The role of water mass dynamics in controlling bacterial abundance and production in the middle Adriatic Sea

Month-to-month fluctuations in the abundance of bacteria and heterotrophic nanoflagellates (HNF) and bacterial production, as well as various chemical (nutrients, oxygen) and physical (salinity, temperature) parameters were analysed at a station located in the open middle Adriatic Sea during one decade (1997-2006). Being influenced by both coastal waters and open Adriatic circulation in the surface layer, and by the deep Adriatic water masses in the deep layers (100 m), this station is quite suitable for detecting the environmental changes occurring in the open Adriatic Sea with respect to the circulation of its water masses and their long-term changes and anomalies. Multivariate methods were used to identify seasonal and inter-annual changes of the investigated parameters, associating observed changes to the changes in Adriatic water masses and circulation regimes. The analyses showed that bacterial abundance and production were controlled by different water mass dynamics during 1997-2001 compared to 2002-2006 period, particularly noticeable in different seasonal patterns of biological parameters. The interplay between North Adriatic Dense Water (NAdDW) and Levantine Intermediate Water (LIW) resulted in a change in the available nutrients (NAdDW is poor in orthophosphates), and as a consequence different bacterial abundance and production. A few periods were examined in detail, such as 2004, when LIW inflow was particularly strong and was accompanied by an increase of bacterial and HNF abundances, as well as of bacterial production.     

Shape optimization of two-dimensional cavitators in supercavitating flows, using NSGA II algorithm

The reduction of energy consumption of high speed submersible bodies is an important challenge in hydrodynamic researches. In this paper, shape optimization of two-dimensional cavitators in supercavitating flows is studied. A two dimensional supercavitation potential flow passes a symmetric two dimensional cavitator, which is placed perpendicular to the flow in a channel of infinite length and immediately a cavity is formed behind the cavitator. This is because of the generation of a gas or vapor cavity between the body and the surrounding liquid due to the change in a high speed flow direction passing the cavitator. Drag force acting on this supercavitating body dictates the thrust requirements for the propulsion system, to maintain a required cavity at the operating speed. Therefore, any reduction in the drag force, by modifying the shape of the cavitator, will lead to decrease this force. This study concentrates on the optimization of two dimensional cavitators in order to decrease drag coefficient for a specified after body length and velocity in a potential flow. To achieve this goal a multi-objective optimization problem is defined to optimize cavitator shapes in supercavitating flow. The so-called NSGA II (Non-dominated Sorting Genetic Algorithm) algorithm is used as an optimization method. Design parameters and constraints are obtained according to supercavitating flow characteristics and cavitator modeling and objective functions are generated using Linear Regression Method. The obtained results are compared with other classic optimization methods, like the weighted sum method, for validation.     

Dissolved iron in the Australian sector of the Southern Ocean (CLIVAR SR3 section): Meridional and seasonal trends

We report measurements of dissolved iron (dFe, <0.4 μm) in seawater collected from the upper 300 m of the water column along the CLIVAR SR3 section south of Tasmania in March 1998 (between 42°S and 54°S) and November–December 2001 (between 47°S and 66°S). Results from both cruises indicate a general north-to-south decrease in mixed-layer dFe concentrations, from values as high as 0.76 nM in the Subtropical Front to uniformly low concentrations (<0.1 nM) between the Polar Front and the Antarctic continental shelf. Samples collected from the seasonal sea-ice zone in November–December 2001 provide no evidence of significant dFe inputs from the melting pack ice, which may explain the absence of pronounced ice-edge algal blooms in this sector of the Southern Ocean, as implied by satellite ocean-color images. Our data also allow us to infer changes in the dFe concentration of surface waters during the growing season. South of the Polar Front, a comparison of near-surface with subsurface (150 m depth) dFe concentrations in November–December 2001 suggests a net seasonal biological uptake of at least 0.14–0.18 nM dFe, of which 0.05–0.12 nM is depleted early in the growing season (before mid December). A comparison of our spring 2001 and fall 1998 data indicates a barely discernible seasonal depletion of dFe (0.03 nM) within the Polar Frontal Zone. Further north, most of our iron profiles do not exhibit near-surface depletions, and mixed-layer dFe concentrations are sometimes higher in samples from fall 1998 compared to spring 2001; here, the near-surface dFe distributions appear to be dominated by time-varying inputs of aerosol iron or advection of iron-rich subtropical waters from the north.     

Data-based forecasting of beach volumes on monthly to yearly timescales

Data-based methods for forecasting beach volumes are tested using ground-measured bathymetry from Duck, North Carolina, comprising 26 profiles, 20 year duration and one-month resolution. Derived beach volume time series show weak seasonal and strong event signals. The forecasting methods used are: Holt–Winters (standard and modified), three types of linear regression, and a default forecast in which the latest measurement persists unchanged into the future. Improved forecast accuracies are obtained by two modifications to Holt–Winters, involving an autocorrelation correction and long-term trend-damping, and by smoothing the fitting data using running medians or wavelet approximations. Beach volume forecasts are tested mainly at monthly intervals up to 12 months ahead, with further tests at up to 36 months ahead. Overall, modified Holt–Winters performs best and the default forecast second-best. With an added artificial seasonal signal, modified Holt–Winters outperforms the other methods more substantially.     

杭州湾及其邻近海域表层沉积物的沉积环境分区及重金属污染特征分析

于2017年春季和2018年春季,分两个航次,在杭州湾及其邻近海域采集了表层沉积物样品,并对其粒度组成及重金属含量进行了测定。结果表明,研究区域表层沉积物的粒级组成以砂和粉砂为主,平均占比分别为38.0%和55.4%。根据粒级组成的区域分布特征,将研究区域分为长江河口现代沉积区(Ⅰ-1)、钱塘江河口现代沉积区(Ⅰ-2)、长江羽状锋面积聚区(Ⅱ-1)、长江次级锋面积聚区(Ⅱ-2)、岛屿风化影响区(Ⅲ)、残留砂混合沉积区(Ⅳ)等4大类6个亚区。通过比较不同区域重金属含量发现,总体分布趋势为Ⅱ-1区和Ⅱ-2区含量较高,Ⅰ-2区和Ⅳ区含量较低,Ⅰ-1区和Ⅳ区相对居中。单因子污染指数评价结果显示,Ⅱ-1区和Ⅱ-2区的Cu、Pb、Zn、As、Cd、Hg已呈现出污染态势,需引起关注;Cr则未呈现出污染态势。     

疏肝消瘿方联合西药治疗甲状腺功能亢进症40例临床观察

目的：观察疏肝消瘿方联合西药治疗甲状腺功能亢进症（甲亢）的临床疗效。方法：将80例甲亢患者随机分为治疗组和对照组,每组各40例。对照组给予甲巯咪唑治疗,治疗组在对照组的基础上给予疏肝消瘿方治疗,2组均以4周为1个疗程,随访12周后,比较2组患者的临床疗效、甲状腺功能及治疗前后服用西药剂量的变化。结果：总有效率治疗组为92.5%,对照组为75.0%,2组比较,差异有统计学意义（P<0.05）;2组TSH、FT3、FT4及TRAb水平治疗前后组内比较及治疗后组间比较,差异均有统计学意义（P<0.05）;2组甲巯咪唑服用剂量治疗前后组内比较及治疗后组间比较,差异均有统计学意义（P<0.05）。结论：疏肝消瘿方联合西药治疗甲状腺功能亢进症疗效优于单用西药组,值得临床推广应用。     

Influx of Streaming Methane into Anoxic Waters of the Black Sea Basin

Oceanology - Based on long-term data on the spatial distribution and fluxes of streaming (bubbling) methane in the Black Sea, the study considers various types of streaming gas emissions...     

Oceanographic Studies in the Northwest Pacific and Seas of Japan and Okhotsk on Cruise 73 of the R/V Professor Gagarinskiy and Cruise 53 of the R/V Akademik Oparin

Oceanology - During cruise 73 of the R/V Professor Gagarinskiy and cruise 53 of the R/V Akademik Oparin, oceanographic studies of the Sea of Japan and Sea of Okhotsk and the Northwest Pacific were...     

Variability of Ice Conditions of the Bering Sea and Assessment of Their Possible Modeling

Oceanology - Various aspects of the seasonal and interannual variability of the sea ice cover are estimated based on all available Bering Sea ice data from 1960 to 2017. The possibility of...