Depression of feeding and growth rates of the seastar Evasterias troschelii during long-term exposure to the water-soluble fraction of crude oil

To test the effect of petroleum hydrocarbons on predation by the seastar Evasterias troschelii (Stimpson, 1862) on the mussel Mytilus edulis (L.), we exposed the predator with the prey to six concentrations of the water-soluble fraction (WSF) of Cook Inlet crude oil. Seastars and mussels were collected at Auke Bay, Alaska, in November 1980. During a 28 d exposure in a flow-through system, seastars were more sensitive to the WSF than mussels: the LC₅₀ for the seastars was 0.82 ppm at Day 19 and, although no mussels were exposed to WSF for more than 12 d, none died. Daily feeding rates (whether in terms of number of mussels seastar^-1 d^-1 or dry weight of mussels seastar^-1 d^-1) were significantly reduced at all concentrations above 0.12 ppm. At 0.20, 0.28 and 0.72 ppm WSF, daily feeding rates (in terms of dry weight of mussels) were, respectively, 53, 37, and 5% of the control rate; at the two highest concentrations (0.97 and 1.31 ppm WSF), the seastars did not feed. Seastars at concentrations greater than 0.12 ppm WSF grew slower than individuals from the control group and the 0.12 ppm-treatment group combined. These laboratory results show that E. troschelii is more sensitive to chronic low levels of the WSF of crude oil. The possibility that such oil pollution could reduce predation and permit M. edulis to monopolize the low intertidal zone of southern Alaska remains to be studied.     

Accumulation of cadmium in the mussel Mytilus edulis: kinetics and importance of uptake via food and sea water

In a short-term (162 h) accumulation experiment with mussels Mytilus edulis exposed to 100 ppb Cd and fed algal cells (Phaeodactylum tricornutum) in 1986, it was found that uptake via food played an insignificant role compared to direct uptake from ambient water (19 S). From measurements of the filtration rate and Cd uptake rate, it was estimated that the fraction of Cd taken up per liter of water filtered was about 0.15%. The initial uptake of Cd was linear with time and about three times higher in fed than in starved mussels. From the measured uptake of Cd in starved mussels collected in 1982 and exposed to 10, 100 and 200 ppb in long-term experiments (up to 242 d), it was found that the Cd Accumulation rate was not linear with time, and that the Cd uptake was not directly proportional with the exposure concentration. Values as high as 100 to 1 300 ppm Cd (dry wt of soft parts) were measured. It was found that the Cd elimination rate was not directly proportional with the Cd body burden in long-term exposed mussels, thus indicating that a certain fraction of Cd may have been immobilized to metallothioneins.     

Formation of metallothioneins in relation to accumulation of cadmium in the common mussel Mytilus edulis

Accumulation rates of Cd have been studied in the common mussel Mytilus edulis L. under different laboratory conditions. Semi-static and through-flow experiments were carried out at Cd concentrations of 200 ppb and 50/100 ppb in the water, respectively. A linear uptake of Cd throughout the experimental periods of 36 or 124 d was found in all experiments. The accumulation rate was 3.10 ppm d^-1 at 50 ppb in the through-flow water experiment, 4.1 ppm d^-1 in starved and 6.6 ppm d^-1 in fed mussels in the semi-static experiments with 200 ppb Cd in the water. The Cd-accumulation rate in various fractions of soft parts decreased in the order: body>mantle>muscles. Elution patterns obtained from gel-filtrations showed an increasing amount of Cd-binding proteins (metallothioneins) when the body burden of Cd increased. The Cd content in the body fraction of mussels transferred to clean water for 42 d after first being exposed to Cd during 124 d decreased from 564 ppm on a dry weight basis to 417 ppm while the fraction of Cd bound to metallothioneins rose from 22 to 78% during the same period.     

The assimilation and chronic effects of sub-lethal concentrations of Endosulfan on condition and spawning in the common mussel Mytilus edulis

The rate of uptake of Endosulfan by Mytilus edulis L. exposed to pesticide concentrations of 0.1, 0.5, and 1.0 mg/l, and its subsequent elution on removal to clean sea water, was investigated. Higher residue levels were recorded for mussels exposed to higher concentrations of the pesticide, but concentration factors were reduced. There was a rapid initial fall in tissue residue levels on transfer to clean sea water due, it is suggested, to elution of Endosulfan adsorbed on particulate matter assimilated in the gut. The spawning period was prolonged at higher concentrations and, at 1.0 mg/l, the onset of spawning was delayed, possibly due to interference with gamonic action. At 0.1 mg/l, the minor protraction of the spawning period may reflect the effect of experimental tank conditions. No seasonal trend was obvious, and there was an exaggeration of the expected fall in condition in mussels exposed to higher concentrations of Endosulfan. In controls, the expected seasonal trend was reduced.     

Role of the kidney in determining the whole soft tissue zinc concentration of individual mussels (Mytilus edulis)

Mussels (Mytilus edulis) were collected from an unpolluted site in Newfoundland in 1984 and 1985 in order to determine the zinc levels of the whole soft tissues and individual organs. Individuals were collected in such a way as to eliminate all known physiological and environmental factors which might have led to differences in zinc concentration between individual mussels. The inherent variability of the whole soft tissue zinc concentration was found to be very high with a coefficient of variation (CV) around 40%. Most individual organs had relatively low mean zinc concentrations with small values for CV (10–18%). However, the kidney showed a relatively high mean zinc concentration (828 ppm) with a remarkable degree of variability (94–3 410 ppm) (CV=78%) and is responsible not only for the high degree of inherent variability in the population but also for the high levels of zinc found in the whole soft tissue of some individual mussels. Those individuals with high whole soft tissue zinc concentrations often had high kidney zinc concentrations and stored as much as 53% of their zinc load in the kidney (which accounted for only 1–3% of the total weight). However, other individual mussels with low whole soft tissue zinc concentrations had low kidney zinc concentrations and stored as little as 3% of their body zinc load in the kidney. Hence, the role that the kidney plays in zinc storage varies markedly from mussel to mussel.M.S.R.L. Contribution No. 624     

Toxizität und anreicherung von blei bei der miesmuschel Mytilus edulis im laborexperiment

In a laboratory experiment, conducted over 130 days, three batches of a total of 100 common mussels, Mytilus edulis, were maintained in media containing different lead concentrations. Two vessels served as controls. There was no acute injury to the mussels; but, over an extended period of time, a marked increase in mortality occurred which was related to the lead concentration in the medium. The median lethal time (LT₅₀) was computed to be 218 days for the control, 150 days with 0.5 mg Pb/l in the medium, 129 days with 1 mg/l, and 105 days with 5 mg/l. Quantitative analyses of the soft parts of M. edulis by flameless atomic-absorption-spectrophotometry revealed a distinct accumulation of lead. From a natural lead content of 8.4 μg Pb/g dry weight, the lead concentration increased to 12,840 μg/g at 0.5 mg/l, to 20,770 μg/g at 1 mg/l and to 39,830 μg/g at 5 mg/l. The ratio of the concentration of lead in the soft parts of M. edulis to the concentration in the medium remained in the same order of magnitude both under laboratory conditions using high lead concentrations and under in situ lead levels. Over a period of 130 days, lead uptake expressed as percentage of lead offered was 10.9% at 0.5 mg/l, 9.5% at 1 mg/l, and 3.4% at 5 mg/l, respectively.     

Prototype design for a closed marine system employing quarternary water processing

A small 2, 271-1 (600-gallon) prototype recirculating marine water system was designed and evaluated (26 months). The system employed a quaternary (mechanical, algal, bacterial and chemical) series of processing units with the aim of achieving long-term seawater quality and constancy without water replacement. Total ammonia (0.05±0.005 ppm), un-ionized ammonia (0.0036±0.0003 ppm), nitrite (0.10±0.014 ppm), nitrate (24.6±2.0 ppm), phosphate (14.0±2.1 ppm), dissolved oxygen (6.5–7.2 mg/l) and pH (7.80 to 8.25) were maintained at acceptable levels for the entire period. The biomass load (1.82 kg/397 l) consisted of 4 nurse sharks which were fed ad-lib twice a week. Further, low levels of total bacteria (1.5×102 bacteria/ml) and coliforms [most probable number (MPN) index 17/dl] were present in the seawater. The system design is suggested for use in laboratory and mariculture installations.     

Removal of malachite green from water samples by cloud point extraction using Triton X-100 as non-ionic surfactant

A surfactant mediated cloud point extraction (CPE) procedure has been developed to remove color from wastewater containing malachite green using Triton X-100 as non-ionic surfactant. The effects of the concentration of the surfactant, temperature and salt concentration on the different concentrations of dye have been studied and optimum conditions were obtained for the removal of malachite green. The concentration of malachite green in the dilute phase was measured using UV–Vis spectrophotometer. It was found that the separation of phases was complete and the recovery of malachite green was very effective in the presence of NaCl as an electrolyte. The results showed that up to 500 ppm of malachite green can quantitatively be removed (>95%) by CPE procedure in a single extraction using optimum conditions.     

Microprofiles of oxygen in epiphyte communities on submerged macrophytes

Mussels (Mytilus edulis) transferred in net bags from clean to chronically mercury polluted water readily accumulated mercury during an exposure period of three months. Growth of the transplanted mussels had a diluting effect on the mercury concentration, but the absolute weight of mercury uptake increased throughout the entire period, though there was a tendency for decreased efficiency of the removal of mercury per liter of water filtered by the mussels. Mussels were also translocated from polluted to clean (laboratory) water to depurate mercury. The biological half-lives of mercury was 293 d for M. edulis from the chronically polluted area in contrast to only 53 d for mussels from a temporary massive mercury polluted area near a chemical deposit. In both cases about 75% of the total mercury in the mussels was inorganic, and it is suggested that both inorganic and organic mercury species were immobilized in mussels from the long-term mercury polluted area, whereas the immobilization capacity was exceeded in the short-term mercury exposed mussels near the chemical deposit. Very slow elimination of mercury was observed in the deposit-feeding bivalve Macoma balthica from the chronically polluted area, and about 6% of the total mercury was methyl-+phenyl-mercury. This is more than three times lower than found in M. edulis from the same collecting site. A pronounced difference in the mercury speciation (i.e., total mercury, total organic mercury, methyl-mercury and phenyl-mercury) in M. edulis from the two mercury polluted areas is thought to reflect the different character of the mercury pollution in the two areas.     

Studies on factors affecting survival of nile fish in the Sudan. III. The effect of oxygen

Tilapia nilotica L. were exposed to different levels of ambient oxygen concentrations for 24 h periods. Nitrogen was bubbled through the water to reduced the oxygen concentration to the respective test level. When testing concentrations of oxygen between 2.5 and 0.4 ppm over 24 h periods of exposure, the median tolerance limits (TLM) over 24 h were attained at 1.41 ppm of oxygen.     

Assessment of deposition of MEMC (seed dressing fungicide) in exposed rice grain through study of seedling growth parameters

Rice seed grains exposed to 240 ppm of seed dressing fungicide, MEMC showed increase in deposition of mercury with increase in period of observation (0h to 48h) in 765+/-5 mg of intact endosperm. The gradual increase in mercury deposition in intact endosperm caused simultaneous decrease in mercury content of the seed coat. Exposure periods of 5 to 20 min with 240 ppm of MEMC showed 5.5 to 8.72 microg of mercury deposition in 765+/-5 mg of intact endosperm. Increase in period of exposure (3 to 20 min) to 240 ppm of MEMC and also increase in chronic treatment to lower concentrations (1.5 ppm to 24 ppm) to seed grains have shown similar results in seedling growth parameters. Lower period of exposure or exposure to lower concentrations, both showed a significant inhibition of root growth, however the shoot growth showed stimulation. But higher exposure period or exposure to higher concentrations brought inhibition of both root and shoot growth. The exposure period showing 50% of root growth inhibition of 72h old seedling was calculated to be 10 min So also the chronic treatment showing the 50% of root growth inhibition was calculated to be 9 ppm. Ten min exposure of rice grain to 240 ppm of MEMC showed deposition of 7.11 microg of mercury in 765+/-5 mg of intact endosperm at 48h of observation (optimal phase of germinating process). Regression analysis indicated that by the time of 72h the intact endosperm and developing seedling might have acquired with a minimum amount of 10.23 microg of mercury from the seed coat. Finally it can be said that 10.23 microg of MEMC might be bringing 50% root growth inhibition in 72h old seedlings and 16.71 microg of mercury causing 50% inhibition of both root and shoot growth of 120h old seedlings.     

Accumulation and release of fuel-oil-derived diaromatic hydrocarbons by the polychaete Neanthes arenaceodentata

Male and gravid female Neanthes arenaceodentata (Moore) (Polychaeta: Annelida) were experimentally exposed to a sublethal concentration of No. 2 fuel oil seawater extract for 24 h. Within 1 h both sexes had incorporated, in equal proportions, most of the diaromatic hydrocarbons (naphthalene, methylnaphthalenes) eventually accumulated. No net loss of accumulated naphthalenes was observed during the exposure period. When returned to hydrocarbon-free seawater, male worms slowly released naphthalenes down to undetectable (< 0.1 ppm) levels in 400 h (17 days). Gravid females retained essentially all of the originally accumulated naphthalenes for 3 weeks, at which time they released their eggs during fertilization, with subsequent dramatic decreases in naphthalenes content. Zygotes and trochophore larvae from exposed females contained 18 ppm naphthalenes, accounting for a majority of those amounts initially present in parent females. As trochophore larvae developed into 18-segment juveniles, naphthalenes concentrations dropped to near undetectable levels (0.4 ppm) in 21-day old juveniles (= 18-segment worms). When sampled at the next stage of development (32-segment worms) 5 days later (1050 h after exposure of gravid females), offspring were free of naphthalenes. Results suggest the importance of lipid-rich eggs in the accumulation and retention of diaromatic hydrocarbons by marine polychaetes.     

Neurotoxicity and oxidative stress induced by permethrin in gills of the freshwater mussel Unio ravoisieri

Pyrethroids are contaminants found in the aquatic environment, and their toxicological effects on aquatic organisms have received extensive attention. However, the impact on freshwater bivalve of exposure to these chemicals is still largely unknown. Freshwater mussels Unio ravoisieri were exposed to two nominal permethrin (PM) concentrations C1?=?50?µg/L and C2?=?100?µg/L during 7 days. The measured concentrations of PM using gas chromatography (GC/ECD) in the treated aquariums were, respectively, 28.7–62.3?µg/L. Catalase (CAT), Glutathione-S-transferase (GST), and Acetylcholinesterase (AChE) activities, Glutatione (GSH) and Malondialdehyde (MDA) levels were determined in gills of U. ravoisieri. Significant increase in CAT activity by the lowest concentration and decrease by highest concentration were observed. Additionally, GST activity was increased in a concentration-dependent manner. However, statistically significant decrease in GSH levels (about 39%) was observed only at high concentration of this compound (100?µg/L). PM generated an increase in MDA levels reaching the highest value at the high concentration. AChE activity of mussel ranging from 51% inhibition at lowest concentration 50?µg/L to 89% inhibition at highest concentration 100?µg/L. The results indicated that oxidative stress and cell damage might be one of the main mechanisms of PM toxicity to freshwater mussels.     

Effects of the juvenile hormone mimic ZR-512 (Altozar®) on larval development of the mud-crab Rhithropanopeus harrisii at various cyclic temperatures

Effects of the juvenile hormone (JH) mimic hydroprene (Altozar^®: ZR-512), which exhibits high activity against Lepidoptera, were studied on the larval development of the mud-crab Rhithropanopeus harrisii (Gould) (Brachyura: Xanthidae). Larvae reared in 20 S at 3 cycles of temperature of 20° to 25°C, 25° to 30°C and 30° to 35°C, were exposed to 0.01, 0.1 and 0.5 ppm hydroprene from hatching to the first crab stage. Larvae were also exposed to 0.1 and 0.5 ppm hydroprene only from the megalopa stage to the first crab stage. When larvae were treated with hydroprene throughout larval life, survival was significantly reduced with increasing concentrations of the compound at all temperature cycles. Synergistic effect between hydroprene and temperature on survival of zoeal larvae was not observed. On the average there was 11% less survival in the zoeal stages at the 0.01 ppm concentration. of hydroprene than in the control, an additional reduction of 13% occurred at 0.1 ppm, and finally there was a further decrease of 46% at 0.5 ppm hydroprene. Significant decrease in survival in the megalopa stage occurred only in the 0.5 ppm concentration of hydroprene at the lowest temperature cycle when larvae were exposed to the compound from hatching. When larvae were treated with hydroprene only within the megalopa stage, a significant reduction in survival was not observed. First-stage zoeae were the most sensitive of the larval stages to hydroprene. Duration of zoeal development was significantly delayed at 0.5 ppm hydroprene at the two lower temperature cycles, whereas in the megalopa stage the delay began at the 0.1 ppm level at all 3 temperature cycles when larvae were exposed to hydroprene from hatching. A significant delay was also observed at 0.1 ppm hydroprene at the two lower cycles when larvae were exposed to hydroprene only in the megalopa stage; at 30° to 35°C a significant delay was observed only at the 0.5 ppm level. The results show that metamorphosis to the first crab stage was not inhibited at the 0.5 ppm level of hydroprene or lower. Reduction in survival and increase in duration of larval development were presumably related to stress conditions caused by hydroprene. The results also suggest an interaction between temperature and hydroprene on survival of megalopa larvae and duration of larval development.     

Spatial and temporal trends in heavy metal concentrations in mussels from Northern Ireland coastal waters

Data are presented on the heavy metal concentrations in mussels, Mytilus edulis (L), sampled over a 1 yr period (August 1980–August 1981) from Northern Ireland coastal waters. The study was aimed at investigating the spatial extent and temporal trends in heavy metal contamination and highlighting any areas with exceptionally high levels of toxic metals. With the exception of two sites with high values for mercury and chromium, respectively, contamination by metals was relatively low. Significant spatial and temporal differences in the concentrations of several metals were found. There were also significant spatial x temporal interactions for all the metals studied. Significant negative correlations between the percentage dry matter content of mussels and the concentrations of several metals were found. There were also significant positive correlations between certain pairs of metals. It is proposed that small variations in contamination of the marine environment can be detected by subtle differences in the concentration of metals in mussels and that mussel condition may be adversely affected by metal contamination.     

Light and electronmicroscopic studies of the acute and long-term toxic effects of N-nitrosodipropylamine and N-methylnitrosurea on the marine mussel Mytilus edulis

The acute (1) and long-term (2) toxic effects of N-nitrosodipropylamine (NDPA) and N-methylnitrosurea (NMU) were studied by light and electronmicroscopy following injection of the chemicals into the foot of the mussels Mytilus edulis (L.) (1) Mussels reveived one injection of NDPA at concentrations of 0.25, 0.5, 1.0, and 2.0 mg NDPA mussel^-1, and one injection of NMU at concentrations of 0.25, 0.5, 1.0, and 4.0 mg NMU mussel^-1. Within 12d, necrosis of the epithelial lining of the digestive diverticula took place, and the vesicular connective tissue in the digestive diverticula were heavily infiltrated by eosinophilic granular leucocytes. (2) Mussels received four weekly injections of 0.5 mg NDPA mussel^-1, and 0.5 mg NMU mussel^-1. NDPA-exposed mussels were examined for a period of 17 weeks, and NMU-exposed mussels were examined for a period of 24 weeks. Both chemicals produced progressive tissue damage, characterized by destruction of digestive tubules and ducts in the digestive diverticula. Destroyed tubules and ducts were replaced by collagenous scars, and granulocytomas were frequently seen.     

Metallothioneins and lysosomes in metal toxicity and accumulation in marine mussels: the effect of cadmium in the presence and absence of phenanthrene

It has been confirmed that metallothioneins play an important role in the accumulation of cadmium (Cd) in the digestive gland cells of mussels (Mytilus galloprovincialis Lam.). The content of Cd in the tissue of mussels exposed for 9 d to the metal (estimated dosage of 180 g Cd mussel^-1 d^-1) was 66.2 ppm. This value is about the same as the metal content found in the digestive gland of Cd-exposed mussels kept in clean water for a recovery period of 28 d. At the end of the recovery period, however, the Cd bound to thionein had increased by approximately 250%. Our data demonstrate that the stability of lysosomes, a biological parameter adopted as a cellular stress index, is extremely low in mussels exposed to Cd for 9 d, but returns to control values in the digestive gland cells of mussels allowed to recover for 28 d in uncontaminated sea water. At this point most of the Cd present in the cytosol is bound to thionein. These data demonstrate the importance of metallothionein induction in the reduction of the cytotoxic effects exerted by high levels of Cd accumulation. The results of tests designed to clarify the reasons for the long biological half-life of Cd demonstrated that, in the digestive gland of mussels, the lysosomes are not able to eliminate Cd either bound to insoluble thionein polymers or to lipid peroxidation products such as lysosomal lipofuscin, both of which are apparently involved in the elimination of copper. The absence of these two mechanisms of metal sequestration and elimination via excretion of residual bodies (tertiary lysosomes) is in agreement with the persistence of cadmium in the digestive gland of mussels. Finally, the results also demonstrate that simultaneous exposure of mussels to Cd and phenanthrene, an established lysosomal membrane destabilizer, did not significantly alter the accumulation of Cd or the kinetics of the metal in mussels.     

野生及养殖背角无齿蚌中元素的生物积累特征

作为建立渔业生态环境“淡水贝类观察”体系的基础研究之一,以宜兴养殖水域（N=7）和太湖三山岛自然水域（N=7）采集的背角无齿蚌（Anodonta woodiana）为对象,运用电感耦合等离子质谱仪测定了背角无齿蚌软组织中元素Na、K、Ca、Mg、Mn、Fe、Co、Ni、Se、Cu、Cr、Cd的质量分数范围,并对各种元素积累水平的差异进行比较研究。结果表明,两水域中背角无齿蚌对元素的积累高低顺序具有相似的趋势。其中Ca质量分数最高,Co、Cr的质量分数最低,其它元素界于其间。养殖蚌样中的常量元素Na、K、Ca、Mg和微量元素Mn、Co的积累质量分数高于或接近自然水域蚌样中的相应元素,但后者中的重金属元素Cr、Cu、Cd、Ni质量分数显著地高于前者。养殖水域蚌样中的Mg-K、Mg-Ca、Mg-Ni、Mg-Mn、K-Ca、K—Co、K．Mn、Ca—Co、Ca—Ni、Ca．Mn、Ni—Mn、Cr-Co、Cu-Cd以及自然水域蚌样中的Mg—K、Ca-Cr、Ca—Mn、Ca-Ni、Ca-Cd、Cr—Mn、Cr-Ni、Cr-Cd质量分数之间呈现显著的相关性。     

Retrospektives Monitoring von Organozinnverbindungen in biologischen Proben aus Nord- und Ostsee – sind die Anwendungsbeschränkungen erfolgreich?

Background, aim, and scope Organotin compounds are used as biocides, plastic additives and catalysts. With respect to environmental effects, tributyltin (TBT) and triphenyltin (TPT) compounds are the most relevant, because of their high aquatic toxicity and endocrine effects on mussels and snails. TBT was mainly used as antifouling agents in coatings of ships and boats. In 1989, Germany banned the application to ships <?25?m length. Finally, in 2003, the use of organotin-based antifoulants within the European Union was completely banned. To verify the effectiveness of the restrictions a retrospective monitoring study was initiated. Material and methods A set of appropriate archived samples was retrieved from the German environmental specimen bank (ESB) comprising standardized pooled samples of eelpout (Zoarces viviparus) muscle tissue and of soft bodies of common mussels (Mytilus edulis) sampled at two locations in the North Sea and one in the Baltic Sea. Analysis of organotin compounds included n-hexane extraction, derivatisation with sodium tetraethyl borate, capillary gas-chromatographic separation and atomic emission detection. Results and Discussion Altogether, time series cover the period 1985 to 2006, including data of an earlier study (Rüdel et al. 2003). Until the late 1990s, TBT remained more or less constant in all samples (e.?g. 17?±?3?ng/g wet weight, ww, in mussels from Jadebay/North Sea). The German ban of TBT-based antifoulings for small ships had no effects on environmental concentrations because large ships dominate in the investigated North Sea regions. After the EU-wide ban of TBT in 2003, however, significant decreases in mussel and fish contamination could be observed. In mussels from Jadebay, TBT concentrations were 14 and 6?ng/g ww in 2004 and 2005, respectively. TBT contamination in eelpout of the same region decreased to about 30 percent of the initial concentrations in 2006. Corresponding decreases were detected for TPT. Declining trends were also found in fish and mussels sampled from a Baltic Sea offshore site. Conclusions The results demonstrate the effectiveness of the legal measures undertaken to control organotin inputs into the aquatic environment. Nevertheless, organotin compounds are still relevant pollutants. Water concentrations calculated from the measured tissue concentrations by using the respective bioconcentration factors are still above the Environmental Quality Standards derived in the context of the Water Framework Directive (0.2?ng/l) and the OSPAR mussel EAC (Environmental Assessment Criteria; 2.4?ng/g ww). Thus adverse effects to marine organisms cannot be excluded. Recommendations and perspectives Further studies should be performed to verify the declining trends. More sensitive analytical methods, e.?g. species-specific isotope dilution analysis, are recommended in order to detect lower environmental concentrations.     

Biochemical responses and accumulation of cadmium in Spirodela polyrhiza

The present study focused on biochemical responses of Spirodela polyrhiza to cadmium stresses and its accumulation. The laboratory experiments were conducted for the assessment of biochemical responses and accumulation of cadmium in plants at its various concentrations (0.1, 0.5, 1.5 and 2.0 ppm) at the regular interval for twelve days exposure. Spirodela showed visible symptoms like withering of roots and chlorosis at higher concentration (2.0 ppm), however the plant showed normal growth at lower concentration (0.1 ppm). The estimation of biochemical parameters (total chlorophyll, protein and carbohydrate) of test plants showed a significant increase at lower concentration (0.1 ppm) of cadmium. The biochemical changes decrease with increase in exposure concentration and duration. The toxic effect of cadmium is directly proportional to its concentration and duration. The accumulation of cadmium by Spirodela polyrhiza was maximum at four days exposure duration and gradually decreases.