Heavy metal concentrations (Cd,Cu and Pb) in five aquatic plant species in Tasik Chini,Malaysia

The purpose of this study was to determine the levels of heavy metals namely cadmium (Cd), copper (Cu) and lead (Pb) in the five aquatic plants. For this purpose, the concentration of heavy metals were measured in water and in the five aquatic plant species, Lepironia articulata, Pandanus helicopus, Scirpus grossus, Cabomba furcata and Nelumbo nucifera, in 15 sites from Tasik Chini. The concentrations were different among the plant species as well as among the parts of plants. The highest concentration of heavy metals among the aquatic plants and plant parts was found in the roots of S. grossus. The concentrations of Cd in the leaves and stems of submerged aquatic plant, C. furcata, were higher than concentration of Cd in the leaves and stems of emergent aquatic plant and floating leaf plant. The concentration of Cu in the stem of C. furcata was greater than that in the leaf, while the concentration of Cd was more in the leaf than in the stem. The heavy metal contents of the aquatic plants were in descending order of Pb > Cu > Cd. The metal concentration quotient of leaves/roots and stems/roots (ML/MR and MS/MR) were calculated. The highest internal translocation was found in P. helicopus, while the lowest internal translocation was found in S. grossus.     

Paleoecological analysis of molluscan assemblages in two marl deposits in Waterloo Region, southwestern Ontario, Canada

Mollusc assemblages were studied in two marl deposits at Kitchener and Cambridge, in southwestern Ontario. Lacking datable terrestrial plant material, a chronology was determined by pollen analysis. Similarities in mollusc assemblages and changes allowed five equivalent mollusc assemblage zones to be identified in the two deposits, spanning approximately 12 to 7 ka. In total, 34 mollusc taxa were identified, with 19 common to both sites. Overall, the most abundant taxa were Valvata spp., Gyraulus parvus, Pisidium casertanum, and P. ferrugineum. Terrestrial molluscs (four taxa) were rare. Overall, cool, shallow water with abundant vegetation and quiet conditions were indicated. At around 9 ka, a marked decrease in mollusc abundance and diversity, but relatively stable percentages, is noted at both sites. We speculate this was caused by an increase in sedimentation rate, perhaps caused by a brief warming.Inconsistencies in assemblages at marl sites may be partly attributable to sampling, but a chance factor in dispersal is also suggested. A minimum of two sampling sites at a given sedimentation basin, nearshore and mid-basin, are recommended to maximize assessment of assemblages. More detailed data from living molluscs are needed to enhance paleoenvironmental interpretations.     

贝类四倍体育种研究进展

综述了国内外贝类四倍体育种的研究现状和最新进展。四倍体诱导的方法主要有抑制第1极体或同时抑制2个极体的释放、抑制第1次卵裂、细胞融合、人工雌核发育和利用三倍体诱导四倍体，其中利用三倍体获得四倍体是迄今报道的获得具存活力的四倍体的唯一成功方法。四倍体育种中染色体组操作的结果除了产生整倍体外，还产生大量的非整倍体。四倍体贝类存活力较低，但具有较高的繁殖力，能产生较大的生殖细胞，并能与二倍体杂交产生100％的三倍体。     

A high sensitivity, low volume HPLC method to determine soluble reactive phosphate in freshwater and saltwater

A reverse phase High Performance Liquid Chromatography (HPLC) method was developed to detect soluble reactive phosphate (SRP) in marine and freshwater samples. This technique is scalable over a range of sample volumes from 10 μl to 10 ml, requires minimal sample preparation, and responds linearly from 1 nM to 100 μM (R²>0.964). Standard Murphy–Riley molybdenum blue reagents were used to react with phosphate in samples for analysis. Solid phase extraction tubes were used to clean the mixed complexing reagent prior to combining the reagent with samples. The method was applied to freshwater samples collected in July 2001 along an Andean mountain stream located in the Eastern Cordillera (2400 m) of Peru and marine samples collected in January 2002 within the low marsh of the estuarine Nueces Delta System, Texas Coastal Bend. For method comparison, field samples were analyzed using a standard manual spectrophotometric method. Field sample phosphate concentrations produced from each method were nearly identical. This method offers the advantages of low sample volume (1 ml or less) with high sensitivity, precision, and potential automation.     

中国近海的浮游软体动物 I. 翼足类、异足类及海蜗牛类的分类研究

浮游软体动物是海洋中各种终生营浮游生活的软体动物的概称,为海洋浮游动物的一大类群,一般属于腹足纲(Gastropoda)。如前鳃亚纲(Prosobranchia)中的异足亚目(Heteropoda)及海蜗牛科(Janthiniidae),后鳃亚纲(Opisthobranchia)中的翼足目(Pteropoda)、腹翼螺科(Gastropteridae)、波叶海牛科(Phyllirrhoidae )及海神鳃科(Glaucidae)等。其中以翼足目、异足亚目及海蜗牛科为三个主要类群,其余三科无论种类或数量都非常少。 浮游软体动物大多数为暖水性、营大洋上层生活的种类,仅有极少数冷水种及深水种。有的种类在极海出现数量很大,为鲱鱼、鲸及某些海鸟的普通饵料;某些种类在暖海有时出现数量也相当可观,可能也会有一定的饵科意义(如Okutani, 1960,发现Argonauta boettgeri捕食龟螺;著者1960年在广东水产研究所采集的大眼鲷的胃含物中发现明螺。它们的死壳沉积于海底,为生物性沉积的一个组成部分,在热带海形成有名的翼足类软泥,在海洋学上,有的种类已被取用为水团或海流指标。在海洋动物地理学上,也已根据它们的分布特点,对大洋上层浮游动物区系进行过区划。 我国海浮游软体动物的研究工作,迄今还比较零散。 本文整理了中国科学院海洋研究所历年采集的标本、全国近海调查(1958-1960)的标本、中苏东海渔场调查(1958)的沉积样品及浙江近渔场调查(1960)的部分活体标本,共记录了我国近海浮游软体动物11科、28属、59种及6个变种,其中有1个新属、3个新种及1个新变种。以我国近海来说,其中除15种外,其他全为新记录;就南海与东海的全范围而论,约半数的种类为新记录。在本文记录中,翼足类为7科、19 属、35种及6个变种(Agadina属除外),约占翼足类总种数的1/3;异足类3科、8 属、20种,包括异足类所有的科、所有的属及绝大部分的种;海蜗牛类为2种。 另外的几科浮游软体动物,在我国海也有代表,将在以后另文报告。各种浮游软体动物在我国近海的分布状况,亦将另文论述。文中各种类的描述及插图,都是根据著者的实际观察结果。     

中国近海珍珠贝科的研究

珍珠贝科的种类都属暖水种，广泛分布在热带-亚热带海区。由于珍珠贝能产生价值很高的珍珠，长时期来一直是重要的捕捞对象。在我国不仅有产优质珍珠的母贝，而且还有许多适于珍珠贝生长的良好海湾；大力发展人工养殖和育珠，对增加水产资源、支援我国社会主义建设有着重要的作用。为此，搞清我国沿海珍珠贝科的种类及其分布，也是十分必要的。 珍珠贝科和其他贝类一样，早在Linnaeus(1758)时已有记载。其后Lamarck(1819)，Adams(1857)， Reeve(1857)及Dunker (1872)等都有系统的报道，但由于多数种的形态具有较大程度的变异性，所以在分类上一直存在着比较混乱的现象。早期的分类仅根据模式标本的外部特征，后来虽有些学者也曾注意到珍珠贝的形态变异，但由于当时条件所限，往往将一些变异类型订为不同的种。     

Investigation of the impact of salt and sand harvesting activities on the Timboni well field, Gongoni, Malindi District, Kenya

 The area studied is a north–south oriented, V-shaped, clayey lagoonal depression bordered by Pleistocene sands on the west and Recent dune sands on the east. The freshwater aquifer in the area is the main source of potable water for the urban centres of Gongoni and Timboni and the main Mombasa Salt Works processing plant. The aim of the study was to look at the impact of sand harvesting, and possible saline contamination of the aquifer by activities at the nearby salt harvesting plant and by seawater intrusion. The major factor abetting pollution of the freshwater aquifer is the sand harvesting activity, which exposes the aquifer to the atmosphere. Extension of the salt works closer to the aquifer field, combined with high abstraction rates, may also lead to saline water intrusion and contamination of the aquifer. Received: 6 April 1999 · Accepted: 23 May 2000     

19种淡水鱼类的生活史类型研究

研究了中华鲟、达氏鳇、施氏鲟、青鱼、草鱼、鲢、鳙、鲤、赤眼鳟、大眼鳜、鳜、黄尾密鲴、银鲴、花、、团头鲂、尖头塘鳢、鲫等19种淡水鱼类的生态参数（L∞、W∞、K、Tm、Tmax、M、PF）和生活史类型。3种鲟鱼类属k-选择,青鱼、草鱼、鲢、鳙偏向r-选择,其它12种鱼类属r-选择。种群繁殖力PF的数值大体上可反映出某种鱼类的生活史类型,运用Beverton－Holt平衡产量模式估算表明,只有合理控制捕捞强度和起捕年龄,既能保护资源,又能获得较好的经济效益。     

Late-glacial paleoenvironment of Lake Algonquin sediments near Clarksburg,Ontario

Excavation below the Lake Algonquin gravel beach bar near Clarksburg, Ontario, exposed mollusc-bearing clay over a lens of plant debris. This is the northernmost and most deeply buried Lake Algonquin fossil site found thus far in Ontario. It is the first site to provide dates from directly below the Algonquin beach bar. Two radiocarbon dates of about 11 200 years confirm the age of isostatically transgressing Lake Algonquin. Plant macrofossils (21 taxa), pollen (39 taxa), molluscs (12 taxa), and ostracodes (18 taxa) indicate that the climate was colder than present by several degrees and the forest-tundra ecotone was nearby initially but retreated northward rather quickly. Upward increases in abundances and diversity of molluscs and ostracodes suggest it was a time of rapid migration and colonization of species.Deceased, 1 November 1994This is the 7th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.