The Sullom Voe crude oil terminal has already been almost seven years in the making. I would like to take you all back through those seven years to the halcyon days before Shetland found herself face to face with the unveiling of a geological event which occurred millions of years ago.

Imagine yourself a Shetlander. You are a member of a community of about 17,000 independent, resourceful folk, who had only just stabilised their traditional fishing/agricultural/knitting economy and their population after a century of decline. During that century, or as much of it as you have lived through, you have seen friends and relatives leaving on the 'Clair' with monotonous regularity bound for any place between Aberdeen and Australia. You may have lost some of those friends and relatives on whalers in the wastes of the South Atlantic. You have seen crofts left to go derelict and to waste, and most of your able bodied menfolk having to leave the islands in order to find gainful employment. Latterly, you have just been successful in combating the proposals of the Wheatley Commission to absorb the islands into a Highland Region.

The Shetland Oil Terminal Environmental Advisory Group (SOTEAG) has initiated a programme of environmental monitoring in Sullom Voe, which is funded by the Sullom Voe Association Ltd (S.V.A.Ltd). Its aim is to provide a continuing check on the effectiveness of the regulatory measures in operation at the terminal by providing early warning of harmful environmental effects due to the anticipated low-level, continuous discharge of predominantly oily water effluents and occasional accidental spills. In designing a programme the limitations of available methods for monitoring the biota so as to detect the effects of chronic pollution have been recognised. The programme adopts an integrated approach based on regular quantitative surveys of selected key marine habitats or biota, including rocky shore, soft shore, salt marsh and benthos associated with a programme to monitor levels of hydrocarbons and heavy metals in sediments and the tissues of selected target organisms. The network of sites and sampling stations has been planned to measure gradients of effect over a wide area having the terminal as its focus and primary source of effluent. The programme also includes projects to monitor atmospheric pollution (SO2) and ornithological monitoring. A flexible approach has been adopted and the programme will be modified in the light of experience and circumstances. Results are reported on annually to SOTEAG's Monitoring Committee which oversees the programme and interprets the results for submission to SOTEAG and then to S.V.A. Ltd.

This paper describes briefly the history behind oil pollution contingency planning for Sullom Voe. It describes in detail the environmental factors which have been considered when drawing up the Sullom Voe Harbour Oil Spill Plan. These factors are:

1. The nature of the sea zones within the Oil Spill Control Area.

2. The nature of the coastline within the Oil Spill Control Area.

In both cases accessibility of the various zones, and how this will affect contingency planning, is discussed.

3. Wildlife and conservation interests including: (a) ornithological interests; (b) mammals; (c) inshore fisheries; (d) salt marshes and soft mud shores; (e) houbs and other sensitive shallow water areas; (f) Sites of Special Scientific Interest SSSI's and Nature Reserves; (g) secondary beach structures; (h) sand amenity beaches and (i) other amenity areas, e.g. harbours.

Finally the strategy, based on the factors summarized above, and its effectiveness in the light of an oil spill, is discussed.

In the five years to 1978 hydrographic surveys were conducted in Sullom Voe, Shetland and these have been supplemented since 1976 by current measurements. Conditions varied from year to year mainly due to climatic factors, the most marked changes occurring at the head of the voe where varying degrees of stagnation were encountered.

In summer the voe is weakly stratified. In winter longitudinal gradients are encountered mainly because of a slight reduction in salinity towards the head. Because of this the surface waters of the voe are more readily flushed in summer than in winter when the flushing time, calculated from the freshwater balance, is at least 15 days. The current measurements show that rapid renewal of the surface waters occurs in the summer during storms. Because the voe is open to the north, southerly winds, blowing surface waters out of the voe, drive a much stronger circulation than winds from the north and this is the main reason for the intermittent breakdown of stagnation in the upper basin. Tidal currents are very weak (<7 cm/s) but occasionally seiches, generated by sudden changes in the wind direction, with a period of about 1 hour and current amplitude of 15 cm/s are encountered. Nutrients from the adjacent tidally mixed Yell Sound are intermittently supplied to the voe by these wind-driven processes and as a result, high levels of productivity are encountered at intervals throughout the summer.

Currents were measured along two routes through Yell Sound to Sullom Voe in the Shetland Islands. Current meter moorings were deployed by the consulting engineers Peter Fraenkell and Partners for one month at 20 positions with three meters which measured the flow from near surface to a depth of 20 metres. The accuracy of these measurements is considered and the difficulty of making measurements in this region is illustrated.

The paper discusses the nature and variability of the currents that were measured and resolves the currents into a tidal and non-tidal component. An analysis procedure is developed for removing the tidal component and for producing tidal current vectors for each position. From this the general tidal circulation pattern is constructed and discussed. It is shown that tidal currents along the eastern route are too high at certain states of the tide for safe navigation.

Current surges of significant magnitude are shown to exist throughout the area. These are driven by the tidal motion and it is suggested that they are an effect of travelling gyres which are generated in the lee of islands and shallow banks when the tidal streams are largest.

Determinations of dissolved oxygen and nutrients in the water overlying the sediments, of sedimentation rates, and of redox values, acidity, dissolved sulphide, carbon, nitrogen and cellulose values at different levels in the sediments themselves have been carried out in various parts of Sullom Voe. The effects of oxygen depletion following intermittent stagnation of the bottom water in the inner basin on carbon cycling in the sediments are discussed and contrasted with the chemistry of oxygen-rich sediments elsewhere in the voe.

Data is presented to provide a baseline for assessing heavy metal pollution in Sullom Voe.

Procedures are described for the measurement of concentrations of zinc, chromium, copper, lead, cadmium and nickel in sediment samples and in specimens of Modiolus modiolus (L.).

Analysis showed that the concentration values in Modiolus were similar to those measured in specimens obtained from the Irish Sea.

In the sediment samples, it appeared that the distribution of metals was independent of the concentration and type of metal. The distribution of the metals which were analysed also showed significant dependence on the sediment composition.

After a brief review of some general procedures that have been proposed for the identification of oil spills, details are given of methods that depend on hydrocarbon analyses. Hydrocarbon distributions due to a biological input are compared to those from a petroleum input, utilising hydrocarbon fingerprints obtained by gas chromatographic and combined gas chromatographic-mass spectrometric methods.

It has been shown that most of the sediment samples collected in 1976, 1977 and 1978 from sampling stations in and around Sullom Voe are substantially free from pollution by crude oil; however, three of the samples collected during 1978 do show some signs of pollution. These data will act as a baseline for future studies to be carried out during the operation of the oil terminal.

The results of chemical analyses for hydrocarbon components in the surface water film, water, sediment traps and sediments are presented for samples collected during the period 1973–78. The n-alkane profiles of these samples are used to characterise the hydrocarbons and to help in determining their origin. The amounts of hydrocarbon present are compared to the estimated inputs of petroleum hydrocarbons from operational losses and accidents based upon analogies with worldwide averages and with data taken from other similar oil terminals. Some conclusions are drawn as to the likely fate of this oil in Sullom Voe.

The programme for ornithological monitoring in Shetland has concentrated on selected species of cliffnesting seabirds and inshore waterfowl. Sample study sites throughout Shetland have been selected and standard counting methods derived. These have taken account of factors such as logistics and accessibility, the effects of weather and observer error and of the seasonal and diurnal variations in the numbers of birds.

Changes in seabird and waterfowl numbers between 1975–79 have been observed. These, with the exception of the bird mortality following the Esso Bernicia oil spill, have been attributed to natural variation. From the scale and local differences between these as yet short-term observations, estimates are presented of the minimum percentage change required in either numbers of birds or their nests before such natural variation is exceeded.

The problems of interpreting changes in numbers are discussed.

The number of dead birds picked up in Sullom Voe after the Esso Bernicia spill corresponded closely to that estimated from the monitoring counts before and after the incident.

The distribution and status of grey and common seals around Shetland is reviewed. Recent surveys have produced an accurate picture of the location of breeding sites, grey seals being found at discrete localities mainly in the north and west of the islands and common seals being distributed more widely throughout the archipelago. The population of grey seals is estimated at 3,500 animals and is considered to be relatively constant. The reliability of boat surveys for estimating common seal populations is discussed. It is concluded that the population of Shetland has increased in numbers following protective legislation and it is suggested that there has also been a change in hauling out behaviour. The current population consists of at least 4000 individuals.

Grey seals do not appear to have been affected by oil developments at Sullom Voe so far, but common seal numbers in the Sullom Voe area have not increased at the same rate as elsewhere in Shetland, and the number of pups present has declined. It is suggested that these changes may have arisen as a result of the development of the oil terminal. Study methods which would enable the nature and causes of these changes to be identified are proposed.

The salt marshes of the Sullom Voe area are small in size and few in number, but they are important ecologically in being the vegetated upper parts of soft-sediment shores developed in sheltered locations, and in being likely to act as oil traps in the event of pollution by floating oil slicks. The marshes are species-poor, and are subjected to local erosion and reworking of sediments–factors which must influence any programme for the monitoring of their general ecological health. The salt marsh monitoring programme outlined here has three main components: (a) measurements of accretion and erosion; (b) measurements of stolon length in Puccinellia maritima (as an index of performance in the principal Angiosperm coloniser), and (c) measurements of frequency for eight species (or species groups) on areas of grass-poor salt marsh (the forb salt marsh). The scale of natural variation in these measurements from year to year is not known, so the first few years' data will provide a standard against which subsequent variation can be assessed.

The general character of soft shores in this region is considered briefly. Studies of several aspects of the biology at selected sites were instigated as part of a broader monitoring programme and the results of the baseline study are described in this paper. The structure and growth of populations of Cerastoderma edule (L.) and Macoma balthica (L.) (Mollusca: Lamellibranchiata) are described. Considerable differences in C. edule growth rates were found between sites, and recruitment and survival was sporadic at many sites. The value of C. edule populations in providing some degree of ‘retrospective monitoring’ is considered. C. edule populations were found to contain significant infections of the entocommensal nemertean Malacobdella grossa: this is a new host record for M. grossa. The distribution and abundance of the macrofauna on two sandy shores are discussed in relation to environmental conditions.

The rocky shore ecology of Sullom Voe is described from surveys carried out at 43 sites in and around the Voe. The sites were located partly to provide a description of communities from a wide variety of Shetland rocky shore habitats. Records of the species present and their distribution and abundance were based mainly on check-lists including 8 lichen, 21 algal and 23 animal taxa. Other species present at each site were usually also recorded. A total of 10 lichens, 82 algae and 91 animals were recorded during four surveys in 1976, 1977, 1978 and 1979. Differences in the distribution, abundance and vertical extent of species from site to site were associated mainly with exposure to wave action, slope of the shore and the stability of the substrate. Several species common on shores in the south of the British Isles were absent or rarely recorded in Sullom Voe or Shetland. A few species rarely found or absent in the south of the British Isles were common in Shetland. During the three years of the survey, most changes in communities present on each shore have been small. However, since 1976, the abundance of the green alga Enteromorpha sp. has shown an increase, whilst populations of the barnacle Balanus balanoides have declined. The spillage of 1,100 tonnes of fuel oil in January 1979 resulted in oiling of the upper shore at many sites but with little mortality to intertidal species except where shores had been cleaned mechanically. The Australasian barnacle Elminius modestus has been recorded from Sullom Voe but the populations are probably very sparse. It is concluded that a wide variety of rocky shore communities are present within a small area in the region of Sullom Voe, that the communities show an overall high degree of stability, but they are impoverished with respect to numbers of species compared to shores in the south of the British Isles.

The topographic and sedimentary characteristics of the Voe are briefly described and used to define the distribution of epifaunal and macro- and meio-infaunal communities throughout the Voe. The structural complexity of the communities, their interdependence on one or a group of dominant species, and their trophic relationships are emphasized. Changing distributions with depth and in time are examined in detail, particularly in relation to the intermittently eutrophic conditions occurring in the inner basin of the Voe.

The macrobenthos of Sullom Voe was investigated by grab sampling in 1976, 1977 and 1978. These surveys have provided data for future comparisons and have enabled a description to be made of the natural soft bottom macrobenthos of Sullom Voe in terms of species composition and abundance.

The most common species encountered were Thyasira flexuosa, Glycera ?alba, Nephtys hombergi, Myriochele oculata and Rhodine gracilior, which are widely distributed throughout Sullom Voe. Other species such as Owenia fusiformis and Prionospio malmgreni were restricted to the outer regions whilst Scalibregma inflatum and Venus ovata were largely confined to the inner stations. The most intensive sampling was carried out around the proposed ballast water discharge site and in this area it was possible to define four faunal areas corresponding to the sediment characteristics. This subjective analysis based on species distribution maps was borne out by multivariate ordination and classification of the data.

The macrobenthic diversity of Sullom Voe is compared with other coastal areas such as Milford Haven and some Scottish sea lochs. Sullom Voe supports a relatively diverse community which in terms of species richness compares with the benthos of other sheltered, undisturbed areas elsewhere in Scotland.

1. A general survey of the sub-tidal populations of Modiolus modiolus (L.) to a depth of 18 or 21 m was carried out in five Shetland voes, with particular emphasis in Sullom Voe. Estimations of density distribution and growth rate were made.

2. Commencing in June 1976 samples were collected at three-monthly intervals from two sites in Sullom Voe, and from one site in Cat Firth in 1977, to investigate seasonal variations in flesh and biochemical content. The data indicate that Shetland Modiolus are generally similar in their biology to those from Scottish lochs, and are liable to considerable variation between and within populations, with groups responding to environmental variations of very local extent.

3. A list of animals found associated with Modiolus and their byssus complexes is given. As no effort was made to collect the fauna systematically or quantitatively, the list is not comprehensive.

The base-line study consisted of three visits to Sullom Voe before the oil terminal became operational. General stress indices were used to measure the health and condition of four native and two transplanted populations of mussels (Mytilus edulis). A mobile laboratory was used to measure the physiological responses under ambient field conditions. These were then integrated into the stress indices, scope for growth and oxygen :nitrogen ratio. The general biochemical and cytological stress indices, namely taurine: glycine ratio, gametogenic development and latency of lysosomal β-hexosaminidase were also measured for each population. All these general stress indices indicated that the mussel populations were in a relatively healthy physiological condition. However, mussels from the Houb of Scatsta showed a transient stress response, probably caused by freshwater run-off from the surrounding peat beds.

In addition to the general stress indices, specific cellular responses known to be induced by petroleum hydrocarbons were monitored. The activity of enzymes forming components of the mixed-function oxidase system (NADPH neotetrazolium reductase, G6PDH and NADP-ICDH, and aldrin epoxidation) were measured.

The rationale for measuring these general and specific stress indices as part of a Sullom Voe environmental monitoring programme is discussed in the light of experiments with petroleum hydrocarbons in the laboratory and with reference to the future operation of the oil terminal.

Although the main theme of this Symposium centres on the environmental impact of the Sullom Voe Terminal in Shetland, it was considered desirable, in this last session, to give brief attention to the Flotta Terminal in Orkney. Several aspects of the development have been discussed elsewhere (Johnston and Halliwell 1976; Trainer et al. 1976; Moore 1980).

Three key sources of marine pollution could be recognised from the terminal operations:

1. Tanker accidents with resultant spillage in the approaches to Scapa Flow.

2. Spillage at the S.P.M.s.

3. Effluent discharges from terminal operations.

Since little has been said about effluent discharge at Sullom Voe, it seems appropriate to consider this aspect of our Flotta experience.

The basis to pre-operational and subsequent monitoring studies will be discussed.