PHYTOPLANKTON PRODUCTIVITY AND BIOMASS IN THE CHARLOTTE HARBOR ESTUARINE SYSTEM,FLORIDA1

ABSTRACT: Phytoplankton carbon-14 productivity at a depth of 50 percent of surface light and chlorophyll-α concentrations were measured every other month from November 1985 through September 1986 at 12 stations in the Charlotte Harbor estuarine system. Maximum productivity and chlorophyll-α concentrations occurred during summer or early autumn near the mouths of tidal rivers. Most of the variability in light-normalized productivity and chlorophyll-α could be attributed to two factors derived from Principal Component Analysis of ambient water-quality characteristics. One factor related to seasonal variability and the other to spatial variability. The seasonal factor incorporated the interaction of temperature and nutrients. The spatial factor incorporated the interaction of salinity, nutrients, and water color that resulted from the mixing of freshwater inflow and seawater. Although freshwater inflow increased the availability of nutrients in low salinity (less than 10‰) waters, the highly colored freshwater restricted light penetration and phytoplankton productivity. Maximum productivity and biomass occurred where color associated with the freshwater inflow had been diluted by seawater so that light and nutrients were both available. Concentrations of inorganic nitrogen were often at or below detection limit throughout most of the high salinity (greater than 20‰) waters of the estuary and was probably the most critical nutrient in limiting phytoplankton productivity.     

进水与曝气方式对SBR中活性污泥产率和性能的影响

在实验室SBR几种运行方式研究的基础上，分析了不同进水与曝气方式对SBR中活性污泥产率和性能的影响原因。结果表明：（1）在反应阶段分级曝气方式下，SBR反应器的污泥产率明显低；而短时进水方式下，反应器的污泥性能最佳。（2）克服了SBR反应初期的高需氧率，能大大加速此后的生化反应。     

Specific resistance to filtration of biomass from membrane bioreactor reactor and activated sludge: effects of exocellular polymeric substances and dispersed microorganisms.

This study investigates the effect of dispersed microorganisms and exocellular polymeric substances on biomass dewaterability. Specific resistance to filtration (SRF) was measured for biomass from a membrane bioreactor and a completely mixed activated sludge system. Both laboratory-scale reactors were fed with synthetic wastewater and operated at a high food-to-microorganism ratio (F/M) (1 to 11 kilograms chemical oxygen demand per kilogram mixed liquor volatile suspended solids per day [kgCOD/(kg MLVSS.d)]) and short solids retention times (0.25 to 5 d). The SRF values were affected by strong interactions of three parameters: (1) the mixed liquor suspended solids concentration, (2) the amount of dispersed microorganisms, and (3) the exocellular polymeric substances (EPS) concentration. At F/M smaller than 2 kg COD/(kg MLSS.d) and mixed liquor suspended solids (MLSS) concentration higher than 2000 mg/L, increasing amount of dispersed microorganisms in the biomass yielded higher SRF values. However, at high F/M (> 5 kg COD/kg MLSS.d) and low MLSS concentrations (< 600 mg/L), lower EPS concentrations resulted in slightly smaller SRF values, even though the amount of dispersed microorganisms in the biomass was much higher. Thus, at low MLSS concentrations, EPS concentrations rather than the amount of dispersed microorganisms tend to control SRF.     

Effect of ambient oxygen concentration on activities of enzymatic antioxidant defences and aerobic metabolism in the hydrothermal vent worm, Paralvinella grasslei

The alvinellid Paralvinella grasslei is a common endemic polychaete from the deep-sea hydrothermal vent communities located on the East Pacific Rise (EPR). These organisms colonise a large range of microhabitats around active sites where physico-chemical conditions are thought to generate reactive oxygen species (ROS). Furthermore, in this aerobic organism, ROS could also be generated by the activity of the mitochondrial respiratory chain. In this paper, we investigated the effect of ambient oxygen concentration on the activities of three essential antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX) and their relationships with the activity of enzymes involved in aerobic metabolism (cytochrome c oxidase, COX; citrate synthase, CS). Results of incubation of P. grasslei in a high-pressure vessel with circulating seawater at different oxygen partial pressures indicate that this worm regulates COX and CS activities differently in gills and body wall. CAT and GPX activities increase in these tissues when animals are maintained in filtered surface seawater. Moreover, levels of malondialdehyde increase in gills, testifying that oxidative damage occurs under these conditions. CAT and GPX activities are positively related to COX and CS activities, but no correlation was detected between SOD and the metabolic enzyme activities. In comparison with littoral annelids, SOD activities are very high whereas CAT activities are very low or absent in P. grasslei. The possible reasons for the occurrence of such differences are discussed.     

Comparative toxicity of solid waste leachates to Daphnia magna

The comparative acute and chronic toxicities of municipal, industrial, coal-fired power plant, and synthetic fuel solid waste leachates to the aquatic invertebrate Daphnia magna were determined. Seventeen leachates were laboratory-derived by extraction with 0.5 N acetic acid, and one, an arsenic-contaminated groundwater, was naturally derived. The acute toxicity 48-h LC₅₀ estimates (concentrations of the test materials that killed 50% of the test organisms in 48 h) ranged from 0.0005% for a dye waste leachate to > 100% (i.e., undiluted) for a coal gasification waste leachate. The most toxic leachates were derived from a dye waste, a plater's waste, and the arsenic-contaminated groundwater, and the least toxic were from a soybean process cake waste and a coal gasification waste. Of the 16 leachates used in the 28 day chronic toxicity tests, only the arsenic-contaminated groundwater and a municipal sewage sludge significantly affected D. magna reproduction. The former material at 1.0% concentration and the sludge at 0.1% caused about an 88% reduction in the numbers of young produced by exposed females compared with controls. Generally, the industrial waste leachates were more toxic than those from the power plant and synthetic fuel wastes. Because its presence in the test materials interfered with interpretation of the results, acetic acid may not be an appropriate extraction medium for preparation of leachates.     

Assessment of seasonal variability of biomarkers in three-spined stickleback (Gasterosteus aculeatus L.) from a low contaminated stream: implication for environmental biomonitoring

In this study, wild three-spined sticklebacks were sampled every six weeks, between April and October, in a low contaminated stream. For all fish, physiological indexes, such as condition factor, hepato-, gonado- and nephro-somatic index were calculated to determine fish condition and reproductive status. Moreover, a set of biomarkers including biotransformation enzymes, oxidative stress parameters, neurotoxicity and endocrine disruption markers was measured. The results allowed to determine biomarker variability due to fish gender or sampling season. For example, 7-ethoxyresorufin-O-deethylase activity, glutathione peroxidase as well as vitellogenin and spiggin exhibited strong gender differences. Conversely, lipoperoxidation and acethylcholinesterase activity were characterised by a lack of gender and seasonal variation, and can be considered as more robust parameters for a field application. The present work allowed to establish practical guideline for biomarker measurements in wild sticklebacks and to define a reference system which can be used to analyze variations in future monitoring studies.     

Strategic environmental assessment in Hong Kong

This review examines the development and application of strategic environmental assessment (SEA) process in the planning framework of Hong Kong. Two strategic planning case studies are evaluated within the context of SEA, namely the Territorial Development Strategy Review (TDS Review) and the Third Comprehensive Transport Study (CTS-3). Rapid population growth and urbanisation in Hong Kong, coupled with a historic lack of planning controls and inherent conflicts between government departments have been major obstacles to achieving sustainable development in the territory. Despite these challenges, Hong Kong was one of the first Asian countries to apply SEA to major development plans, where the implementation of the 'SUSDEV 21' study on sustainable development has demonstrated the government's commitment towards integrated environmental protection. The application of SEA has provided decision-makers with key information on potential environment impacts arising from proposed developments, resulting in greater accountability and transparency in the decision-making process. SEA in Hong Kong has also prompted an increased level of environmental awareness and co-operation between government departments and agencies responsible for the management of Hong Kong's natural and urban environments. However, the application of SEA in Hong Kong continues to have notable limitations. SEA needs to evolve beyond its current sectoral application to examine ways in which development decisions can not only pre-empt and prevent environmental damage, but also positively enhance and restore existing natural resources. Current land use plans and transportation strategies still largely determine the pattern of development in the near future without adequate longer-term environmental cost-benefit analysis. Sustainable development includes environmental, social and economic considerations, and these inter-related elements need be suitably balanced. SEA is not a means to obstruct development in Hong Kong, but should be recognised for its inherent socio-economic and ecological value, and fully integrated with the decision-making process. Whilst it is admirable that Hong Kong has taken positive steps in this direction, it is now an opportune moment for the government to have the foresight and tenacity to create a sustainable development framework for Hong Kong into the future.     

Gastral drumming: a nest-based food-recruitment signal in a social wasp

Many social insect species produce signals that either recruit foragers to a specific food source or simply activate more nestmates to become foragers. Both are means of enhancing resource exploitation by increasing the number of individuals devoted to gathering profitable resources. Gastral drumming (GD) has been documented in several species of yellowjackets and hornets (Vespidae: Vespinae). It has been hypothesized that it is a hunger signal, but there is little empirical evidence to support this claim. An alternative hypothesis is that GD recruits workers to forage for food. Here, we report the results of a test between the hunger-signal and food-recruitment hypotheses in the German yellowjacket wasp, Vespula germanica. We show that the rate of performance of GD decreased when colonies were deprived of food and increased when supplemental food was provided. Playback of GD caused increased rates of (1) movement in the nest, (2) trophallaxis, and (3) worker departures from the nest. Together, these results support the conclusion that GD is not a hunger signal as previously asserted but instead is a nest-based food-recruitment signal, the first to be reported for a social wasp.