Sheila V. Evans

Responses Of Mytilus-Edulis On Exposure To The Water-Accommodated Fraction Of North-Sea-Oil

Individuals of Mytilus edulis L., collected from the Erme estuary (S.W. England) in 1978, were exposed to low concentrations (7 to 68 μg l-1) of the water-accommodated fraction (WAF) of North Sea crude oil. The pattern of accumulation of petroleum hydrocarbons in the body tissues was affected by the presence of algal food cells, the period of exposure, the hydrocarbon concentration in seawater, the type of body tissue and the nature of the hydrocarbon. Many physiological responses (e.g. rates of oxygen consumption, feeding, excretion, and scope for growth), cellular responses (e.g. lysosomal latency and digestive cell size) and biochemical responses (e.g. specific activities of several enzymes) were significantly altered by short-term (4 wk) and/or long-term (5 mo) exposure to WAF. Stress indices such as scope for growth and lysosomal latency were negatively correlated with tissue aromatic hydrocarbons.

Seasonal distribution of dissolved pesticides and polynuclear aromatic hydrocarbons in the Humber Estuary and Humber coastal zone

The distribution of atrazine, 2-methylthio-4-tert-butyl-amino-6-cyclopropylamino-s-triazine (Irgarol 1051), lindane, malathion, fluoranthene and pyrene dissolved in the water column of the Humber Estuary and adjacent coastal zone was determined. Atrazine concentrations declined from the head (35–53 ng l−1) to the mouth (5–11 ng l−1) of the estuary; the highest concentrations were found in June. Lindane concentrations also declined through the estuary, although elevations were observed near a sewage outfall, especially in June and September. Irgarol concentrations typically peaked in April, then decreased in June before increasing again in September. The patterns of variation of fluoranthene and pyrene were similar to each other, suggesting common sources. Levels were similar throughout the estuary, with an exceptionally large elevation at a sewage outfall in June. Malathion concentrations were generally very low (<1–9 ng l−1). The concentrations of all compounds were lower off-shore than in the estuary, suggesting that the Humber catchment is a major source of organic micropollutants to the Humber coastal zone. Concentrations of atrazine and lindane were also elevated at stations close to the Wash, suggesting a contribution from rivers into the Wash.

Fluoranthene and pyrene in the suspended particulate matter and surface sediments of the Humber Estuary, UK

Abstract As part of the UK-based Land-Ocean Interaction Study (LOIS) community programme, suspended particulate matter (SPM) and surface sediments have been collected from the Humber estuary, which is a large and complex estuarine system on the east coast of England fed by several rivers including the Trent and Ouse. The samples from four surveys were extracted and analysed to determine the levels of anthropogenic organic contaminants such as fluoranthene and pyrene. Their concentrations in SPM and surface sediments ranged from 44 to 1560 ng g −1 dry weight and 13–1969 ng g −1 dry weight, respectively, and displayed no strong seasonal variation. Mean fluoranthene and pyrene concentrations were higher in the Trent than in the Ouse for both SPM and sediment samples, and were elevated at a sewage outfall, suggesting a multiplicity of inputs for these two compounds. Fluoranthene and pyrene on SPM showed no correlation with salinity, although correlations with suspended solids concentrations (SSC) and particulate organic carbon (POC) have been confirmed.

The partition of fluoranthene and pyrene between suspended particles and dissolved phase in the Humber Estuary: a study of the controlling factors

Abstract Particle–water interactions are one of the most important mechanisms controlling the distribution and movement of hydrophobic organic chemicals such as polycyclic aromatic hydrocarbons (PAHs) in aquatic environments (e.g. estuaries and oceans). To accurately predict the transport and fates of hydrophobic contaminants in estuarine and coastal marine environments, the partition coefficient ( K p ) and organic carbon normalised partition coefficient ( K oc ) are widely used in various biogeochemical models. Such partition coefficients may be calculated from the so-called linear free energy relationships between K p , K oc and more easily measured parameters such as the octanol-water partition coefficient ( K ow ). However K p and K oc values measured for real environmental samples of water and particles obtained from seasonal field surveys in the Humber Estuary, UK deviated from such ideals. For example, K P values showed no correlation with the fraction organic carbon content of particles ( f oc ) and instead of being constant, K oc , values varied with f oc . Both K p and K oc were 1–3 orders of magnitude higher than those predicted from the simple equilibrium–partitioning model, but were in good agreement with several other recently published field studies. To improve our understanding of PAH partitioning, the soot carbon (SC) content of particulate samples was measured so that the simple partition model can be extended to incorporate SC. The partition coefficients derived from the extended partition model are very close to the field K p s. The results suggest that PAHs associated with particles are in fact present in the form of soot and soot-like particles that are not subject to particle–water equilibrations. In other words, the PAHs on soot-like particles are extremely strongly bound and not influenced by further partitioning between the particles and water. However, there are still limitations with the extended partition model as it failed to simulate the field K oc values. No correlation was found between the partition coefficients and salinity, which again we attribute to the non-equilibrium nature of the PAHs. However both K p and K oc generally decreased with increasing suspended solids concentrations (SSC) in the estuary. Such a relationship is probably due to the mixing of soot-like permanently suspended particles with resuspended estuarine sedimentary particles at the higher SSC values, and to the increased concentrations of dissolved organic carbon (DOC) associated with increase in SSC. However, it has been shown that DOC concentrations are not a suitable tool for correcting the SSC effect. There is therefore an urgent need to harmonise the laboratory and field approaches for K p measurements.

Quantitative structure-activity relationships for the effect of hydrophobic organic chemicals on rate of feeding by mussels (Mytilus edulis)

Abstract The effect of hydrophobic organic chemicals on the rate of feeding by mussels ( Mytilus edulis ) was investigated. The effect was expressed as the toxicant concentration in water required to reduce feeding rate by 50% (WEC 50 ). A quantitative structure-activity relationship (QSAR) was derived in which WEC 50 was negatively correlated with log 10 octanol-water partition coefficient (log K ow ) and positively correlated with aqueous solubility, indicating that hydrophobicity has a major influence on toxicity. QSARs calculated between bioconcentration factor, and log K ow and aqueous solubility showed, that hydrophobicity influences toxicity largely through its effect on bioconcentration. This observation was confirmed by expressing toxicity as the toxicant concentration in mussel tissue required to reduce feeding rate by 50% (TEC 50 ). For the compounds tested which have log K ow values 50 was relatively constant, irrespective of molecular structure. Compounds with log K ow values > 5 could be accumulated to much greater concentrations before feeding rate was affected, indicating that there is a ‘molecular weight cut-off’ in the toxicological response. These observations are characteristic of a non-specific narcotic mode of toxic action. The application of the reported QSARs to interpreting results derived from combined chemical contamination and biological effects environmental monitoring studies with mussels is discussed.

Responses of the mussel Mytilus edulis to copper and phenanthrene: Interactive effects

Most investigations of the responses of marine organisms to xenobiotics have concentrated on single contaminants and little is known of possible interactive effects of different classes of xenobiotics. As these latter seldom occur in environmental isolation, it is important to understand any interactions (synergistic or antagonistic) which may occur. This problem has been approached in the mussel Mytilus edulis by exposing estuarine mussels to copper (20 μg litre−1) and phenanthrene (100 μg litre−1) both individually and in combination, and measuring cytochemical subcellular and physiological responses after 3 days exposure and 3 days and 12 days recovery period. Results showed that mussels accumulated both xenobiotics during 3 days exposure. Depuration of copper was complete in 3 days recovery period, while loss of phenanthrene ranged from 30% to 70% of the concentration reached after 3 days exposure. There were no interactive effects on depuration. Both copper and phenanthrene reduced lysosomal hydrolase latency in digestive cells, and copper appeared to have a synergistic effect in preventing recovery of latency of lysosomal N-acetyl-β-hexosaminidase during the recovery period. There was evidence, in the digestive cells, of an antagonistic effect of copper on stimulation of activity of the microsomal respiratory chain (measured as NADPH-neotetrazolium reductase) by phenanthrene. Stimulation of this system by phenanthrene persisted after 12 days recovery period. There was a synergistic interaction of copper and phenanthrene on elevation of oxygen consumption and ammonium excretion. Clearance rates and scope for growth (physiological condition) were depressed by copper but not by phenanthrene after 3 days exposure. These findings are discussed in terms of known effects of copper and phenanthrene and the interactions are considered in terms of environmental effects measurements.

Risk posed by the antifouling agent Irgarol 1051 to the seagrass Zostera marina

Irgarol 1051 (2-(tert-butylamino)-4-cyclopropylamino)-6-(methylthio)-1,3,5-triazine) is a triazine herbicide that is increasingly being used to boost the effectiveness of antifouling paints. Estuarine plants, such as the marine angiosperm Zostera marina L. (eelgrass) may accumulate, and be affected by, Irgarol 1051, in locations with high boat densities. Bioconcentration of Irgarol 1051 within Zostera tissue was determined in field plants and laboratory semi-static exposure experiments. Effects of Irgarol 1051 upon the growth rate and photosystem II photosynthetic efficiency of Zostera were examined over a concentration range of 0 to 25 μg dm−3. Growth rate was assessed by comparison of leaf specific biomass ratios, and was found to be reduced at and above an Irgarol 1051 concentration of 10 μg dm−3. Photosynthetic efficiency was assessed using fluorescence induction kinetics: efficiency was significantly reduced at 0.18 μg dm−3 (0.4 μg g−1 dry weight leaf tissue) and a 10-day EC50 value of 2.5 μg dm−3 (1.1 μg g−1) calculated. Longer-term exposure revealed a 36-day EC50 value of 0.2 μg dm−3. Uptake of Irgarol 1051 was rapid within the Zostera leaves: tissue concentrations (dry weight basis) in excess of 300 times the water concentration were found within 2 days of exposure. Leaf concentrations in excess of 14 times root tissue concentration were found. Estuaries sampled in S.W. England had low aqueous Irgarol 1051 contamination, typically <0.003 μg dm−3, but Zostera leaf tissue concentrations (dry weight basis) were up to 25 000 times the aqueous values; this was only 15 times below the 10-day EC50 value. The reported results will enable the level of risk to isolated Zostera meadows from Irgarol 1051 to be assessed based on leaf tissue concentration and also have implications for the siting of marinas.

QSARs for the sublethal responses of marine mussels (Mytilus edulis)

The marine environment is contaminated with many organic compounds, some of which induce deleterious responses in biota. Biological impact can be assessed by measuring the physiological responses of mussels, though the task of establishing which of the bioaccumulated compounds cause the observed effects is complex. To facilitate this task, quantitative structure-activity relationships (QSARs) for the physiological responses are being established. In this paper, the responsiveness of ciliary feeding to alkanes and benzene-substituted alkanes is described and compared with a QSAR established previously for aromatic compounds. Most of the test compounds with aqueous solubilities greater than 70 micrograms dm-3 were toxic to feeding activity when bioaccumulated to similar concentrations, whereas compounds of lower solubility were less toxic. The only exceptions were the polyaromatic hydrocarbons pyrene and fluoranthene, which were less toxic than predicted from their solubility. These data are consistent with the hypothesis that the toxicity cut-off is due to solubility-related phenomena, the effect perhaps being enhanced for aromatic hydrocarbons dosed near to their solubility limits, by sequestration of crystals within the mussel tissues. These observations indicate that many organic contaminants detected by chemical analysis of mussels have no direct effect on filter feeding, whereas the less frequently determined volatile compounds are toxic.

Application of steam distillation in the determination of petroleum hydrocarbons in water and mussels (Mytilus edulis) from dosing experiments with crude oil

Abstract Steam distillation is shown to provide recoveries in excess of 80% for petroleum hydrocarbons in the volatility range encompassed by toluene and pyrene from water and mussel tissues. These recoveries were achieved with an apparatus based on Dean and Stark water estimators which are commercially available at low cost. Saponification is shown to aid hydrocarbon recovery from mussel tissue. The steam distillates derived from tissues were analysed by u.v. spectrophotometry after clean-up on alumina, or directly by gas-liquid chromatography or normal- and reverse-phase high-performance liquid chromatography (h.p.l.c.). Steam distillates of water did not require prior clean-up. Normal-phase h.p.l.c. of steam distillates on an amino-cyano phase provided a particularly convenient method for petroleum-derived aromatic hydrocarbons. These techniques were examined extensively in laboratory experiments with crude oil, but preliminary results suggest that they may be used also in environmental monitoring of hydrocarbons.

Effect of Neurotoxic Pesticides on the Feeding Rate of Marine Mussels (Mytilus edulis)

The effects of selected neurotoxic pesticides on the feeding rate of marine mussels (Mytilus edulis) were determined. Two organochlorine pesticides, lindane and endrin, two acetylcholinesterase-inhibiting compounds, dichlorvos and carbaryl and two pyrethroids, flucythrinate and permethrin, were studied. No evidence was found for any specific neurotoxic effect of the organochlorines and pyrethroids on feeding efficiency. In contrast, dichlorvos and carbaryl inhibited the enzyme acetylcholinesterase in mussel gills and were more toxic to feeding efficiency than could be explained by a narcotic mechanism of toxicity alone. Dichlorvos also caused clear behavioural changes in the mussels. The significance of these observations for the application of mussels to impact assessment in the marine environment is discussed.