Characterizing benthic substrates of Santa Monica Bay with seafloor photography and multibeam sonar imagery

Seafloor photography from three cruises is combined with multibeam sonar imagery to characterize benthic substrates and associated fauna of Santa Monica Bay, California. The multibeam EM1000 imagery was collected in 1996. Two sampling cruises (in 1998 and 1999) provided photographs at 142 sites throughout the Bay; a final cruise (in 2000) collected still photographs and continuous video along nine transects on the mainland shelf from Pt. Dume to the Palos Verdes peninsula. Muddy substrates (typically low backscatter) were the predominant habitat throughout the Santa Monica Bay, from the 20 m isobath to the adjacent Santa Monica basin floor (780 m). Bioturbation was pervasive as evidenced by abundant open burrows, mounds, and faunal tracks and trails. Sandy substrates (typically intermediate to high backscatter) were restricted to the innermost mainland shelf and a narrow outer shelf band north of Santa Monica Canyon. Cobble and gravel substrates (high backscatter) were restricted to the innermost shelf south of El Segundo and limited parts of the shelf edge. Rocky substrates (high backscatter) with interspersed patches of sand and gravel occurred on the high-relief marginal plateau and along parts of the shelf break offshore of Malibu.     

Microbial dechlorination of dioxins in estuarine enrichment cultures: effects of respiratory conditions and priming compound on community structure and dechlorination patterns

The effect of respiratory conditions and priming compound on dechlorination patterns of heptachlorodibenzo-p-dioxins (HpCDD) was investigated using estuarine sediment-eluted cultures in the presence and absence of 20 mM sulfate, and 0.2 microM 2-bromodibenzo-p-dioxin (2-BrDD) as a priming compound. Electron balance calculations based on fatty acid turnover, hydrogen production, and electron acceptor depletion/methane formation indicated that whereas fermentative processes dominated in sulfate-free incubations, sulfate-reduction was predominant in the sulfate-amended incubations. The dechlorination of 1,2,3,4,6,7,8-HpCDD exhibited the following trends: (i) the relative yields of product formation did not exceed 30% and the presence of 2-BrDD increased the yield by up to 10%; (ii) sulfidogenic conditions resulted in a lower 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) formation, and the presence of 2-BrDD decreased the formation of 2,3,7,8-TCDD by additional 4-5-fold; (iii) the presence of 2-BrDD effected a predominance in lateral (2,3,7,8 positions) over peri (1,4,6,9 positions)-dechlorination. Denaturing gradient gel electrophoresis (DGGE) banding patterns indicated significant shifts of microbial community structure in response to terminal electron accepting processes as well as to the presence of the priming compound. The latter resulted in a similar community structure independent of dioxin spike, indicating that subsets of populations in the sediment are capable of exploiting the new niche provided by the priming compound.     

几个风暴潮预报模型的实例

对给定的地点,可应用几种定型的模型正确地预报潮位。然而,在风暴条件下,潮位的观测值和预报值之间存在着差值,这个差值称作风暴潮。对位于塞纳河河口的勒阿弗尔港,同时用二种风暴潮预报模型:自回归模型和一种需用当地风、气压资料的模型。 自回归模型能用来作时效为5小时的预报;用勒阿弗尔气象台36小时内的风,气压的预报值,便可用第二种预报模型,给出39小时时效的风暴潮预报。     

A Refined Method for Estimating the Annual Extreme Wave Heights at A Project Site

1 .Ｉｎｔｒｏｄｕｃｔｉｏｎ1ＴｈｉｓｗｏｒｋｗａｓｆｉｎａｎｃｉａｌｌｙｓｕｐｐｏｒｔｅｄｂｙｔｈｅＰｈ .ＤｆｏｕｎｄａｔｉｏｎｏｆＥｄｕｃａｔｉｏｎＭｉｎｉｓｔｒｙｏｆＣｈｉｎａ (ＧｒａｎｔＮｏ .2 0 0 0 0 4 2 30 8) . Ｃｏｒｒｅｓｐｏｎｄｉｎｇａｕｔｈｏｒ.Ｅ ｍａｉｌ:ｘｕｄｅｌ@ｍａｉｌ.ｏｕｑｄ .ｅｄｕ .ｃｎ　　Ｂｅｃａｕｓｅｔｈｅｅｓｔｉｍａｔｉｏｎｏｆｌｉｋｅｌｙｅｘｔｒｅｍｅｗａｖｅｃｏｎｄｉｔｉｏｎｓｉｓｃｌｏｓｅｌｙｒｅｌａｔｅｄｗｉｔｈｔｈｅｓａｆｅａｎｄｃｏｓｔｅｆｆｅｃｔｉｖ…     

利用微波辐射计对水淹区和盐渍化土灌制图

水淹和盐度，在海岸地带是两个同等重要的问题。目前还没有一种精确的遥感技术可以用来对受这两个因素影响的地带制图。为了研究采用微波辐射计进行这种制图的可行性，我们通过能够反映水淹区和盐渍区特性的层化模型，进行了亮度温度的数值计算。亮度温度的特性可以显示出水淹区和盐渍区的特征值。本文所提供的结果表明了微波辐射计在对水淹区和盐渍区制图方面的应用价值。     

The impact of oestrogenic and androgenic contamination on marine organisms in the United Kingdom--summary of the EDMAR programme. Endocrine Disruption in the Marine Environment

This paper summarises results of the EDMAR programme which is investigating oestrogenic and androgenic endocrine disruption in UK coastal waters. Most of the data concern fish. Four species (flounder, viviparous blenny and two sand gobies) are experiencing feminisation in industrialised estuaries. In males this includes vitellogenin (VTG) synthesis, ovotestis induction and/or feminised sexual characteristics. Although reproductive success may be impaired in some cases, implications for fish populations are still unclear. Suspected causative contaminants include natural oestrogenic substances and synthetic oestrogen mimics. The majority of the oestrogenic activity is adsorbed to sediments, and routes of exposure may include benthic food chain transfer. Some natural androgenic substances are also being discharged to estuaries, but their activity appears low.     

近海平台管状构件修理工程设计

破坏结构的修理工程设计必须考虑到使该装置继续具有安全性。在设计修理工程之前,必须首先彻底搞清破坏构件在结构中的作用。修理工程设计必须确保在修理过程中结构的其它任何部分不会产生问题。文章着重阐明了保持最新结构模型的重要性。     

The influence of long emersion on biota, ammonium fluxes and nitrification in intertidal sediments of Marennes-Oléron Bay, France

A comparative study between waterlogged and reflooded intertidal sediments was undertaken in March and June 1999 through statistical analysis of selected sediment parameters (biota, salinity, O2, Eh), pool sizes and benthic fluxes of nutrients (NH4+, NO2-, NO3-) and nitrification rates. In March samples, absence of polychaetes and oligochaetes from upper sediment horizons were due to erosional events sweeping away surface sediments. Presence of richer annelid assemblages in June samples indicated more stable hydrodynamic conditions that favoured the development of benthic microalgae biofilms. Dewatering of sediments during a 3-day emersion period promoted a salinity rise on top layers, migration of pore water ions towards the sediment surface, and created sediment fissures that accelerated water exchange on reflooding. Reflooded and waterlogged sediment systems were comparable with respect to the release of NH4+ to overlying water but were different with respect to nitrification rates. Sediment-water NH4+ fluxes were higher (P = 0.011) in March (3.3 mmol m(-2) day(-1) compared to June (1.4 mmol m(-2) day(-1) due to higher macrofauna biomasses and lower benthic microalgae concentrations in March samples. Potential nitrification rates (range from 19 to 60 mmol NO3- (-2) day(-1)) were not statistically different between March and June. A thinner oxic layer in reflooded compared with waterlogged systems reflects a decrease of O2 diffusion into sediment at high salinities which resulted in the fall of the actual nitrification rates (P < 0.05). Our data suggest that long term dessication of intertidal sediments may depress the nitrification process at the ecosystem level.     

南极西部埃尔斯沃思山脉罗斯造山运动的地层学证据：冈瓦纳古太平洋边缘的演化

南极西部埃尔斯沃思山脉罗斯造山运动的地层学证据：冈瓦纳古太平洋边缘的演化Ｐ．Ｍ．Ｇｏｌｄｓｔｒａｎｄ等冈瓦纳重建过程中存在着一个长期的疑问，即埃尔斯沃思山脉的古生代地层的明显整合与横贯南极山脉的大地构造史相矛盾，这两座山脉在中生代冈瓦纳分裂之前通常认...