RECOVERY OF INTERTIDAL BIOTIC COMMUNITIES AT VOE FOLLOWING THE ESSO BERNICIA OIL SPILL OF 1978 Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/461/1742866/2169-3358-1991-1-461.pdf by guest on 01 October 2021

Robert G. Rolan British America 200 Public Square Cleveland, Ohio 44114

Ronald Gallagher Oil Terminal , United Kingdom

ABSTRACT: In December 1978, the Esso Bernicia spilled 8,000 bar- This program was organized by the Shetland Oil Terminal Environ- rels of Bunker C oil during a berthing accident near the Sullom Voe Oil mental Advisory Group (SOTEAG) which has an independent chair- Terminal. About 100 miles of shoreline were oiled, much of that span man and members drawn from the oil industry, the Shetland Islands heavily. Sullom Voe is a bay of the Shetland Islands, north of , Council, conservation groups, and local residents. Most of the mon- an area environmentally similar to Prince William Sound. The highly itoring studies have been carried out by independent groups such as indented, rocky shoreline is inhabited by typical intertidal communities university departments. characterized by fucoid algae (rockweed), barnacles, and snails. Bio- logical survey data for the intertidal communities had been collected for three years prior to the spill. During the cleanup, most of the shores that were accessible to heavy equipment were stripped of oily rock, cobble, and gravel. Other fairly accessible areas were hand-cleaned. Dispersants were tried on a few shores, but were ineffective. Many of the less accessible locations were not cleaned at all. The oiled shorelines were resurveyed every year from 1979 through 1987, except 1982 and 1983. Except for the mechanically cleaned areas, the biological communities in the rocky intertidal zone returned to very near normal within the first year, and have remained so in spite of the presence of traces of weathered oil. Normal populations of snails and small crustaceans have thrived in intimate contact with asphaltic residues that remain in some locations. In contrast, the biological communities at the sites that were cleaned mechanically were obliterated, and still had not fully recovered after almost nine years.

The Shetland Islands, 130 miles north of Scotland, are the site of Europe's largest oil and liquefied gas terminal, at Sullom Voe (Figure 1). The terminal was built in the late 1970s to receive hydrocarbons from over a dozen fields in the East Shetland Basin of the , midway between Shetland and Norway. Operated by British Petro- leum, it handles nearly half of Britain's oil production. The Shetland Islands lie at approximately the same latitude as Prince William Sound, Alaska, i.e., just slightly north of 60°N. Owing to the influence of the Gulf Stream, it has a mild, oceanic climate and extremely high relative humidities. Summer temperatures are very similar to those in Prince William Sound (at Hinchinbrook Island), but average 13° to 14° F warmer in the winter. It is one of the windiest places in Britain, and averages 58 days a year of gales. Sullom Voe, a sea loch, is one of the more protected anchorages in Shetland due to its location on the windward side of . The shores are typically bedrock, boulders, and cobble, indicative of high wave energy levels.11 There has been a continuous program of environmental monitoring at the terminal and surrounding areas since the start of construction. Figure 1. Shetland Islands, showing location of Sullom Voe

461 462 1991 OIL SPILL CONFERENCE

Because of this program of environmental monitoring, there were three years of data on the intertidal communities around the terminal area before it experienced its first and most serious oil spill. Although the intertidal studies had been established to document possible im- pacts from ongoing, routine operations at the terminal, the three years of baseline studies prior to the Esso Bernicia spill and biological recovery data, spanning nine years, provide a unique data set from which to evaluate the effects of a major spill and associated cleanup activities. This paper summarizes the results of these studies, here- tofore available only in unpublished SOTEAG reports.

The spill and response Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/461/1742866/2169-3358-1991-1-461.pdf by guest on 01 October 2021

As a result of a fire aboard one of three attendant tugs, the 190,000- metric-ton tanker Esso Bernicia struck a mooring dolphin at the Sul- lom Voe Terminal on December 30, 1978, puncturing a fuel tank. Approximately 8,000 bbl (1,174 metric tons, t) of Bunker C oil were spilled. Initially, booming confined the oil to the immediate terminal area, but the boom failed on January 3,1979. Wind and strong tidal currents transported the oil widely throughout the Yell Sound area. Most of the oil stranded within Sullom Voe, and the most heavily oiled areas were in the vicinity of the terminal. The oil came ashore on a high tide in these areas, and, while stranding was confined to the upper shore, the covering was extensive. In all, some 100 miles (160 km) of coastline were oiled, about 20 percent of it heavily. Twenty-one intertidal survey sites had been established prior to the spill. Of these, all but four received some degree of oiling from the Esso Bernicia spill. A massive cleanup operation was mounted during the first half of Figure 2. Location of primary sampling sites in Sullom Voe and Yell 1979. The principal cleanup method was manual bagging of oil debris. Sound Roughly 1.3 million lb (600,000 kg) of oil material were collected. About 5,600 gal of BP 1100WD dispersant were used, with some success, to disperse oil on the water, but trial applications on the oiled primary sites. However, resampling of the two "reference sites" (3.8 shore were ineffective. At more remote locations on Yell Sound and its and 6.11) at Voe was discontinued in 1985. Notably, of the five islands and many locations in Sullom Voe, very limited or no cleanup most heavily oiled sites in the Esso Bernicia spill, two had been was attempted, and the oil was left to degrade naturally. These shores mechanically cleared (5.2 and 6.12), two were cleaned manually (4.1 were predominantly bedrock or large boulders. and 4.3), and one was left to natural cleansing (6.13). The other two Most importantly, at certain accessible beaches near the terminal the mechanically cleared sites (6.2 and 6.4) were at locations which had beach material was stripped by bulldozer, dragline, and front-end been less heavily oiled. The degree of oiling of each site from the Esso loader. Survey sites 5.2, 6.2, and 6.4 were cleared in mid-January. Bernicia spill and whether it was mechanically cleared are indicated in Clearing was largely restricted to the upper shores, where the oil was Table l,8 along with years in which each of the sites were sampled. thickly deposited. At Scatsta Ness, another heavily oiled location, one stretch of shoreline was mechanically cleared in mid-May and an adjacent stretch was left uncleared in order to allow side-by-side com- parison of biological recovery following such fundamentally different Sampling methods treatments. At each of the 21 prespill sites, a permanent tidal datum marker was established. A transect was laid out from the low water of spring tide level to the splash zone. Stations were laid out along the transect at 20- Sampling sites cm vertical height intervals. The number of stations at each site ranged between 9 and 31, but typically were around 15 to 19. At the two new In 1976,18 primary intertidal sampling sites were established at the sites established following the Esso Bernicia spill, the locations of the locations indicated in Table 1 and Figure 2. In 1977, two additional stations were established at matching elevations relative to sea level. primary sites in Vidlin Voe (3.8 and 6.11) were established as reference Only stations above low water neaps were surveyed, because the lower sites because they were thought to be far enough from the terminal to shore had not been oiled and the communities were intact at both sites. be beyond any adverse influence. The 20 primary sites were to be Each year at sampling time, a tape was laid down the transect from resampled on an annual basis. A similar number of secondary sites the marker along exactly the same line as in previous years, as deter- were also established and sampled in the first year, but there was no mined by a combination of previous station marks, site photographs, intention to resample them every year and, in fact, most have not been and compass bearings. The sites were photographed each year, the resampled regularly or at all. marks were reestablished when necessary. At each station along the In 1979, following the Esso Bernicia spill, two new primary sampling tape, abundances of intertidal organisms were determined in a trans- sites were established at the heavily oiled shore at Scatsta Ness (sites verse swath 3 m wide (1.5 m on each side of the tape) by approximately 6.12 and 6.13). The sites were chosen because bedrock was present at 30 cm deep. Limpets and barnacle spat were counted at the same similar levels on the shore and the sites were as near to one another as stations each year using randomly located quadrats (20 cm by 20 cm possible. One of these sites had been mechanically cleared of oil and and 10 cm by 10 cm, respectively). Species abundances were recorded the other was deliberately left untouched. The purpose of the new sites in terms of a scale of abundance categories, each category being a was to study the recolonization of the cleared bare rock in comparison range of numbers of organisms per square meter. to the uncleared oiled community on the adjacent shore, and also to Surveys were conducted at the period of spring tides, generally record changes on the oiled shore that might be attributable to the between two hours before and after low water. From 1976 through spill.8 1981, the surveys were conducted in mid- to late-May. In 1981, the In addition, secondary site 6.2 (south of Jetty 2) was redesignated as sampling period extended into the first week of June. In 1984, the a primary site following the spill, to ensure that this oiled and cleared sampling period was changed to August, to allow establishment of site would be sampled each year.8 Thus, from 1979 on there were 23 populations more clearly characteristic of the year. Hiscock stated that FATE AND EFFECTS 463

Table 1. List of intertidal survey sites, indicating years in which sampled and degree of oiling from Esso Bernicia spill

Year Site number Site name 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 Extremely abundant—More than 80% cover 4.1 Grunn Taing X X X X X X X X X X 4.3 The Kames X X X X X X X X X X 5.2 Jetty 3 (cleared) X X X X X X X X X X 6.12 Scatsta Ness (cleared) X X X X X X X 6.13 Scatsta Ness (uncleared) X X X X X X X

Abundant—20 to 49% cover Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/461/1742866/2169-3358-1991-1-461.pdf by guest on 01 October 2021 3.3 Noust of Burraland X X X X X X X X X X 3.4 Gluss Island East X X X X X X X X X X 3.7 Swarta Taing X X X X X X X X X X 5.1 South of Skaw Taing X X X X X X X X X X 6.1 Fugla Ayre X X X X X X X X X X Common—1 to 19% cover 6.4 Runway Scatsta (cleared) X X X X X X Frequent—large scattered patches 3.1 Between Skaw and Swarta Taing X X X X X X X X X X 6.2 South of Jetty 2 (cleared) X X X X X X X X X Occasional 2.5 Ay Wick X X X X X X X X X X 4.6 Voxter Ness X X X X X X X X X X 6.10 Sullom Pier X X X X X X X X X X Rare—only one or two patches 2.2 Skaw Taing X X X X X X X X X X 2.3 Roe Clett X X X X X X X X X X 6.11 Kirkabister X X X X X X Unoiled 1.1 West of Mio Ness X X X X X X X X X X 3.5 South of Swarta Taing X X X X X X X X X X 3.8 Vidlin Ness X X X X X X 6.9 East X X X X X X X X X X

the change in sampling date would cause no substantial problems in species present in the intertidal community. The species list for the interpreting the data in year-to-year comparisons.2 Sullom Voe area includes 53 species or other taxonomic designations.1 The following observations on changes in the intertidal communities Based on the first five years of survey data, Hiscock concluded that are taken from the work of Hiscock and colleagues and of Howson.1"9 there was a high degree of similarity among the sampling sites in species abundances and distributions of intertidal plants and animals.1 This was especially so for lichen populations and for certain algae such Changes in intertidal communities on the uncleared as Pelvetia canaliculata and Fucus spp., the snails Spirorbis spp., Patella vulgata, and Littorina neglecta, and the mussel Mytilus edulis. In shores contrast, species which were very changeable in abundance and distri- bution from year to year included Enteromorpha sp., filamentous Rocky intertidal communities in the vicinity of Sullom Voe show green algae, the red alga Porphyra sp. and the isopod crustacean Idotea typical vertical zonation resulting, basically, from the relative resist- sp. ance to desiccation of the various species during low tides. With consid- While most of the species population fluctuations at the uncleared erable simplification, the typical, mature community can be described sites were site-specific and apparently without pattern, there were as follows. The supralittoral fringe is dominated by lichens (Verrucaria some notable general trends during the years of the survey. These spp.) and a snail, the rock periwinkle (Littorina saxatilis). Below this, trends were observed at all the uncleared sites regardless of their but above the mean high water spring tide line, is a zone of L. saxatilis degree of oiling from the Esso Bernicia spill. The green seaweed and the brown algal seaweeds Pelvetia canaliculata and Fucus spiralis. Enteromorpha increased from 1976 to 1979, followed by a decline in The true littoral zone occurs between the levels of mean high water 1980 attributed to warm weather and consequent desiccation. Entero- springs and mean low water neaps, and has two major belts of organ- morpha populations stabilized in 1980 and apparently have fluctuated isms. The top belt is the barnacle zone, dominated by the acorn little through 1987. The barnacle, Semibalanus balanoides, decreased barnacle (Semibalanus balanoides), the common periwinkle (Littorina in abundance from 1976 through 1978, and then increased greatly from littoralis), a predatory snail, the dog whelk ( Nucella lapillus), the 1979 through 1981. By 1984, barnacle populations were greater than in common limpet (Patella vulgata), and green algal seaweeds (Entero- any of the previous years of the survey, and they remained high through morpha spp. and spp.). Below this is the belt of brown algal 1987. Populations of the dog whelk followed essentially the same rockweed or wrack (Fucus vesiculosus and F. serratus), the smooth pattern as the barnacle, upon which it depends heavily as a prey periwinkle (Littorina littorea), the common blue mussel (Mytilus ed- species, with perhaps a bit of a lag, best seen in 1979. Rockweed (Fucus ulis), and limpets. Below this, at sheltered sites only, is a belt domi- spp.) populations were relatively low through 1979 and began to re- nated by another brown algal seaweed, Ascophyllum nodosum. cover in 1980 and on through 1987. Further down is the infralittoral zone, characterized by the presence The periwinkles (Littorina saxatilis and L. littoralis) decreased in of a kelp (Laminaria digitata). This zone is uncovered only by extreme 1979 at most locations, but began to recover in 1980. In 1981, peri- low tides (mean low water springs). There are, of course, many other winkle populations increased generally and seem to have fully recov- 464 1991 OIL SPILL CONFERENCE ered. The 1979 decline in periwinkles was attributed to an increase in littorea, L. neglecta, and Nucella lapillus. Enteromorpha was the main wave scour and/or depressed populations of rockweed, upon which the colonizing species. periwinkles graze, not to any effect of the Esso Bernicia spill. The fact Site 6.12 (Scatsta Ness) was cleared above station 7. The biota above that periwinkles actually increased in 1979 at site 4.1 and at the station 5 were destroyed, but between stations 7 and 5 there were low uncleared site at Scatsta Ness (6.13), both of which had been heavily abundances of a number species. These species were even more abun- oiled, supports this conclusion. There was excess mortality dant in the uncleared stations below 7. The presence of the reduced ("bleaching") of kelp in 1984, which was attributed to prolonged sunny community between stations 7 and 5 was a remnant from superficial weather and overexposure to solar radiation and drying during ex- clearance of the bedrock rather than the effect of biotic recovery. This treme low tides. In general, the population fluctuations in the intertidal site had been cleared on May 14 and 15, and there was no sign of communities from 1973 through 1985 were deemed to be within nor- recolonization at the time of the survey on May 26. mal ranges and attributable to natural causes,3 and this picture contin- In summary, intertidal organisms had been mostly destroyed on the ued through 1987.9 cleared stations, and those present had one of four origins:8 • New settlement of sessile organisms following bulldozing {Entero-

morpha and Urospora) Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/461/1742866/2169-3358-1991-1-461.pdf by guest on 01 October 2021 • Remnants of previously established populations (fucoids on bed- Impacts on the uncleared shores rock) • Displaced species on rocks (lichens) Oiling of the shores within Sullom Voe was restricted to the upper • Migration of mobile organisms into the area (periwinkles). shore, usually above the Fucus vesiculosus zone, and on many shores was present only above the Pelvetia canaliculata and Fucus spiralis zone.8 Oil did not adhere to the shore in the lower 30 percent of the tidal range, i.e., below the level of the Fucus vesiculosus belt. Above Recovery at the cleared shorelines this, the percentage of surface covered by oil increased to the level of mean high water springs, then rapidly decreased towards the top of the While a few species recovered rapidly on the cleared sites, most did splash zone.11 Table 1 indicates the maximum oiling at any transect not. By as late as 1987, none of the cleared sites was back to "normal" station at the given site. Five sites received more than 80 percent as compared to the uncleared sites (oiled or unoiled). Among the covering of oil, another five had 20 to 49 percent cover, and the plants, lichens recovered within a year or two at all four sites. Urospora remainder had lesser amounts. Four sites received no oil whatsoever. and other early-recolonizing filamentous green algae were mostly gone Hiscock and colleagues, in 1979, concluded that, for oiled sites that by 1980, but Enteromorpha declined more gradually and still was not were not cleared mechanically, there were few changes in the intertidal uncommon through 1987. Fucus vesiculosus was recolonizing at all four communities attributable to the oiling from the Esso Bernicia spill.8 At cleared sites by 1981 and may have been fully recovered by 1986. Fucus sites 3.4, 4.1, 4.3, 6.1, and 6.10, the lichen populations in the supralit- spiralis began recolonizing at site 5.2 in 1980 and seemed well on its toral fringe were lost due to smothering by the oil. At sites 3.4,4.3,6.2, way to recovery at 5.2, 6.2, and 6.4 by 1987, but had not reappeared at and 6.4, there was a reduced abundance and bleaching of "lithotham- site 6.12 even at that late date. nia," i.e., calcareous red algae that are often found encrusting rock in Ascophylum nodosum recolonized site 6.4 in 1981,6.12 in 1984, and the lower part of the littoral zone. This was also attributed to the spill. 5.2 and 6.2 in 1985. However, it still was not abundant at any of the four The green alga Entermorpha increased at sites 4.1,4.3, and 5.1., which cleared sites in 1987. Pelvetia canaliculata, the slowest of all the plants may also have been due to the effects of the spill. to recover, was first recorded at site 5.2 in 1985, five and one-half years There were no significant effects on the abundance of animal popu- after the mechanical stripping of the shore. It reappeared at sites 6.2 lations on the uncleared shores which could be attributed to the Esso and 6.4 in 1986, but still had not been detected at site 6.12 in 1987. Bernicia spill.8 The oil may have killed limpets at site 4.3, but the Recovery of animal populations showed similar mixed results at the decrease in the population was not considered significant. Limpets cleared sites. Barnacles began recolonizing in 1980 at site 5.2, and by actually increased at one of the heavily oiled sites (4.1) and held steady 1984 recovery was well underway at all sites. Limpets, first noted at site at the others. The most notable decrease in limpet populations was at 6.12 in 1980, had achieved prespill levels by 1985 everywhere except at one of the unoiled sites (3.5). All other changes at the uncleared oiled site 5.2, where recovery took until 1987. Periwinkles were recolonizing sites were judged to be normal and/or due to natural causes. well at all sites in 1980 except site 6.4, where recolonization was just beginning, and were generally back to prespill levels at all sites by 1985. Dog whelks had recovered well at sites 6.4 and 6.12 by 1984, but were seen that year at site 5.2 in very low numbers. Whelks were not fully Immediate impacts on the cleared shores recovered at site 5.2 by 1987, and had not by that time been recorded at site 6.2. The slow recovery of the whelks at these two jetty sites may At site 5.2 (Jetty 3), oil and biological communities had been re- have been due, in part, to tributyltin leaching from paint on the hulls of moved by bulldozing between stations 8 and 13. The lowest station, 14, tankers, but this speculation is questionable in view of the recovery of was undamaged. Oil remained on the upper shore (stations 1 to 7), and periwinkles and barnacles at these sites. its thickness made it very difficult to conduct the biological survey, but Another effect of the mechanical shore cleaning relates to the access it was possible to determine that Pelvetia canaliculata was similar in road of stone aggregate that had been built along the top of the shore in abundance to previous years. The community in the bulldozed area order to move equipment to site 6.4. In 1987, Howson noted that the was largely destroyed, and the cleared area was being colonized by fine aggregate had slumped due to wave action into the intertidal zone filamentous green algae {Urospora spp.) and a "green algal stain." between sites 6.4 and 6.12., resulting in new surfaces for colonization, The periwinkles, L. neglecta and L. saxatilis, were found in both the but also a very unstable, unconsolidated substrate that was not allow- bulldozed and oiled areas in slightly lesser numbers than in previous ing for development of a normal community.9 In 1987, the stones years. The lichen Verrucaria maura was fairly common on loose rocks lacked Fucus spiralis and Pelvetia canaliculata, but were covered with in the littoral zone, an alien habitat for this supralittoral species. barnacles (S. balanoides), and amphipods (shrimp-like crustaceans, Presumably these were displaced rocks from the upper shore and the often called sand hoppers) were numerous under the stones. Physical lichen were in the process of dying out. stabilization and biotic recovery in this area is expected to take de- Site 6.2 (south of Jetty 2) had been bulldozed down to station 11 (of cades. 13), which destroyed most of the biota. The intact stations on the lower shore had reduced abundances of Fucus vesiculosus and F. serratus and Littorina saxatilis and L. littorea. Lithothamnia were absent. Recolo- nization was by both Enteromorpha and Urospora, which were abun- Effects of other spills in Sullom Voe dant. Site 6.4 (Runway Scatsta) had been bulldozed above station 7. Plant There have been a number of small crude oil spills at the terminal populations destroyed on the upper shore included Verrucaria spp., since 1979, which might complicate interpretation of biological recov- Ascophylum nodosum, and Fucus vesiculosus. Animal populations ery after the Esso Bernicia spill, including seven of more than 100 bbl destroyed or almost destroyed were Patella, Littorina littoralis, L. each. With the exception of the 457-bbl BP Vision spill of April 1985, FATE AND EFFECTS 465 these have had no discernible effect on the intertidal communities. Oil There is no evidence that the persistent oil is ecologically harmful. from the BP Vision stranded mainly at two locations, the south side of Hiscock, in 1984, reported periwinkles (Littorina spp.) thriving in oil- Spur Boom Site 7 (between sites 4.3 and 5.2) and between Scatsta Ness filled pools behind the rock at site 4.3,2 and in 1987, Shears found and Runway Scatsta (between sites 6.12 and 6.4). The upper shore was "considerable numbers" of L. saxatilis and amphipods underneath oiled at both locations, and most of the amphipods and rock peri- patches of asphalt pavement and oiled rocks at sites 5.2, 6.2, and winkles (L. saxatilis) were killed. However, the shores appeared nor- 6.13.11 "Healthy populations of amphipods and littorinids were ob- mal within and below the Fucus spiralis zone. Also, at the beach near served burrowing into the oil" at these sites in 1987, according to Scatsta Ness, which was still heavily oiled and where the surface Howson.9 population had been wiped out, many live rock periwinkles were found under stones (Hiscock, 1985). In 1986, the ecological effects of the BP Vision spill could not be detected at either location. Amphipods were abundant under stones in References both locations, and in the area between Scatsta Ness and Runway Scatsta rock periwinkles were abundant and there were no signs of 1. Hiscock, Keith, 1983. Assessment of Rocky Shore Surveys in Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/461/1742866/2169-3358-1991-1-461.pdf by guest on 01 October 2021 residual oil.4 There were no direct or obvious effects on any of the Sullom Voe 1976-1981. Report to the Shetland Oil Terminal established sampling sites with the possible exception of site 6.4 (Run- Environmental Advisory Group by the Field Studies Council Oil way Scatsta), where thick, viscous oil was found at a depth of 3 to 4 cm Pollution Research Unit, Pembroke, U.K. into the sediment, which was suspected to be from the BP Vision spill 2. Hiscock, Keith, 1984. Surveys of Rocky Shores in the Region of rather than Esso Bernicia spill (Howson, 1988). Regardless, there is no Sullom Voe, Shetland, August 1984. Report to the Shetland Oil evidence from the biological data that there was any effect of the BP Terminal Environmental Advisory Group by the Field Studies Vision spill at this site. Council Oil Pollution Research Unit, Pembroke, U.K. 3. Hiscock, Keith, 1985. Surveys of Rocky Shores in the Region of Sullom Voe, Shetland, August 1985. Report to the Shetland Oil Terminal Environmental Advisory Group by the Field Studies Persistence of the stranded oil Council Oil Pollution Research Unit, Pembroke, U.K. 4. Hiscock, Keith, 1986. Surveys of Rocky Shores in the Region of A comprehensive survey of residual oil from the Esso Bernicia spill Sullom Voe, Shetland, August 1986. Report to the Shetland Oil was undertaken in 1987.n Prior to that survey, there were occasional Terminal Environmental Advisory Group by the Field Studies observations on the presence of residual oil in the reports of the Council Oil Pollution Research Unit, Pembroke, U.K. biologists conducting the intertidal surveys. Hiscock and colleagues 5. Hiscock, K., J. H. Crothers, A. Thomas, and A. Little, 1978. A reported only a slight reduction between 1979 and 1980 in the percent- Resurvey of Rocky Shores Transects in the Region of Sullom Voe, age oil cover on the upper shore.6 Between 1980 and 1981, the oil cover Shetland, May 1978. Report to the Shetland Oil Terminal Envi- on rock on shores that had been heavily oiled had generally fallen by ronmental Advisory Group by the Field Studies Council Oil Pollu- "one to two abundance categories."7 No oil was recorded at site 3.4 in tion Research Unit, Pembroke, U.K. 1981, where it had been "common" in 1980, but at sites 3.3 and 4.3, 6. Hiscock, K., J. H. Crothers, D. C. Emerson, and A. Thomas, thick oil (probably from one of the more recent spills) was noted as 1981. A Resurvey of Rocky Shores Transects in the Region of present among gullies and in pools behind the biological survey tran- Sullom Voe, Shetland, May 1980. Report to the Shetland Oil sects. In 1984, oil was found at several sites, usually as solid thin Terminal Environmental Advisory Group by the Field Studies patches in the splash zone. Near the jetties (sites 5.2 and 6.2), liquid oil Council Oil Pollution Research Unit, Pembroke, U.K. was found under upper shore boulders and cobble and under a solid 7. Hiscock, K., D. C. Emerson, A. Thomas, and K. Iball, 1981. A skin in a few pools behind rock outcrops. At Scatsta Ness (site 6.13), Resurvey of Rocky Shores Transects in the Region of Sullom Voe, there was some "tarmac pavement," i.e., asphaltic residue mixed with Shetland, May/June 1981. Report to the Shetland Oil Terminal pebbles and sand.2 In 1986, Hiscock reported as a change the absence Environmental Advisory Group by the Field Studies Council Oil of sheen on the pools where Esso Bernicia oil had been trapped. Pollution Research Unit, Pembroke, U.K. In his 1987 survey, Shears found what may have been Esso Bernicia 8. Hiscock, K., A. Thomas, D. C. Emerson, and H. Howcroft, 1979. oil at some sheltered locations (sites 4.1, 4.3, 5.2, 6.2, and 6.13). With A Resurvey of Rocky Shores Transects in the Region of Sullom the exception of site 6.2, these were among the most heavily oiled Voe, Shetland, May 1979. Report to the Shetland Oil Terminal locales in 1976. The oil cover at these sites were generally very low (less Environmental Advisory Group by the Field Studies Council Oil than 20 percent) and consisted of hard, crusty patches confined to the Pollution Research Unit, Pembroke, U.K. splash zone. One or two small patches of weathered asphalt pavement 9. Howson, Christine M., 1988. Surveys of Rocky Shores in the were found behind the transects at several other sites. He noted that Region of the Sullom Voe, Sheltand, August 1987. Report to the attrition rates at site 6.13 by wave action were remarkably high given its Shetland Oil Terminal Environmental Advisory Group by the sheltered location, and that within three years of the spill its oil cover Field Studies Council Oil Pollution Research Unit, Pembroke, had been only slightly higher than on the cleared site 6.12. Shears, U.K. nonetheless, concluded that the self-cleaning of rocky shores after the 10. Richardson, M. G., 1979. The Environmental Effects of the Esso Esso Bernicia spill was faster on the more exposed, steep bedrock Bernicia fuel oil spill, Sullom Voe, Shetland, January 1979. Un- shores than on sheltered, flat, wave-cut platforms or gravel beaches, published report to the Nature Conservancy Council, Northern and was primarily a function of different shoreline wave energy levels. Isles Section, Shetland He further concluded that the stable nature of the remaining residual 11. Shears, John, 1987. Survey of oil pollution around Sullom Voe, oil, and its position above mean high water, suggested that it is likely to Shetland, August 1987. Report to the Shetland Oil Terminal Envi- persist for many years to come. ronmental Advisory Group Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/461/1742866/2169-3358-1991-1-461.pdf by guest on 01 October 2021