names in the literature, such as Heraultia varensalensis Cobbold, 1935, H. sibirica Missarzhevsky, 1974, Heraultipegma yunnanensis He and Yang, 1982, H. yannanese He and Yang, 1982, Watsonella yunnanensis, W. crosbyi Grabau, 1900, etc. Taxonomic revision shows that other species are junior synonyms of W. crosbyi. Analysis of functional morphology implies that W. crosbyi may be rather a helcionelloid than a rostroconch since its univalved conch is untorted endogastric and lacks a rostrum and a true internal pegma. Replicas of the original microstructures preserved on the surfaces of phosphatic internal moulds confirm that the shell consists of two layers. The inner layer is lamello-fibrillar, and the outer layer is spherulitic prismatic. The widespread geographical occurrences in both siliciclastic and carbonate rocks of the late Terreneuvian indicate that W. crosbyi is an important index fossil for global correlations and subdivision of the Cambrian Series 1 (Terreneuvian). The first appearance datum (FAD) of W. crosbyi is suggested to be a potential GSSP (Global Boundary Stratotype Section and Point) candidate marker for defining the base of the Cambrian Stage 2.     

泉州湾洛阳江红树林自然保护区潮间带软体动物多样性及分布

为了解洛阳江红树林自然保护区不同生境的潮间带软体动物物种多样性、数量时空分布及群落结构现状,国家海洋局第三海洋研究所于2009年4月和11月在洛阳江红树林自然保护区内选择了光滩（Qch1）、屿头红树林区（Qch2）、增墁红树林区（Qch3）和米草区（Qch4））4条断面共3种生境,进行软体动物调查。共鉴定软体动物16科...     

Multivariate discriminant analysis distinguishes metal- from non metal-related biomarker responses in the clam Chamaelea gallina

Molecular biomarkers are among the most sensitive and earliest responses to pollutants. However, lack of detailed knowledge on variability of responses and their possible seasonal variation limit their use. In addition, the seasonality of biological processes modulates the response of organisms to pollutant stressors. Using multivariate statistics, we have studied the influence of environmental and biological factors on the response of a battery of molecular biomarkers in the clam Chamaelea gallina collected along the South-Spanish littoral. Multivariate discriminant analysis clearly distinguished biomarker response between clean and polluted areas, using heavy metals as indicator of pollution. Such differences disappeared when the dataset was normalised for metal content, thus indicating that pollution was the main significant cause of the changes observed between clean and polluted sites. In conclusion, this work shows that, when applying a complete biomarker panel, multivariate statistical tools can be used to discern pollutant- from non pollutant-related responses.     

三种软体动物闭壳肌-壳界面结构研究

闭壳肌的疤痕部位（AMS）是闭壳肌和壳的固定点。它是一个重要的有机-无机界面和应力分布面。尽管有一些近期的研究进展,我们对AMS组成和结构的了解仍然是有限的。这里,我们研究比较了三种双壳类动物：厚壳贻贝、栉孔扇贝、菲律宾蛤仔的AMS。结果表明这三种动物的AMS明显不同。厚壳贻贝和栉孔扇贝在AMS的壳结构珍珠片层上部有一柱状层,该层在厚壳贻贝中的结构更有规律。菲律宾蛤仔缺乏此柱状层。原子力显微镜结果显示在三种软体动物中AMS的结构比珍珠层结构更光滑。傅立叶变换红外分析结果显示珍珠层和AMS层组成成分略有不同。聚丙烯酰胺凝胶电泳蛋白分离结果显示在厚壳贻贝界面柱状层存在一种约70 kDa的蛋白。对这种蛋白的进一步分析显示其还有较高摩尔比的Asx（Asp+Asn）,Glx（Glu+Gln）和Gly。AMS的特殊结构和组成对其稳定性、粘性以及在该应力分散部位的功能有重要作用。     

香港海区双壳类帘蛤科一新种

帘蛤科一新种——扁平美女蛤Circe(Laevicirce)hongkongensis sp.nov.系于1988年采自香港大潭湾潮下带。新种的主要特征是两壳极扁平,铰合部宽阔,区别于本亚属的其他种。