The following is the text of a speech given by Sir Hector Monro to open the Conference held at the Royal Society of Edinburgh on Tuesday 21 September 1993.

This conference marks a dramatic and lasting achievement at Sullom Voe. I intend in these remarks to make clear the Government's appreciation of it. Yet all of us in this room must be aware, as we approach today's business, that as little as nine months ago Shetland, and Scotland, were in the midst of a major oil spill accident.

During these two days this conference will review the environmental management and monitoring at Sullom Voe Oil Terminal since 1974. To understand the part played by Shetland, its people, and the successive Island Councils we have to look further back. Many individuals, many organisations of varying motivations, of differing gifts have been contributors; have set the pattern.

Who were they all? As a good citizen I will place the Government first – not necessarily in importance. These days a County Convener must be cautious in his utterances! In the early 1970s politically safe oil held many attractions. The recent BBC2 programme so graphically evokes the period. There was also the massive potential income so near to the homeland.

The Shetland Islands lie between latitudes of approximately 60° and 61° North, over 100 miles north of the Scottish mainland. They are influenced by the North Atlantic Drift so that the climatic conditions are much less severe than for other land masses, for example in Southern Greenland where the mean temperature for five months of the year is below freezing. The environment in all its considerable heterogeneity is well described in The Natural Environment of Shetland (Goodier 1974) and in The Natural History of Shetland (Berry & Johnston 1980). Briefly the islands lie on the western oceanic fringe of Europe, have approximately 1450 kilometres of coastline and an area of 1468 square kilometres. The geology is varied and geomorphologically the islands constitute a drowned range of glaciated hills situated on the continental shelf. The coast consists of extensive areas of cliffs and voes with relatively few beaches. In general, the ‘outer’ coasts, especially on the west, are exposed high energy environments. In contrast, the inner coasts, often voes, are deep sheltered inlets. The land itself tends to be hilly and, where it has not been stripped for agricultural use, is blanketed with peat, with the main vegetation heather (Calluna vulgaris) and cotton sedge (Eriophorum angustifolium). Approximately 10% of the land is covered by rushy vegetation and there is very little relict scrub though there are one or two planted woodland plots. The original scrub was largely eradicated by man who arrived in Shetland from Iberia about 3500 BC. Colonisers from Scandinavia arrived in the eighth century and have had a lasting influence on the culture of the islands. In 1971 the human population was about 17327 and in 1989 was 23 214 (SIC 1992).

Sullom Voe Terminal has been in operation since November 1978, processing crude oil from the East Shetland Basin. Gas processing was initiated in April 1981, with full LPG production commencing in May 1982. The terminal is operated by BP Exploration, while port operations are controlled by Shetland Islands Council. This paper will summarise both terminal and port operations, to highlight those areas which involve a discharge or emission to the environment. Variation of the discharges with time will also be indicated to provide a background against which the results of the environmental monitoring programme can be set.

Senior staff of the Shetland Islands Council Marine Operations Department (see Appendix 1) and the terminal operator with responsibility for the prevention of oil pollution or its containment and recovery are in agreement that every effort made to prevent pollution is worth many times the effort subsequently applied to effecting a cure. Tankers and combination carriers engaged in the oil trade probably present the greatest statistical risk of oil pollution within port limits because of the quantities of oil transferred in their operations. For that reason the thrust of this paper is directed at the handling of such vessels. However, the measures outlined can be readily adapted or modified to reduce the likelihood of oil pollution originating from almost any floating craft within a harbour.

Two chemical monitoring programmes have operated in Sullom Voe since 1978, a statutory programme which measures levels of contaminants in the area of the diffuser outfall and the SOTEAG programme which measures contamination in the wider area of Sullom Voe and Yell Sound. Both programmes were in place prior to the operation of the terminal and had gathered useful information. The subsequent information provided annually by the two monitoring programmes during the operations of the terminal has allowed accurate assessment of the levels of contamination in the area of operation and has shown that the contamination from heavy metals and hydrocarbons in the Sullom Voe area is at the lower end of the range of levels encountered in mainland estuarine regions.

The aims, methods and techniques of the macrobenthic monitoring programme in Sullom Voe and Orka Voe are described together with an analysis of the data obtained from surveys that began in 1978 and continue to the present. The distribution of the benthic macrofauna is discussed in relation to the sedimentological and hydrocarbon data obtained and compared with data from other Shetland waters. The macrofauna is considered to be typical of five of the six Facies used to describe the communities of the voes around Shetland. The possible effects of the terminal operations on the macrofauna are assessed and it is concluded that the disturbance noted to the macrofauna in Garths Voe, close to the diffuser at Calback Ness and in Orka Voe, essentially follows the same pattern seen in modifications to Shetland macrofauna that occurs where naturally occurring organic carbon enrichment exists.

Mussels (Mytilus edulis), collected from up to nine sites, were used to monitor the degree of chemical contamination (by petroleum hydrocarbons and organotins) and the associated sublethal biological effects (scope for growth) in the vicinity of the North Sea oil terminal at Sullom Voe from 1982 to 1989. Gluss Voe represented a ‘clean reference’ site at which mussels showed a very low level of contamination and a consistently high ‘scope for growth’ (>20 J g−1 h−1). Spatial and temporal changes in the concentration of polyaromatic hydrocarbons in the mussel tissues reflected the major sources of oil inputs and the number and size of oil spillages around the tanker loading jetties. Hydrocarbon concentrations in mussels at the oil tanker jetties were typically 10-fold higher than mussels at Gluss Voe. The concentrations of tributyltin in the tissues were greatest in the area near the tanker jetties and showed a steady decline between 1986 and 1989 which correlated with a decline in tanker activity (r = +0.98).

The results demonstrated a significant correlation between the net quantity of oil spilled during the month prior to sampling and the accumulated aromatic hydrocarbons in the mussel tissues (r = +0.89). In addition, there was a significant negative relationship between scope for growth and the log concentration of aromatic hydrocarbons in the mussel tissues (r = −0.83). Toxicological interpretation of tissue residue data indicated that the decline in SFG was caused by accumulated PAHs rather than TBT. Although mussels showed a significant reduction in scope for growth in Sullom Voe they were still able to grow, reproduce and maintain their populations. When these results are placed in a wider geographical context and compared with other UK sites, it is apparent that the ‘clean reference’ site in the Shetland has the lowest recorded levels of organic contaminants, and that other sites in the vicinity of the Sullom Voe Oil Terminal are less contaminated and impacted than many estuaries on the UK mainland.

Common dogwhelks (Nucella lapillus) show a characteristic response to exposure to tributyltin compounds. Females develop male sexual characteristics, a phenomenon termed imposex. Dogwhelks have been collected for assesment of imposex from sites throughout Sullom Voe and Yell Sound in 1987, 1990 and 1991.

Results of the 1991 survey have indicated that dogwhelks were completely absent from the terminal area, on the promontory of Calback Ness. The degree of imposex was highest in the population from Kames, the site closest to the terminal. Juveniles were completely absent from this site. Incidence of imposex was high in populations throughout the Voe and 91% of the females examined from within the Voe were reproductively unviable due to blockage of their reproductive tracts with vas deferens tissue. Outside the Voe, in the well flushed waters of Yell Sound, imposex was much lower, but only fell to levels associated with populations from areas distant from tributyltin (TBT) contamination in the two most northerly sites surveyed.

Results of the survey have indicated that activities associated with the oil terminal are the source of TBT contamination to the area, and that contamination arising from the terminal operations has not only affected dogwhelks in Sullom Voe, but populations throughout Yell Sound.

Comparison of the imposex levels from 1987 and 1990 data indicates that the reproductive capacity of females has progressively declined and that populations within the Voe are gradually being eliminated. Forty-six percent of females sampled from populations within the Voe were sterile in 1987, compared to 65% in 1990, and 91% in 1991. In 1987, both adult and juvenile dogwhelks were present in the jetty area, although 94.5% of the females were sterile. In 1990, juveniles were absent from this area, and all females were sterile. No dogwhelks were found in the terminal area during the 1991 survey and, at Kames, the next closest site, juveniles were absent.

Water from the separation plant at Sullom Voe is discharged into the sea under agreed conditions from a diffuser situated to the north of Calback Ness, close to natural scallop (Pecten maximus) beds.

As part of the arrangements to monitor potential effects of the discharge, Torry Research Station was asked to assess, for petroleum taint, shellfish which would be sampled at intervals from Sullom Voe. To avoid depletion of the natural shellfish beds, queen scallops (Chlamys opercularis) or scallops, whichever were available from other areas, were set out in cages suspended (or on the bottom) 100–1250 m eastwards of the outfall for a period, and then recovered, frozen, and assessed subsequently at the laboratory by a trained taste panel, and compared with the same species unexposed.

The cages were laid on 10 occasions from March 1980 to February 1987. Initially, no petroleum taint was detected. In August 1980 and May 1981, a different flavour, but not recognisable as a petroleum taint, was detected at 800–1000 m from the outfall after three days exposure. In May 1982, 33% of the queen scallops in the cage on the bottom, 100 m south east of the diffuser, were dead after six days exposure, and taint was detected at the threshold level in shellfish in the cage at 300 m. In May 1983, taint and petroleum derived hydrocarbons were detected in the sample from the cage on the bottom, 100 m south east of the diffuser, after seven days exposure. In May 1984, taint was again detected at the bottom, 200 m south east of the outfall, after 10 days exposure.

Enquiries established that the diffuser was not operating with maximum efficiency. Subsequently, monitoring revealed an improvement. Taint assessment proved to be a sensitive detector of petroleum contamination.

Twenty-one species of seabirds breed regularly in Shetland, some of them in huge, spectacular, multi-species colonies on cliffs. The Sullom Voe Environmental Advisory Group Environmental Impact Statement (SVEAG 1976) provides a table showing the relative importance of seabird species in terms of Scotland and the British Isles. We have updated these data in the light of the Seabird Colony Register (Lloyd et al. 1991) and present data for seven species, vulnerable to oil pollution, in Table 1. It is clear that these populations are of national importance and indeed several are internationally important. Separately, an estimate was provided by SVEAG of the numbers of sea ducks and divers wintering in Shetland waters and updated estimates are given by Suddaby (1992) (Table 2). Chief among these is the eider duck (Somateria mollissima) which is apparently resident in Shetland throughout the year (Heubeck 1993a). In its Eighth Report, on Oil Pollution at Sea, the Royal Commission on Environmental Pollution (1981) recognised the vulnerability of seabirds to oil pollution and this was clearly a matter of concern in Shetland and elsewhere when the flow of enormous quantities of crude oil into Sullom Voe via undersea pipelines and out of Sullom Voe by large tankers became a reality. The risk to seabirds of oil pollution is well documented (Bourne 1968; RSPB 1979). Dunnet (1974, 1980, 1982, 1987) has reviewed the situation in relation to the North Sea oil industry.

A Shetland-wide beached bird survey was established in March 1979 and monthly surveys have continued since. This paper presents results from March 1979 to December 1992 during which time a total of 34 320 corpses of seabird and seaduck were found, of which 34023 (99.1%) were specifically identified. Corpses of guillemot (8911), fulmar (8707), kittiwake (4421), herring gull (2264), shag (1843) and great black-backed gull (1785) comprised 82.1% of the identified total, the remainder being made up of 31 other species. The relationship between the numbers of each species found, and their numbers and occurrence in Shetland waters is discussed. A total of 2781 corpses were judged to have been oiled before their deaths, of which 2732 (98.2%) were specifically identified. The six species most frequently found oiled were guillemot (1170 corpses), fulmar (543), kittiwake (184), razorbill (131), puffin (111) and shag (99).

Variations in both the percentage of corpses found that were oiled, and the number of oiled corpses found per kilometre of beach surveyed, are examined and discussed. Comparison is made with results from beached bird surveys elsewhere in the British Isles and in other countries bordering the North Sea. In some species, notably the pelagic auks, there was considerable annual variation in the numbers of unoiled corpses found while in other species the number of unoiled corpses found changed more gradually over the 14 years. Reference is made to similar changes observed in other beached bird surveys and possible reasons for these changes are discussed.

Rocky shores in Sullom Voe were first surveyed in 1976 and, apart from a break of two years (1982–83), have been surveyed annually since. The aim of the surveys is to monitor the health of the rocky shore communities by identifying any major changes in the abundance of the fauna and flora and distinguishing anthropogenic effects from natural fluctuations. The 23 primary sites are spread around Sullom Voe, from Mavis Grind, at the head, to Mioness, just outside the entrance. A belt transect method is employed, and categorical abundances of conspicuous species on a checklist are recorded. Graphical analysis of the data for selected species and sites is presented to illustrate the most important changes that have been observed.

The rocky shore communities in Sullom Voe are dynamically stable, except where physical disturbance has not allowed them to reach a state of long-term stability. The effects of, and the recovery from, the 1979 Esso Bernicia oil spill and its clean-up are described. While recovery of communities was rapid on shores where no clean-up was attempted, the communities on shores which were mechanically cleaned were showing continued effects in 1993. The deterioration of dogwhelk populations affected by the antifouling paint additive tributyltin (TBT) has been followed in recent years. Dogwhelk populations close to the terminal jetties are very small and are dominated by adults. Natural fluctuations in abundances of barnacles, dogwhelks, limpets, fucoid algae and littorinid gastropods over the period 1976 to 1992 are also described.

Annual variations in a number of parameters over the period 1977–84 are described: they were generally site-specific in character. Linear shell dimensions of Cerastoderma edule populations (seven sites) remained stable but trends in both shell and soft-tissue dry weights changed over this period. Population structure and growth rates of C. edule are described using growth-ring analysis: they provide evidence of sporadic recruitment and persistent dominance by one or more yearclasses, although several populations are particularly individual in character. Populations of Macoma balthica (two sites) had a stable structure. Populations of both species at one site (inner Houb of Scatsta) declined markedly following the Esso Bernicia oil spill in 1982 and had not recovered before the study was terminated. Studies of transects at two sites are described: sedimentary changes were small while infaunal community characteristics showed both persistent environmental trends for some species and random fluctuations in others. The communities at each site showed high diversity, with generally stable structures upon which are superimposed annual and site-specific fluctuations in abundance of component species.

This programme was intended to assess the environmental health of the Sullom Voe salt marshes and, if any deterioration proved to have occurred, to suggest whether activities at the oil terminal could have been responsible.

The main study has been in the growth of the important halophytic grass Puccinellia maritima as measured by tiller/stolon elongation. This has been used as a measure of salt marsh vitality.

The salt marshes within Sullom Voe have suffered statistically significant declines in plant vigour in the detailed study areas over the period 1976 to 1987 (accompanied by local erosion and deterioration of the marsh edges), in contrast to comparable sites outside Sullom Voe, which have shown no overall decline. All sites however have shown conspicuous and loosely synchronised variations in tiller/stolon length, which may be explained in part by changes in sea level.

Although some local damage to sites can be attributed to oil-related activities, no cause can be identified for the wider deterioration within Sullom Voe because of the absence of data on factors which might be inhibiting grass growth. This problem in identifying causes is a serious weakness in monitoring programmes which use plant performance to assay changes.

A brief description is given of the accident to the tanker Esso Bernicia that resulted in the release of 1174 tonnes of heavy fuel oil into the harbour at Sullom Voe. The measures taken to deal with the spill and the resulting oil pollution are described and their effectiveness assessed. Aspects of the environmental effects are considered with particular reference to birds, otters and sheep. Wide-ranging inquiries were made into the cause of the incident, the adequacy of the response, and the effects of the pollution. The actions that resulted are described. Finally the significance of the event is considered in relation to the subsequent development of oil spill contingency planning at Sullom Voe, and in the wider context of Shetland.

Monitoring in the marine environment is selectively reviewed and illustrated by examples of programmes covering water, sediments and biota at both global and site-specific levels. Against this background the monitoring work at Sullom Voe is considered, and the optimal approach to oil terminal monitoring is discussed.