A. D. McIntosh

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.

Toxic equivalency factors for PAH and their applicability in shellfish pollution monitoring studies

Fish and shellfish are exposed to a wide range of polycyclic aromatic hydrocarbons (PAH) following oil spills at sea, and can become contaminated as a result. Finfish have a more effective mixed-function oxidase enzyme system than shellfish, and are therefore able to metabolise and excrete PAH more effectively than the invertebrates. Thus, contamination by high-molecular weight PAH, including those with carcinogenic potential and so of concern with regard to human consumers, is therefore usually observed in shellfish, and particularly in bivalve molluscs. Oil spills are not the sole source of PAH, however, as parent compounds are also generated by a wide range of combustion processes. In this paper, consideration is given to monitoring data gathered following recent oil spills (both of crude oil and diesel fuel), alongside data from other studies. These include studies conducted around a former gasworks site and downstream of an aluminium smelter in the UK, and from mussel monitoring studies undertaken in the UK and the USA (including the Exxon Valdez oil spill and the National Status and Trends programme), and in other countries in Europe. For comparative purposes the PAH concentrations are summed and also expressed as benzo[a]pyrene equivalents, their relative concentrations being weighted in relation to the carcinogenic potential of individual PAH compounds using toxic equivalency factors (TEF). Our aim was to assess the utility of this approach in fishery resource monitoring and control following oil spills. Certainly this approach seems useful from the data assessed in this study. and the relative ranking of the various studies seems to reflect the relative degree of concern for human consumers due to the differing contamination sources. As a simple tool for control purposes it is equally applicable to PAH derived from oil spills, and from industrial and combustion sources.

Elevation of hepatic monooxygenase activity in the dab (Limanda limanda L.) in relation to environmental contamination with petroleum hydrocarbons in the northern North Sea

Abstract Dab ( Limanda limanda L.) were caught at various distances from a group of oil platforms in the northern North Sea. Hepatic ethoxyresorufin-O-deethylase (EROD) and cyanoethoxycoumarin-O-deethylase (cECOD) activity were elevated in both male and female fish caught close to the platforms. This effect was more marked in females which showed a 10–20-fold increase in activity compared to a 4-fold increase in males for both EROD and cECOD. Both aliphatic and aromatic hydrocarbon analyses were carried out to determine the extent of sediment contamination at each trawling site and to measure the contamination of the livers of fish caught at each site. The results show significant contamination of sediments with base oil, unresolved mixtures of aliphatics and n -alkanes close to the platform. However, there was not a significant relationship between sediment contamination and levels of the monooxygenase enzymes measured in the livers of dab. In contrast, the concentrations of both aliphatic and aromatic hydrocarbons in the liver showed a significant negative regression to distance from the platform. Examination of the relationship between liver contamination and the levels of both EROD and cECOD showed a significant positive correlation for all groups of hydrocarbons measured and that this was most significant for the 5–6-ring aromatics.

Analysis of sediments from Shetland Island voes for polycyclic aromatic hydrocarbons, steranes and triterpanes

A few days after the grounding of the oil tanker Braer on 5 January 1993, an Exclusion Zone was designated by Order under the Food and Environment Protection Act 1985, prohibiting the harvesting of farmed or wild shellfish within the Zone to prevent contaminated products reaching the market place. The order was progressively lifted for species that were found to be free of petrogenic taint and for which the polycyclic aromatic hydrocarbon (PAH) levels were within the range for reference samples. This Order, however, still remains in place for mussels (Mytilus edulis) as the PAH levels are higher than in reference mussels. To investigate the possible source of PAHs found in these mussels, sediments were collected from three reference and three Zone sites and their hydrocarbon compositions studied using the n-alkane composition and concentration, PAH composition and concentration and the sterane and triterpane composition. The reference site at Olna Firth was found to have the highest levels of 2-6-ring parent and branched PAHs, the highest concentration in one of the pooled sediments being 4,530 ng g(-1) dry weight. Values in the other two reference sites (Vaila Sound and Mangaster Voe) ranged from 248.7 to 902.2 ng g(-1) dry weight. PAH concentrations at the Zone sites (Sandsound Voe, Stromness Voe and Punds Voe) ranged from 641.0 to 2,766 ng g(-1) dry weight. The PAH data were normalised to the percentage of organic carbon and log-transformed prior to being analysed using principal component analysis. The mean total PAH concentrations for Zone sites were found not to be significantly different from the reference sites. The PAH concentration ratios were consistent with the main source of PAHs being pyrolysis. However, there was a petrogenic contribution, suggested by the presence of alkylated PAHs, with Punds Voe having the largest petrogenic hydrocarbon content. This was supported by the triterpane profiles and the presence of a UCM in the aliphatic chromatograms from Punds Voe sediments.

Hydrocarbon concentrations in the northern North Sea and effects on fish larvae

Abstract Two surveys were carried out in 1993 and 1994 to measure the concentrations of oil in water and the associated effects on fish larvae along two north-south sections (between 57.00°N and 62.00°N at longitude 0.0°E and 1.5°E) through the northern North Sea. At each station occupied hydrocarbon concentrations were logged continuously from a towed in situ fluorimeter attached to a MIKT net used to sample larvae and deployed on an oblique tow from surface to bottom. The results show a distinct north-south gradient in hydrocarbon concentration peaking around installations associated with oil and gas exploration and production. Depth averaged data show that the mean concentration in the top 50 m was between 3 and 4 μg l −1 at latitudes between 56.00 and 59.00°N falling to values as low as 0.2–0.5 μg l −1 in the more pristine waters to the north and west. The hydrocarbon levels in the top 50 m between 56.00 and 59.00°N were elevated compared to those in deeper water. 7-Ethoxyresorufin O -deethylase (EROD) activity was measured in pooled samples of both sandeel and gadoid larvae. For both species the range of EROD activities was large and variable and this is probably due to damage to larvae associated with capture and subsequent denaturation of the enzyme. Despite this the results show elevated EROD activity in samples taken on the southern end of the transect where hydrocarbon fluorescence in the water was highest and there is a significant regression of EROD activity on hydrocarbon concentration. The results therefore suggest a significant elevation of hydrocarbons in a large area of the northern North Sea (5–10 times the true background) and that these concentrations are capable of inducing biological responses associated with deleterious effects in fish larvae.

Measurement of organic contaminants and biological effects in Scottish waters between 1999 and 2005

Concentrations of organic contaminants were determined in sediment and fish collected annually at six sites around Scotland between 1999 and 2005, as part of the UK National Marine Monitoring Programme. Polycyclic aromatic hydrocarbons (PAHs) and chlorobiphenyls (CBs) were measured in sediment, while CBs and ethoxyresorufin-O-deethylase (EROD) activities were measured in the fish. Highest PAH concentrations in sediment were found at sites where higher coastal influences would be expected (e.g., Clyde and Solway) and four of the six sites gave PAH concentrations above OSPAR background assessment concentrations (BACs). A significant downward trend in the median total PAH concentrations, normalised to total organic carbon (TOC), was found at one of the six sites (Minches). The PAH profiles at all sites were consistent over the 6 year period, indicating that the sites are relatively stable and PAH sources are not changing. There was an indication of a greater petrogenic input on the west coast, with sediment from the Clyde, Solway and Minches having a greater proportion of 2- and 3-ring PAHs and a lower proportion of 5-ring PAHs. CB concentrations at all sites were low compared with UK estuarine sites and similar to sediment from more remote areas: however, BACs were exceeded. No significant trends were detected in either the sediment CB concentrations or patterns at any of the six sites. CB concentrations were significantly higher in fish liver collected from the Clyde. Concentrations at the other five sites were low, with the majority of samples having concentrations for the ICES7 CBs of <500 microg kg(-1) lipid weight. However, individual CB concentrations were still above the BACs. Hepatic EROD activities were measured in male plaice from 2002-2005 and were generally low (<10 pmol min(-1) mg protein(-1)). No temporal trends were detected in either CB concentrations or the EROD activity.