Ian M. Davies

Effects of sewage effluent and ethynyl oestradiol upon molecular markers of oestrogenic exposure, maturation and reproductive success in the sand goby (Pomatoschistus minutus, Pallas)

Male fish in several UK estuaries are known to be exposed to oestrogenic contamination, and whilst a limited number of studies have shown that exposure to oestrogens can reduce the reproductive success of fish, the impact of environmentally relevant exposures is less clear. The aim of this study was, therefore, to investigate the effects of exposure to environmentally realistic concentrations of a sewage effluent and the synthetic oestrogen 17alpha-ethynyl oestradiol (EE(2)) upon the reproductive success of a marine fish. Sand goby (Pomatoschistus minutus) were exposed for 7 months to EE(2) or a sewage effluent containing known xeno-oestrogens (alkylphenol polyethoxylates) and bred using within treatment crosses. Nominal exposure concentrations were 6 ng l(-1) EE(2), 0.3 or 0.03% v/v sewage effluent. At the end of the breeding trials, expression of hepatic zona radiata protein (Zrp) and vitellogenin (Vtg) mRNA were determined using two recently developed cDNA probes. Exposure to 6 ng l(-1) EE(2) induced Zrp and Vtg mRNA expression in male and female sand goby, impaired male maturation and reproductive behaviour, reduced female fecundity and reduced egg fertility. As a consequence, fertile egg production of the EE(2)-exposed population was reduced by 90%. Exposure to sewage effluent (0.3% v/v) increased adult mortality and female Zrp and Vtg mRNA expression, but did not induce male vitellogenesis. Exposure to EE(2) and 0.3% v/v sewage effluent impaired development of the male urogenital papilla. Fish exposed to 0.03% v/v sewage effluent produced more fertile eggs than those exposed to 0.3% effluent, or those receiving no effluent. It is concluded that male vitellogenesis in an oestrogenically exposed population may be accompanied by reduced reproductive success, but that it may not be indicative of altered reproductive output in a population exposed to an industrial sewage effluent.

Localised remobilization of metals in a marine sediment

Trace metals and Fe and Mn were measured at vertical spatial resolutions of 2.5 and 5 mm in the top 35 cm of the profundal sediment of a Scottish sea-loch using DGT (diffusive gradients in thin films) technique. DGT probes lower adjacent metal concentrations in pore waters and induce a flux of metal from the solid phase to porewater. The concentrations of metals in porewaters at the interface of the probe were measured during its deployment in a box core. These measurements reflect porewater concentrations of metals and their rates of resupply from the local solid phase of a very small volume (25 microl) of sediment. There was pronounced horizontal and vertical structure in the interfacial concentrations. Horizontal variations were shown by results from adjacent DGT assemblies being markedly different in detail, while vertical structure was measured directly by the DGT-depth profiles. Iron and Mn varied systematically with depth, with both broad and detailed features of Co aligning with those of Mn. There was, however, evidence of additional localised sources of Co that were apparently unrelated to the redox behaviour that Mn typifies, but associated with the remobilization of Ni, possibly from mineral dissolution. Arsenic(III) was remobilized in well-defined zones. Detailed correspondence of As(II) with some Fe features suggest that its release is mechanistically-related to iron oxide dissolution, but the 3 orders of magnitude higher concentrations of Fe may sometimes obscure the association. These results demonstrate that, within sediments, metals may be released in discrete locations that are not measured by conventional porewater sampling techniques due to their horizontal averaging.

Implications from a field study regarding the relationship between polycyclic aromatic hydrocarbons and glutathione S-transferase activity in mussels.

An aluminium smelter on the west coast of Scotland discharges an aqueous effluent containing polycyclic aromatic hydrocarbons (PAHs) at the head of Loch Leven. The loch also supports two mussel (Mytilus edulis) farms. Data are presented on burdens of PAHs in the soft tissues of mussels and the effect of these contaminants on glutathione S-transferase (GST) activity in mussel hepatopancreas. GST activity is shown to be correlated with total PAH burden and also with the concentrations of certain individual PAHs. These field data show that high molecular weight PAHs are closely correlated to GST activity, whereas low molecular weight PAHs are not. This suggests that 5- and 6-ring PAHs have a more pronounced role than 2- to 4-ring compounds in inducing GST activity in mussels from Loch Leven. It is proposed that it may be more appropriate to link GST activity with 5- and 6-ring compounds only, rather than with the total PAH burden.

Trace metal concentrations in deep sea fish from the North Atlantic

Abstract Specimens of six species of continental slope fish (17 orange roughy Hoplostethus atlanticus, 84 roundnose grenadier Coryphenoides rupestris, 37 roughhead grenadier Macrourus berglax, 27 Mediterranean grenadier Coryphenoides [Chalinura]mediterranea, 25 spear-snouted grenadier Coelorhyncus labiatus and five armed grenadier Coryphenoides [Nematonurus] armatus), were collected between 1987 and 1995, and their muscle tissue subsequently analysed for mercury, lead, cadmium, copper and zinc. The early samples were collected in the Rockall Trough area by the research vessel Challenger. The 1995 samples were obtained from commercial landings at Lochinver fishing port by fishing vessels which had been operating on the Hebridean Continental Slope, in ICES areas 43E0, 44E0, 45E0, 46E1, 47E3 and 48E3. Sub-samples of the muscle tissue of individual fish whose ages ranged from 3 to > 70 y, were analysed for the above trace metals using atomic absorption spectrophotometry, following nitric acid digestion. The mean mercury concentrations in all species were below 0.5 mg/kg, ranging from a mean value of 0.06 mg/kg in roundnose grenadier to 0.42 mg/kg in orange roughy. However, individuals from three of the six species were found to have concentrations greater than 0.5 mg/kg but less than 1.0 mg/kg (orange roughy up to 0.86 mg/kg, roughhead grenadier 0.89 mg/kg and armed grenadier 0.65 mg/kg). In all species, concentrations of mercury were found to increase with both age and length. Mean concentrations in shallow water commercial fish species are normally less than 0.1 mg/kg, although some long-lived fish predators can contain 1 mg/kg or more. The ranges of mean concentrations of zinc (2.2–6.7 mg/kg), copper (0.01–0.47 mg/kg) and cadmium (0.002–0.02 mg/kg) for all species were similar to those observed in commercially exploited shallow water marine fish landed at Scottish ports, although some of the lead concentrations (means 0.004–0.72 mg/kg) were rather higher. In Mediterranean grenadier, the concentrations of copper, zinc, cadmium and lead decreased with increasing length/age offish. Although this was also observed in orange roughy, the relationships were not as significant as those in the Mediterranean grenadier.

Environmental risk of ivermectin to sediment dwelling organisms

Abstract Ivermectin (22,23-dihydroavermectin B1) has been proposed as a feed additive to alleviate sea lice infestation of farmed salmon. The present study investigated the acute toxicity of ivermectin in sediment to two sediment-dwelling organisms, the amphipod, Corophium volutator and the starfish, Asterias rubens . The degradation of ivermectin in sediment was studied over a three-month period, by chemical measurements and observation of changes in toxicity of the contaminated sediment with time to C . volutator in whole sediment bioassays. The 10 day LC50s of ivermectin to C . volutator and A . rubens were 0.18 mg kg −1 and 23.6 mg kg −1 , respectively. The estimated NOECs of ivermectin for mortality to C . volutator and A . rubens were 0.05 mg kg −1 and 5 mg kg −1 , respectively. The lowest observed concentration which had a sublethal effect (LOEC) on the ability of A . rubens to turn themselves over after the 10-day test was 20 mg kg −1 . Measured concentrations of ivermectin in the sediment, and the decrease in toxicity, indicated that the half-life of ivermectin in marine sediments is greater than 100 days. An initial assessment of the potential risk to the marine environment from sediment-associated ivermectin indicated that there may be significant risk to infaunal polychaetes in sediment immediately below and around the fish cages.

Tributyltin in Scottish sea lochs, as indicated by degree of imposex in the dogwhelk, Nucella lapillus (L.)

Abstract The development of male characteristics (termed imposex) in females of the dogwhelk Nucella lapillus is a sensitive indicator of tributyltin contamination. In Lochs Crinan, Laxford and Sween on the west coast of Scotland, observations of this effect and of the accumulation of tin in female dogwhelks have identified areas of contamination associated with seasonal small boat activity and salmon cage farms.

Effects of feeding status on biliary PAH metabolite and biliverdin concentrations in plaice (Pleuronectes platessa)

Relationships between feeding status and the biliary concentrations of biliverdin and metabolites of polycyclic aromatic hydrocarbons (PAH) have been investigated in plaice (Pleuronectes platessa) from the Firth of Clyde, Scotland. Plaice were caught at three times of the day, and kept, without feeding, in tanks for up to 24h. The mean concentrations of biliary PAH metabolites 2-OH naphthalene, 1-OH pyrene and 3-OH benzo-[a]-pyrene (3-OH B[a]P) were found to increase slightly over a 24h non-feeding period (only significant for 3-OH benzo-[a]-pyrene). This effect was not observed for mean biliary concentrations of 1-OH phenanthrene. During this period of starvation, bile volume, total amounts of all PAH metabolites in the gall bladder, and biliary biliverdin concentrations all significantly increased. No significant relationships (P>0.05) were found between indicators of feeding status and individual PAH metabolite concentrations, confusing the rationale for normalisation of data to account for differences in feeding status between fish. Normalisation of PAH metabolite concentrations to biliverdin concentrations did not consistently reduce the variance of the metabolite data for fish sampled after the same starvation period. However, the variation between mean metabolite concentrations of fish suffering different starvation periods was reduced by biliverdin normalisation for most of the metabolites measured. It is therefore recommended that biliary PAH metabolite data should be presented as raw concentrations, except in cases where there may be significant differences in feeding status between groups of fish. In such instances biliverdin normalised data should also be reported and observational guides such as bile volume and stomach contents may aid in the interpretation of data.

Environmental risk from dissolved ivermectin to marine organisms

Abstract Ivermectin (22,23-dihydroavermectin B1) has been proposed as a chemotherapeutant for the treatment of farmed salmon infected with sea lice. The present study investigated the acute toxicity of dissolved ivermectin to the mysid shrimp Neomysis integer , a non-target crustacean found in Scottish coastal waters, and also the ability of the mussel, Mytilus edulis , to bioaccumulate ivermectin from solution, and the subsequent depuration rate. The 96 h LC50 of ivermectin to N. integer was 70 ng l −1 , with 95% confidence limits of 44 ng l −1 and 96 ng l −1 . The mussels bioconcentrated ivermectin from water at 6900 ng −1 for 6 days by a factor of 750 (confidence limits 720–790), and showed estimated depuration half-times of 22 days, or 235 degree days. An initial assessment of the potential risk to the marine environment from dissolved ivermectin from use on fish farms indicates that ratios of the Predicted Environmental Concentrations to the Predicted No Effect Concentrations (PEC/PNEC) are small (0.02–5.10 −6 and acute direct toxic effects are unlikely. Mussels in the vicinity of fish farms are unlikely to accumulate detectable concentrations of ivermectin.

Cypermethrin induces glutathione S-transferase activity in the shore crab, Carcinus maenas

Cypermethrin is a synthetic pyrethroid that is particularly toxic to crustacea. It is therefore applied as a chemotherapeutant in the salmonid aquaculture industry for the treatment of sea lice infestations. After use, cypermethrin is released directly into the marine environment, to be diluted by fresh seawater. The shore crab, Carcinus maenas is found in the vicinity of fish farms, and may come into contact with released cypermethrin. The detoxification enzyme, glutathione S-transferase (GST) has been implicated in cypermethrin metabolism in terrestrial arthropods, but this has not yet been demonstrated in crustacea. In this paper we investigate the response of GST activity in Carcinus to cypermethrin exposure, and also the time course of the induction process. GST activity is significantly increased in Carcinus exposed to nominal concentrations of 50 and 500 ng/l of water-borne cypermethrin. Carcinus demonstrate a significant elevation in GST activity following intra-cephalothoracic injection with 10 ng of cypermethrin. GST activity returns to basal levels after 36 h. The potential application of GST activity in Carcinus as a biomarker of cypermethrin exposure is discussed.

Experimental and field studies of effects of dichlorvos exposure on acetylcholinesterase activity in the gills of the mussel, Mytilus edulis L.

Abstract Dichlorvos (DDVP) is an organophosphate medicine, used to treat ectoparasitic sea lice infestations of farmed salmon. Effects of this chemical on a non-target organism were investigated. Experimental exposure of mussels (Mytilus edulis L.) to dichlorvos (DDVP) resulted in changes in gill acetylcholinesterase (AChE) activity with a hormetic increase at lower concentrations, and 50% inhibition at 3.6 μg l−1 after 24 h exposure. Repeat exposures resulted in cumulative inhibition. Twenty-four hour exposure to DDVP impaired the ability to close shells (EC50 of 1700 μg l−1) and caused mortalities at high concentrations (LC50 of 8200 μg l−1). AChE levels in mussels collected from sea lochs were indicative of DDVP inhibition related to the quantities of DDVP used. The use of AChE as a sublethal indicator of DDVP usage in the field is discussed.