Taxonomic diversity of fish assemblages in the Changjiang Estuary and its adjacent waters

Taxonomic diversity of fish assemblages in the Changjiang Estuary(Yangtze River Estuary) and its adjacent waters was analyzed based on bottom trawl surveys carried out by R/V Beidou in June,August and October 2006.Four groups of fishes were identified for each survey by the twoway indicator species analysis(TWIA).Taxonomic distinctness,species richness and phylogenetic diversity were used to detect changes in taxonomic structure of fish assemblages.Most dominant fish species mainly belonged to Perciformes,Pleuronectiformes,Clupeiformes,Scorpaeniformes and Tetraodontiformes.Species richness in offshore waters of the survey area was higher than that in the other area.The average taxonomic distinctness value(AvTD,△+ ) of each fish assemblage was close to the average taxonomic distinctness of master list in the Changjiang Estuary(79.9),and had a positive correlation with species richness and Shannon diversity index(H ).A negative correlation was found between variations in taxonomic distinctness(VarTD,Λ + ) and traditional diversity indices,which were caused by fish species component that led to longer average path lengths among species.Taxonomic diversity index(△) had the similar results with species richness,H ,Simpson diversity index(D) and Pielou's evenness index(J ).VarTD also kept stable,which further certificated that fish assemblages and ecological environment were in equilibrium.Taxonomic distinctness index(△* ) was relatively stable in most of fish assemblages,and had higher values in some fish assemblages for a few absolutely dominant species.The present study showed that fish community formed new equilibrium stability in 2006 in the Changjiang Estuary when compared with those in the corresponding months of annual survey from 1985 to 1986.And AvTD in each sampling station was lower than AvTD of master list in the Changjiang Estuary,so some ecological niches were absent in each sampling stations from taxonomic or phylogenetic relationships,these would be helpful to stock natural resource and maintain ecological equilibruim of fish assemblages.     

EST-derived microsatellites in Pseudosciaena crocea and their applicability to related species

Simple sequence repeat (SSR) markers were obtained for the large yellow croaker Pseudosciaena crocea using 1 205 expressed sequences tags (ESTs) from the NCBI database. Primers for 48 ESTSSR loci were designed and screened with 30 P.crocea specimens captured from Guanjingyang sea area in Fujian Province of China. Sixteen of the loci were polymorphic, which were amplified with 3 to 11 alleles per locus and the mean of 6.13. The observed and expected heterozygosity per locus ranged from 0.091 to 0.844 (mean 0.544) and from 0.118 to 0.892 (mean 0.644), respectively. Polymorphic information content (PIC) ranged from 0.115 to 0.866 (mean 0.593). The results for cross-species amplification of the 16 large yellow croaker EST-SSRs on P. polyactis, C. niveatus, C. lucidus, A. argentatus and J. belengeri revealed that 14, 12, 11, 7 and 6 loci were successfully amplified with 1 to 10 alleles with an average of 4.5 per locus, respectively, which are suitable for population genetics studies of these species and useful for phylogenetic relationship analysis among these species. Overall, this study provides a set of type I markers for population genetics studies and genome mapping for large yellow croaker and its closely related species.     

Bacterial methane in the Atzbach-Schwanenstadt gas field (upper Austrian Molasse Basin), Part II: Retracing gas generation and filling history by mass balancing of organic carbon conversion applying hydrogeochemical modelling

In the Austrian Molasse Basin bacterial methane gas accumulations occur in Upper Oligocene to early Miocene deepwater clastic sediments. Gas is produced from the Upper Puchkirchen Formation (Aquitanian) in the Atzbach-Schwanenstadt gas field.     

Recovery of the biogenic nest habitat of Limaria hians (Mollusca: Limacea) following anthropogenic disturbance

The rate of regrowth of Limaria hians nest material, following a simulated dredging impact, was examined on an extensive L. hians bed off the west coast of Scotland. Within an area of complete coverage of the sea bed by a turf of L. hians nest material, the turf was cleared by diver from 10 × 0.25 m² plots and the sediment subsequently raked to simulate the passage of a scallop dredge. The areal extent and pattern of nest regrowth were recorded after 6 and 12 months. Control plots showed no significant change in 100% nest cover over the year. In the treated plots regrowth generally occurred from extension of peripheral nest material. Over the initial 6 autumn and winter months treatment plots displayed a mean regrowth of 9.2% of the cleared area, increasing to 15% in the second 6-month spring and summer period. However, no significant difference in growth was found between these periods. After 12 months half the treatment plots exhibited <25% nest cover and none of them contained nest of a thickness comparable to the surrounding bed. Conversion of regrowth rates within the treated plots to the rate of nest advance along a linear front, gave a value of 3.2 cm per year, highlighting the susceptibility of this species-rich biotope to scallop dredging.     

Changes in zooplankton diversity and distribution pattern under varying precipitation regimes in a southern temperate estuary

The influence of climate variability on the diversity and distribution patterns of zooplankton communities was investigated in the Mondego estuary (Portugal) during four consecutive years characterized by highly variable precipitation and, consequently, river flow regime. Monthly samples were collected along the estuarine gradient at five sampling stations. Seasonal, inter-annual and spatial distributions were evaluated by multivariate analyses and three diversity indices were applied (Species number, Shannon Diversity and Average Taxonomic Distinctness). A two-year drought period presented significant differences in salinity values, especially in 2005 (extreme drought event). During the study period, copepoda was the main dominant group and Acartia tonsa the most abundant species, with the exception of autumn 2006, where high abundances of the cladoceran Penilia avirostris were noticed. Multivariate analysis indicated that zooplankton communities changed from a pre- to a post-drought period indicating the influence of hydrological parameters in communities' structure. The dry period was associated with an increase in zooplankton density, a reduction in seasonality and higher abundance and prevalence of marine species throughout the year. Seasonally, winter/spring communities were distinct from those in summer/autumn. Spatially, salinity-associated differences between upstream and downstream communities were reduced during the drought years, but during the post-drought year, these differences were detected again.     

东海中部夏季鱼类群落结构及其多样性分析

根据2008年8月东海区主要渔场重要渔业资源调查资料,分析东海中部鱼类的种类组成、区系特征、多样性等群落结构特征。结果表明:共调查捕获鱼类88种,其中暖水种59种,占67.0%;暖温种29种,占33.0%。相对重要性指数(IRI)值大于500的优势种鱼类共有5种,分别为带鱼、刺鲳、小黄鱼、六斑刺鲀和鳄齿鱼;种类丰富度指数变动范围为0.10～2.31,平均为0.88;Shannon-Wiener多样度指数变动范围为0.01～1.86,平均为0.87;种类均匀度指数变动范围为0.01～0.92,平均为0.41;东海中部夏季鱼类多样性指数与往年相比有下降的趋势。     

大黄鱼野生与养殖群体遗传结构的比较研究

采用垂直板型不连续聚丙烯酰胺凝胶电泳技术对福建野生与养殖大黄鱼(Pseudosciaena crocea)4个群体(湄洲野生群体、宁德野生群体、宁德养殖群体、连江养殖群体)的遗传结构进行了比较研究。结果表明,4个大黄鱼群体的平均每位点有效等位基因数为1.1250～1.1293,多态位点百分数为12.50%～18.75%,观察杂合度为0.1250,期望杂合度为0.0636～0.0677。湄洲湾野生群体的遗传多样性高于养殖群体。4个大黄鱼群体间的遗传分化很低,4个大黄鱼群体间遗传距离在0.0000～0.0001,平均遗传距离为0.0005,遗传分化系数(Fst=0.0004)低,基因流(Nm=609.6667)大。     

黑足鲍COⅠ基因序列在遗传分析中的初步研究

对引自新西兰的黑足鲍(Haliotis iris)的线粒体DNA 13个蛋白基因之一细胞色素C氧化酶亚基Ⅰ(COⅠ)基因进行了特异性扩增和测序,并分析了524 bp的碱基序列。结果显示,在37个野生个体的基因序列中检测到3个变异位点,定义了3个单倍型,个体间序列差异很小。单倍型多样性(Hd)和核苷酸多样性(Pi)分别为0.249和0.000 79,遗传多样性水平很低。在以贻贝(Mytilus edulis)为外群构建的系统发育树上,黑足鲍处于相对适中的位置。本次研究以期为了解黑足鲍的遗传学背景提供科学依据,同时为鲍COⅠ基因的研究提供资料。     

中国近海5个黑鲷地理群体的遗传变异

为有效保护和利用黑鲷(Acanthopagrus schlegeli)资源,本研究测定了中国近海5个群体(北方海域的营口与崂山群体,南方海域的闽清、大亚湾、东兴群体)各10尾黑鲷线粒体控制区5′端722bp序列以分析其遗传多样性和遗传结构。结果发现42个单倍型,56个多态位点;群体单倍型多样性为0.978～1.000,群体核苷酸多样性为0.0067～0.0116。中性检测和核苷酸不对称分布分析表明,中国近海黑鲷在晚更新世(165～41kaBP)曾经历过种群的快速扩张。北方群体与南方群体之间的Fst值为0.1145(P=0.00),表明存在中等程度的分化,建议将中国近海黑鲷作为两个管理单位。     

Microbial plankton abundance and heterotrophic activity across the Central Atlantic Ocean

The role of microorganisms in the transfer of carbon of marine systems is very important in open oligotrophic oceans. Here, we analyze the picoplankton structure, the heterotrophic bacterioplankton activity, and the predator-prey relationships between heterotrophic bacteria and nanoflagellates during two large scale cruises in the Central Atlantic Ocean (∼29°N to ∼40°S). Latitud cruises were performed in 1995 between March-April and October-November. During both cruises we crossed the regions of different trophic statuses; where we measured different biological variables both at the surface and at the deep chlorophyll maximum (DCM). The concentration of chlorophyll a varied between 0.1 and 0.8 mg m⁻³, the abundance of heterotrophic bacteria varied between <1.0 × 10⁵ and >1.0 × 10⁶ cells ml⁻¹, and that of heterotrophic nanoflagellates between <100 and >1.0 × 10⁴ cells ml⁻¹. The production of heterotrophic bacteria varied more than three orders of magnitude between <0.01 and 24 μgC L⁻¹ d⁻¹; and the growth rates were in the range <0.01-2.1 d⁻¹. In the Latitud-II cruise, Prochlorococcus ranged between <10³ and >3 × 10⁵ cells ml⁻¹, Synechococcus between <100 and >1.0 × 10⁴ cells ml⁻¹, and picoeukaryotes between <100 and >10⁴ cells ml⁻¹.Two empirical models were used to learn more about the relationship between heterotrophic bacteria and nanoflagellates. Most bacterial production was ingested when this production was low, the heterotrophic nanoflagellates could be controlled by preys during Latitud-I cruise at the DCM, and by predators in the surface and in the Latitud-II cruise. Our results were placed in context with others about the structure and function of auto- and heterotrophic picoplankton and heterotrophic nanoplankton in the Central Atlantic Ocean.