Trophic structure and production in the macrobenthos of a temperate Australian estuary

The soft-bottom fauna of Gunnamatta Bay, Port Hacking, N.S.W., was sampled to estimate the abundance, trophic structure and net production of the macrobenthos. The samples were classified into groups from spatially distinct strata, the groups differing in species abundance and diversity and in the identity of the dominant species. The composition and community structure of the fauna was generally similar to that in other sheltered embayments on the southeastern coast of Australia. Estimated production values were low for an estuary, ranging from 10 kJ m^?2 year^?1 in an intertidal stratum of well sorted sand to 210–450 kJ m^?2 year^?1 in shallow subtidal strata with an admixture of silt. Estimated net production over all strata was 160 kJ m^?2 year^?1. Polychaetes dominated production, providing 45% of the total; crustaceans provided 20%, and molluscs and echinoderms 12% each. Detritus-feeders were dominant in most strata: the bivalve Theora fragilis, the polychaetes Australonereis ehlersi and Notomastus torquatus, and the urchin Echinocardium cordatum were major contributors to overall biomass and to net production. Substantial biomass and net production was also contributed by the suspension-feeding bivalve Corbula vicaria and a carnivorous crab Ceratoplax cf. glaberrimus. Overall, detritus-feeders contributed 61% of estimated net production, carnivores 32% and suspension-feeders 7%. Production estimated for carnivores was higher than could be supported by the non-carnivore populations, suggesting that some of the species considered to be carnivores have additional feeding modes. Excessive harvesting of bivalves by humans is suggested as the main reason for the low biomass of, and therefore low production by, suspension feeders.     

Radon-222 in medicinal groundwaters of Szczawno Zdrój (Sudety Mountains, SW Poland)

 Radon is a significant component of the groundwaters that discharge in the springs of Szczawno Zdrój and are recognized as medicinal. However, among the five exploited springs adjoining each other, it is only in Marta Spring that radon occurs in large concentrations (up to 325.6 Bq/dm³). Therefore, the authors have made an attempt to describe and clarify this fact. They found out from their own research and archival data that ²²²Rn dissolves in the waters of Marta Spring after acidulous waters of deep circulation have mixed with poorly mineralized shallow waters in their outflow zone. The genesis of the gas is determined by the content of its parent nuclide, ²²⁶Ra, in the sandstones in the vicinity of the intake. The volume of the rocks providing radon to the waters of this intake has been estimated at several hundred cubic metres. No seasonal fluctuations in radon concentration have been observed and ²²²Rn concentration changes do not seem to be influenced by changes in the concentration of other chemical components of the waters or by the discharge of the intake. The process of dissolving ²²²Rn in the medicinal groundwaters of Marta Spring is the last, the shortest, and the most local of the processes that form the chemical composition and the physical properties of these waters. Received: 7 January 2000 · Accepted: 12 August 2000     

Sensitivity of estuarine phytoplankton to hexavalent chromium

Experiments were conducted in which we tested the effects of hexavalent chromium on both natural assemblages of phytoplankton and cultures of Thalassiosira pseudonana clone 3H. Water was collected from various locations in Yaquina Bay, Oregon, with salinities ranging from 32·5‰ to 0·03‰. A variety of nutrient regimes were tested by adding major nutrients and micro-nutrients, and/or stripping micro-nutrients with activated carbon. In one high salinity experiment, chromium was stimulatory, as were micro-nutrient additions. In other high and medium salinity experiments, chromium was neither stimulatory nor inhibitory, at levels up to 1·9 μ mole l^?1 Cr. There was, however, slight inhibition of growth at 19·0 μ mole l^?1 Cr, due specifically to inhibition of Skeletonema costatum. In our freshwater experiments, chromium was very inhibitory at 1·9 μ mole l^?1 Cr, and slightly inhibitory at 0·19 μ mole l^?1 Cr. Species inhibited by chromium were Surirella ovata, Detonula confervacea, and Cyclotella sp. Experiments were conducted with T. pseudonana grown over a wide range of salinities. Chromium was found to be very inhibitory in freshwater and became progressively less toxic as the salinity increased. Most inhibition was neutralized by a salinity of 2·1‰.     

Bar and dune development during a freshet: Fraser River Estuary, British Columbia, Canada

Bi-weekly multi-track sonar surveys collected along a 2-km reach of the estuarine South Arm of the Fraser River, British Columbia, Canada, during seasonal high flows document the initiation, development and interaction of dune and bar morphologies. Bedforms of several scales developed in well-delineated fields. Bedforms that appear to fit accepted equilibrium depth-scaling developed in the main channel during rising discharge when there was little local aggradation. During the rising stage, a bar also formed along the tidal shelf of the channel, migrated downstream and expanded into the main channel. Dunes that formed along the bar crest, a region of rapid deposition, lagged flow conditions and were larger than expected based on depth-scaling relations. The larger dunes developed simultaneously, although bar growth lagged dune development and was initially partially obscured by the more rapidly developing dune field. It appears that rapid deposition enhances dune development along the channel tidal shelf to dimensions larger than would be expected by simple depth-scaling rules. Smaller dunes that fit equilibrium depth-scaling relations re-established themselves throughout the study area during falling discharge when there was again little or no aggradation. Bed-material transport rates estimated from the migration rates of the large dunes suggest that, at high flows, the dunes transport the majority of the material found within the bar.     

柴达木盆地西部第三系油田卤水资源可利用性分析

通过对柴达木盆地油气钻孔资料的整理分析发现,对第三系地层中进行油气勘探时,经常伴有自井中喷出矿化度较高的卤水———油田水。通过对柴达木盆地构造演化分析,早期残留的古湖水经干旱蒸发条件,发生浓缩,将导致有用物质组分的富集;在此基础上,2002年对柴达木盆地西部第三系地层分布区的油井新取了水样,证实该卤水中含有较高的钾硼锂碘组分。通过盐田蒸发试验,可以得到质量较好的钾石盐、硼钾混盐、含锂碘的母液。     

Identification of Anomalous Aluminium Contents in Surface and Ground Water in the Alba Territory (NW Italy)

Aluminium was determined in surface and ground waters in the Alba region of NW Italy to provide information on natural and anthropogenic sources of contamination. Determinations were made by a spectrophotometric method based on the aluminium-pyrocatechol complex. The total aluminium content of waters was determined as well as the toxic form of monomeric aluminium, obtained from samples that had been passed through 0.20 μm cellulose filters to remove colloidal and particulate material. Results were correlated with mortality data associated with Alzheimer's disease. There appeared to be a correlation between mortality data and areas having the highest aluminium content of water.     

Instrumental Neutron Activation Analysis of Estuarine Sediment as a Proposed Reference Material for Environmental Studies

The International Atomic Energy Agency (IAEA) Marine Environmental Studies Laboratory (MEL) organised an intercomparison exercise, through its Analytical Quality Control Services (AQCS), for the determination of trace elements in estuarine sediment IAEA-405, well suited for the characterisation of sediments. The instrumental neutron activation analysis technique (INAA) was developed using a 27 kW low power research reactor. Forty elements in the sediment were determined with a measurement precision varying from 1.8% to 12.3%. IAEA reference materials SL-1 and SD-M-2/TM were analysed throughout this work as quality assurance samples.     

二类水体水色遥感的主要进展与发展前景

Ⅱ类水体水色遥感是海洋水色遥感的难点和热点。针对Ⅱ类水体的光谱特性和海洋现象的特点，综述了水色卫星传感器在光谱波段配置、辐射探测性能和时空分辨率等方面的设计要求与技术进步。从水色遥感资料反演的两大关键技术——大气校正和生物光学算法两个方面，概述了Ⅱ类水体水色反演算法的研究现状和发展方向。根据我国近海的水体特点，提出了我国水色遥感研究需要解决的关键问题。