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The Dona Marika oil spill
The Dona Marika Oil Spill Last Aagmt, 3,000 teas of petrol (gueleae) was spilled in Milford Haven when the tanker, Dona Marika, ran Siaee meet decewmed etl spals in Briti/waters have been of crude ell, there is ¢emidemble interest in knowing the damage caused by this spillage of a refined ell product. The l l,000-ton Liberian-registered tanker, Dona Marika, was blown on to the rocks of Longberry Point, opposite the entrance to Milford Haven, at 21.04 on Sunday, 5 August, while carrying 5,000 tons of Esso 4 Star petrol to the Esso terminal. The crew members were hauled to safety up the cliffs, but the risk of explosion from petrol, leaking from a long gash in her starboard side, was so great that the normal antipollution measures (including booms) could not be used; and at one time the nearby village of St Ishmaels was evacuated. Fortunately, the gale force winds and heavy seas that caused the incident confined the spilt petrol to a relatively small area of rocky bays. By Wednesday morning, 8 August, leakage appeared to have ceased, but plans to reduce the pollution threat by transferring the bunker oil were prevented by strong winds. As the ship was blown ashore on a spring tide, successive lower tides caused the rocks to penetrate more deeply into her keel. This produced a fresh spillage of petrol on Friday, 10 August, and the risk of explosion again delayed transfer operations until petroleum gas concentrations had fallen to safe levels. On Monday, 13 August, foam was pumped from the cliff top into the damaged tanks to seal them and displace their dangerous gases. The petrol was then transferred to the undamaged port tanks and on 15 August a shallow draft tanker was moved alongside. All remaining petrol was removed by 18 August and the bunker and fuel oil transferred by 21 August, leaving the ship, literally, high and dry. The latest report, on 6 September, was that she was soon to be refloated and probably broken up. A spill of petrol of this magnitude is unusual in UK waters and several lessons have been learned. Recent experimental small-scale spillages of petrol at sea by the DTI had indicated a very rapid evaporation rate with very little dispersion into the water, and the virtual disappearance of the spilt petrol within a few hours, thus confirming the classification of petrol as a nonpersistent oil. However, the Dona Marika spilled some 3,000 tons of petrol, over two periods of about 48 and 36 hours, into a small area of enclosed bays and during high winds and heavy seas. Under these conditions, the petrol did not behave as a non-persistent oil. Leakage was so rapid that the surf apparently formed water-inpetrol emulsions before much evaporation could take place,
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Fig. 1 Map of part of Milford Haven,showingpositionof stranded tanker, and five transects. Inset: Map of Wales showing position of Milford Haven. only evaporated further, to a straw-coloured emulsion of some 15 ml after 24 hours. This suggests that the thick slicks of emulsified residues, ranging in colour from yellow to a deep rusty red, which were observed following the second Dona Marika leakage, were due solely to the escape of petrol and involved no loss of the heavier oils.
Biological examination of shore The shore between Little Castle Head and Watch House Point (Fig. 1) was examined two days after the accident. Over most of this area, there was evidence of limpet (Patella spp) detachment, and retraction of winkles (Littorina spp), top shells (Gibbula spp), and dog whelks (Nucella lapillus) into their shells. Mussels (Mytilus edulis)near the ship were gaping. Effects were severe between Watch House Point and. Great Castle Head, and minor between Great Castle Head and Little Castle Head. Detached Patella, and retracted Littorina, Gibbula and Nucella were taken back to the laboratory, washed, and kept in clean aerated seawater. Within a day at least 50~oof each species had apparently recovered. Thus the initial effect of the petrol was narcotic rather than lethal. Five of the transects (for positions, see Fig. 1) which form part of the Milford Haven monitoring programme, as described by Crapp (1971), were re-surveyed. Details, including abundance scales, are given by Crapp; but briefly, the abundance of all common species are estimated at 0.6 m height intervals over the intertidal zone. Results for Patella vulgata are given in Fig. 2. Data from two surveys, shown as kite histograms, are superimposed to show changes. The dates of the two surveys are given in Table 1.
Behaviour o f petrol in water Subsequent work at the MAFF Fisheries Laboratory, Burnham-on-Crouch, showed that evaporation of 100 ml of Esso 4 Star petrol over an undisturbed seawater column of 900 ml left a red residue of 2.5-3.5 ml after 24 hours. However, after evaporation of the petrol to about 20 ml, agitation of the residues formed a yellow water-in-petrol emulsion of about the same volume. This
I 1
TABLE 1 Transect survey dates. MusselwickEast Watch House Point Rook's Nest Point LittleCastle Head SouthHook Point
lstsurvey 5.3.69 16.2.69 17.2.69 5.3.69 4.3.69
2ndsurvey 20.8.73 17.8.73 14.8.73 15.8.73 20.8.73 181
KEY f
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The Milford Haven Port Health Authority collected a number of sand and mollusc samplesi and their lead . content was determined by the public analyst. The results !no~ • are compared with previous data (Gregory, 1973) in m l increase Table 2. × no data~ 2nd survey The highest lead concentration found was in the sand from Gelliswick Bay, which was not contaminated by ~ petrol from the tanker; the reasons for this lead level are not known. Results (although few in number) generally do not provide any evidence for lead accumulaMHWN tion in the area near the accident.
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Reports from the general public
Observations made by people in the area, which we MLWN have not been able to follow up, are: (1) up to 100 dead gulls in St Brides Bay (north of Milford Haven). It was suggested that these were ME WHo RkN LCs ~k MLWS killed by eating petrol-contaminated limpets, etc. This is a possibility, but we have found no dead Fig. 2 Abundance of Patella vulgata: pre- and post-spill data from gulls in the area where they were feeding; five transects. (2) gaping cockles in Sandyhaven (inlet between Little Castle Head and South H o o k Point); The Watch House Point and Rook's Nest Point (3) mackerel tasting of petrol, caught near Sandyhaven transects show a large reduction in limpet numbers, and near the south shore of Milford Haven; from abundant (i.e. over 50 per m 2) to occasional (4) reports of dead fish have not been verified, and it (i.e. 1-10 per dm2). The other transects show changes seems unlikely that there was any large fish between abundant and common, i.e. between more than mortality. 50 per m 2 and 10--50 per m 2. Changes of this magnitude between surveys are common, due to natural yearly fluctuations, seasonal variation, and different observers. D i ~ ' l l ~ i o n A leakage of petrol near the shore, lasting for several days, meant that the input exceeded the evaporative Sub-littoral effects output sufficiently for the fauna of Lindsway Bay Peter Hunnam, of Dale Fort Field Centre, dived in (between Watch House Point and Great Castle Head) the area following the accident, and reported narcotized to be severely affected. Death of molluscs, particularly bivalves and large numbers of dead Echinocardium. of limpets, resulted from prolonged anaesthesia, or, more usually, from predation by gulls. There does not seem to have been a significant accumulation of lead, Lead analyses and no obvious traces of petrol remained on the rocks Since the spilled petrol contained an anti-knock lead one week after the accident. additive, fears were expressed that the public might be A large growth of seaweed is to be expected following exposed to lead poisoning from residues on the beaches the death of large numbers of limpets, and within four or contained in fish and shellfish, although there are no weeks of the accident; Enteromorpha was growing rapidly commercial fisheries of significance in this part of the and giving the whole bay a particularly green appearance. Haven. Work at Burnham-on-Crouch has shown that of the We would like to thank the police force, the coastguard, and the Esso petroleum company for their co-operation, and Mr W. J. 600 mg/1 of lead in the petrol, over 939/0 evaporated Allen,chief inspector for the Milford Haven Port Health Authority, from an undisturbed seawater column in 24 hours, while for lead analysis results. over 83% evaporated in the same time from a column R . A . A . BLACKMAN agitated to form a water-in-petrol emulsion. The lead Ministry of Agriculture, Fisheries and Food, additive itself is virtually insoluble in water. Fisheries Laboratory,
Remembrance Avenue, Burnham-on-Crouch, Essex, UK. JENIFER M. BAKER
TABLE 2lead content shown as ppm, Pre- and post-spillage lead analyses: by weight of wet tissue for mollusc samples. Pre-spill Post-spill Sand
Lindsway Bay (near ship) 7.7 Control: Gelliswick Bay (near town of Milford Haven) 18.8
Patella vulgata
S. Hook Point Gelliswick Bay
1 1
Great Castle Head
1"8
Great Castle Head
1"4
Mytilus edulis
S. Hook Point 5-8 Gelliswick Bay 1 Littorina littorea
182
JOHN JELLY SUSAN REYNARD
FieM Studies Council, Oil Pollution Research Unit, Orielton Field Centre, Pembroke, Wales. Crapp, G. B. (1971). Monitoring the rocky shore. In- The Ecological Effects of Oil Pollution on Littoral Communities (ed E. B. Cowell), pp. 102-113. Institute of Petroleum: Gregory, J. B. (1973). An investigation of the trace heavy metal concentrations in shellfish from the South :Wales Coastline. B.Se, Fourth year project, Kingston Polytechnic.
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,
~,'~
9I ten
'Dona Marika' " $ .ff~ ~.~
~
- ~ Great ~ ~" C =r ¥.~ Castle "~. ~ ' Head ~ MILFORDHAVEN
Fig. 1 Map of part of Milford Haven,showingpositionof stranded tanker, and five transects. Inset: Map of Wales showing position of Milford Haven. only evaporated further, to a straw-coloured emulsion of some 15 ml after 24 hours. This suggests that the thick slicks of emulsified residues, ranging in colour from yellow to a deep rusty red, which were observed following the second Dona Marika leakage, were due solely to the escape of petrol and involved no loss of the heavier oils.
Biological examination of shore The shore between Little Castle Head and Watch House Point (Fig. 1) was examined two days after the accident. Over most of this area, there was evidence of limpet (Patella spp) detachment, and retraction of winkles (Littorina spp), top shells (Gibbula spp), and dog whelks (Nucella lapillus) into their shells. Mussels (Mytilus edulis)near the ship were gaping. Effects were severe between Watch House Point and. Great Castle Head, and minor between Great Castle Head and Little Castle Head. Detached Patella, and retracted Littorina, Gibbula and Nucella were taken back to the laboratory, washed, and kept in clean aerated seawater. Within a day at least 50~oof each species had apparently recovered. Thus the initial effect of the petrol was narcotic rather than lethal. Five of the transects (for positions, see Fig. 1) which form part of the Milford Haven monitoring programme, as described by Crapp (1971), were re-surveyed. Details, including abundance scales, are given by Crapp; but briefly, the abundance of all common species are estimated at 0.6 m height intervals over the intertidal zone. Results for Patella vulgata are given in Fig. 2. Data from two surveys, shown as kite histograms, are superimposed to show changes. The dates of the two surveys are given in Table 1.
Behaviour o f petrol in water Subsequent work at the MAFF Fisheries Laboratory, Burnham-on-Crouch, showed that evaporation of 100 ml of Esso 4 Star petrol over an undisturbed seawater column of 900 ml left a red residue of 2.5-3.5 ml after 24 hours. However, after evaporation of the petrol to about 20 ml, agitation of the residues formed a yellow water-in-petrol emulsion of about the same volume. This
I 1
TABLE 1 Transect survey dates. MusselwickEast Watch House Point Rook's Nest Point LittleCastle Head SouthHook Point
lstsurvey 5.3.69 16.2.69 17.2.69 5.3.69 4.3.69
2ndsurvey 20.8.73 17.8.73 14.8.73 15.8.73 20.8.73 181
KEY f
- - ]
The Milford Haven Port Health Authority collected a number of sand and mollusc samplesi and their lead . content was determined by the public analyst. The results !no~ • are compared with previous data (Gregory, 1973) in m l increase Table 2. × no data~ 2nd survey The highest lead concentration found was in the sand from Gelliswick Bay, which was not contaminated by ~ petrol from the tanker; the reasons for this lead level are not known. Results (although few in number) generally do not provide any evidence for lead accumulaMHWN tion in the area near the accident.
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[ ' '1docroase
t 9 , II 7
A /\
c~ d 6-
@s4 31 i 21 i 1]
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]
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Reports from the general public
Observations made by people in the area, which we MLWN have not been able to follow up, are: (1) up to 100 dead gulls in St Brides Bay (north of Milford Haven). It was suggested that these were ME WHo RkN LCs ~k MLWS killed by eating petrol-contaminated limpets, etc. This is a possibility, but we have found no dead Fig. 2 Abundance of Patella vulgata: pre- and post-spill data from gulls in the area where they were feeding; five transects. (2) gaping cockles in Sandyhaven (inlet between Little Castle Head and South H o o k Point); The Watch House Point and Rook's Nest Point (3) mackerel tasting of petrol, caught near Sandyhaven transects show a large reduction in limpet numbers, and near the south shore of Milford Haven; from abundant (i.e. over 50 per m 2) to occasional (4) reports of dead fish have not been verified, and it (i.e. 1-10 per dm2). The other transects show changes seems unlikely that there was any large fish between abundant and common, i.e. between more than mortality. 50 per m 2 and 10--50 per m 2. Changes of this magnitude between surveys are common, due to natural yearly fluctuations, seasonal variation, and different observers. D i ~ ' l l ~ i o n A leakage of petrol near the shore, lasting for several days, meant that the input exceeded the evaporative Sub-littoral effects output sufficiently for the fauna of Lindsway Bay Peter Hunnam, of Dale Fort Field Centre, dived in (between Watch House Point and Great Castle Head) the area following the accident, and reported narcotized to be severely affected. Death of molluscs, particularly bivalves and large numbers of dead Echinocardium. of limpets, resulted from prolonged anaesthesia, or, more usually, from predation by gulls. There does not seem to have been a significant accumulation of lead, Lead analyses and no obvious traces of petrol remained on the rocks Since the spilled petrol contained an anti-knock lead one week after the accident. additive, fears were expressed that the public might be A large growth of seaweed is to be expected following exposed to lead poisoning from residues on the beaches the death of large numbers of limpets, and within four or contained in fish and shellfish, although there are no weeks of the accident; Enteromorpha was growing rapidly commercial fisheries of significance in this part of the and giving the whole bay a particularly green appearance. Haven. Work at Burnham-on-Crouch has shown that of the We would like to thank the police force, the coastguard, and the Esso petroleum company for their co-operation, and Mr W. J. 600 mg/1 of lead in the petrol, over 939/0 evaporated Allen,chief inspector for the Milford Haven Port Health Authority, from an undisturbed seawater column in 24 hours, while for lead analysis results. over 83% evaporated in the same time from a column R . A . A . BLACKMAN agitated to form a water-in-petrol emulsion. The lead Ministry of Agriculture, Fisheries and Food, additive itself is virtually insoluble in water. Fisheries Laboratory,
Remembrance Avenue, Burnham-on-Crouch, Essex, UK. JENIFER M. BAKER
TABLE 2lead content shown as ppm, Pre- and post-spillage lead analyses: by weight of wet tissue for mollusc samples. Pre-spill Post-spill Sand
Lindsway Bay (near ship) 7.7 Control: Gelliswick Bay (near town of Milford Haven) 18.8
Patella vulgata
S. Hook Point Gelliswick Bay
1 1
Great Castle Head
1"8
Great Castle Head
1"4
Mytilus edulis
S. Hook Point 5-8 Gelliswick Bay 1 Littorina littorea
182
JOHN JELLY SUSAN REYNARD
FieM Studies Council, Oil Pollution Research Unit, Orielton Field Centre, Pembroke, Wales. Crapp, G. B. (1971). Monitoring the rocky shore. In- The Ecological Effects of Oil Pollution on Littoral Communities (ed E. B. Cowell), pp. 102-113. Institute of Petroleum: Gregory, J. B. (1973). An investigation of the trace heavy metal concentrations in shellfish from the South :Wales Coastline. B.Se, Fourth year project, Kingston Polytechnic.