The distribution of cadmium,copper, lead,and zinc in eelgrass (Zostera marina L.)

The distribution of Cd, Cu, Pb, and Zn in eelgrass (Zostera marina L.) was studied at three locations with different heavy metal loads in the Limfjord, Denmark.The eelgrass was fractionated into roots, rhizome, stem, and leaves according to age, and the heavy metal concentrations in each fraction were determined. The distribution patterns of the four heavy metals in eelgrass were independent of the heavy metal loads at the sampling stations. The concentrations of all metals were greater in the roots than in the rhizomes. In the aerial¹ parts two different age-dependent distribution patterns were observed. The concentrations of Cd, Pb, and Zn increased with age while the opposite was true for Cu. The distribution of lead correlated with the distribution of ash content. These age-dependent distribution patterns were maintained throughout the observation period and were most pronounced for Cu and Zn in winter.The heavy metal distribution in eelgrass is discussed in relation to gross morphology, especially age-structure. It is suggested that the accumulation of Cd, Pb, and Zn is due to a slow irreversible uptake or to the existence of more binding sites in old leaves. The distribution of Cu can be explained by translocation within the plant, dilution due to growth or leakage from the older leaves.     

Mechanisms of bioaccumulation of a herbicide (atrazine, s-triazine) in a freshwater mollusc (Ancylus fluviatilis müll.) and a fish (Coregonus fera jurine)

The herbicide atrazine was used to study mechanisms of bioaccumulation in a freshwater mollusc (Ancylus fluviatilis) and a fish (Coregonus fera). Measurements were performed with non-labelled and [¹⁴C]ring-labelled atrazine as well as tritiated water. The kinetics of accumulation indicate that atrazine is accumulated via gills, and that other organs are contaminated via blood.The exchange of atrazine was investigated at the equilibrium state of accumulation. The total residue in organisms is subject to an exchange process; the rates of atrazine accumulation and atrazine exchange are similar. Investigations of the water balance revealed that water exchange in organisms is the main mechanism of atrazine accumulation and exchange.     

Improved rotatory-flow technique applied to Cod (Gadus morrhua L.)

An improved version of rotatory-flow apparatus is described, allowing tests of fitness with fish of different size at constant temperature. Cod (Gadus morrhua, L.) was used as experimental animal, and its treatment and behaviour during different phases of the test are described in some detail. Each test results in determination of the “critical rev min⁻¹” at which the fish is just brought to rotate with the water. The mean of a series of 10 critical rev min⁻¹ with the same fish, multiplied by the interior circumference of the rotational tube used, gives the “critical peripheral velocity” of the specimen. Critical peripheral velocities of a sample of fish, plotted against the standard length of the fish, arrange themselves along a straight line which intersects the vertical axis near the origin. Divided by the corresponding standard lengths the critical peripheral velocities give “reaction quotients”, the mean of which describe the reaction of the whole sample of fish.Optimal experimental conditions have been found by investigating the effects of systematic variation in streaming velocity, relationship between rotational tube diameter and fin-breadth, temperature, and effects of repetition of test-series on successive days etc. on the results of testing.     

Uptake pathways and elimination of a nonionic surfactant in cod (Gadus morrhua L.)

The uptake and elimination of a labelled surfactant, the nonionic nonylphenol ethoxylate, was studied in cod (Gadus morrhua L.) exposed to a concentration of 5 ppm. The amount of labelled surfactant was analyzed by the scintillation counting method in various tissues from the fish. A penetration especially through the gills, but also some intestinal resorption was found. Eight hours from start a steady state condition was obtained. High concentrations were found especially in gall bladder and liver. The elimination process in clean sea water was quite rapid and after 24 h the residues     

Cardiovascular-respiratory responses of rainbow trout (Salmo gairdneri) during chronic exposure to sublethal concentrations of cadmium

The effects of exposure to 3.6 and 6.4 μg l⁻¹ cadmium for periods up to 178 days on cardiac and ventilatory rates, hematocrit, hemoglobin concentration and erythrocyte adenosine triphosphate concentration in adult rainbow trout, Salmo gairdneri, were investigated. Except for slight transitory responses, 3.6 μg l⁻¹ cadmium had no effect on any of the cardiovascular/respiratory parameters. Significant increases in cardiac and ventilatory rates, blood hematocrit and hemoglobin were observed in fish exposed to 6.4 μg l⁻¹ Cd over the entire exposure period while erythrocyte ATP concentration declined during the last stages of exposure. Further experiments on the responses of fish exposed to 6.4 μg l⁻¹ Cd for 30 days demonstrated an impairment of oxygen transfer across the gill. The results are discussed in terms of possible gill impairment and hyperactivity as toxic responses to cadmium.     

Chronic toxicity of a copper, cadmium and zinc mixture to the fathead minnow (Pimephales promelas rafinesque)

Fathead minnows were exposed to a series or concentrations of a copper, cadmium and zinc mixture during a 12.5 month chronic test in water of 200 mg 1⁻¹ total hardness. The metal concentrations in the mixture were selected on the basis of results obtained during previous chronic exposures to each of the metals individually in the same water. Strict summation of the chronic toxicities of the metals was not indicated when they were tested in combination. Toxic effects of the mixture attributable to copper appeared to be increased, but that attributable to cadmium was reduced. The effects thought to be due to zinc were similar in degree to those observed in the single chronic exposure. Summation of effects resulting from a mixture containing about the same proportions of copper, cadmium and zinc occurred at a much higher, acutely lethal concentration. A lethal threshold was attained in the mixture when each metal was present at a concentration of 0.4 or less of its individual lethal threshold.     

Toxicity of cadmium, cobalt, uranium and zinc to Zoogloea ramigera

The toxic effects of cadmium, cobalt, uranium and zinc to the bacterium Zoogloea ramigera have been studied. This organism, which is abundant in sewage-treatment plants, responded to media supplemented with heavy metals by showing a prolonged lag phase and by decreasing its growth rate. The length of the lag phase was proportional to the metal concentration when Z. ramigera was exposed to cadmium, cobalt and zinc. When exposed to uranium (uranyl ions) the organism altered its growth behavior by showing an extended lag phase almost independent of the metal concentration. The order of toxicity of the metals to Z. ramigera was Cd²⁺ = Zn²⁺ > Co²⁺ > UO₂²⁺.     

Studies on the toxicity of copper sulphate to stone loach Noemacheilus barbatulus (L.) in hard water

The toxicity of copper sulphate to Noemacheilus barbatulus was studied for 64 days in a water of total hardness 249 mg l⁻¹ as CaCO₃. The 63-day lc₅₀ was approximately 0.25 mg Cu l⁻¹. Larger fish survived longer, and at concentrations greater than 0.29 mg l⁻¹ fish hid less during daylight. Noemacheilus surviving 0.12 mg Cu l⁻¹ for 64 days shed copper when placed in clean water for 7 days: gill, muscle, eye and vertebrae lost significant amounts of copper during this period. The opportunity to shed copper during a short period when the poison supply to their tank failed, may have allowed fish exposed to 0.49 mg l⁻¹ to live 12 days longer than expected. The sensitivity of Noemacheilus to copper, cadmium and zinc was compared with that of rainbow trout. Salmo gairdneri.     

Histopathological and physiological responses of rainbow trout (Salmo gairdneri richardson) to sublethal levels of lead

Rainbow trout (Salmo gairdneri) were exposed to sublethal levels of water-borne or dietary lead for 32 weeks. The study included a histopathological assessment of all organs, examination of red cell morphology, and a comparison of oxygen consumption in liver homogenates from exposed and control fish. No effects of lead toxicity were noted in these parameters. The most sensitive and reliable indicator of lead toxicity was the development of black tails and spinal curvature. These changes were observed in 30% of trout exposed to 120 ± 31 μg Pb 1⁻¹ of water-borne lead after 30 weeks. No other effects of lead toxicity were noted.     

Time-dependent variation of mercury in a stream sediment and the effect upon mercury content in Gammarus pulex (L.)

A 3-month investigation has been carried out in a stream environment, on the fluctuation of the level of mercury within the sediment and the Gammarus pulex population. A positive correlation is found between the organic content and the mercury content (μg g⁻¹ dry wt) of the samples. The mean mercury concentration in the organic fraction can be read from the regression line. Of the units: μg g⁻¹ dry wt, μg g⁻¹ ashfree dry wt and μg cm⁻³, the values expressed g⁻¹ ashfree dry wt are considered to be of greatest validity for comparing different localities, and for establishing the pollution level in a stream sediment. Within the investigation period a very high fluctuation is found in the mercury content of analyzed Gammarus pulex. The phenomenon may be explained through fluctuations in the methylating processes within the sediment. No positive correlation is found between mercury in Gammarus pulex and in sediement taken from identical sample locations.     

Role of dissolved and particulate cadmium in the accumulation of cadmium in cultured oysters (Crassostrea gigas)

Pacific oysters (Crassostrea gigas) collected on the coast of British Columbia, Canada have occasionally shown cadmium (Cd) concentrations at or above 2 microg g(-1) (wet weight), which has resulted in the loss of some international markets. This study investigated the source and transfer of Cd to oysters by focusing on the role of dissolved and particulate Cd in seawater. Parameters monitored for 1 year at two oyster farm sites on Vancouver Island included: oyster tissue mass and shell length, Cd in oysters, dissolved Cd, particulate Cd, temperature and salinity. Results show that dissolved Cd was the main source of Cd to the oysters and that Cd was mainly concentrated in the gut tissues. A seasonal trend was observed in Cd in oysters, in which levels were lowest during periods of higher temperatures. Results also indicate that the local oceanographic inputs and sediment diagenesis directly affect dissolved Cd and thereby influence the Cd levels in oysters. Particulate matter was not found to be a source of Cd in oysters, and was actually negatively correlated. This was likely due to the uptake of dissolved Cd by phytoplankton and the effect of phytoplankton on oyster tissue mass.     

Morphological changes in the gill of carp (Cyprinus carpio L.) exposed to acutely toxic concentrations of methyl bromide

The acute toxicity of methyl bromide (CH₃Br) to carp (Cyprinus carpio L.) was determined in experiments with a 4 h exposure period. The 4 h-LC₅₀ was calculated at approx. 17 mg 1⁻¹, i.e. the order of magnitude of actually encountered peak concentrations in surface water. The concentration-effect curve was found to be very steep and the response was somewhat delayed. Morphological damage to the gill epithelium, indicative of alkylation of cell membranes, was the most pronounced effect of CH₃Br. It consisted of initial swelling of the lymphatic space and vacuolization of the epithelial cells, followed by disintegration of the epithelium and invasion of leucocytes. Death of the fish was probably caused by suffocation.     

The usefulness of Lymnaea stagnalis L. as a biological indicator in toxicological bio-assays (model substance α-HCH)

Short- and long-term studies with α-hexachlorocyclohexane (α-HCH) were carried out on the pond snail (Lymnaea stagnalis L.), to test the usefulness of this organism as a biological indicator of pollutants in surface water.Based on mortality and immobilization in the short-term study (2 days) an ec₅₀-value of 1200 μg α-HCH 1⁻¹ could be determined.In the long-term study (70 days) an inverse time-independent relation was found between egg production rate (= number of eggs produced per unit of time) and the α-HCH concentration in the water. Based on this egg production inhibition an EC⁵⁰ of 250 μg α-HCH 1⁻¹ could be determined. The percentage of fertilized eggs per capsule was not affected. No morphological abnormalities were noticed during the embryonic development, although a significantly dose-related delay occurred with respect to the hatching of the eggs. Based on the number of eggs which did not hatch, a lc₅₀ of 230 μg α-HCH 1⁻¹ could be determined. The combination of (1) the inhibition of the egg-production of the adult snails (caused by a significant prolongation of the oviposition interval and by a significant decrease of the number of eggs per capsule) and (2) the mortality of the young during their development caused a 50° reduction of the overall reproductivity at 65 μg α-HCH 1⁻¹. The heart-rate of newborn snails was slowed significantly by α-HCH. Replacing the snails into an α-HCH-free medium for 16 days, after a 40-day exposure to α-HCH, did not result in the disappearance of the effects mentioned above.The susceptibility of Lymnaea stagnalis to α-HCH did not differ much from that of Daphnia magna (a crustacean). This organism proved to be the most sensitive one of all tested organisms (Chlorella, Daphnia, Lebistes, Salmo) in previous studies with α-HCH. Therefore Lymnaea stagnalis might be useful as a test organism in future environmental toxicity studies, although these kinds of experiments have to be considered as very laborious and costly.     

Study of dissolved silicon and nitrate dynamics in a freshwater stream.

Dissolved reactive silicon and nitrate were measured at weekly intervals over a 3 year period (1991-94) on a 1.2km reach of a gauged Dorset Mill Stream. In addition, dissolved nitrite was measured over a 8 month period from the spring to late autumn in 1992. Two intensive studies with sampling at 2h intervals were also completed in low and high riverflow conditions. The results were analysed using a mass-balance approach with the loss and gains in nutrients dissolved in the water expressed in terms of areal rates. Losses of both nutrients occurred during periods of low streamflow in spring and summer. Losses of silicon are attributed to growth of epilithic diatoms whereas nitrate losses are consistent with a number of processes including the growth of aquatic plants, the development of epilithic biofilms and nitrogen transformations, such as denitrification, in bed-sediments. Stream water gained dissolved nitrite during its passage through the section. Silicon losses from the stream amounted to between 52 and 63 mmol m(-2) d(-1) (expressed per area of bed-sediment) for the spring periods in 1992-94. Nitrate losses were more variable with overall rates between 24 and 89 mmol m(-2) d(-1) for the summer periods in 1991-93.     

Addition of NaOH, limestone slurry and finegrained limestone to acidified lake water and the effects on smolts of atlantic salmon (Salmo salar L.)

A neutralization experiment comparing NaOH, limestone slurry and finegrained limestone was performed using smolts of Atlantic salmon as testfish. Smolts were raised on chronically acid Lake Liervatn (pH = 4.9–5.4, conductivity = 55 μ S cm⁻¹, Ca = 1.3 mg l⁻¹, labile Al = 40 μg l⁻¹). As a result testfish were sublethally stressed prior to the experiment, as indicated by low levels of plasma chloride. During the experiment, smolts were held in keepnets in the middle of large plastic enclosures without sediment contact. Rapid changes in pH and Al-speciation were recorded after addition of the neutralizing agents. No mortality of fish occurred during the 3 days exposure. Plasma chloride levels in fish exposed to limestone slurry, limestone and the lowest concentration of NaOH (pH = 5.9) did not differ significantly from levels in fish from the reference group. Fish exposed to the highest concentration of NaOH (pH > 7.45), however, experienced a significant decrease in plasma chloride levels. Increased sublethal stress in treatments with NaOH was presumably caused by the presence of aluminate ions [Al(OH)₄⁻] at high pH and by low concentrations of Ca. The importance of maintaining pH below 7 when using bases with monovalent cations is emphasized. Adding inorganic aluminium to the lake water induced loss of plasma chloride within 48 h at 70 μg labile Al l⁻¹ at pH 5.1 and 1.2 mgCa l⁻¹.     

Effects of naturally occurring aquatic organic fractions on cadmium toxicity to Simocephalus serrulatus (daphnidae) and Gambusia affinis (poeciliidae)

Cadmium toxicity to Simocephalus serrulatus and Gambusia affinis in soft well water, highly organic pond water and well water containing various sized organic fractions isolated from pond water was determined and compared to Cd binding capacity of each water type. Pond organics were separated into three nomial molecular diameter fractions (> 0.0183 μm; 0.0183 < > 0.0032 μm; 0.0032 < > 0.0009 μm) using ultrafiltration. Cadmium binding capacity was determined using selective ion electrodes. Pond water and organic fractions bound Cd. reducing the amount of free Cd²⁺ as determined by Cd selective ion electrode. Whole pond water reduced Cd toxicity to S. serrulatus but had little effect on Cd toxicity to G. affinis. The three larger molecular diameter organic fractions reduced Cd toxicity to S. serrulatus, while the smallest fraction slightly increased Cd toxicity. Cadmium 96 h LC₃₀ values cannot be predicted from Cd binding capacities determined by selective ion electrode.     

Natural tritium levels in tender and ripe coconut fruit (Cocos nucifera L.): a preliminary examination

Tissue Free Water Tritium concentrations (TFWT) were determined in tender coconut (Cocos nucifera L.) water, ripe coconut water, and kernel milk water, and compared with the same in groundwater collected from the vicinity of the trees. Samples with a very low tritium content were enriched by the alkaline electrolysis method. All of the samples were analyzed for tritium content in an ultra-low level liquid scintillation spectrometer. The TFWT in kernel milk water was found to be approximately 20-40 times higher than that in the groundwater. The tritium concentration in descending order in these samples is: kernel milk water, ripe coconut water, tender coconut water, and groundwater. The concentration of tritium increases as the fruit grows and the significantly high concentration in the kernel milk water suggests enrichment during the growth of the fruit.     

An evaluation of the relative importance of food and water as sources of p,p′-DDT to the goldfish, carassius auratus (l.)

Goldfish (Carassius auratus) were simultaneously exposed to p,p′-DDT from two sources—food ([³⁶Cl]p,p′-DDT) and water ([¹⁴C]p,p′-DDT). The concentration of p,p′-DDT in food was maintained at about 1 μg g⁻¹ while the water concentration of p,p′-DDT was varied for each experiment (2, 20 and 177 ng dm⁻³). In these experiments the contribution of p,p′-DDT from food to the total body residue varied over the duration of the exposure from 0 to 81% (water concentration about 2 ng dm⁻³) and from 3.8 to 4.8% (water concentration about 171 ng dm⁻³). The results from these experiments were compared with those of experiments in which some goldfish were exposed to DDT-contaminated food and others to DDT-contaminated water. Comparison suggested that goldfish exposed to DDT-contaminated food and water simultaneously, had accumulated p,p′-DDT from the two sources additively.The data supports the concept that p,p′-DDT residues in fish can be derived from both food and water. We suggest that the importance of each source is determined by its relative concentration over the period of exposure. p,p′-DDT taken up by goldfish was converted, slowly at first, then more rapidly to p,p′-DDE reaching a maximum of > 80% from both water and food sources after about 40 days. Dietary p,p′-DDT was converted to p,p′-DDD to a greater extent (max. 15.9%) than water-borne p,p′-DDT is converted to p,p′-DDD (max. 2.8%).     

Geochemical factors complicating the use of aufwuchs to monitor bioaccumulation of arsenic, cadmium, chromium, copper and zinc

Material accumulating on submerged glass slides was sampled from five sites associated with coal ash settling basins and a control site. Correlation analyses demonstrated a strong, positive correlation between the five elements, arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu) and zinc (Zn) and concentrations of associated iron or manganese. Negative, weak or nonsignificant correlations were noted between the concentrations of these five elements and microfloral cell densities or per cent ash free weight of the material. Scanning electron microscopy and X-ray analyses indicated that the majority of the material was abiotic and the elemental levels associated with the abiotic components were generally higher than those of the biotic components. Hydrous iron and manganese oxides likely play dominant roles in determining the trace element concentrations in these procedurally-defined aufwuchs. These findings indicate the potential for misinterpretation of biomonitoring data employing procedurally-defined aufwuchs.