微宇宙理论及其在生态毒理学研究中的应用

简述微宇宙理论,发展史和主要类型,并着重综述了微宇宙在生态毒理学研究中的主要应用情况,以及与实验室单物种试验和野外试验比较微宇宙的优缺点,并对微宇宙的未来发展趋势也作了简要讨论。     

A research strategy for using stream microcosms in ecotoxicology: Integrating experiments at different levels of biological organization with field data

Environmental pollutants and other stressors can haveeffects at many different levels of biologicalorganization and a key step in the design ofecotoxicological studies is the formulation ofhypotheses that explicitly state the level(s) ofbiological organization that the study is meant toaddress. For example, single species studies at theindividual organism level can provide key informationon individual growth rates and physiologicalresponses, while multispecies studies at the communitylevel allow food web investigations to be undertakenand potentially allow indirect effects of toxicants tobe identified. The integration and understanding ofprocesses operating over several different levels ofbiological organization can often be greatlyfacilitated by the incorporation of microcosmexperiments conducted at the appropriate scale. Suchexperiments provide replication as well as greatercontrol over relevant variables which allows morerigorous hypothesis testing and important insight intomechanisms of biotic responses to pollutants. Wesuggest an appropriate use for stream microcosms inecotoxicology is in integrated assessment strategieswhere experimental results are linked with fieldmonitoring data. Under an integrated assessmentscenario, concordance of results between fieldobservations and dose-response exposures in microcosmscan provide important weight-of-evidence for guidancein management action or monitoring programs. We alsoidentify a number of other issues that must be addressedwhen utilizing stream microcosms; these includedecisions on exposure type, relative test duration,experimental design, biota source and type oftaxonomic assemblage, environmental realism, andchoice of end points. This kind of integratedassessment strategy has been applied to the Athabasca,Fraser, and Thompson Rivers in western Canada, wheremeasurement of similar end points in microcosms andfield sites has produced concordance of results and animproved understanding of causality instressor/response relationships.     

Multiple-end-point bioassays using microorganisms

Since the 1950s, the numbers of species and chemicals produced have significantly increased. Despite the fact that industrial chemicals have given us numerous benefits, there is no doubt that they have damaged the environment. The chemicals being dispersed on the earth should be carefully controlled to prevent adverse effects. Bioassay is one of the methods to assess chemical safety. In bioassay systems, chemical safety is estimated by monitoring biological responses to environmental pollutants and newly synthesized chemicals. This report introduces multiple-end-point bioassay systems that are based on chemical sensitivities of microorganisms, responses of one kind of organism, and micro-array technology. Multiple-end-point bioassays enable the prediction of chemicals in the environment and the understanding of toxicities of newly synthesized chemicals.     

Toxicity analysis of freshwater and marine sediments with meio- and macrobenthic organisms: a review

Benthic metazoans play a key role as test organisms in toxicity analyses of aquatic ecosystems. This report gives an overview of the species of benthic metazoans used for the assessment of toxicity in freshwater and marine sediments, as well as of the criteria relevant to the choice between test species and procedures. The main applications of these organisms are mono-species bioassays, test-batteries, analyses of benthic communities and bioaccumulation studies. Sediment toxicity assays, including acute and chronic exposures, have been developed for nematodes, insects, oligochaetes, polychaetes, crustaceans, molluscs and echinoderms. At least 30 species of freshwater and 71 species of marine and estuarine benthic metazoans have thus far been used in sediment toxicity bioassays. Although aquatic pollution is a world-wide problem, most sediment toxicity bioassays have been developed for organisms native to Europe and North America. The most common bioassay endpoints are mortality, development, growth and behavioural responses. The value of genetic, biochemical, physiological and pathological responses as toxicity endpoints is currently being investigated. The quest for additional test species and protocols is still a worthwhile endeavour in sediment ecotoxicology.     

Assessing the impact of transgenic plant products on soil organisms

Little is known about the impact of transgenic plant products on soil organisms. However, previous research with synthetic organics, allelochemicals, and extracellular enzymes can be used to guide future research in this area. Projects designed to quantify the impact of transgenic plants on soil organisms must clearly establish that the gene products are responsible for any observed changes. This can only be achieved by determining the fate of transgenic plant gene products during the period of the soil bioassay. The overall impact of transgenic plants will be dictated by not only the primary gene product, but secondary products resulting from abiotic and biotic soil reactions. Primary and secondary products may exhibit both acute and chronic impacts. Such impacts are best quantified using a soil microcosm in which fungal populations and micro- and mesofauna are monitored.     

A sediment suspension system for bioassays with small aquatic organisms

Exposure of aquatic organisms to suspended sediments can impair growth and survival and increase bioaccumulation of sediment-associated contaminants. However, evaluation of the effects of suspended sediments and their associated contaminants on aquatic organisms has been hampered by the lack of a practical and inexpensive exposure system for conducting bioassays. We present a cost-effective system for assessing the effects of suspended sediments and associated contaminants on small aquatic organisms. A 7-day suspension test was conducted with nominal sediment concentrations ranging from 0.0 to 5.0 g 1^–1. The system maintained relatively constant suspended sediment concentrations, as measured by turbidity, and caused minimal mortality to test organisms.     

Functional bioassays utilizing zooplankton: a comparison

Functional zooplankton bioassays based on ingestion, reproduction and respiration are described, with methods for a new ingestion bioassay included. All bioassays are compared using three indices, including the variability of controls, the range of experimental responses, and a listing of contaminants causing inhibition/stimulation of response. The ingestion bioassay showed the greatest range of response, and was sensitive to pesticides, PCBs and heavy metals. It was also commonly characterized by a hormesis response. The reproduction bioassay showed the lowest variability, illustrated a reduced range of response, and was sensitive to nutrients and heavy metals. In one study, the respiration bioassay was sensitive only to PCBs.     

Evaluation of bioassays to quantifyCylindrocaldium inocula in soil

Leaf discs provided better recovery ofCylindrocladium candelabrum from soil than stem, or twig segments. Leaf discs of eucalypt (Eucalyptus grandis), azalea (Rhododendron sp.), and geranium (Pelargonium sp.) were the best of seven plant baits evaluated. Twig segments of azalea and eucalypt also provided a high percentage of the pathogen recovery, whereas stem segments of pine seedlings (Pinus elliottii) proved unsatisfactory. Although slightly less effective, twig segments were easier to handle than leaf discs which were quickly decomposed in soil. Colonization of eucalypt twig segments byCylindrocladium spp. varied with inoculum level, soil moisture content, and incubation period. The highest percentage of recovery ofC. candelabrum (approx. 95%) was calculated at a field capacity moisture level of 155.9% after 75h of incubation.     

Analysis of coastal lagoon metabolism as a basis for management

This work was carried out in a shallow eutrophic coastal lagoon (St. André lagoon, SW Portugal) which is artificially opened to the sea each year in early spring. Macrophytes, mainly Ruppia cirrhosa, are keystone species in this ecosystem covering up to 60% of its total area with peak biomasses over 500 g DW m^–2. The main objectives were to study ecosystem metabolism, to evaluate the metabolic contribution to the community of the macrophyte stands and their influence in the development of thermal stratification and bottom oxygen depletion.The work combined an experimental and a modelling methodology. The experimental approach included open water, mesocosm and microcosm seasonal experiments. During these experiments several physical, chemical and biological parameters were monitored in the lagoon and in plastic enclosures (mesocosms) for periods of 24 hours. The microcosm experiments followed the light-dark bottle technique. The simultaneous use of these different methodologies allowed the analysis of the contribution of the planktonic and benthic compartments to the ecosystem's oxygen budget.The modelling work was based on the mathematical simulation of heat and gas exchanges in a vertically resolved water column, under different macrophyte densities. Several simulations were carried out, in order to investigate the importance of the macrophytes in the development of water column stratification and anoxia.The simulation results suggest that macrophytes may greatly influence thermocline and oxycline development. This influence is proportional to their biomass and canopy height. It is suggested that controlled macrophyte biomass removal of up to 25% of available biomass in summer, may be useful in preventing bottom anoxia without compromising benthic net primary production.     

Hypothesis formulation and testing in aquatic bioassays: a deterministic model approach

The paper examines the significance of toxicant kinetics information obtained from aquatic toxicity bioassays and bioconcentration tests. The data, bioconcentration kinetics and acute mortality versus exposure-duration information for juvenile American flagfish (Jordanella foridae) exposed to 1,4-dichlorobenzene, are interpreted in terms of a one-compartment, first-order kinetics model. The output of the model is used to formulate a testable hypothesis regarding the comparison of toxicant kinetics derived from both bioconcentration test exposures and toxicity bioassays. The model's estimates of the toxicant body burden attained at mortality are compared with theoretical and observed body burdens from literature sources. The use of a simple, deterministic residue-based, one-compartment, first-order kinetics model to evaluate existing data, as well as to formulate hypotheses to direct experimental designs, is examined.     

Experimental effects of elevated salinity on three benthic invertebrates in Pyramid Lake,Nevada

Salinity of Pyramid Lake increased from 3.7 to 5.5 between 1933 and 1980. Concern over future reductions in overall species richness prompted experiments to assess responses of dominant lake organisms to elevated salinity. Salinity tolerances of three important benthic invertebrates, Hyalella aztecta, Chironomus utahensis, and Heterocypris sp., were tested in controlled laboratory bioassays and also in a semi-natural environment consisting of large (47 m³) mesocosms.Densities of H. azteca in mesocosms were significantly lower at salinities of 8.0 and 11.0 compared with 5.6 controls in year one, but not in 8.5 salinity mesocosms in year two. The 96-h LC₅₀ for H. azteca was high at 19.5. Short-term mortalities of C. utahensis were 100% at salinities of 13.3 and greater. Fifty-seven percent fewer larvae matured from third to fourth instar at 8.9 than at 5.5 salinity in 17 day subacute bioassays. Furthermore, larval chironomid densities and emergence of adults from mesocosms were significantly reduced at salinities of 8.0 and higher compared with controls. Mortality of Heterocypris sp. was 50% at a salinity of 18.6 in laboratory bioassays and populations in mesocosms ranged between 40 and 100% lower at salinities of 8.0 and 11.0 than in controls.Multiple generation mesocosm experiments indicated all three invertebrates were more sensitive to elevated salinity than results of short-term bioassays. Our studies suggest populations of these invertebrates may be reduced from present levels if Pyramid Lake's salinity were to double, although none are expected to be extirpated. Food habit shifts and reduced production of lake fishes are likely consequences of salinity-induced disruption in the benthic invertebrate forage base.     

Effect of temperature on the photoproperties of luminescent terbium sensors for homogeneous bioassays

We developed a luminescent terbium sensor (LTS) based on energy resonance transfer for homogeneous bioassays. The effect of temperature on photoluminescence and time‐resolved fluorescence of the LTS was investigated. When the temperature was increased from 277 K to 369 K, the photoluminescence quantum yield decreased by up to 25 %, time‐resolved fluorescence decreased by up to 54 %, and the lifetime shortened dramatically. Studies showed that both photoluminescence and time‐resolved fluorescence quantum yields were largely recovered after samples were heated from 298 to 310, 333 or 369 K and subsequently cooled to 298 K. These results indicate that the homogeneous bioassay with LTS is sensitive to temperature and should be conducted at a constant temperature to ensure the temperature effect does not influence data and to increase the accuracy of the results. The results of this study are important for LTS applications in homogeneous bioassays. Copyright © 2012 John Wiley & Sons, Ltd.     

DNA bioassays based on the fluorescence ‘turn off’ of silver nanocluster beacon

Recognition and quantification of oligonucleotide sequences play important roles in medical diagnosis. In this study, a new fluorescent oligonucleotide‐stabilized silver nanocluster beacon (NCB) probe was designed for sensitive detection of oligonucleotide sequence targets. This probe contained two tailored DNA strands. One strand was a signal probe strand containing a cytosine‐rich strand template for fluorescent silver nanocluster (Ag NC) synthesis and a detection sections at each end. The other strand was a fluorescence enhancing strand containing a guanine‐rich section for signal enhancement at one end and a linker section complementary to one end of the signal probe strand. After synthesis of the Ag NCs and hybridization of the two strands, the fluorescence intensity of the as‐prepared silver NCB was enhanced 200‐fold compared with the Ag NCs. Two NCBs were designed to detect two disease‐related oligonucleotide sequences, and results indicated that the two target oligonucleotide sequences in the range 50.0–600.0 and 50.0–200.0 nM could be linearly detected with detection limits of 20 and 25 nM, respectively. The developed fluorescence method using NCBs for oligonucleotide sequence detection was sensitive, facile and had potential for use in bioanalysis and diagnosis.     

Effects of natural sediment properties on test results in bioassays with oyster larvae (Crassostrea gigas) on sediment elutriates

Toxicity tests with oyster larvae are becoming increasingly important as sensitive bioassays for assessing water and sediment quality. In 1983 a procedure was presented specifically for the testing of seawater elutriates of sediment samples. Testing sediment elutriates with oyster larvae in a sediment-water system invokes specific problems related to natural sediment characteristics. Experiments were set up to study the effects of these sediment properties on the bioassay results. The effects of sediment grain size, suspended solids, elutriation period, as well as the possible effects of naturally occurring toxic nutrients, like ammonia, were studied. Also the effect of presence or absence of the elutriated sediment and the distribution of larvae in the test vessels were studied.It is concluded that natural sediment properties can have substantial effects on the test results in elutriate tests with sediment present in the test vessel. Recommendations are formulated to minimize these effects or to use other test fractions for predicting bulk sediment toxicity.     

Applications of likelihood asymptotics for nonlinear regression in herbicide bioassays

Dose-response models are intensively used in herbicide bioassays. Despite recent advancements in the development of new herbicides, statistical analyses are commonly based on asymptotic approximations that are sometimes poor. This paper presents the use of recent results in higher order asymptotics for likelihood-based inference in nonlinear regression. The methods presented provide accurate approximation for the distribution of test statistics and for prediction limits. Analyses of the fit and measures of detection limits of the bioassays are considered, and the potential of the methods is illustrated by examples with real data.