Sequential expression of biomarkers in Bluegill Sunfish exposed to contaminated sediment

Metabolic implications of exposure to wastewater effluent in bluegill sunfish

Effluent from wastewater treatment plants (WWTP) contains a complex mixture of contaminants and is a major worldwide source of aquatic pollution. We examined the effects of exposure to treated effluent from a municipal WWTP on the metabolic physiology of bluegill sunfish (Lepomis macrochirus). We studied fish that were wild-caught or experimentally caged (28 d) downstream of the WWTP, and compared them to fish that were caught or caged at clean reference sites. Survival was reduced in fish caged at the effluent-contaminated site compared to those caged at the reference site. Resting rates of O₂ consumption (MO₂) were higher in fish from the contaminated site, reflecting a metabolic cost of wastewater exposure. The increases in routine MO₂ did not reduce aerobic scope (difference or quotient of maximal MO₂ and resting MO₂), suggesting that physiological compensations accompanied the metabolic costs of wastewater exposure. Fish exposed to wastewater also had larger hearts and livers. The activity of mitochondrial enzymes (cytochrome c oxidase, citrate synthase) per liver mass was unaltered across treatments, so the increased mass of this organ increased its cumulative oxidative capacity in the fish. Wastewater exposure also reduced glycogen content per liver mass. The effects of caging itself, based on comparisons between fish that were wild-caught or caged at clean sites, were generally subtle and not statistically significant. We conclude that exposure to wastewater effluent invokes a metabolic cost that leads to compensatory physiological adjustments that partially offset the detrimental metabolic impacts of exposure.

Polycyclic Aromatic Hydrocarbons (PAHs) in inland aquatic ecosystems: Perils and remedies through biosensors and bioremediation

Polycyclic Aromatic Hydrocarbons (PAHs) are among the most ubiquitous environmental pollutants of high global concern. PAHs belong to a diverse family of hydrocarbons with over one hundred compounds known, each containing at least two aromatic rings in their structure. Due to hydrophobic nature, PAHs tend to accumulate in the aquatic sediments, leading to bioaccumulation and elevated concentrations over time. In addition to their well-manifested mutagenic and carcinogenic effects in humans, they pose severe detrimental effects to aquatic life. The high eco-toxicity of PAHs has attracted a number of reviews, each dealing specifically with individual aspects of this global pollutant. However, efficient management of PAHs warrants a holistic approach that combines a thorough understanding of their physico-chemical properties, modes of environmental distribution and bioaccumulation, efficient detection, and bioremediation strategies. Currently, there is a lack of a comprehensive study that amalgamates all these aspects together. The current review, for the first time, overcomes this constraint, through providing a high level comprehensive understanding of the complexities faced during PAH management, while also recommending future directions through potentially viable solutions. Importantly, effective management of PAHs strongly relies upon reliable detection tools, which are currently non-existent, or at the very best inefficient, and therefore have a strong prospect of future development. Notably, the currently available biosensor technologies for PAH monitoring have not so far been compiled together, and therefore a significant focus of this article is on biosensor technologies that are critical for timely detection and efficient management of PAHs. This review is focussed on inland aquatic ecosystems with an emphasis on fish biodiversity, as fish remains a major source of food and livelihood for a large proportion of the global population. This thought provoking study is likely to instigate new collaborative approaches for protecting aquatic biodiversity from PAHs-induced eco-toxicity.

Metabolic Costs of Exposure to Wastewater Effluent Lead to Compensatory Adjustments in Respiratory Physiology in Bluegill Sunfish

Municipal wastewater effluent is a major source of aquatic pollution and has potential to impact cellular energy metabolism. However, it is poorly understood whether wastewater exposure impacts whole-animal metabolism and whether this can be accommodated with adjustments in respiratory physiology. We caged bluegill sunfish (Lepomis macrochirus) for 21 days at two sites downstream (either 50 or 830 m) from a wastewater treatment plant (WWTP). Survival was reduced in fish caged at both downstream sites compared to an uncontaminated reference site. Standard rates of O₂ consumption increased in fish at contaminated sites, reflecting a metabolic cost of wastewater exposure. Several physiological adjustments accompanied this metabolic cost, including an expansion of the gill surface area available for gas exchange (reduced interlamellar cell mass), a decreased blood-O₂ affinity (which likely facilitates O₂ unloading at respiring tissues), increased respiratory capacities for oxidative phosphorylation in isolated liver mitochondria (supported by increased succinate dehydrogenase, but not citrate synthase, activity), and decreased mitochondrial emission of reactive oxygen species (ROS). We conclude that exposure to wastewater effluent invokes a metabolic cost that leads to compensatory respiratory improvements in O₂ uptake, delivery, and utilization.

Effect-directed analysis supporting monitoring of aquatic environments--An in-depth overview

Aquatic environments are often contaminated with complex mixtures of chemicals that may pose a risk to ecosystems and human health. This contamination cannot be addressed with target analysis alone but tools are required to reduce this complexity and identify those chemicals that might cause adverse effects. Effect-directed analysis (EDA) is designed to meet this challenge and faces increasing interest in water and sediment quality monitoring. Thus, the present paper summarizes current experience with the EDA approach and the tools required, and provides practical advice on their application. The paper highlights the need for proper problem formulation and gives general advice for study design. As the EDA approach is directed by toxicity, basic principles for the selection of bioassays are given as well as a comprehensive compilation of appropriate assays, including their strengths and weaknesses. A specific focus is given to strategies for sampling, extraction and bioassay dosing since they strongly impact prioritization of toxicants in EDA. Reduction of sample complexity mainly relies on fractionation procedures, which are discussed in this paper, including quality assurance and quality control. Automated combinations of fractionation, biotesting and chemical analysis using so-called hyphenated tools can enhance the throughput and might reduce the risk of artifacts in laboratory work. The key to determining the chemical structures causing effects is analytical toxicant identification. The latest approaches, tools, software and databases for target-, suspect and non-target screening as well as unknown identification are discussed together with analytical and toxicological confirmation approaches. A better understanding of optimal use and combination of EDA tools will help to design efficient and successful toxicant identification studies in the context of quality monitoring in multiply stressed environments.

Gamma radiation induced cell cycle perturbations and DNA damage in Catla Catla as measured by flow cytometry

Gamma radiation induced cell cycle perturbations and DNA damage in Catla catla were analyzed in erythrocytes at different time points using flow cytometry (FCM). Protracted exposure to radiation induced damage between days 12 and 45. Disturbances in cell cycle machinery, i.e., proportional increase and decrease in Gap0 or quiescent/Gap1 (G0/G1), Synthesis (S) and Gap2/Mitotic (G2/M) phases were observed at both acute and protracted treatments. Both acute and protracted exposures induced apoptosis with a notable significance between days 3 and 6 at protracted and on day 45 at acute doses. Fish exposed protractedly avail some DNA repair mechanisms than acutely exposed. This is the first study to analyze radiation induced DNA damage under laboratory conditions and suggests that flow cytometry can also be an alternate tool to screen genotoxicity induced by ionizing radiation in fish.

The slider turtle as an environmental sentinel: multiple tissue assays using flow cytometric analysis

We used flow cytometry (FCM) to conduct a multiple-tissue assay on slider turtles (Trachemys scripta) inhabiting radioactive seepage basins. Duplicate samples of blood, heart, spleen and kidney were analysed on two different cytometers (Leitz MPV and Coulter Profile II), each employing distinct staining protocols (DAPI and PI, respectively). Both DAPI and PI assays of spleen cells demonstrated significantly greater variation in DNA content for the basin turtles than for 'control' animals from nearby, uncontaminated sites. Basin turtles also exhibited significant cell-cycle effects for blood and spleen, again revealed by both assays. These corroborative findings demonstrate the consistency and repeatability of FCM assays in environmental monitoring and identify the particularly sensitive nature of turtle blood and spleen to mutagenic agents. Our survey complements previous FCM studies on sliders from contaminated sites and thereby underscores the species' potential as a sentinel for biomarker assays.

DNA damage in cichlids from an oil production facility in Guatemala

This study focused on several wetlands in Laguna del Tigre National Park (Guatemala) as part of Conservation International's Rapid Assessment Program. Sediment and water samples were collected from a laguna near Xan field, Guatemala's largest oil facility, and three other sites for determination of levels of polycyclic aromatic hydrocarbons (PAHs). Cichlid fish (Thorichthys meeki and Vieja synspila) were collected for determination of DNA strand breakage (by gel electrophoresis), chromosomal breakage (flow cytometry), and fin erosion. For T. meeki from Xan field, chromosomal breakage and strand breakage was greater than in at least two of the three reference sites. For V. synspila, chromosomal breakage and strand breakage were greater in Xan than one of the two reference sites. Fin erosion was observed only at the Xan laguna. Genetic biomarker effects and fin erosion, along with patterns of aqueous PAH concentrations, indicate that fish are affected by anthropogenic contaminants. PAHs were elevated at some reference sites, but environmental forensic analysis suggested a pyrogenic or diagenic origin. It is possible that oil field brines injected into the ground water caused fin erosion and genotoxicity in fish at Xan field, and it is also possible that pyrogenic PAHs influence levels of DNA damage in reference sites. These analyses represent one of the first efforts to examine genotoxicity in native Mesoamerican cichlids.

Assessing the toxicity of TBBPA and HBCD by zebrafish embryo toxicity assay and biomarker analysis

Tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) are two of the most widely used brominated flame retardants (BFRs). The biological toxicity effect of TBBPA and HBCD was studied by means of zebrafish embryo toxicity assays in combination with three biomarkers, including superoxide dismutase (SOD), lipid peroxidation, (LPO), and heat shock protein (Hsp70). The standard zebrafish embryo assay showed that high concentrations of TBBPA (> or =0.75 mg/L) can cause lethality or malformation. For HBCD within the concentration range (0.002-10 mg/L), no endpoint was observed. Furthermore, SOD activities of zebrafish embryos exposed to TBBPA were increased with the increasing concentrations. SOD activities in the group treated by HBCD showed an increase followed by a decline. Regardless of TBBPA or HBCD, LPO were increased along with the increase of the concentration. The change pattern of Hsp70 levels was the same with LPO. All these results showed that TBBPA and HBCD could cause oxidative stress and Hsp70 overexpression, inducing acute toxicity to zebrafish embryo in a short-term exposure. The study also indicates that the zebrafish embryo assay in combination with the biomarkers is effective in aquatic environmental toxicology and risk assessment.

Assessment of environmental stress in Parablennius sanguinolentus (Pallas, 1814) of the Sicilian Ionian coast

The blenny Parablennius sanguinolentus was selected as a useful bioindicator of environmental pollution. Chemical parameters in water and sediments from three different sampling sites along the Sicilian Ionian coast were determined and metal concentrations in fish muscle were measured. DNA fragmentation and oxidation in erythrocytes and hepatocytes was determined by the Comet assay and HSP70 expression levels were evaluated in the liver. The results show an increased level of chromium in sediments and high polycyclic aromatic hydrocarbon (PAH) concentrations in water at one site. The bioaccumulation of metals in muscle tissue shows high concentrations of lead in some samples. A high percentage of DNA damage in blood and liver cells, as well as high hepatic levels of HSP70, were found in all the sites. The results demonstrate the usefulness of an integrated chemical and biological approach for the determination of environmental stress.

In situ biomonitoring of PAH-contaminated sediments using juvenile coho salmon (Oncorhynchus kisutch)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous marine and freshwater sediment contaminants. Extensive data exist to confirm that PAHs are toxic to aquatic receptors. However, limited information is available regarding the bioavailability and genotoxicity of sediment PAHs to aquatic organisms. This study investigated an integrated biomonitoring approach using chemical analyses and biomarkers to characterize the bioavailability and genotoxicity of a complex PAH mixture in freshwater lake sediments associated with a former manufactured gas plant (MGP). Sediment PAH genotoxicity was assessed by flow cytometry (FCM), DNA adduct (32)P-postlabeling, and erythrocyte micronuclei in juvenile coho salmon (Oncorhynchus kisutch) caged in the water column. Significant PAH-induced genotoxicity was observed with FCM and (32)P-postlabeling, but not with erythrocyte micronuclei. Chromosome damage in peripheral blood and hepatic DNA adducts correlated with sediment, but not water column PAH concentrations. Total hepatic DNA adducts in salmon caged nearest the former MGP facility was 39+/-6.5 (RALx10(9)), while salmon caged in a reference lake had 28+/-2.3 total hepatic DNA adducts per 10(9) nucleotides. These results indicate that in situ biomonitoring using biomarkers and caged fish can be a sensitive indicator of genotoxic PAHs in sediments.

Biomarkers of metals exposure in fish from lead-zinc mining areas of southeastern Missouri, USA

The potential effects of proposed lead-zinc mining in an ecologically sensitive area were assessed by studying a nearby mining district that has been exploited for about 30 y under contemporary environmental regulations and with modern technology. Blood and liver samples representing fish of three species (largescale stoneroller, Campostoma oligolepis, n=91; longear sunfish, Lepomis megalotis, n=105; and northern hog sucker, Hypentelium nigricans, n=20) from 16 sites representing a range of conditions relative to mining activities were collected. Samples were analyzed for metals (also reported in a companion paper) and for biomarkers of metals exposure [erythrocyte delta-aminolevulinic acid dehydratase (ALA-D) activity; concentrations of zinc protoporphyrin (ZPP), iron, and hemoglobin (Hb) in blood; and hepatic metallothionein (MT) gene expression and lipid peroxidation]. Blood lead concentrations were significantly higher and ALA-D activity significantly lower in all species at sites nearest to active lead-zinc mines and in a stream contaminated by historical mining than at reference or downstream sites. ALA-D activity was also negatively correlated with blood lead concentrations in all three species but not with other metals. Iron and Hb concentrations were positively correlated in all three species, but were not correlated with any other metals in blood or liver in any species. MT gene expression was positively correlated with liver zinc concentrations, but neither MT nor lipid peroxidase differences among fish grouped according to lead concentrations were statistically significant. ZPP was not detected by hematofluorometry in most fish, but fish with detectable ZPP were from sites affected by mining. Collectively, these results confirm that metals are released to streams from active lead-zinc mining sites and are accumulated by fish.

DNA integrity determination in marine invertebrates by Fast Micromethod

This study was focused toward the adaptation of the previously developed Fast Micromethod for DNA damage determination to marine invertebrates for the establishment of biomonitoring assessment. The Fast Micromethod detects DNA damage (strand breaks, alkali-labile sites and incomplete excision repair) and determines DNA integrity in cell suspensions or tissue homogenates in single microplates. The procedure is based on the ability of the specific fluorochrome dye PicoGreen to preferentially interact with high integrity DNA molecules, dsDNA, in the presence of ssDNA and proteins in high alkaline medium, thereby allowing direct fluorometric measurements of dsDNA denaturation without sample handling and stepwise DNA separations. The results presented herein describe the influence of the DNA amount and the pH of the denaturation media on slopes of the kinetic denaturation curves and calculated strand scission factors (SSFs). The optimal amount of DNA in Mytilus galloprovincialis gills homogenate was found to be 100 ng ml(-1) and the greatest differences in DNA unwinding kinetics (slopes and SSF values) were reached at pH 11.5. The induction of DNA damage and loss of DNA integrity was measured in native DNA isolated from cotton-spinner Holothuria tubulosa, marine sponge Suberites domuncula cells and mussel M. galloprovincialis gills homogenate. DNA damage and loss of DNA integrity were detected after induction by different doses of (gamma-rays, generated by 137Cs 1800 Ci; 0-500 rad in marine sponge S. domuncula cells up to SSFx(-1) values 0.082 +/- 0.012 for the highest radiation dose). Analysis by chemical xenobiotics based on the in vitro action of bleomycin (bleomycin-Fe(II) complex 0-50 or 0-83 microg ml(-1) (microM)) with native DNA from cotton-spinner H. tubulosa and mussel M. galloprovincialis gills homogenate yielded values of 0.537 +/- 0.072 and 0.130 +/- 0.018, respectively. In vivo experiments with mussel M. galloprovincialis gills homogenate by 4-nitroquinoline-N-oxide (NQO; 0-1 microg g(-1) NQO mussel) and benzo[a]pyrene (B[a]P; 0-20 microg g(-1) B[a]P mussel) indicated SSFx(-1) values of 0.121 +/- 0.016 and 0.090 +/- 0.007, respectively, for the highest applied doses of chemical xenobiotics. The analytical technique described here allows simple and fast analysis of DNA integrity, requires very short time for multiple analyses (less than 3 h) and even less than 100 ng DNA per single well (50 ng DNA isolated from cotton-spinner, 12,500 sponge cells or about 10 mg of mussel gills homogenate) in a microplate. This makes the Fast Micromethod applicable for the measurement of DNA integrity of small samples for genotoxicity assessment (biomonitoring), the effects of genotoxins on lower marine taxa or sessile invertebrates in marine environment (e.g. sponges, mussels) and the estimation of directional changes and harmful effects in the ecosystem.

Detection of DNA strand breakage in a marine amphipod by agarose gel electrophoresis: exposure to X-rays and copper

This article describes the leading steps to develop an assay of DNA damage for the marine amphipod Gammarus locusta, using agarose gel electrophoresis (AGE). To test the sensitivity and feasibility of the AGE technique, X-ray assays were performed with naked DNA and with live amphipods. These positive controls demonstrated the effectiveness of the AGE technique to not only discriminate distinct levels of DNA strand breakage in a dose-dependent manner, but also to identify and quantify the type of strand breakage induced. It was also shown that it is possible to detect DNA damage using whole-body DNA extracts from amphipods. To explore the potential of this technique for use in ecotoxicological studies with amphipods, a 96-h waterborne-copper toxicity test was performed. Copper-induced DNA strand breakage was first observed after 24 h of exposure, and was recorded again at 96 h, at a copper concentration of 20 microg l(-1). The absence of strand breakage after 48 h of exposure is discussed in the light of the underlying mechanisms of copper toxicity and DNA repair. These studies demonstrated the feasibility of including DNA damage as a biomarker in ecotoxicological studies with amphipods. Information gained from the use of this biomarker would help with the interpretation of chronic toxicity tests and would contribute to our understanding of the impact of genotoxic insult in marine invertebrates, particularly crustaceans.

Heat-shock protein (HSP70) response in the eastern oyster, Crassostrea virginica, exposed to PAHs sorbed to suspended artificial clay particles and to suspended field contaminated sediments

Sediments are a potentially significant source of pollutants, containing not only organic contaminants but heavy metals as well. The heat shock protein response (HSP70 family) in the eastern oyster exposed to suspended clay particles spiked with polynuclear aromatic hydrocarbons (PAHs) and to suspended field contaminated sediments (SFCS) was investigated. In experiment 1, oysters were exposed to 1.0, 1.5 or 2.0 g suspended clay particles with concentrations of 65.6, 159.0 and 242 micro g PAHs per g of wet clay particles, respectively, and sampled after 40 days. Controls were exposed to 0, 1.0, 1.5, and 2.0 g suspended unspiked clay particles. In experiment 2, oysters were exposed to 0, 1.0, 1.5, and 2.0 g SFCS and the HSP70 expression was determined after 5, 10, 20 and 40 days exposure. Oysters exposed to suspended clay particles spiked with PAHs showed a significant increase in HSP70 levels, while oysters exposed to 1.0, 1.5 or 2.0 g suspended unspiked clay particles did not show changes (P=0.78) in HSP70 levels compared to the group receiving 0 g clay particles. Exposure to the SFCS resulted in a significant increase in HSP70 as a function of exposure (P<0.001) and treatment (P=0.006). The response, however, was not dose dependent. Compared to the control group (0 g SFCS), groups exposed to 1.0, 1.5 and 2.0 g SFCS reached significantly higher levels in HSP70 at 40 days of exposure, with those exposed to 2.0 g SFCS expressing the highest levels. The HSP70 expression for each treatment showed fluctuations at various time intervals. No mortalities were recorded during the exposure experiments. The major contaminants in the SFCS were PAHs, heavy metals and polychlorinated biphenyls (PCBs). These results reveal that exposure to PAHs sorbed to clay particles and to SFCS induced a HSP70 response in the eastern oyster.

Assessment of tolerant sunfish populations (Lepomis sp.) inhabiting selenium-laden coal ash effluents. 2. Tissue biochemistry evaluation

Sunfish were collected from a fly ash pond-receiving stream and an Ohio River reference site to assess biochemical responses to coal ash effluent exposure. Selenium levels in sunfish from the receiving stream were higher than toxic thresholds associated with adverse population effects and reproductive impairment. Tissue biochemistry was found to be indicative of metal exposure and effect, but varied widely. Liver glycogen was positively correlated with increased liver metal levels, indicating no adverse effect upon stored carbohydrate levels. Lipid levels decreased with increasing metals, indicating possible nutritional stress. Protein levels increased with increasing metal levels, possibly due to the synthesis of proteins to sequester the metals. ATPase, dUTPase, and alkaline phosphatase activity generally decreased with exposure to ash pond metals, but remained within normal physiological ranges. Fish condition factors and liver somatic indices were correlated with liver lipid levels, dUTPase activity, and gill ATPase and alkaline phosphatase activity. Exposure to coal ash effluents produced biochemical markers of exposure that were associated with fish condition indicators; however, the indices themselves were not significantly affected by effluent exposure.

Applications and pitfalls of stress-proteins in biomonitoring

The vast number of potentially hazardous chemicals and the complex interactions that can occur between them in environmental mixtures, call for inexpensive, early and sensitive endpoints that reflect their biological effect. The existing validated bioassays, mostly based on lethality or reproduction, have been shown to be inadequate in respect of their sensitivity, the duration and expense of the test. In contrast, changes at biochemical level are usually the first detectable responses to environmental perturbation. Because these alterations underlie all effects at higher organisational level, they have often been shown to be very sensitive indicators of pollution. Stress-proteins (also referred to as heat-shock proteins or hsp) have recently been recognised as being one of the primary defence mechanisms that are activated by the occurrence of denatured proteins in the cell. Four major stress-protein families of 90,70,60 and 16-24 kDa are the most prominent and are frequently referred to as hsp90, hsp70, hsp60 and low molecular weight (LMW) stress-proteins. Three aspects of stress-proteins have been characterised that are essential if they want to be used as biomarkers of pollution: (1) they are part of the cellular protective response; (2) their synthesis is likely to be induced by a large number of chemicals; and (3) they are highly conserved in all organisms from bacteria to plants and man. Also, field studies have shown (be it for a limited number of stressors) that the stress response can occur even at the minute concentrations of pollutants that are usually found in the environment. However, increasing knowledge on the kinetics and persistence of the stress response to complex environmental mixtures, on the influence of both physiological and environmental parameters (pH, eutrophication, ellipsis), on the constitutive levels of stress-proteins and on the acquisition of tolerance, is required before one could safely apply stress-proteins to assess on-site pollution. Still, included in a test battery of complementary bioassays, stress protein may be very valuable as tier I biomarkers, i.e. broad response biomarkers that are used for preliminary screening of the environment.

Ethoxyresorufin-O-deethylase (EROD) activity in fish as a biomarker of chemical exposure

This review compiles and evaluates existing scientific information on the use, limitations, and procedural considerations for EROD activity (a catalytic measurement of cytochrome P4501A induction) as a biomarker in fish. A multitude of chemicals induce EROD activity in a variety of fish species, the most potent inducers being structural analogs of 2,3,7,8-tetracholordibenzo-p-dioxin. Although certain chemicals may inhibit EROD induction/activity, this interference is generally not a drawback to the use of EROD induction as a biomarker. The various methods of EROD analysis currently in use yield comparable results, particularly when data are expressed as relative rates of EROD activity. EROD induction in fish is well characterized, the most important modifying factors being fish species, reproductive status and age, all of which can be controlled through proper study design. Good candidate species for biomonitoring should have a wide range between basal and induced EROD activity (e.g., common carp, channel catfish, and mummichog). EROD activity has proven value as a biomarker in a number of field investigations of bleached kraft mill and industrial effluents, contaminated sediments, and chemical spills. Research on mechanisms of CYP1A-induced toxicity suggests that EROD activity may not only indicate chemical exposure, but also may also precede effects at various levels of biological organization. A current research need is the development of chemical exposure-response relationships for EROD activity in fish. In addition, routine reporting in the literature of EROD activity in standard positive and negative control material will enhance confidence in comparing results from different studies using this biomarker.

DNA adduct formation and persistence in liver and extrahepatic tissues of northern pike (Esox lucius) following oral exposure to benzo[a]pyrene, benzo[k]fluoranthene and 7H-dibenzo[c,g]carbazole

The formation and persistence of DNA adducts in liver, intestinal mucosa, gills and brain of juvenile northern pike (Esox lucius) following oral exposure to benzo[a]pyrene (BaP), benzo[k]fluoranthene (BkF) and 7H-dibenzo[c,g]carbazol (DBC) were analysed by 32P-postlabelling. The dosage was 25 micromol/kg body weight of each substance, administered on 5 occasions with an interval of 12-14 days. Sampling was carried out 9 days after the second treatment, and 9, 16, 33 and 78 days after the fifth treatment. Pikes were also fed with the substances singly for comparison of adduct patterns. A complex pattern of adducts was detected in all examined tissues from fish treated with the mixture. Total adduct levels were highest in intestine (347+/-17.4 nmol adducts/mol nucleotides, mean+/-SE), followed by liver (110+/-9.3), gills (69+/-6) and brain (14+/-4.2). In pike treated with BaP alone, one major adduct was detected in all examined tissues. This BaP-adduct made up approximately 50% of the total amount of adducts in the brain. Corresponding values in liver, intestine and gills were 23, 31 and 34%, respectively. One relatively weak BkF-adduct and at least 10 different DBC-adducts were detected in all analysed tissues. Total adduct level in the intestine declined to 29.4% of the maximum value 78 days after the last exposure, while there was no significant decline in adduct levels in liver, gills or brain. The results suggest that intestine is more susceptible to adduct formation than liver after oral exposure, and that adduct levels in the intestine represent ongoing or relatively recent exposure. DNA adducts in the other investigated tissues were much more persistent and may therefore accumulate during long-term exposure.

Biomarker assessment of the effects of coal strip-mine contamination on channel catfish

A suite of biomarkers was used to evaluate acute (1-day) to semichronic (3-month) heavy metal-induced toxicity in channel catfish, lctalurus punctatus, caged at an abandoned strip mine and a noncontaminated reference site. Assays performed include indicators of metabolic, hematological, osmoregulatory, and genotoxic stress. Two cage designs were used to evaluate the importance of exposure routes: one excluding contact with the sediments and the other allowing contact with water and sediments. Significant DNA strand breakage was observed in catfish exposed to both exposure regimens, but evidence of DNA repair was observed only in water-exposed catfish. Transient increases in hemoglobin, delta-aminolevulinic acid dehydratase, and hematocrit levels were observed at 1 month's exposure for both exposure regimens, followed by a return to control levels for the duration of the study. Environmental conditions (i.e., weather-related changes in water quality) may have contributed to the variable plasma chloride and glucose levels observed in all catfish exposed to strip-mine wastes. The transient changes in biomarkers followed by a return to reference values represent an initial stress and an acclimation to normal levels.

Effect of different environmental variables on the synthesis of Hsp70 in Raphidocelis subcapitata

Heat-shock proteins (Hsp) or stress proteins are strong candidates for biomarkers of environmental pollution since they are activated very early in the cascade of cellular events that follow toxic exposure and at concentrations below the lethal dose. Included in a test battery comprised of different bioassays, Hsp induction could provide a general purpose tier I indicator of pollution. Still, little is known on the induction of Hsp under different environmental conditions. In the present study we have made use of an Enzyme Linked Immunosorbent Assay (ELISA) to detect the synthesis of Hsp70 in Raphidocelis subcapitata in response to changes in pH, temperature, humic acids, nitrates and phosphates. The results show that algae respond to these changes in the environment by a transient increase in Hsp70 levels, the extend of which is dependent on the actual parameter under investigation. Out of these five parameters studied, only temperature and possibly pH were able to induce acquired tolerance, i.e. algae grown at a pH or at a temperature different from control conditions were shown to have acquired resistance to a subsequent challenge with Zn (10(-5) M). Adjustment of the pH and temperature in two physico-chemically different natural surface waters was demonstrated to be sufficient to obtain similar induction patterns of Hsp70 upon exposure to zinc. These results qualify Hsp70 as a good biomonitor for environmental pollution provided essential environmental parameters such as pH and temperature are kept constant.

DNA strand breakage in aquatic organisms and the potential value of the comet assay in environmental monitoring

This review considers the potential for DNA strand breaks, particularly as measured by the comet assay, to act as a biomarker of genetic toxicity in fish and other aquatic species. The background need for such biomarkers is introduced in relation to carcinogenicity, reproductive effects and other adverse effects of pollution. Sensitive measurements of DNA strand breakage can be achieved, e.g., by alkaline elution, alkaline unwinding or by single cell gel electrophoresis (comet) techniques. The DNA damage can be a reflection, not only of direct strand breakage, but also of alkali-labile sites and of repair enzyme-mediated breakage (i.e., is non-specific). A range of genotoxic chemicals (both with and without the requirement for metabolic activation) give positive effects in various cell types of vertebrate and invertebrate aquatic species, following in vitro and in vivo exposures under laboratory conditions. A limited number of analyses of organisms exposed to polluted waters or sediments in the field have implicated DNA strand breakage as a relatively sensitive, rapid and broad specificity indicator of genotoxic pollutant exposure. The comet assay deserves further exploitation to assess inter-individual and inter-cell variability in response to pollutants and naturally occurring genotoxic stimuli, and to assess the persistence of these effects.

Dose-dependent induction of heat shock protein 70 synthesis in Raphidocelis subcapitata following exposure to different classes of environmental pollutants

In this study an enzyme-linked immunosorbent assay (ELISA) was developed to detect the stress protein Hsp70 in the green alga Raphidocelis subcapitata. Using this ELISA, the response to a variety of pollutants, including ZnCl2, SeO2 (heavy metals), lindane (organochlorine pesticide), pentachlorophenol (PCP, chlorinated hydrocarbon insecticide and fungicide), carbaryl (carbamate pesticide) and sodium dodecyl sulphate (SDS; surfactant) was tested. Our results show that Hsp 70 is produced in a dose-dependent way in response to most chemicals investigated (except PCP) and at concentrations below the range of classical cytotoxicity testing (i.e. growth inhibition, lethality). Still, the potential to induce Hsp70 varied among the pollutants tested, the heavy metals ZnCl2 and SeO2 being the strongest inducers of Hsp70. Combined with the existing literature, these results indicate that Hsp70 in R. subcapitata is a sensitive biomarker for a wide range of environmental pollutants.

Incorporation of the biomarker concept in ecotoxicology calls for a redefinition of terms

: Biomarkers have received a lot of attention but the biomarker concept has not yet been defined properly. As a consequence, various interpretations of the term 'biomarker' exist, some of which overlap with well-established ecotoxicological concepts. To allow incorporation of the biomarker concept within the framework of modern ecotoxicology, a clarification of terms is needed. In this paper, definitions are presented for the terms 'biomarker', 'bioindicator' and 'ecological indicator', which do not overlap and are linked to different levels of biological organization. The use of these concepts for ecological effects assessment is discussed.

Stress proteins in aquatic organisms: an environmental perspective

The cellular stress response protects organisms from damage resulting from exposure to a wide variety of stressors, including elevated temperatures, ultraviolet (UV) light, trace metals, and xenobiotics. The stress response entails the rapid synthesis of a suite of proteins referred to as stress proteins, or heat-shock proteins, upon exposure to adverse environmental conditions. These proteins are highly conserved and have been found in organisms as diverse as bacteria, molluscs, and humans. In this review, we discuss the stress response in aquatic organisms from an environmental perspective. Our current understanding of the cellular functions of stress proteins is examined within the context of their role in repair and protection from environmentally induced damage, acquired tolerance, and environmental adaptation. The tissue specificity of the response and its significance relative to target organ toxicity also are addressed. In addition, the usefulness of using the stress response as a diagnostic in environmental toxicology is evaluated. From the studies discussed in this review, it is apparent that stress proteins are involved in organismal adaptation to both natural and anthropogenic environmental stress, and that further research using this focus will make important contributions to both environmental physiology and ecotoxicology.