Semi-static Test Research Articles

Effects of ECF-Kraft pulp mill effluent treated with fungi (Rhizopus oryzae) on reproductive steroids and liver CYP1A of exposed goldfish (Carassius auratus)

The toxicity of bleached Kraft pulp mill effluents (BKME) is usually attributed to chemical compounds which are produced and released throughout various stages of pulp and paper production. The main objective of the present work was to detect sub-lethal responses of goldfish (Carassius auratus) to secondary treated BKME which was treated with Rhizopus oryzae. A total of 96 carps (C. auratus; 11 +/- 3 g) were exposed to different concentrations of the post-treated effluent (0, 1, 10, 25, 50, and 100%), in 28 days semi-static tests. Several biomarkers were then evaluated to assess the toxicological effects: induction of CYP1A (metabolic processes of organic compounds in liver), change in steroid profiles (11-Ketotestosterone, 17beta-estradiol), histopathology of liver and gonads and somatic indices (GSI, HSI) for endocrine disruption and other physiological disturbances. The most significant results show an induction of CYP1A in both sexes and a decrease of 17beta-estradiol concentrations in females. Histopathological changes such as liver tissue degeneration were observed in fish exposed to 50 and 100% of the BKME. Although the BKME was biologically treated there are some chemical compounds in the effluent that are capable to affect fish physiology, however, a clear evidence for endocrine disruption was not found.

Sublethal cyfluthrin toxicity to carp ( Cyprinus carpio L.) fingerlings: Biochemical, hematological, histopathological alterations

This study measures a whole series of biological endpoints, and histopathological and behavioral changes of carp ( Cyprinus carpio L.) fingerlings in order to investigate the adverse effects of a sublethal concentration of 10 μg/L cyfluthrin for 48 h and one week using the semi-static test system. The most significantly altered findings of this study was that total antioxidant status levels decreased in 48 h, chloride levels decreased in one week, and sodium and phosphorous levels increased in the 48 h-exposed group. Plasma cortisol increased in both the 48 h-exposed and the one-week-exposed groups. The unique tissue was the brain that had an increased level of malondialdehyde after one week of exposure. Such biomarkers may be used in assessing adverse/toxic effects of pesticides as environmental stressors. Potential oxidative-stress-inducing effect of synthetic pyrethroid cyfluthrin, as lipid peroxidation, in addition to its sodium channel blocking, is reported for the first time as an additional mechanism of action.

Toxicity of titanium dioxide nanoparticles to rainbow trout ( Oncorhynchus mykiss): Gill injury, oxidative stress, and other physiological effects

Mammalian and in vitro studies have raised concerns about the toxicity of titanium dioxide nanoparticles (TiO 2 NPs), but there are very limited data on ecotoxicity to aquatic life. This paper is an observational study where we aim to describe the toxicity of TiO 2 NPs to the main body systems of rainbow trout. Stock solutions of dispersed TiO 2 NPs were prepared by sonication without using solvents. A semi-static test system was used to expose rainbow trout to either a freshwater control, 0.1, 0.5, or 1.0 mg l −1 TiO 2 NPs for up to 14 days. Exposure to TiO 2 NPs caused some gill pathologies including oedema and thickening of the lamellae. No major haematological or blood disturbances were observed in terms of red and white blood cell counts, haematocrit values, whole blood haemoglobin, and plasma Na + or K + concentrations. Tissue metal levels (Na +, K +, Ca 2+ and Mn) were generally unaffected. However, some exposure concentration-dependent changes in tissue Cu and Zn levels were observed, especially in the brain. Exposure to TiO 2 NPs caused statistically significant decreases in Na +K +-ATPase activity (ANOVA, P < 0.05) in the gills and intestine, and a trend of decreasing enzyme activity in the brain (the latter was not statistically significant). Thiobarbituric acid reactive substances (TBARS) showed exposure concentration-dependent and statistically significant (ANOVA or Kruskal–Wallis test, P < 0.05) increases (two-fold or more) in the gill, intestine and brain, but not the liver during exposure to TiO 2 NPs compared to controls. TiO 2 NP exposure caused statistically significant (ANOVA, P < 0.05) increases in the total glutathione levels in the gills, but depletion of hepatic glutathione compared to controls. Total glutathione levels in the brain and intestine were unaffected. Liver cells exposed to TiO 2 NPs showed minor fatty change and lipidosis, and some hepatocytes showed condensed nuclear bodies (apoptotic bodies). Fish probably ingested water containing TiO 2 NPs during exposure (stress-induced drinking) which may have resulted in some areas of erosion on the intestinal epithelium. Overall we conclude that titanium dioxide nanoparticles are not a major ionoregulatory toxicant, or haemolytic, at the concentration and exposure times used. Respiratory distress is a concern and sub-lethal toxicity involves oxidative stress, organ pathologies, and the induction of anti-oxidant defences, such as glutathione.

The SWIFT periphyton test for high-capacity assessments of toxicant effects on microalgal community development

The SWIFT periphyton test was developed as a simple and high-capacity approach for assessing toxicant effects on the succession of natural communities. Attached microbial communities (periphyton) were developed over a 7 to 9 day period on artificial glass substratum submerged at sea and then transferred to a controlled indoor environment for 4 day incubation with toxicants. Added nutrients and continuous light over the test phase facilitated periphyton growth and consequently accelerated the rate of ecological succession. The structure and physiology of the algal community can be analysed using any suitable method. In this paper we suggest HPLC-based analyses of community pigment profiles as a fast and less laborious alternative to e.g. microscopic species counts. Several crucial properties of the SWIFT test were evaluated: the biological complexity of the periphyton used for testing, the consequences of the 4 day incubation under artificial conditions, toxicant effects on community structure and the feasibility of using pigment profiles as descriptors of periphyton communities. The performance of SWIFT as an ecotoxicological test system was evaluated using the three antifouling agents irgarol 1051, Sea-Nine™ 211 (DCOIT) and TBT (tri- n-butyltin). Periphyton communities used in SWIFT were of high taxonomic richness and diversity, and there were no indications for adverse changes in these characteristics over the 4 day test phase. Community pigment profiles discriminated between different communities with a resolution equally good to microscopic species counts. Comparative concentration–response studies with a two-week microcosm experiment and SWIFT revealed similar concentration and toxicant-dependent shifts in the relative abundances of species. This shows that despite the methodological simplifications in SWIFT, crucial ecological features such as competition and species sensitivity profiles were still the major factors determining the ecological succession under toxicant exposure. The sensitivity of SWIFT was equal to that of the flow-through microcosms for irgarol and TBT and lower for DCOIT, probably because of the semi-static test regime in SWIFT. Species composition and pigment profiles over seasons, together with toxicant-induced effects on the diatom xantophyll cycle and the relative content of beta-carotene, shows that pigment profiles reflect both the taxonomy and the physiology of a community. Similar to encountered changes in species composition, pigment profiles were specifically influenced by the tested toxicants.

A protocol for conducting 7-day daily renewal tests with Lemna gibba

Lemna gibba (a duckweed) is a freshwater macrophyte commonly used in toxicity testing, and Lemna spp are currently the only aquatic higher plants required for evaluation of pesticides under the pesticide registration guidelines of the EPA. The methods currently available for toxicity testing by various organizations and agencies, including ASTM, OECD, EPA and Environment Canada, are largely static or semistatic tests with unspecified renewal intervals (OECD) and may not provide a consistent means of exposure owing to short toxicant half-life in aquatic media, uptake of chemical by plants and evaporation of nutrient media. The procedure outlined here details a simple and efficient 7-day daily static renewal procedure for conducting toxicity tests with L. gibba, the appropriate end points to assess, the statistical criteria necessary for analyzing the toxicity data, as well as the steps required to culture and maintain L. gibba. This protocol is based on a modified version of a widely accepted static method.

Toxicity of single walled carbon nanotubes to rainbow trout, ( Oncorhynchus mykiss): Respiratory toxicity, organ pathologies, and other physiological effects

Mammalian studies have raised concerns about the toxicity of carbon nanotubes (CNTs), but there is very limited data on ecotoxicity to aquatic life. We describe the first detailed report on the toxicity of single walled carbon nanotubes (SWCNT) to rainbow trout, using a body systems approach. Stock solutions of dispersed SWCNT were prepared using a combination of solvent (sodium dodecyl sulphate, SDS) and sonication. A semi-static test system was used to expose rainbow trout to either a freshwater control, solvent control, 0.1, 0.25 or 0.5 mg l −1 SWCNT for up to 10 days. SWCNT exposure caused a dose-dependent rise in ventilation rate, gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus secretion with SWCNT precipitation on the gill mucus. No major haematological or blood disturbances were observed in terms of red and white blood cell counts, haematocrits, whole blood haemoglobin, and plasma Na + or K +. Tissue metal levels (Na +, K +, Ca 2+, Cu, Zn and Co) were generally unaffected. However some dose-dependent changes in brain and gill Zn or Cu were observed (but not tissue Ca 2+), that were also partly attributed to the solvent. SWCNT exposure caused statistically significant increases in Na +K +-ATPase activity in the gills and intestine, but not in the brain. Thiobarbituric acid reactive substances (TBARS) showed dose-dependent and statistically significant decreases especially in the gill, brain and liver during SWCNT exposure compared to controls. SWCNT exposure caused statistically significant increases in the total glutathione levels in the gills (28%) and livers (18%), compared to the solvent control. Total glutathione in the brain and intestine remained stable in all treatments. Pathologies in the brain included possible aneurisms or swellings on the ventral surface of the cerebellum. Liver cells exposed to SWCNT showed condensed nuclear bodies (apoptotic bodies) and cells in abnormal nuclear division. Overt fatty change or wide spread lipidosis was absent in the liver. Fish ingested water containing SWCNT during exposure (presumably stress-induced drinking) which resulted in precipitated SWCNT in the gut lumen and intestinal pathology. Aggressive behaviour and fin nipping caused some mortalities at the end of the experiment, which may be associated with the gill irritation and brain injury, although the solvent may also partly contributed to aggression. Overall we conclude that SWCNTs are a respiratory toxicant in trout, the fish are able to manage oxidative stress and osmoregulatory disturbances, but other cellular pathologies raise concerns about cell cycle defects, neurotoxicity, and as yet unidentified blood borne factors that possibly mediate systemic pathologies.

Toxicity assessment of polycyclic aromatic hydrocarbons using an air-tight algal toxicity test

The existing toxicity data on the effects of polycyclic aromatic hydrocarbons (PAHs) on Pseudokirchneriella subcapitata (green alga) are quite insufficient. These data were derived using different test techniques (e.g. conventional batch test, closed-system test, semi-static test). The relative toxicity relationship for various PAHs is thus difficult to interpret. Consequently, the current toxicity database is insufficient and also inadequate for analyses of the effects of PAHs on P. subcapitata. This study evaluated the toxicity of eleven PAHs using an air-tight test technique. The relative toxicity relationship was determined on a uniform basis, and was different from the relationship based on current available data. P. subcapitata. was found to be more susceptible to PAHs than Daphnia magna, fathead minnow, and Scenedesmus subspicatus. Quantitative structure-activity relationship (QSAR) was established based on the chemical's hydrophobicity with R(2) equal to 0.88. Photo-induced toxicity for various PAHs was also explored by exposing PAHs under UV-photoactivation. Toxicity of anthracene, benzanthrone, and benzo[a]anthracene was found to increase 3.5 to 25 times after UV exposure. Phototoxicity was observed when the HOMO-LUMO gap varied between 6.8 and 8.0 eV.

Acute toxicity to freshwater organisms of antiparasitic drugs for veterinary use

The acute toxicity of five antiparasitic drugs used in the veterinary field-amprolium hydrochloride (APH), bithionol (BT), levamisole hydrochloride (LVH), pyrimethamine (PYM) and trichlorfon (TRC)-to the aquatic organisms Oryzias latipes, Daphnia magna, and Brachionus calyciflorus was examined. The toxicity test with O. latipes was conducted in accordance with the OECD Guidelines for the Testing of Chemicals (1993) to determine the 24-, 48-, 72-, and 96-h LC(50) values. In addition, 24- and 48-h EC(50) values for D. magna and a 24-h EC(50) for B. calyciflorus were determined with the DAPHTOXKIT F(trade mark) magna (Creasel, Belgium) and the ROTOXKIT F(trade mark) (Creasel, Belgium), respectively. High-performance liquid chromatographic analysis revealed that APH, LVH, and PYM were stable in water, but BT was unstable, decreasing by 84% on average at 24 h. TRC rapidly decomposed, with only 0.7% of the initial concentration remaining after 96 h, forming dichlorvos. The toxicity of TRC to O. latipes was determined in two ways: exposure to the same medicated water for 96 h (static test) and exposure to medicated water replaced every 24 h (semistatic test). AMP, LVM, and PYM were tested in the static condition, and BT was tested in the semistatic condition. BT was most toxic to O. latipes, with a 96-h LC(50) of 0.24 mg L(-1), followed by PYM, with a 96-h LC(50) of 5.6 mg L(-1). The 24-, 48-, 72-, and 96-h LC(50) values of TRC in the static test were 92.0, 45.2, 29.5, and 17.6 mg L(-1), respectively, which tended to be lower than those in the semistatic test, especially late in the observation period. D. magna was the most susceptible to TRC, with a 48-h EC(50) as low as 0.00026 mg L(-1). The 48-h EC(50) values of BT, PYM, and LVH for D. magna were 0.3, 5.2, and 64.0 mg L(-1), respectively. B. calyciflorus was the most susceptible to BT, with an EC(50) of 0.063 mg L(-1), followed by PYM, with an EC(50) of 15.0 mg L(-1). Among the test compounds, APH was the least toxic to all the freshwater organisms tested, with a 96-h LC(50) of >600 mg L(-1) for O. latipes, a 48-h EC(50) of 227 mg L(-1) for D. magna, and an EC(50) of 403 mg L(-1) for B. calyciflorus.

The effects of endosulfan on the great ramshorn snail Planorbarius corneus (Gastropoda, Pulmonata): a histopathological study

In this study the great ramshorn snail ( Planorbarius corneus), one of the most abundant gastropod of Turkish limnic systems, was investigated to determine the histopathological effects of endosulfan on the digestive gland, foot and mantle under laboratory conditions. Samples were collected from small artificial pools in Karaot at Gelendost-Isparta (Southwest of Turkey), where agricultural activities are widespread. The snails were exposed to two sublethal concentrations of endosulfan (0.4 and 0.8 mg/l) for periods of 10, 20 and 30 days. Fifteen snails were kept in 2.5 l glass jars containing dechlorinated tap water and exposed under semi-static test (daily exchange of test water). All the testing was carried out on adult specimens, and snails were maintained on a photothermal period with 16 light hours at 22 ± 2 °C. The histopathological examinations revealed the following changes: amoebocytes infiltration, dilatation in hemolymphatic spaces between the tubules, degeneration of cells, abnormal lumen, necrosis of cells and atrophy in the connective tissue of digestive gland; desquamation of the epithelium cells, changes in the number of mucocytes and protein gland cells, lipid vacuolus and atrophy of the columnar muscle fibers of the foot and mantle tissues. Pycnotic state of cells was also seen in the mantle tissues. Endosulfan caused significant histopathological alterations in the digestive gland, foot and mantle tissues of the snail, irrespective of concentrations of the pesticide and its exposure periods. The results are discussed, particularly in comparison to those of other aquatic organisms.

Histopathological responses of newly hatched larvae of whitefish ( Coregonus lavaretus s.l.) to UV-B induced toxicity of retene

Positively phototactic fish larvae may be exposed to increased ultraviolet-B (UV-B) radiation alone or, potentially and in addition, to polycyclic aromatic hydrocarbons (PAHs) such as retene (7-isopropyl-1-methylphenanthrene) at the egg or larval stages. Suspended and sedimental particulate material near pulp and paper mills may act as sources of retene in chemically contaminated lake areas. In laboratory conditions whitefish larvae were pre-exposed to retene (10, 32 and 100 μg/l), with relevant controls, and irradiated in semi-static tests for 3 h once a day (2 consecutive days) with two UV-B doses (CIE-weighted 2.8 or 5.4 kJ per m 2 per day) or with visible light only. These UV-B doses correspond with slightly subambient and 80% increases relative to the natural maximum daily doses of the solar UV-B in Finland in early May. The UV-B radiation alone increased mortality only slightly (2.7 and 4.0%, respectively). Similarly, no mortality was observed due to retene alone. On the contrary, simultaneous UV-B and retene exposure caused very high mortality to whitefish and all larvae died in the highest retene concentration. The photoinduced acute LC 50 for retene was 13.3 μg/l. Retene treated fish exhibited signs of behavioral irritation and hypoxia during and after the exposure to UV light. Severe skin damages were detected in larvae exposed simultaneously to retene and UV-B. The structural signs of sunburn could also be seen in UV-B and solvent controls (DMSO) with UV-B. Even at the lowest retene concentration, the number of mucous cells increased significantly in simultaneous chemical and UV-B treatment. We consider the tissue reaction as protective response against UV induced retene toxicity. Further, regarding liver parenchyma, fish exposed to retene with UV-B had lesions, revealing hepatotoxicity. We suggest that synergism of the UV-B radiation and the photoactivating pollutants such as retene is a potential risk factor to be taken into consideration in lake areas chemically contaminated by the pulp and paper industry.

Effects of endocrine modulating substances on reproduction in the hermaphroditic snail Lymnaea stagnalis L

Various man-made agents like pesticides, industrial chemicals and some natural substances have the potential to alter hormonal pathways that regulate reproductive processes in certain species of wildlife. Until now, only a few investigations have been undertaken to determine the effects of these substances on reproductive capacities (fecundity and fertility) in exposed invertebrate aquatic species. In this study one of the most abundant mollusc of European limnic systems, the hermaphroditic gastropod Lymnaea stagnalis was investigated to determine the effects of endocrine modulating substances on reproductive parameters. Known endocrine modulating substances were tested using the following nominal concentrations; Tributyltin (TBT in ng Sn/l) and β-sitosterol at 1, 10 and 100 ng/l, respectively, and 4-nonylphenol (4-NP) at 1, 10 and 100 μg/l. In addition, experiments were carried out with 1, 10 and 100 ng/l of t-methyltestosterone. All the testing was carried out on recently matured adults of Lymnaea. Fifteen to twenty snails per treatment were exposed for between 7 and 12 weeks in a semi-static test with a weekly exchange of testwater. Shell height and weight and mortality of the adults, egg production, hatching rate of the eggs, and histopathology of the adult snails were analysed. The same parameters were investigated on F 1 generation snails from exposed parents at two dates (1 week after exposure and at the end of the exposure duration). Treatments with TBT and 4-NP had only slight effects on the egg production of the adults and hatching rate of the eggs. However, increased histopathological changes were observed in epithelial tissues of the adult snails, e.g. lung and foot also characterised by extreme inflammatory processes. While β-sitosterol and t-methyltestosterone had no effect on the shell height and weight or the mortality of adult snails nor on the egg production or ensuing egg hatching rate, β-sitosterol treated snails presented a distinct atrophy of the albumen gland and so did t-methyltestosterone, albeit with a lower degree of atrophy. The observed histopathological effects due to exposure to tributyltin or 4-NP are suggested to lead to long-term adverse reproductive effects mediated by an impairment of the fitness of the snails. In the experiments the steroid-dependant (β-sitosterol and t-methyltestosterone) degeneration of the albumen gland caused no obvious adverse effects on the fecundity nor fertility of the adults or on F 1-generation. However, the impact on fertility following a prolonged exposure to high concentrations of the phytoestrogen cannot be predicted.

Internal lethal concentration and internal lethal volume fraction of chlorobenzenes in mosquito fish ( Gambusia affinis)

The internal lethal concentration (ILC) and internal lethal volume fraction (ILVF) of a series of chlorobenzenes with mosquito fish ( Gambusia affinis) were measured by a semistatic test approach in closed jars. Their variation with exposure times were also investigated. With different aqueous chemical concentrations and different exposure periods, the measured ILC values on wet weight and lipid weight bases ranged from 3–12 mmol kg −1 and 46–208 mmol kg −1 lipid, respectively. Measured ILVF values covered a range from 0.008-0.025 (L toxicant L −1 lipid). These values are consistent with those found in literature. Generally ILC and ILVF values decreased with increasing exposure time with rate constants ranging from 0.03 to 0.33 day −1 (wet and lipid weight) for ILC and 0.03 to 0.31 day −1 for ILVF.

Acute and Subacute Toxicity of Atrazine to Carp (Cyprinus carpio L.)

Investigations of acute and subacute atrazine toxicity in carp (Cyprinus carpio L.) were carried out. Acute toxicity was investigated in a semi-static test during a 96-hr exposition. The estimated LC-50 value was 18.8 mg/l. Subacute toxicity was investigated by exposing fish (carp) to different atrazine concentrations (1.5, 3.0, and 6.0 mg/l) for 14 days. Biochemical and histopathological changes in certain organs and tissues were investigated. The results show that atrazine leads to changes of varying intensity depending on the parameter tested, the organs and tissues examined, as well as the atrazine concentration. Biochemical changes were most prominent in the alkaline phosphatase, glutamic-oxaloacetic transaminase, and glutamic-pyruvic tranaminase activities whereas the most severe histopathological changes were observed in the gills.

Lethal and sublethal threshold values of aluminium and acidity to pike ( Esox lucius), whitefish ( Coregonus lavaretus pallasi), pike perch ( Stizostedion lucioperca) and roach ( Rutilus rutilus) yolk-sac fry

The newly-hatched fry of four fish species were exposed for 10 days in semistatic tests at pH values of 4.00–6.00 to AI at nominal concentrations of 0–800 μg 1 −1. Test waters were made in lake water (Ca 0.11 mmol 1 −1 by adding H 2SO 4 and Al 2(SO 4) 3. Based on the observations on mortality (LC 50) and swimming activity (EC 50), the four species had the following ranking for their sensitivity to acidity and Al: roach > pike perch > whitefish > pike. At the end of the 10-day test the LC 50 and EC 50 values of Al were identical for the most sensitive species, roach, whereas those for pike and whitefish were significantly different at that time. Al and low pH clearly retarded pike and roach yolk-sac fry growth, which was coincident with a slower absorption of the yolk. Al decreased pike growth at pH values ≤ 5.25 and roach growth even at pH 5.75. In whitefish, which have a small yolk sac; the effects of pH and Al on growth were not so clear. In general, the more Al the water contained, the more toxic was the acidic water. The threshold pH values (lowest pH for survival and safe pH) for the four species were, depending on the Al concentration: pike 4.0–5.3 whitefish 4.5–5.5 pike perch 4.8–5.8 and roach 5.0–6.0.

Toxicity of endosulfan to native and introduced fish in Australia

AbstractSemistatic bioassays of endosulfan with native and introduced Australian fish indicated that they are sensitive to this insecticide at low concentrations. The introduced European carp (Cyprinus carpio) was the most sensitive species, with a measured 96‐h LC50 of 0.1 μg/L, whereas the native eastern rainbow fish (Melanotaenia duboulayi) and silver perch (Bidyanus bidyanus) were the least sensitive, with measured 96‐h LC50 values of 2.4μg/L. The measured 96‐h LC50 values of endosulfan for bony bream (Nematolosa erebi), golden perch (Macquaria ambigua), and rainbow trout (Oncorhynchus mykiss) were 0.2, 0.5, and 1.6 μ/L, respectively. Toxicities of endosulfan in Sydney mains water and Mehi River water were similar when rainbow fish, golden perch, and silver perch were used as test animals. The initial measured concentration was about 42% of the nominal concentration, whereas final measured concentration after 24 h in semistatic tests declined to 5.6% of the nominal concentration. The toxicity of endosulfan was similar in Australian native and introduced fish and in overseas fish, but varied markedly with test method. The 96‐h LC50 values for one species, the rainbow fish, varied from 0.5μg/L when reported as measured concentrations in a flow‐through test to 11.4 μg/L as nominal values in a static test. These differences span much of the variation found in 96‐h LC50 values for all fish species described in the world literature.

Bioconcentration of polycyclic heteroaromatic hydrocarbons in the guppy ( Poecilia reticula)

Bioconcentration factors (BCFs) of 19 parent and hetero polycyclic aromatic hydrocarbons (PAH) were obtained from static bioconcentration experiments with Poecilia reticulata by monitoring the decrease in the initial aqueous concentration. The BCFs were obtained by fitting the observed concentrations to a one-compartment first-order kinetic model. The BCFs thus obtained showed a satisfactory linear relationship with the experimental n-octanol/water partition coefficient, log K ow ( r = 0.91, s = 0.30). By comparison with a limited number of semi-static tests, it was concluded that the static bioconcentration experiment is a satisfactory alternative for more laborious bioconcentration tests to obtain BCFs of (hetero) PAH. However, the static tests are less valuable for the acquisition of kinetic bioconcentration parameters such as, e.g., uptake or elimination rate constants. For several of the compounds in this study, the estimates resulting from the static tests did not match with those from a limited number of depuration experiments carried out in this study or with values expected from the relationship between the depuration rate constant and the log K ow, reported in the literature. The distribution of three parent PAH within the fish after a 7-day semi-static exposure was also investigated. Relatively high concentrations were found in liver and kidneys. The major part of the body burden was found in muscle and the gastro-intestinal tract.

Bulk sediment bioassays with five species of fresh-water oligochaetes

A semistatic test procedure was developed to measure the toxicity of contaminated sediments. Tubifex tubifex, Limnodrilus hoffmeisteri, L. udekemianus, L. claparedeanus, and Potamothrix hammoniensis were cultured in unpolluted and variously polluted lake sediments for 0.5 to 1.5 yr at c. 20 °C with and without additions of food. Growth and reproduction were generally affected earlier than survival in sediments polluted by heavy metals. The worms were generally much more sensitive to pollutants in sediments from oligotrophic to mesotrophic lakes than m those from eutrophic lakes. Addition of food weakened the response to pollutants.

Influence of aquatic humus on the bioavailability of chlorinated micropollutants in Atlantic salmon.

The possible influence of natural humic water on the uptake of 2,4,6-trichlorophenol, tetrachlorguaiacol, lindane and 2,4′,5-trichlorobiphenyl in Atlantic salmon underyearlings has been studied, using a semistatic test procedure. Springtime humus water reduced the bioconcentration factors for both the 2,4,6-trichlorophenol and lindane about 18 percent compared to lake water. No reduction in the bioconcentration factor was observed for tetrachloroguaiacol. Autumn humus water reduced the bioconcentration factor of 2,4′,5-trichlorobiphenyl 30 percent compared to lake water, while no reduction was observed for lindane. The results have shown that natural humus water can reduce the bioavailability of organic micropollutants towards fish. The effect is different for different compounds and also depends on the nature of the humus.