DNA damage as a bivalve biomarker

Bivalves have been used in numerous environmental assessment studies, chiefly because they are sessile deposit or suspension feeding organisms found in or near sites of environmental concern, and they can be easily collected, sorted and deployed at sites of interest. Monitoring studies utilizing bivalves currently rely on the comparison of growth, survival, and contaminant bioaccumulation. Data gathered from 'reference' sites are compared with those of populations at assessment sites. These studies require extended periods of exposure, lasting weeks to months, and the use of a well defined population of test organisms of similar size, age, and condition. In many cases time and resources require researchers to restrict their sampling to the organisms on-hand at a particular site without the benefit of any reference data. Therefore more versatile and sensitive assessment methods are needed. Because effects at higher levels of organization such as growth, development, and survival are initiated at the molecular and cellular levels attempts have been made to identify useful biomarkers at these levels. The proposed advantages of molecular/cellular biomarkers are that they will respond to stress predictably and more rapidly, and will be indicative of the mechanisms of toxicity thereby yielding a rudimentary characterization of the contaminant(s) influencing them. In the following communication we will report on past and current developments in the monitoring of DNAdamage as an environmental biomarker.     

Effects of contaminants on genetic patterns in aquatic organisms: a review.

There is increasing awareness of the need to evaluate the effects of contaminants at the population level. Genetic techniques offer a powerful approach to assess contaminant-induced changes in populations. Yet studies to date are relatively few and not always carefully designed to maximize the utility inherent in this approach. We present a summary of contemporary genetic assessment methods and a review of published studies of genetic effects in field-exposed aquatic organisms. We discuss evaluations of genetic patterns that use genetic adaptation, allozyme variation, and molecular genetic (DNA) variation. Direct tests of genetic adaptation are very effective in establishing a concrete, and potentially deleterious population-level effect of contaminant exposure, but they are difficult to accomplish with most field-exposed organisms. Allozyme surveys are relatively simple and common, and may provide data that are suggestive of contaminant effects. However, these are rarely conclusive, primarily because few allozyme loci are variable and these few loci represent extremely small portions of the genome. Molecular genetic techniques have the potential to be very effective. But, there is a tendency to emphasize the power of the techniques, rather than the underlying causes of the molecular genetic patterns observed. The strength of the conclusions of each study varies widely, partially derived from variation in the strength of the techniques. We caution that all these approaches are greatly improved by careful experimental design that includes adequate numbers of reference and contaminated sites and sample size. In addition, careful exposure assessment is required, including site and tissue chemistry, biomarker responses, and measures of potentially deleterious effects, such as DNA damage, or reduced reproductive output or survival.     

Ancestry-Tracking of Stress Response GPCR Clades: A Conceptual Path to Treating Depression

The environmental complexity in which living organisms found themselves throughout evolution, most likely resulted in various encounters that would continuously challenge the organisms' ability to survive. Coping with this stress can prove energetically demanding and might require the proper coupling between mechanisms aimed at sensing external stimuli and cellular strategies geared at producing energy. In this issue of BioEssays, Lovejoy and Hogg hypothesize that preservation of this bifaceted coupling can be detected by the maintenance and evolution of stress response mechanisms at the genomic, molecular and cellular levels. Through ancestry-tracking, they identify a group of related G protein-coupled receptor systems with intersecting stress-modulating properties which might represent an essential part of a complex organism's coping mechanisms to stress, an attribute that they suspect may be affected in individuals suffering from mood disorders such as depression.     

The use of biomarkers in biomonitoring: a 2-tier approach assessing the level of pollutant-induced stress syndrome in sentinel organisms

The paper outlines a 2-tier approach for wide-scale biomonitoring programmes. To obtain a high level of standardization, we suggest the use of caged organisms (mussels or fish). An "early warning", highly sensitive, low-cost biomarker is employed in tier 1 (i.e. lysosomal membrane stability (LMS) and survival rate, a marker for highly polluted sites). Tier 2 is used only for animals sampled at sites in which LMS changes are evident and there is no mortality, with a complete battery of biomarkers assessing the levels of pollutant-induced stress syndrome. Possible approaches for integrating biomarker data in a synthetic index are discussed, along with our proposal to use a recently developed Expert System. The latter system allows a correct selection of biomarkers at different levels of biological organisation (molecular/cellular/tissue/organism) taking into account trends in pollutant-induced biomarker changes (increasing, decreasing, bell-shape). A selection of biomarkers of stress, genotoxicity and exposure usually employed in biomonitoring programmes is presented, together with a brief overview of new biomolecular approaches.     

Changes in antioxidant defense system in gills of Capoeta umbla caught from Uzuncayir Dam Lake,Turkey

The aim of this work was to determine the seasonal changes in the activities of selected biomarkers in Capoeta umbla (Heckel, 1843) caught from Uzuncayir Dam Lake (Tunceli, Turkey) and to evaluate the effects of environmental factors on these activities. Fish were sampled on seasonal basis, and superoxide dismutase, catalase, glutathione peroxidase activities and levels of glutathione and malondialdehyde in gills were determined. Significant variations of oxidative stress biomarkers were observed between seasons and sites. The results of this study show that seasonal variations of oxidative stress responses and lipid peroxidation in gills of C. umbla are sensitive to the contaminants present in water of Uzuncayir Dam Lake and selected parameters are in valuable biomarkers for monitoring of water systems, since they give an early warning signal of effects of xenobiotics on aquatic organisms at molecular levels which help to prevent their effects at organismal level.     

环境污染物对水生生物产生氧化压力的分子生物标志物

为了能够建立一种简单、快速、准确的环境污染监测预警体系,人们进行了广泛的研究,其中有关环境污染物对分子生物标志物的影响已成为研究热点。生物体内的氧自由基和其它活性氧分子（ROS）对组织和细胞成分造成的伤害,称之为氧化压力,环境中的有毒物质能够对生物体产生不同程度的氧化压力。生物体内的强氧化剂或体外因素（如环境污染物）引起的强氧化物与抗氧化防御系统之间的平衡能够用于评估环境压力对生物体产生影响的程度,尤其适合于评估不同种化学物质引起氧化损伤的程度。这些抗氧化防御系统及其对氧化压力的敏感性在环境毒物学研究中占有非常重要的地位,大量研究结果表明：过渡金属、多环芳烃、有机氯和有机磷农药、多氯联苯、二氧芑和其它异型物质都能够对生物体产生氧化压力。这些有毒物质能够引起各种有害影响,如对膜脂、DNA和蛋白产生损伤;改变抗氧化酶的活性等。总结了这种氧化压力的研究进展情况,并讨论了这些分子生物标志物在水生生物中的应用。     

Historical Case Analysis of Uranium Plume Attenuation

Groundwater plumes containing dissolved uranium at levels above natural background exist adjacent to uranium ore bodies, at uranium mines, milling locations, and at a number of explosive test facilities. Public health concerns require that some assessment of the potential for further plume movement in the future be made. Reaction-transport models, which might conceivably be used to predict plume movement, require extensive data inputs that are often uncertain. Many of the site-specific inputs are physical parameters that can vary spatially and with time. Limitations in data availability and accuracy means that reaction-transport predictions can rarely provide more than order-of-magnitude bounding estimates of contaminant movement in the subsurface. A more direct means for establishing the limits of contaminant transport is to examine actual plumes to determine if, collectively, they spread and attenuate in a reasonably consistent and characteristic fashion. Here a number of U plumes from ore bodies and contaminated sites were critically examined to identify characteristics of U plume movement. The magnitude of the original contaminant source, the geologic setting, and the hydrologic regime were rarely similar from site to site. Plumes also spanned a vast range of ages, and no complete set of time-series plume analyses based on the spatial extent of U contamination exist for a particular site. Despite the accumulated uncertainties and variabilities, the plume data set gave a clear and reasonably consistent picture of U plume behavior. Specifically, uranium plumes: ??Appear to reach steady-state, that is, they quit spreading, rapidly (within a few years). ??Exceed roughly 2 km in length only in special cases (e.g., where in situ leaching has been carried out). The majority are much smaller. ??Exhibit very similar U chemistry between sites. This implies analogous contaminant attenuation mechanisms despite their location.     

Transcriptomics and proteomics. Applications to ecotoxicology

Researchers from Europe and the USA met at the Joint Research Center (JRC) of the European Commission to discuss how to integrate gene and protein expression analyses with bioinformatic tools in the field of ecotoxicology and how this new approach could be translated in improved risk assessment procedures. The measurements of gene and/or protein expression levels, upon exposure to a chemical or a stressor, can be used to develop robust molecular biomarkers that will allow the early detection of environmental stress, study long-term exposure and infer the mechanism of action. These molecular biomarkers should be linked to phenotypic end points of exposure such as adverse effects in growth and reproduction in single organisms and populations. At environmentally realistic exposure levels there could be “non-linear” dose-response curves, which should be accounted for in the experimental design and in the analyses of microarray and proteomic data. The application of gene and protein expression profiling in ecotoxicology will have a significant impact on the ecotoxicology field in the near future and international collaborations will play an important role in accelerating the application of those techniques.     

生物标志物（Biomarkers）在海洋环境监测中的研究与进展

污染物的存在给海洋环境和生态健康带来了巨大的压力,如何监测这些污染物并对其毒性进行科学的评价,成为当今环境科学关心的热点问题。生物标志物（Biomarkers）是毒理学研究的重要工具,它能对污染事件进行早期预警,并能在一定程度上评估生态风险。对近十多年来生物标志物的研究与应用进行了回顾,总结了不同水平（分子、细胞、个体、系统）生物标志物的种类、特征、检测方法和应用特点,并对现存挑战和未来发展趋向进行了展望,旨在系统的认识生物标志物,并为其在海洋环境监测中的合理应用提供理论借鉴。     

Biomarkers of Dissolved Oxygen Stress in Oysters: A Tool for Restoration and Management Efforts

The frequency and intensity of anoxic and hypoxic events are increasing worldwide, creating stress on the organisms that inhabit affected waters. To understand the effects of low dissolved oxygen stress on oysters, hatchery-reared oysters were placed in cages and deployed along with continuously recording environmental data sondes at a reef site in Mobile Bay, AL that typically experiences low oxygen conditions. To detect and measure sublethal stress, we measured growth and survival of oysters as well as expression of three biomarkers, heat shock protein 70 (HSP70), hypoxia inducible factor (HIF) and phospho-p38 MAP kinase, in tissues from juvenile and adult oysters. Survival rates were high for both juvenile and adult oysters. Expression levels of each of the 3 isoforms of HSP 70 were negatively correlated to dissolved oxygen (DO) concentrations, suggesting that HSP 70 is useful to quantify sublethal effects of DO stress. Results for HIF and phospho-p38 MAP kinase were inconclusive. Test deployments of oysters to assess expression of HSP 70 relative to environmental conditions will be useful, in addition to measuring abiotic factors, to identify appropriate sites for restoration, particularly to capture negative effects of habitat quality on biota before lethal impacts are incurred.     

Changes with growth rate in the membrane lipid composition of and amino acid utilization by continuous cultures of Campylobacter jejuni

Methods and media (defined and complex) are described which permit studies designed to determine the influence of single environmental factors on the survival and virulence of Campylobacter jejuni. The effect of growth rate on selected physiological traits (amino acid utilization, membrane lipid composition, motility, cell morphology) was studied in continuous culture. In both media, growth was at the expense of amino acid (serine, aspartate, glutamate and proline) catabolism. Slow growth in the complex medium shifted amino acid utilization from more (serine and aspartate) to less preferred substrates (glutamate, proline and possibly amino acids from the proteolysis of peptones). Low growth rates promoted the conversion of unsaturated 11-octadecenoic acid substituted phosphatidyl ethanolamines to corresponding 11-methylene substituted species, a feature correlated with stationary phase and exposure to environmental stress in other organisms. During continuous growth, cells lost motility although they still possessed flagella. Slow growth resulted in longer cells. Future studies will investigate the independent effects of nutrient stress and growth rate on the virulence and persistence of cells.     

Effects of pulp and paper mill effluents on estuarine and marine ecosystems in Canada: a review

This review examines the impact of pulp and paper mill effluents by comparing effects from Canada's east and west coasts at a time when revisions to the federal Fisheries Act (Pulp and Paper Effluent Regulations) are being finalized. Pulp and paper mill effluents from Canadian coastal mills were usually acutely toxic at source, and in many cases had marked deleterious effects on receiving waters due to toxicity, high biochemical oxygen demand (BOD), and total suspended solids (TSS) loadings. Extreme reductions in ambient dissolved oxygen, impacts on benthic and intertidal organisms, changes in water colour and primary productivity, have been demonstrated over the years and continue to cause environmental damage. Contamination of biota by a wide range of chlorinated organic compounds has been more recently the focus of investigations.While sublethal effects of lowered dissolved oxygen levels and suspended solids on the water column and bottom communities are well known, the potential effects of major organochlorine contamination of water (measured as Adsorbable Organic Halogens=AOX), sediments, and biota are not fully understood, especially under natural and perturbated conditions. The findings of recent North American and Scandinavian studies which describe liver enzyme activation, histological damage, reproductive and population level changes in fish, are a major concern as they are a sign of ecosystem stress and pathology.The environmental effects described herein are long-term impacts which will not respond quickly to changes in pollutant loading. Integrated site-specific assessments need to be undertaken to document ecosystem response to process and treatment improvements at mill sites. Current biomonitoring techniques including measures of population structure and ecosystem function are needed in addition to sensitive biochemical indicators of contaminant exposure.     

内分泌干扰物的生物学检测和评价方法

内分泌干扰物(endocrine disrupters,EDs)是近年来环境科学研究的热点之一。EDs不仅对陆生动物和人类具有潜在的危害,还可以通过不同途径到达水环境中,影响水生动物的生长和繁殖等。因此,建立EDs快速、灵敏的检测和评价方法非常必要。此外,生物检测方法还能在一定程度上反映化学污染物对生物体的毒害效应。本文就研究EDs的离体和在体实验方法进行了介绍,并从个体、组织细胞、生化与分子(蛋白质、酶、RNA、激素)等不同水平上,重点综述了鱼类生物标志物在检测和评价EDs方面的研究进展。     

Prospects for incorporation of epigenetic biomarkers in human health and environmental risk assessment of chemicals

Epigenetic mechanisms have gained relevance in human health and environmental studies, due to their pivotal role in disease, gene × environment interactions and adaptation to environmental change and/or contamination. Epigenetic mechanisms are highly responsive to external stimuli and a wide range of chemicals has been shown to determine specific epigenetic patterns in several organisms. Furthermore, the mitotic/meiotic inheritance of such epigenetic marks as well as the resulting changes in gene expression and cell/organismal phenotypes has now been demonstrated. Therefore, epigenetic signatures are interesting candidates for linking environmental exposures to disease as well as informing on past exposures to stressors. Accordingly, epigenetic biomarkers could be useful tools in both prospective and retrospective risk assessment but epigenetic endpoints are currently not yet incorporated into risk assessments. Achieving a better understanding on this apparent impasse, as well as identifying routes to promote the application of epigenetic biomarkers within environmental risk assessment frameworks are the objectives of this review. We first compile evidence from human health studies supporting the use of epigenetic exposure‐associated changes as reliable biomarkers of exposure. Then, specifically focusing on environmental science, we examine the potential and challenges of developing epigenetic biomarkers for environmental fields, and discuss useful organisms and appropriate sequencing techniques to foster their development in this context. Finally, we discuss the practical incorporation of epigenetic biomarkers in the environmental risk assessment of chemicals, highlighting critical data gaps and making key recommendations for future research within a regulatory context.     

Activities of biomarkers in multiple life stages of the model crustacean, Palaemonetes pugio

Increased urbanization of coastal areas has led to increased contaminant levels in adjacent sediments and waters. Consequently, many studies have been conducted to determine the potential impacts on estuarine organisms, including the grass shrimp, Palaemonetes pugio. This study investigated baseline levels of four cellular biomarkers (glutathione (GSH), lipid peroxidation (LPx), acetylcholinesterase (AChE), and cholesterol (CHL)) in multiple life stages (stage IV, V, VI, and VII embryos, newly-hatched larvae, 18-day-old larvae, juveniles, and adults) of P. pugio to determine which biomarkers may potentially be useful as indicators of contaminant exposure. There was a similar pattern in both LPx and AChE levels, with a clear increase occurring from the embryonic to the adult stages. Detectable levels of AChE did not occur until embryo stage V. Glutathione shared a similar pattern to LPx and AChE from the newly-hatched larvae through the adult stage, however, it did not exhibit any distinguishable pattern overall with highly variable levels among all life stages. Likewise, CHL did not exhibit any distinguishable pattern, but in contrast, CHL levels were similar throughout all life stages. This research provides valuable background information that may be used in future assessments of grass shrimp population health.     

Biomarker responses and accumulation of hazardous substances in mussels (Mytilus trossulus) transplanted along a pollution gradient close to an oil terminal in the Gulf of Finland (Baltic Sea)

Baltic Sea blue mussels (Mytilus trossulus) were used as sentinel organisms to detect the biological effects of chemical contamination in the low salinity environment. Mussels naturally adapted to a salinity of ca. 6.0 PSU were caged for 30 days at four sites along an assumed pollution gradient (salinity ca. 4.5 PSU) in the vicinity of Finland's largest oil refinery and harbor Kilpilahti in the Gulf of Finland. Tissue concentrations and accumulation rates of especially organic contaminants (PAHs, PCBs and organotins) were clearly elevated at the innermost coastal stations near the harbor area. Biological effects of contaminant exposure on caged mussels were evaluated by measuring a suite of biomarkers including catalase, glutathione S-transferase, superoxide dismutase, glutathione reductase, lipid peroxidation, acetylcholinesterase activity and lysosomal membrane stability. Mussels transplanted near the harbor area were able to elevate their antioxidant defense in response to environmental contamination. Reduced morphometric condition index and soft tissue growth rate together with increased lipid peroxidation and low lysosomal membrane stability were also observed at the most contaminated site. The results suggest that caging of M. trossulus for four weeks at lower salinity is a feasible method for the detection of environmental pollution also in low salinity areas of the Baltic Sea.     

Molecules are more than markers: new directions in molecular microbial ecology

Macromolecules such as DNA, RNA, and proteins are widely used to quantify diversity in natural communities, to monitor the dispersal of organisms and their genes, and to trace phylogenetic relationships among organisms. With such widespread use of molecules as markers, it is easy to forget that they perform functions that are integral to the survival of organisms. The structural and functional properties of macromolecules have been intensively studied in genetics, biochemistry, and physiology. These fields, however, have not generally focused on the ecological significance of molecular variation, but instead have used defective variants as tools for identifying structure and function. Understanding the significance of molecular variation for organismal success or failure is a central problem in ecology, one whose solution will require the integration of diverse approaches and perspectives from ecology, molecular biology, genetics, physiology, and evolutionary biology. I review several studies of bacterial populations evolving in simple environments that have begun to integrate these approaches and perspectives in order to examine the consequences of molecular variation for ecological performance.     

Levels of diversity in endomycorrhizal fungi (Glomales,Zygomycetes) and their role in defining taxonomic and non-taxonomic groups

Diversity in glomalean fungi is manifested at the molecular, morphological, and ecological levels. Characters at any of these levels can be ordered into hierarchical patterns defining taxonomic groups if they are conserved enough to be heritable through geologic time in all descendants of a common ancestor. At present, only morphological characters associated with mode of spore formation and in subcellular structure of spores are sufficiently stable and diverse to recognize at least 150 species. Ontogenetic comparisons indicate that species integrity, despite asexual reproduction, is the result of rigid internal constraints imposed on variation during the process of spore subcellular differentiation. Epigenetic factors dominate because the differentiation sequence is linear and each new stage is causally linked to preceding stages. Some morphological characters of the fungal mycelium also exist, but they define more inclusive groups at the family level and above. Most diversity in the mycorrhizae consists of life-history traits associated with abundance and architecture of fungal components, their rate of formation and longevity, and their cost in the symbiosis. These characters participate in processes at the molecular and ecological levels, so they are autonomous from morphological determinants. They often are labile or affected by external environmental conditions, so fewer stable taxonomic characters are likely to be discovered. Instead, molecular and ecological diversity has greater potential to define; (a) niche specificity of organisms/populations and (b) causal processes linked to host-fungus compatibility and mycorrhizal efficiency. Any taxonomic characters that relate to mycorrhizal functions will come only from comparative studies involving organisms from shared habitats rather than those having shared spore morphologies.     

Multiple biomarker response in rainbow trout during exposure to hexavalent chromium

This research investigated hexavalent chromium toxicity in rainbow trout using a panel of biomarkers at different levels of biological organization. A time-course experiment in which rainbow trout were exposed in hard water (63.5 mg/L CaCO3) to a sublethal concentration of hexavalent chromium (10 mg/L) for a period of 28 days was conducted. The responses of multiple biomarkers were measured in gill and liver tissues at varying time points. Significant differences in metallothionein induction, superoxide dismutase activity, lipid peroxidation, cellular morphology, and growth were observed. Results indicated that gill tissues were more sensitive than hepatic tissues to chromium toxicity, yet hepatic tissues appeared to play a larger role in the organism's adaptive response to chromium compared to gill tissues. This study highlights the importance of using a set of integrated biomarkers to assess contaminant exposure and effects.