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The ecological impact on and near shores by the Amoco Cadiz oil spill
Marine Pollution Bulletin
The Ecological Impact on and near Shores by the AMOCO CADIZ Off Spill C. CHASS]~ Institute d'etudes Marines, Universit~ de Bretagne Occinental, 29283 Brest, Cedex, France
The significance of this 'black tide' is assessed up to four months after the shipwreck. During the first week heavy pollution was spread by strong winds, waves and currents along 140 km of highly dissected coastline to the east of Portsall; in April pollution spread more lightly also to the west and south covering in all some 375 km of coast. Great disturbance was caused because the economy and mode of life of the people of the whole region are closely linked to the sea. Consistent with its interest in the region, the Universit6 de Bretagne Occidentale immediately mobilized its students, teaching and research staff. Its Institut d'Etudes Marines undertook to follow up the immediate effects of the pollution and its long-term consequences in collaboration with the Societ6 pour l'Etude et la Protection de la Nature in Bretagne. Already there is a considerable body of qualitative and quantitative information on the fauna and flora of the beaches, rocky shores estuaries and the shallow offshore grounds of the polluted coast, so it is now possible to draw up a provisional balance sheet of the effects of the pollution on the coastal communities.
Populations of Rocky Shores The algae and the intertidal reefs were polluted along almost 200 km of coast over an area equivalent to 70 kmL By mid-June most of the shoreline was no longer oily, pollution being by then confined to the higher levels of the shore in sheltered inlets, particularly those facing west (less if facing east). These were still heavily polluted with little sign that they would improve on their own. Algal nett photosynthesis, measured on 16 April, showed similar levels for several dominant species in oiled and non-oiled areas. The Laminaria beds which occur at levels between + 3 and - 15 m, and which cover an area of 300 km 2 are still intact. Only the beds of Laminaria digitata in the upper part of the range are exploited by 600 specialized gatherers. A slight retardation of growth was noted on 26 April at 1 km from the wreck. On 25 M a y beds of Laminaria harvested 5 km farther to the east were of normal length for the season. Smaller red algae which live beneath the fronds of the Laminaria were well developed during the spring. On 1 July abundant sporelings and strong growth of Fucus spiralis was noted (up to 12 cm) at Portsall. Land plants, Crithmum maritimum (rock samphire) and Honkeynia peploides (sea sandwort), had been seen in May sprouting and flowing through 1-3 cm of black weathered oil above H.W. The oil had smothered lichens and any 298
associated fauna (M. F. Spooner, personal communication). Effects on rocky shore fauna have shown wide variations according to the species and to the intensity, age (reduction of toxicity), renewal and persistence of the oil. Heavy mortality occurred among herbivorous gastropods (Fig. 1). These were studied at 160 sites along the whole coast, in particular at Beg-en-Fry, Callot, Roscoff (10 sites), Mogueriec, Plouguerneau, Portsall and Le Conquet. Patella (limpets) suffered mortalities varying from 0-10007o with a mean of 20°7o. Littorina, Gibbula and Monodonta (winkles and topshells) suffered greater losses, 50-99070. Mortalities were particularly great at high levels, which were in general more polluted, but where oil was more evenly spread lower levels were also severely hit. At the beginning of July an abundant recruitment of young Littorina littoralis was seen on the shore at Portsall, which had received a maximum amount of pollution. On the lower part of shores no mortality occurred among the barnacles Chthamalus and Balanus perforatus nor in Mytilus (mussels) nor Sabellaria (sand reef building worm). Crustaceans free-living among the intertidal algae have everywhere shown a high mortality and particularly in the neighbourhood of the wreck. Amphipods have disappeared almost as far as Plouguerneau and isopods and adult shore crabs (Carcinus maenas) are rare. At the beginning of July there was a strong recruitment of small shore crabs, even at Portsall. At this time there were abnormally high populations of harpacticid copepods which live on the surface of the algae. These were perhaps 20 times as numerous as in comparable unpolluted areas (Table 1). (Note that in the nearby sediments the epipsammic harpacticids were practically absent, there being a high concentration of hydrocarbons in the interstitial water.) This population explosion among the meiofauna of the persistent cover of macroalgae, fucoids, Ulva and Enteromorpha was apparently related to the great reduction in herbivorous macrofauna and to the intense proliferation of bacteria and diatoms (often filamentous) and small Phaeophyceae which literally covered the large algae by then clean of oil. Shrimps (Leander serratus) have become 2-2.5 times as abundant as usual apparently attracted to and fattening on the outburst of meiofauna. The populations in shaded overhangs and crevices were found to be intact in the Bay of Morlaix at Ile Callot. At Portsall they were diminished in numbers and still affected by oil, particularly at high levels on the shore.
Volume 9 / N u m b e r 11/November 1978
E or W or S of wreck Km
0 1 L P 0 L L UT I 0 N Days Quantities after wreck
L 0 CA L I T I E S
HERBIVOROUS G A S T R 0 P 0 D S OF SEAWEEDS ON ROCKS Mean Biomass.m -2 Mean numbers.m -2 rough wet weight Gr. ( adults )
limpets (Patella)
periwinkles / ( Littorina / + ___J______/_......:Gibbula)/..:
Survival %
~." ;': . - ' ? . . . . . ~ 05
PAIMPOL
147
PLOUGRESCANT TRESTEL TREGASTEL ILE GRANDE TREBEURDEN
113 105 92 86 86
BEGLEGUER
LOCQUIREC BEG AN FRY PRIMEL TREGASTEL
LE GUERSlT SAINT SAMSON E
1
2
4
8
16 32
500 I
o '
' • ~--x'xx~x~~
87
~,~-4-
+ e- + + 4- -f- + +
~
67 67 57
+
-F-~+
55
4-+ + + .4.--+-
PORTSALLi
TREMAZAN LANHALLES ILE SEGAL
N S
56
~__--
_
÷+ ÷* -F +
.
---
• ~'.
÷
: •I'
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23
STE ANNE PORTZIC
50
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41 ,~ 30 , 4- 4- 421 ~ 4- -r 4- + 416 94 -~ - ~~ H - - F ~ 3 7 15 15
~\\ 4- 4- 4~ 4-- 4- 4-
--~/J.~2~,
+4
4- +
•
B.
TREPASSES PENMARC°H
60 IO0
MOUSTERLIN
128
'
H-+ 4- +
55
6
100
~ - - I -
56
E
50
" . : .. - •. . . . . . . ' '.. '.: •" .'.:~'_
4- H-4- Jr +-
N
F O,L, C PLOUESCAT BRIGNOGAN LE CURNIC PLOUGUERNEAU ABERWRAC'H ABERBENOIT
0
-4--
79 74 69
S
ILE VERTES
0
÷ + + ++ :4- H- -F
0
ABER
100
I ~ _ ----
+ 4H- -r 4- if" ÷ -i-+ +
O F
200
+ +
57 57 57
C
300
L
4-
ILE DE N TY-SAOZONs W
R
400
o
added with
('~-F-~ + Bohlen spill r .L-'. • , J,
?
,
• • I'///~
":"
[ ~
"'"";" !
Fig. 1 Herbivorous Gastropods of seaweeds on rocks in relation to oil pollution from AMOCO CADIZ. Four unaffected stations are shown (O). During the eastward spread of oil (upwards in figure) loss of toxicity with approximate age is suggested by cross-hatching. Oil arriving on shores to W and S probably left the wreck at a late stage. °70 Survival, based on definite pre-spill data ; where deduced from similar hydrodynamic situations . . . .
Populations on the underside of boulders resting on sediments were clearly impoverished at Portsall, less so at the mouth of Aber Benoit and at Roscoff, even where the sessile fauna appeared normal, freeliving species were scarcer and depleted, We have not observed the same massive proliferation of Enteromorpha (green algae) on polluted shores as was seen in Cornwall after TORREY CANYON(Smith, 1968). This may be due to the almost complete persistence of cover by macroalgae, offering fewer available habitats than on naturally barer shores, and to the lesser mortality of herbivorous gastropods,
Sedentary Fauna of Sands and Muds In the proximity of the wreck and where oil slicks had accumulated and been stranded thickly, particularly in the first weeks on beaches exposed to the west, there were many dead animals in the strand line at high water and accumulations of drift. The dead animals were identified, counted and measured. They belonged to certain sensitive s p e c i e s - others, closely related and perhaps from the same communities, were poorly represented. Some edible species of bivalves taken noncommercially were badly hit. On the whole, however, the survival of macrofaunal associations on particular 299
Marine Pollution Bulletin TABLE 1 Meiofauna and herbivorous gastropods of algae on rocks ( 2 - 7 July 1978).
Locality Distance from wreck in km Intensity of pollution Gastropods % adult survival
Numbers per m 2 Gastropods new settlement Harpacticoids Nematodes Amphipods, young Isopods, young
Rade de Brest (St A n n e du Portzic) exposed sheltered 50
50
unpolluted 100
1130
Le Conquet South
Ile S6gal North
Portsall Porsquey very sheltered
23
16
15.5
0
+
+ +
+ + +
+++ + + +
82
88
95
8
0 ÷+q-+ + + + 3
Aber Benoit
Plouguerneau
6
16
+++ + + +
+ + +
3
65
?
?
4320
1450
1030
410
?
4600
1880
2000 ? ? ?
10 000 ? ? ?
25 000 880 1200 473
2000 50 45 1024
8000 1590 160 567
35 000 1910 3 0
350 000 ? 0 ?
199 000 ? 0 2000
31 000 ? 229 264
beaches was estimated as about 80% of normal densities (range 4 0 - 9 0 % ) . Where the meiofauna has been heavily damaged as at Portsall, Plouguerneau and Roscoff, the harpacticid and ostracod populations in particular are depleted, but nematodes have become more numerous, The turbellarian Convoluta roscoffensis is still very common, The survival of various species of in-fauna was investigated on 15 beaches of differing types from Portsall to St Efflam some 94 km from the wreck, Observations made from April to July included beaches which initially received very heavy oil deposits to those which had moderate to slight pollution. A wide range of specific susceptibilities was seen and some examples out of over 50 species of in-fauna are given below:
traces of oil. In over 200 sampling holes an iridescent film was always found on the surface of interstitial water and sometimes also droplets of brown emulsion. This occurred at all levels in the beach and in all types of sediment. The level of hydrocarbons is high even where coastal water is no longer polluted. This explains why mortalities still occur in the sediments and the meiofauna has not been re-established. Damage to burrowing macrofauna has been more severe below low tide mark, notably in the Abers, and bays of Morlaix and Lannion, sometimes to depths of 40 m. In fact the dead animals washed ashore came largely from the subtidal populations, these being no doubt less adjusted to withstand stress than those of the intertidal zone.
Polychaetes were remarkably resistant
The Mobile Fauna
Arenicola marina (lug worm) apparently not affected at all and m a n y other species of burrowing worms likewise Opheliidae spp (characteristic of very clean sand) and Lanice conchylegia (sand tube builder)only slightly hit
There was a very obvious mortality of both fish and crustaceans during the first week for a distance of 10 km around the wreck. There was also a lesser mortality at Roscoff, but elsewhere it was negligible. Specimens were collected, identified and measured. Among fish the principal mortalities were among the Ammodytidae (sand eels) followed by the Labridae and then the Syngnathidae. Dead specimens of Gobiidae, Blenniidae, Callionymidae and littoral gadoids were also c o m m o n and all other littoral groups represented by several specimens. It is of interest that at Portsall and Roscoff 70 individuals of the northern gadoid Raniceps raninus were found. This species had previously been known in Brittany from a single specimen caught in 1908. Their presence in the samples is evidence not only of the gaps
Lamellibranchs, mostly quite seriously depleted Solen, Ensis spp, Pharus(razor shells) almost total kill Cardiumedule(cockle)afewsurvivors Tellina spp (pink tellin) survived very well Mya arenaria (brackish water clam) seemingly no deaths
Crustacea Talitrussaltator (sand h o p p e r ) o f H.W. zone, heavy kill Haustorius arenarius Bathyporeia spp of lower tidal level,
Eyrydicepulchra much less mortality Ampelisca brevicornisM.T, to L.W. all killed
Echinoderms Echinocardium cordatum (heart urchin) nearly all killed Acrocnida brachiata (brittle star) a few survivors Leptosynapta gallieni (worm-like holothurian) good survival
Vulnerability of species to hydrocarbons is specific and differs from that shown to oxygen-lack or reduced salinity. It more nearly resembles the effects from effluents of the paper manufacturing industry. At the beginning of July at all sites at Portsall and in the bays of Morlaix and Lannion, the beach sediments though appearing to be clean were impregnated with 300
in our knowledge of ecology but also of the rapid diffusion of oil through the whole water column. The probable habitat of this rare species is in the Laminaria beds, between - 3 to - 1 5 m, a zone inaccessible to fishermen from land or by boat. As a footnote it has been reported that, since the beginning of August, 5 0 - 8 0 % Mugi! (grey mullet) have been found with ulcerations of the skin on the body. This suggests that we may not have seen the last of the effects of the oil. Crustacean mortalities were mainly of Cancer pagurus (edible crab), Portunus puber, Crangon
Volume9/Number 11/November1978
crangon and Leander serratus (shrimps), Galathea squamifera and G. strigosa and especially Carcinus maenas (shore crab). The latter was thought to be exceptionally resistant to all kinds of pollutants so its abundance in the strandings of dead animals and the relative rarity of living crabs subsequently are evidences of the severity of the pollution in the early days. Taking account of the places where the collections were made and the sampling methods used, the strandings represent less than 10000 inshore fish of all kinds and a similar number of crustaceans. This is a relatively small number and very localized even if allowance is made for dead animals not stranded. Some exploratory fishing was carried out by the Institute ScientifiqueetTechniquedes P~chesMaritimes with the following results: On 5 April at Plouguerneau, in crab pots at 30 m depth, numbers of Cancer pagurus appeared normal but tasted of oil. On 12, 24 and 28 April at Portsall, close to the wreck, Mugil (grey mullet), Gadus pollachius (pollack) and Scomber scomber (mackerel) were emaciated but most often untainted. On 14 April at Brignogan, specimens of Maia squinado (spider crab) had a smell of oil. On 28 April, close to wreck at Portsall, Cancer and Main tasted normal, F r o m 15-30 April at Plouguerneau, as at Roscoff and Carantec, Cancer, Maia, Palinurus and Homarus (crabs and lobsters of important commercial shell fisheries) were normal in quantity and quality, To sum up, from the end of April, the dilution of hydrocarbons in the water (0.05 ppm) was such that fish and crustaceans were mainly free of taint in offshore waters. By the end of May this had been achieved in all remaining areas, except in the Abers.
Conclusions The above account was written at the beginning of July 1978. By comparison with previous pollution accidents and taking into account the enormous quantity of oil spilled at Portsall, the provisional balance sheet indicates rather less damage to the marine environment than might have been expected (Table 2). (1) There is now evidence that intertidally and close inshore direct mortalities have been localized, seldom heavy and always selective and partial. (2) Contamination of organisms and products of commercial fisheries at sea have been transitory. Oyster culture alone has been badly damaged. (3) The algal crop is now exploitable for industrial use. (4) The general cover of macro-algae has survived the incident.
TABLE 2 Summaryof ecologicaleffects 3 months after theArnoco Cadiz spill on a heavilyand on a lightlyoiled locality.
Pollutionintensity Algae on rocks Barnacles Herbivores (limpets and winkles) Meiofauna on algae
Meiofaunain sand Macrofaunain sand
Percentage survival Portsall Plouguerneau + ++ ++++ + 90 95 100 100 8 65 >500
12 40
>300
17 80
Populations of herbivorous gastropods have partially succumbed but there is already evidence of some important fresh recruitment. There has been no general development of green weed on the intertidal rocks. The causes of this modest impact may be ascribed to: (1) Limited use of dispersants which are now less toxic: they were used sparingly and only on a few shores. The main use of under 2000 tons was offshore (more than 8 km from the coast). (2) High turbulence of the sea around the wreck and in the polluted sea areas, produced rapid dispersion of the oil. This caused heavy mortalities over a limited area with greatly diminished effects everywhere else. The mortalities were caused by the oils themselves, particularly in the first few days before the most toxic volatile fractions had evaporated. (3) A prompt and intensive collection of the stranded oil by many civilian volunteers and 6000 troops amounted to at least 15-20000 tonnes of reclaimed oil. The most serious aspect of the pollution has been the accumulation (likely to be long-lasting) of petroleum hydrocarbons in sediments and in their interstitial water. Here the total hydrocarbon concentration is 1-16 ppm, as against 0.03 ppm in coastal water in early July. This interstitial oil is most significant in the black reducing sediments (where other hydrocarbons are being formed naturally). Even if oil is prevented from direct entry into estuarine muds because they are charged with interstitial water, the very numerous burrows permit penetration of oil to considerable depths. This oil spill disaster has affected not only the ecology and economy of Brittany, but has been psychologically, aesthetically and politically disturbing. Chasse,C. (1972). Economie sedimentaireet biologique (production) des estrans meubles des cotes de Bretague. These d'Etat Paris VI 293 pp. Smith, J. E., (ed.)(1968). Torrey C a n y o n Pollution and Marine Life.
CambridgeUniversitypress. Southward, A. J. & Southward, E. C. (1978). Recolonization of rocky shores in Cornwall after use of toxic dispersants to clean up the Torrey Canyon spill. J. Fish. Res. Bd. Can., 3 5 , 6 8 2 - 7 0 6 .
301
The Ecological Impact on and near Shores by the AMOCO CADIZ Off Spill C. CHASS]~ Institute d'etudes Marines, Universit~ de Bretagne Occinental, 29283 Brest, Cedex, France
The significance of this 'black tide' is assessed up to four months after the shipwreck. During the first week heavy pollution was spread by strong winds, waves and currents along 140 km of highly dissected coastline to the east of Portsall; in April pollution spread more lightly also to the west and south covering in all some 375 km of coast. Great disturbance was caused because the economy and mode of life of the people of the whole region are closely linked to the sea. Consistent with its interest in the region, the Universit6 de Bretagne Occidentale immediately mobilized its students, teaching and research staff. Its Institut d'Etudes Marines undertook to follow up the immediate effects of the pollution and its long-term consequences in collaboration with the Societ6 pour l'Etude et la Protection de la Nature in Bretagne. Already there is a considerable body of qualitative and quantitative information on the fauna and flora of the beaches, rocky shores estuaries and the shallow offshore grounds of the polluted coast, so it is now possible to draw up a provisional balance sheet of the effects of the pollution on the coastal communities.
Populations of Rocky Shores The algae and the intertidal reefs were polluted along almost 200 km of coast over an area equivalent to 70 kmL By mid-June most of the shoreline was no longer oily, pollution being by then confined to the higher levels of the shore in sheltered inlets, particularly those facing west (less if facing east). These were still heavily polluted with little sign that they would improve on their own. Algal nett photosynthesis, measured on 16 April, showed similar levels for several dominant species in oiled and non-oiled areas. The Laminaria beds which occur at levels between + 3 and - 15 m, and which cover an area of 300 km 2 are still intact. Only the beds of Laminaria digitata in the upper part of the range are exploited by 600 specialized gatherers. A slight retardation of growth was noted on 26 April at 1 km from the wreck. On 25 M a y beds of Laminaria harvested 5 km farther to the east were of normal length for the season. Smaller red algae which live beneath the fronds of the Laminaria were well developed during the spring. On 1 July abundant sporelings and strong growth of Fucus spiralis was noted (up to 12 cm) at Portsall. Land plants, Crithmum maritimum (rock samphire) and Honkeynia peploides (sea sandwort), had been seen in May sprouting and flowing through 1-3 cm of black weathered oil above H.W. The oil had smothered lichens and any 298
associated fauna (M. F. Spooner, personal communication). Effects on rocky shore fauna have shown wide variations according to the species and to the intensity, age (reduction of toxicity), renewal and persistence of the oil. Heavy mortality occurred among herbivorous gastropods (Fig. 1). These were studied at 160 sites along the whole coast, in particular at Beg-en-Fry, Callot, Roscoff (10 sites), Mogueriec, Plouguerneau, Portsall and Le Conquet. Patella (limpets) suffered mortalities varying from 0-10007o with a mean of 20°7o. Littorina, Gibbula and Monodonta (winkles and topshells) suffered greater losses, 50-99070. Mortalities were particularly great at high levels, which were in general more polluted, but where oil was more evenly spread lower levels were also severely hit. At the beginning of July an abundant recruitment of young Littorina littoralis was seen on the shore at Portsall, which had received a maximum amount of pollution. On the lower part of shores no mortality occurred among the barnacles Chthamalus and Balanus perforatus nor in Mytilus (mussels) nor Sabellaria (sand reef building worm). Crustaceans free-living among the intertidal algae have everywhere shown a high mortality and particularly in the neighbourhood of the wreck. Amphipods have disappeared almost as far as Plouguerneau and isopods and adult shore crabs (Carcinus maenas) are rare. At the beginning of July there was a strong recruitment of small shore crabs, even at Portsall. At this time there were abnormally high populations of harpacticid copepods which live on the surface of the algae. These were perhaps 20 times as numerous as in comparable unpolluted areas (Table 1). (Note that in the nearby sediments the epipsammic harpacticids were practically absent, there being a high concentration of hydrocarbons in the interstitial water.) This population explosion among the meiofauna of the persistent cover of macroalgae, fucoids, Ulva and Enteromorpha was apparently related to the great reduction in herbivorous macrofauna and to the intense proliferation of bacteria and diatoms (often filamentous) and small Phaeophyceae which literally covered the large algae by then clean of oil. Shrimps (Leander serratus) have become 2-2.5 times as abundant as usual apparently attracted to and fattening on the outburst of meiofauna. The populations in shaded overhangs and crevices were found to be intact in the Bay of Morlaix at Ile Callot. At Portsall they were diminished in numbers and still affected by oil, particularly at high levels on the shore.
Volume 9 / N u m b e r 11/November 1978
E or W or S of wreck Km
0 1 L P 0 L L UT I 0 N Days Quantities after wreck
L 0 CA L I T I E S
HERBIVOROUS G A S T R 0 P 0 D S OF SEAWEEDS ON ROCKS Mean Biomass.m -2 Mean numbers.m -2 rough wet weight Gr. ( adults )
limpets (Patella)
periwinkles / ( Littorina / + ___J______/_......:Gibbula)/..:
Survival %
~." ;': . - ' ? . . . . . ~ 05
PAIMPOL
147
PLOUGRESCANT TRESTEL TREGASTEL ILE GRANDE TREBEURDEN
113 105 92 86 86
BEGLEGUER
LOCQUIREC BEG AN FRY PRIMEL TREGASTEL
LE GUERSlT SAINT SAMSON E
1
2
4
8
16 32
500 I
o '
' • ~--x'xx~x~~
87
~,~-4-
+ e- + + 4- -f- + +
~
67 67 57
+
-F-~+
55
4-+ + + .4.--+-
PORTSALLi
TREMAZAN LANHALLES ILE SEGAL
N S
56
~__--
_
÷+ ÷* -F +
.
---
• ~'.
÷
: •I'
LE CONQUET
23
STE ANNE PORTZIC
50
.\~
....,.
t
" ° : ° ~
'.'.' "...._'.'. "'"
~
L
".~." : '. "..'.-~I~##~ I:.F//44, -I 1 j
4- 4--4- 4- 4- -4-4- -F-4- + + 4- 4- 4- + -I-
,,'<
"° "
I
41 ,~ 30 , 4- 4- 421 ~ 4- -r 4- + 416 94 -~ - ~~ H - - F ~ 3 7 15 15
~\\ 4- 4- 4~ 4-- 4- 4-
--~/J.~2~,
+4
4- +
•
B.
TREPASSES PENMARC°H
60 IO0
MOUSTERLIN
128
'
H-+ 4- +
55
6
100
~ - - I -
56
E
50
" . : .. - •. . . . . . . ' '.. '.: •" .'.:~'_
4- H-4- Jr +-
N
F O,L, C PLOUESCAT BRIGNOGAN LE CURNIC PLOUGUERNEAU ABERWRAC'H ABERBENOIT
0
-4--
79 74 69
S
ILE VERTES
0
÷ + + ++ :4- H- -F
0
ABER
100
I ~ _ ----
+ 4H- -r 4- if" ÷ -i-+ +
O F
200
+ +
57 57 57
C
300
L
4-
ILE DE N TY-SAOZONs W
R
400
o
added with
('~-F-~ + Bohlen spill r .L-'. • , J,
?
,
• • I'///~
":"
[ ~
"'"";" !
Fig. 1 Herbivorous Gastropods of seaweeds on rocks in relation to oil pollution from AMOCO CADIZ. Four unaffected stations are shown (O). During the eastward spread of oil (upwards in figure) loss of toxicity with approximate age is suggested by cross-hatching. Oil arriving on shores to W and S probably left the wreck at a late stage. °70 Survival, based on definite pre-spill data ; where deduced from similar hydrodynamic situations . . . .
Populations on the underside of boulders resting on sediments were clearly impoverished at Portsall, less so at the mouth of Aber Benoit and at Roscoff, even where the sessile fauna appeared normal, freeliving species were scarcer and depleted, We have not observed the same massive proliferation of Enteromorpha (green algae) on polluted shores as was seen in Cornwall after TORREY CANYON(Smith, 1968). This may be due to the almost complete persistence of cover by macroalgae, offering fewer available habitats than on naturally barer shores, and to the lesser mortality of herbivorous gastropods,
Sedentary Fauna of Sands and Muds In the proximity of the wreck and where oil slicks had accumulated and been stranded thickly, particularly in the first weeks on beaches exposed to the west, there were many dead animals in the strand line at high water and accumulations of drift. The dead animals were identified, counted and measured. They belonged to certain sensitive s p e c i e s - others, closely related and perhaps from the same communities, were poorly represented. Some edible species of bivalves taken noncommercially were badly hit. On the whole, however, the survival of macrofaunal associations on particular 299
Marine Pollution Bulletin TABLE 1 Meiofauna and herbivorous gastropods of algae on rocks ( 2 - 7 July 1978).
Locality Distance from wreck in km Intensity of pollution Gastropods % adult survival
Numbers per m 2 Gastropods new settlement Harpacticoids Nematodes Amphipods, young Isopods, young
Rade de Brest (St A n n e du Portzic) exposed sheltered 50
50
unpolluted 100
1130
Le Conquet South
Ile S6gal North
Portsall Porsquey very sheltered
23
16
15.5
0
+
+ +
+ + +
+++ + + +
82
88
95
8
0 ÷+q-+ + + + 3
Aber Benoit
Plouguerneau
6
16
+++ + + +
+ + +
3
65
?
?
4320
1450
1030
410
?
4600
1880
2000 ? ? ?
10 000 ? ? ?
25 000 880 1200 473
2000 50 45 1024
8000 1590 160 567
35 000 1910 3 0
350 000 ? 0 ?
199 000 ? 0 2000
31 000 ? 229 264
beaches was estimated as about 80% of normal densities (range 4 0 - 9 0 % ) . Where the meiofauna has been heavily damaged as at Portsall, Plouguerneau and Roscoff, the harpacticid and ostracod populations in particular are depleted, but nematodes have become more numerous, The turbellarian Convoluta roscoffensis is still very common, The survival of various species of in-fauna was investigated on 15 beaches of differing types from Portsall to St Efflam some 94 km from the wreck, Observations made from April to July included beaches which initially received very heavy oil deposits to those which had moderate to slight pollution. A wide range of specific susceptibilities was seen and some examples out of over 50 species of in-fauna are given below:
traces of oil. In over 200 sampling holes an iridescent film was always found on the surface of interstitial water and sometimes also droplets of brown emulsion. This occurred at all levels in the beach and in all types of sediment. The level of hydrocarbons is high even where coastal water is no longer polluted. This explains why mortalities still occur in the sediments and the meiofauna has not been re-established. Damage to burrowing macrofauna has been more severe below low tide mark, notably in the Abers, and bays of Morlaix and Lannion, sometimes to depths of 40 m. In fact the dead animals washed ashore came largely from the subtidal populations, these being no doubt less adjusted to withstand stress than those of the intertidal zone.
Polychaetes were remarkably resistant
The Mobile Fauna
Arenicola marina (lug worm) apparently not affected at all and m a n y other species of burrowing worms likewise Opheliidae spp (characteristic of very clean sand) and Lanice conchylegia (sand tube builder)only slightly hit
There was a very obvious mortality of both fish and crustaceans during the first week for a distance of 10 km around the wreck. There was also a lesser mortality at Roscoff, but elsewhere it was negligible. Specimens were collected, identified and measured. Among fish the principal mortalities were among the Ammodytidae (sand eels) followed by the Labridae and then the Syngnathidae. Dead specimens of Gobiidae, Blenniidae, Callionymidae and littoral gadoids were also c o m m o n and all other littoral groups represented by several specimens. It is of interest that at Portsall and Roscoff 70 individuals of the northern gadoid Raniceps raninus were found. This species had previously been known in Brittany from a single specimen caught in 1908. Their presence in the samples is evidence not only of the gaps
Lamellibranchs, mostly quite seriously depleted Solen, Ensis spp, Pharus(razor shells) almost total kill Cardiumedule(cockle)afewsurvivors Tellina spp (pink tellin) survived very well Mya arenaria (brackish water clam) seemingly no deaths
Crustacea Talitrussaltator (sand h o p p e r ) o f H.W. zone, heavy kill Haustorius arenarius Bathyporeia spp of lower tidal level,
Eyrydicepulchra much less mortality Ampelisca brevicornisM.T, to L.W. all killed
Echinoderms Echinocardium cordatum (heart urchin) nearly all killed Acrocnida brachiata (brittle star) a few survivors Leptosynapta gallieni (worm-like holothurian) good survival
Vulnerability of species to hydrocarbons is specific and differs from that shown to oxygen-lack or reduced salinity. It more nearly resembles the effects from effluents of the paper manufacturing industry. At the beginning of July at all sites at Portsall and in the bays of Morlaix and Lannion, the beach sediments though appearing to be clean were impregnated with 300
in our knowledge of ecology but also of the rapid diffusion of oil through the whole water column. The probable habitat of this rare species is in the Laminaria beds, between - 3 to - 1 5 m, a zone inaccessible to fishermen from land or by boat. As a footnote it has been reported that, since the beginning of August, 5 0 - 8 0 % Mugi! (grey mullet) have been found with ulcerations of the skin on the body. This suggests that we may not have seen the last of the effects of the oil. Crustacean mortalities were mainly of Cancer pagurus (edible crab), Portunus puber, Crangon
Volume9/Number 11/November1978
crangon and Leander serratus (shrimps), Galathea squamifera and G. strigosa and especially Carcinus maenas (shore crab). The latter was thought to be exceptionally resistant to all kinds of pollutants so its abundance in the strandings of dead animals and the relative rarity of living crabs subsequently are evidences of the severity of the pollution in the early days. Taking account of the places where the collections were made and the sampling methods used, the strandings represent less than 10000 inshore fish of all kinds and a similar number of crustaceans. This is a relatively small number and very localized even if allowance is made for dead animals not stranded. Some exploratory fishing was carried out by the Institute ScientifiqueetTechniquedes P~chesMaritimes with the following results: On 5 April at Plouguerneau, in crab pots at 30 m depth, numbers of Cancer pagurus appeared normal but tasted of oil. On 12, 24 and 28 April at Portsall, close to the wreck, Mugil (grey mullet), Gadus pollachius (pollack) and Scomber scomber (mackerel) were emaciated but most often untainted. On 14 April at Brignogan, specimens of Maia squinado (spider crab) had a smell of oil. On 28 April, close to wreck at Portsall, Cancer and Main tasted normal, F r o m 15-30 April at Plouguerneau, as at Roscoff and Carantec, Cancer, Maia, Palinurus and Homarus (crabs and lobsters of important commercial shell fisheries) were normal in quantity and quality, To sum up, from the end of April, the dilution of hydrocarbons in the water (0.05 ppm) was such that fish and crustaceans were mainly free of taint in offshore waters. By the end of May this had been achieved in all remaining areas, except in the Abers.
Conclusions The above account was written at the beginning of July 1978. By comparison with previous pollution accidents and taking into account the enormous quantity of oil spilled at Portsall, the provisional balance sheet indicates rather less damage to the marine environment than might have been expected (Table 2). (1) There is now evidence that intertidally and close inshore direct mortalities have been localized, seldom heavy and always selective and partial. (2) Contamination of organisms and products of commercial fisheries at sea have been transitory. Oyster culture alone has been badly damaged. (3) The algal crop is now exploitable for industrial use. (4) The general cover of macro-algae has survived the incident.
TABLE 2 Summaryof ecologicaleffects 3 months after theArnoco Cadiz spill on a heavilyand on a lightlyoiled locality.
Pollutionintensity Algae on rocks Barnacles Herbivores (limpets and winkles) Meiofauna on algae
Meiofaunain sand Macrofaunain sand
Percentage survival Portsall Plouguerneau + ++ ++++ + 90 95 100 100 8 65 >500
12 40
>300
17 80
Populations of herbivorous gastropods have partially succumbed but there is already evidence of some important fresh recruitment. There has been no general development of green weed on the intertidal rocks. The causes of this modest impact may be ascribed to: (1) Limited use of dispersants which are now less toxic: they were used sparingly and only on a few shores. The main use of under 2000 tons was offshore (more than 8 km from the coast). (2) High turbulence of the sea around the wreck and in the polluted sea areas, produced rapid dispersion of the oil. This caused heavy mortalities over a limited area with greatly diminished effects everywhere else. The mortalities were caused by the oils themselves, particularly in the first few days before the most toxic volatile fractions had evaporated. (3) A prompt and intensive collection of the stranded oil by many civilian volunteers and 6000 troops amounted to at least 15-20000 tonnes of reclaimed oil. The most serious aspect of the pollution has been the accumulation (likely to be long-lasting) of petroleum hydrocarbons in sediments and in their interstitial water. Here the total hydrocarbon concentration is 1-16 ppm, as against 0.03 ppm in coastal water in early July. This interstitial oil is most significant in the black reducing sediments (where other hydrocarbons are being formed naturally). Even if oil is prevented from direct entry into estuarine muds because they are charged with interstitial water, the very numerous burrows permit penetration of oil to considerable depths. This oil spill disaster has affected not only the ecology and economy of Brittany, but has been psychologically, aesthetically and politically disturbing. Chasse,C. (1972). Economie sedimentaireet biologique (production) des estrans meubles des cotes de Bretague. These d'Etat Paris VI 293 pp. Smith, J. E., (ed.)(1968). Torrey C a n y o n Pollution and Marine Life.
CambridgeUniversitypress. Southward, A. J. & Southward, E. C. (1978). Recolonization of rocky shores in Cornwall after use of toxic dispersants to clean up the Torrey Canyon spill. J. Fish. Res. Bd. Can., 3 5 , 6 8 2 - 7 0 6 .
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