Entrapment of pollutants in Mediterranean sediments and biogeochemical indicators of their impact

The transit and fate of certain pollutants (Cd, Pb, Zn and P) transported to the western Mediterranean sea-floor and a method to assess their impact are described. The spatial distribution of pollutant concentrations in the Rhône prodelta shows that their decline with distance from their source is due both to mixing with unpolluted sediments, release from contaminated particles during transit and release from sediments after deposition. Beyond the continental shelf, metals of anthropogenic origin, mainly incorporated in faecal pellets, sink and become entrapped in deep sea sediments. Because subsaturating concentrations of trace metals are often found in surface pore waters and storage, therefore, still occurs, co-precipitation with other metal ions existing in slightly supersaturated states has also to be considered. Although phosphate tends to precipitate as apatite after entering sea water, its `definitive' storage in sediments is hindered by certain forms of pollution. Low pH and reducing conditions in sediments enhance phosphate release to the overlying water . Eutrophication may then occur in localised areas. The effects of urban waste water contamination on biogeochemical processes in sediments are examined, in particular processes responsible for the transformation of organic nitrogen. Sediment quality appears to be better defined by the effectiveness of diagenetic processes than by pollutant concentration per se. In general, polluted sediments possess weak capacities to transform organic nitrogen relative to the quantities of organic matter that are available. Such sediment characteristics are indicated by the preferential growth of Caulerpa taxifolia over that of Posidonia oceanica.     

A new lycopsid megaspore cone from the Upper Devonian of Chaohu, China

A new small lycopsid cone, Minostrobus chaohuensis gen. et sp. nov. , is described from the upper part of Wutung Formation (Famennian) of Chaohu, Anhui, China. Six sporophylls in each whorl are tightly arranged on the cone axis. Each sporophyll consists of a short pedicel and a narrow lamina with smooth margins. One spherical to spherical-ellipsoidal sporangium is attached directly to the adaxial surface of each sporophyll. Each sporangium contains four megaspores. A solid exarch protostele occurs at the centre of the cone axis, and a mesarch protostele in the base of the sporophyll. M. chaohuensis is interpreted as a small, herbaceous, heterosporous lycopsid.     

Effect of Vitamin E and Its Analogues Having Various Molecular Structures on the Growth and Lipid Composition of Pythium debaryanum

The effect of exogenously added vitamin E and its synthetic analogues (the hydrophilic form of vitamin E and chromans C₁₃and C₁) at a concentration of 9.86 × 10^–5M on the growth, lipogenic activity, and the fatty acid composition of the eicosapolyenoic acid–synthesizing oomycete Pythium debaryanumwas studied. The effect was found to depend on the molecular structure of particular compounds. For instance, vitamin E and chroman C₁₃stimulated fungal growth, whereas chroman C₁inhibited it. The hydrophilic form of vitamin E enhanced the lipogenic activity of the oomycete. The studied compounds, which possess antioxidant activity, did not exert any noticeable effect on the content of eicosapolyenoic acids and the degree of the unsaturation of fungal lipids.     

Ecological Strategy of Bacteria: Specific Nature of the Problem

An attempt is made to sum up the results of the many years of using the conception of ecological strategy in bacterial ecology. Taking into account the specificities of microorganisms and their natural selection and the coevolution of microorganisms within evolving microbial communities, an inference is derived that the ecological strategy of most bacteria is the sum of a number of particular canonical strategies, some of which are common to higher organisms. It is proposed to call these particular strategies ecological tactics. The author considers this review to be a basis for a discussion.     

辽西中上侏罗统土城子组植物化石的新发现

报道产自辽宁北票三宝营土城子组２种木化石及１０种植物化石（包括５新种）。它们反映了干旱气候条件下沙漠绿洲型的植被特征,时代属时代属中晚侏罗世。     

长江口潮沟大型底栖动物群落的初步研究

通过对长江口崇明东滩潮沟系统与大型底栖无脊椎动物进行取样调查 ,研究了潮沟不同生境的底栖动物群落及其多样性 ,分析了潮沟生境异质性与底栖动物群落的关系。研究发现 :①潮沟剖面中出现明显的动物群落分带现象 ,从潮沟底、潮沟边滩到草滩 ,底栖动物种类、生活型组成和生活类群比例反映了河口潮滩潮沟底栖动物生态系列 ;②密度和生物量的分布皆为潮沟边滩 >草滩 >潮沟底 ,但密度与生物量的面上群 /面下群值格局却有不同 ,说明了密度和生物量的优势生活型和生活类群随潮沟生境的差异而变化 ;③潮沟系统 3种生境的多样性指数D ,H′和J值均为草滩 >潮沟边滩 >潮沟底 ,是潮沟系统生境结构分化的结果。潮沟底和潮沟边滩等特殊生境的存在 ,提高了淤泥质河口潮滩的生境异质性 ,说明了潮沟系统在维持河口生态系统底栖动物物种多样性中的重要作用。     

A new species of Lepidostrobus from the Upper Devonian of Xinjiang, China and its bearing on the phylogenetic significance of the order Isoëtales

Lepidostrobus xinjiangensis sp. nov. is described from Upper Devonian rocks of the eastern Junggar Basin, Xinjiang, north-west China. It provides new insights into the reproductive diversification and phylogenetic relationships of lycopsids in the Late Devonian. The strobilus shares more characteristics with arborescent lycopsids than any herbaceous forms, and falls within the diagnosis of Lepidostrobus . Each sporophyll consists of a deltoid pedicel and a triangular lamina. Sporophylls are horizontally inserted into the strobilus axis in low spirals. The pedicel, with lateral alations and an abaxial keel, extends distally into the upturned lamina and downturned heel, producing a peltate appearance. A single sporangium with terminal longitudinal dehiscence is a radially elongate, dorsiventrally flattened ovoid and is attached along its length to the adaxial surface of the pedicel. A column-like subarchesporial pad is found in the sporangium. A possible ligule occurs on the adaxial surface of the pedicel distal to the sporangium. The strobilus is microsporangiate, containing Lycospora -type spores with granulate ornamentation and an equatorial flange. Based on this new species, the reproductive diversification and evolutionary pattern in arborescent lycopsids from the Devonian through the Carboniferous are discussed in a phylogenetic framework. We suggest that the reproductive strategies represented by bisporangiate- and monosporangiate-strobili had proliferated by the Late Devonian, which implies that phylogenetically advanced arborescent lycopsids bearing Lepidostrobus strobili had an earlier origin than previously thought.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 143 , 55−67.     

Contemporary transport of suspended material and its deposition in the Vistula River,Poland

The rate of suspended material transported with the current and its deposition in the Vistula River and its main tributaries was estimated to determine the effects of river regulation in the following periods: (1) between the beginning of engineering works on the Vistula River and the construction of the first dams on its tributaries, (2) in the years 1946-1995 when transport measurements were taken, (3) after the planned completion of the dam system. Those estimates were based on the results of long-term measurements of the rivers, carried out by the State Hydrological Survey at numerous gauging stations, as well as on analysis of maps published after 1780. The combined methods allowed estimating both the differences in deposition of the suspended material along the river and the long-term variability of that process. The initial increase in transport and deposition of the suspended material in the Vistula River during the four decades succeeding the river regulation (1890s–1930s) was followed by a rapid decrease of the material transport caused by the construction of dams and changes in land-use in the river basin.     

桂林上泥盆统的串管海绵

串管海绵的Amblysiphonella属在桂林地区融县组的发现,填补该属在晚泥盆世地质历程中的空白。在此之前,国内、外已出版地质文献中未记载该属在泥盆系发现的种。