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and mich less a Islas Naranjos mad Isla Margarita (19). Moreover, similar differences occurred over just a few hundred meters between shores directly aposed to ar shclered from the wind-driven oil (201. On an cven smaller scal, extreme low rides between 10 and 19 May (6, 21) caused oil to carmulate along the seaward borders of reef flats, whereas just shoreward much less oil contacted the substratum. In general, intercidal babicas just above mean low water were the most heavily oiled, including mangrove roots and sedi
Fig. 2 Region of the Republic of Pa affected by the 27 April 1986 oil spill, shown as increasing cadangoscens (A o C). (A) Location within Panama, just cast of the Canbbean carance to the Panama Canal. (B) The boxed area includes the most heavily one coastal habitats. Punta Galeta, insick the boxed area is 924N, 79°52'W. Lightly oiled and unoiled study sates are cast of Bahia bas Minas, car Portobelo and Isla Grande. (C) Detail of the most heavily oiled ara and location of study sites. Encircled "R" on Isla Pavardi marts the refinery wtore the oil spill occurred. Horizontal hacching denotes ambarmemes where like all penetrated. Symbols for types of study sites (open symboks, worked as highly oiled sites, filled symbols, osled sites): 4, mangrove root, scara bed; O, subtidal coral reef, data collected only after the oil pit: , suboidal coral reef, data collected both before and after the oil spilt the four sites near Portobelo and Isla Grande were not oiled, the site a Isla Margria was moderately oiled, and the site at Punta Galet was heavily oiled; , roffa somatopods; mulcirayed star, reef flat communicy, Punia Galleta, s-payed symbol, mangrove forest.
Fig. 3. Organisms and habitus faced by the
6 JANUARY 1989
ments, reef-flat seagrass beds, coral rock, and beaches. In contrast, sis of aromacic hydrocarbon fractions (22). Preliminary results higher than normal seas after the Witwater spill caused heaviest oiling generally parallel dassificacion of sites based on visual inspection, as in high inceridal and supercidal habitats, with much more transport shown here for the concentracion of saturated hydrocarbons in of oil into mangroves far from shore (4). Much less oil was observed tissues of the coral Siderastrea sidera (Table 1). subridally.
In addition to these qualitative observations, samples of water, substrata, and organisms were collected for analysis of hydrocarbon Biological Effects by means of gas chromatography and ultraviolet fluorescence analy.
Consequences of the spill were assessed differendy, depending on
the types of data available from before the oil spill (23). Ideall, Channel Open
biological parameters should have been measured & oiled and
unoiled sites before and after the spill. This condition was satisfied Live
for biota of mangrove roots and suboidal corals. Extensive prespill
sites after the spill, confounding the treatment (oiling) and geogra.
phy (Bahia las Minas verus the region between Portobelo and Isla
Mangrove communities. Red mangrove, Rhizophora mangle, forms Sessile animals
nearly all of the fringing forest along this coast (17). By September 1986, a band of dead or dying trees marked the zone where oil washed ashore between Punta Galeta and Islas Naranjos (Fig. 3); no such band appears in photographs taken just as the oil was coming ashore. By November 1987 dead mangroves occurred along an estimated 27 km of the coast (25). Seedlings transplanted to heavik: oiled sites did not produce new leaves, in contrast to transplants ar an unoiled site (20).
The prop roots of R. mangle are overgrown by algae and invertebrates that vary in species composition with exposure to che sca (Fig. 3) (6, 27). The epibiota on roots in three different habitats were sampled before and after the spill (Fig. 2) (28). Before the spill (Fig. 4), roots of trees directly facing the open occan were covered with foliose algac and sessile invertebrates such as sponges, hy.
droids, and ascidians. In mangrove channels, the edible oyster, Fig. 4. Percent cover of formerly abundant taxa and oil on mangrove roots in Crassostrea rhizophorae, and a barnacle, Balanus improvisus, were most nivcrine, channel, and open coast habitats before and after the oil spill. Q, abundant on roots. Roots in small rivers were dominated by the Prespill data; O, unoiled sites; and, oiled sites. Means are plotted = 1 SE, converted from arcsinc transformations. Some crror bars lic within the
false mussel Mytilopsis domingensis and B. improvisus. Certain groups plotting symbols, except for sampling time 3, when n = 1. ND, no data.
were more abundant a few years before the oil spill (1981 to 1982) "Leafy algac" include Polysiphonia, Acanthophora, and Ceramium as common than in 1986 to 1987 at unoiled sites (Fig. 4), possibly because of genera; the most abundant sessile animals” include hydroids and sponges. natural fluctuations in abundance. After the spill, the cover of all Sampling dates: 1 = September to October 1981; 2 = January 1982; 3 = June 1982; 4 = July to August 1986; 5 - October to November 1986;
major groups was very greatly reduced in each oiled habitat (Fig. 4). 6 = February 1987; and 7 = May 1987. Results of repeated measures
There has been parchy recovery in the open habitat of foliose algae analysis of variance for oiled and unoiled sites after the spill are shown on
and sessile invertebrates, although not of the same relative abuncach graph, NS, P >0.05; ', P < 0.05; **, P < 0.01; ***, P<0.001. dance of species. In the channels, cover of both the oyster and
Percent cover on roots
Fig. 5. Abundance or biomass per sample of cight major infaunal taxa in three oiled (O) and four control (O) scagrass beds 5, 7, and 9 months after the oil spill (30). Means are plotted +1 SE, backtransformed from in (x + 1); some crror bars lic within the plotting symbols. “Burrowing shrimp" include alpheids (most abundant), processids, callianassids, and upogebids. NS, P>0.05; * P < 0.05 by repeated measures analysis of variance. Number per sample is shown at two scales. Data for polychactes are shown as grams per sample.
barnack dropped gready and have since rocovered litde. False
70 mussets and barnacles disappeared in oiled rivers and were not
60 recorded again weil 15 months after the spill.
RT The greatest cover an roots in a ciled habicats after the spill was
SO 9 oil (Fig. 4). In addition, most roots sampled for epibiota (28) were
IN dead, broken, ar routing by August 1987 (54% on open coasts, 56%
30 in channck, and 66% in rivers oiled sites versus 8%, 1%, and 3%,
20 respectively, a mnoiled sites). Thus the mangrove-fringe roor habior has been largely destroyed a coled sites and will not be restored
10 unless new trees grow. Seagrasses. Extensive meadows of the seagrass Thalassia testudinum
30 cover much of the intertidal roof platforms and subcidal floors of
corallinen shallow embayments and lagoons along this coast (24). Entire beds of intercidal Thalassia were killed an some heavily oiled reef flats, as
10 shown by abundant oil-covered dead kaves washed ashore and dead bur intact root-rhizome mets (for comple, the site a Largo Remo
0 North) (Table 2). In contrass, suboidal Thalassia survived every
Halimeda where after the spill, alchongth kaves became brown and heavily fouled by algas for several months in heavily oiled areas.
80 Thalassia provides food, babies, and refuge for dense populations
ficroalgon of invertebrates and fishes (246, 29). Before the spill, amphipods, small decapods, optiuroids and other chinoderms, bivalves, gastro pocs, polychectes, and small fates were all abundant in seagrass within the study area (29) and all are in unoiled beds (Fig. 5). Sampling of infauna began September 1986 at three oiled and four unoiled sites (30 (Fig. 2). Four two of invertebrates were significandy less abundane in oiled grassbods afver the spill, but four others
20 showed no such difference (Fig. 5). Abundances of most cara increased between September and January; preliminary analyses of
10 body size indicate that recruitment caused these increases. Only the
0 abundance of harmic arabs ingrcared in oiled relative to unoiled arcas (7.3 versus 3.4 crabo per stampas, respectively, in January 1987,
Zoanthus P<0.05, repeated measures matysis of variance), perhaps because of a surplus of shells of recently dead snails (31).
Intertidel reef fests. Placforms of fringing reefs from extensive shallow to intercidal flass throughout the study region (Fig. 3) (7,9, 17, 32). Populations on the roof flar a Punta Galeta have been
2 monitored for up w 15 years (9) (Fig. 2). Damage was most antensive a the seaward borda, where the oil accumulated at low cick. Immediately after the spill a bloom of microalgae covered
Porites & recendy vacated subetracom (33) (Fig. 6). This area had been
Milleport dominated by perennial macroalgas particularly the fleshy red alga Lawrencia papillosa, custose corallines, and the articulated calcareous green alga Halimeda aprantia. Cover of all these plants was reduced to. kevels well below those observed previously, but had regained or
Palythoa exceeded typical abundance within 12 to 18 months, concurrent with a reduction of the microalgae. The most common sessile animals before the pill were zoanthids (Zoanthus sociatus and Palythoa spp.), hydrocorals (Millepora spp.), and scleractinian corals (Porites spp.). As the scaward border of the reef lat, populations of all these animals were severely reduced, and only Zoanthus had returned to typical abundance after 18 months (Fig. 6). Densities of sea urchins on the roof flat varied over three orders of magnitude
Echinometra before the spill (Fig. 6) (9. Ar the seaward edge, the most abundant
100 Fig & Pre- and postspill comparisons of the abundance of algae and sessile animals (cop seven panels) and the sea urchin Echinometra luaunter (bottom
10 panel) on the scaward portion of the Galeta roof flat (33). Filled symbols denotes the heavily oiled zone dorest to the water's edge at low tide (Fig. 3); Open symbols and the sonoodh Kine in the E. facranter graph indicare less oiled (more handward) habitans, and more postspill surveys of percent cover
83 84 &S
87 that were significandy higher or lower than any prespill survey a P s 0.05
oll Spill and P s 0.õl, respectively. ladas, differences were significant only in
Your the heavily oiled zone (O). Covar was compared survey by survey with the use of paired teres marched by individual transects within surveys. Abundances of E. lucunter were compared with the use of residuals from regressions (34).
Urchins per 10 m2
6 JANUARY 1969
urchin Echinometra lucunter was reduced by about 80% within a few Subtidal reefs. Populations of subtidal sessile organisms were days of oiling, and the reef Alat was littered with its skeletons. surveyed on six fringing reefs between Isla Margarita and Isla Although this decrease was small in an absolute sense relative to Grande within 1 year before and 4 months after the oil spill (Fig. 2) changes in abundance among years, it nevertheless departed signif. (41). These include the heavily oiled reef at Punta Galeta, a lightly candy from the average trend in abundance between months of May oiled reef at Isla Margarita, and four unoiled reefs cast of Portobelo. and June over the last 8 years (34). Farther inshore, no such Abundance of most common scleractinian coral genera in depths reductions occurred.
53 m decreased at Galeta by 51 to 96%, and total coral cover
particularly shrimps above suboidal seagrasses. In summary, the spill
menos examined, infauna and epifauna, and members of all trophic
levels including primary producers, herbivores, carnivores, and
Patterns of Responses and Their Significance
The severe damage to intercidal biocas and their response, such as
abundance of many organisms at the seaward edge of the reef Alat
In contrast, other results were not expected, and in some cases contradict widely held views about the effects of oil spills and the ways they are studied. First, extensive mortality of subridal corals and infauna of seagrasses had not been demonstrated before (1, 3) and contradicts undocumented assertions that these organisms are
not affected by oil spills. In part, subtidal effects may have been Percent cover beton oll spill
caused by the use of dispersant (51) but it seems unlikely that this Fig. 7. Percent cover of corals before the oil spill plotted against their cover
was the only reason, given the regional breadth of the impact and afterward. The diagonal lines represents no change in coral cover; points
the relatively small amount of dispersant employed (14). below this line indicate a decrease after the spill, and points above the line Second, the magnitude of subtidal coral mortality and injury show an increase. The points are means = 1 SE; some crror bars lic within within Bahia las Minas is in striking contrast to findings of no the plotting symbol. Oiling significantly affected coral cover only at the shallowest depth (42). Abbreviations: 3, 0-to 3-m depth: 6.3-70 -m depth lasting change in coral condition or growth after exposure to oil, and 12, 6 to 12-m depth. JUG and PALW are located just west of Isla
with or without chemical dispersant, in small-scale experiments (51, Grande, DMA and DONR are northeast of Portobelo, GAL is at Punta 52). Such discrepancies underlic the importance of detailed longGaleta, and MAR3 is at Isla Margarita (Fig. 2, half-filled circles).
term ecological studies, and the dangers inherent in extrapolation to
Percent cover after oil spill
Porcent of colonies with recent Injury
4. K. Rutzlar and W. Sterrer, BioScience 20, 222 (1970). 5. C. Burkcland, A A. Reimer, J. R. Young, Survey of Marine Communities in Panama
and Experiments wish Oil (Publ. EPA-600/3-76-028, Environmental Protection
Agency Ecological Rescarch Series, Narragansen, RI, 1976). 6. J. D. Cubit at a., in 1987 OJ Spill Conference (Publ. 4452, American Petroleum
Institute, Washington, DC, 1987), pp. 401-406. 7. J. Cubit and S. Williams, Atoll Res. Bull. 269, 1 (1983). 8. J. D. Cubit, R C. Thompson, H. M. Caffey, D. M. Windsor, Smithsonian Contrib
Mar Sa. 32, 1 (1988); L. G. Macintyre and P. W. Glynn, Am. Assoc. Petrol. Geol
Bull. 60, 1054 (1976). 9. G. L. Hendler, in Proceedings of the Third Interational Coral Reef Symposium. D. L.
Tavlor, Ed. (University of Miami, Miami, FL 1977), vol. 1, pp. 217-223; J. D. Cubit, D. M. Windsor, R. C. Thompson, J. M. Burgen, Estuarine Coastal Shell Sa.
22, 719 (1986). 10. J. C. Ogden and E. H. Gladfcker, UNESCO Tech. Pap. Mar. Sa. 23, 1 (1983).
Important species in common throughout the tropical western Atlantic are red mangrove mangle, seagrass T testudinom, mos reef corals and algae, and
commercially important lobsters (Permalinus spp.) and oysters (C. reizophoree). 11. Ongoing drilling and refining off Yucatan and possible production along the west
coast of Florida 12. The oil type was 70% Venczuclan chade, 30% Mexican Isthmus crude, specific
gravity 27 (Amencan Petroleum Institute). Percent composition determined at the Bermuda Biological Station by cohamn chromatography with the use of alumina and subca gels: 47.4% saturates (fraction I, herane); 6.4% light aromatics (fraction 2, 10% ether/90% hexane); 4.8% heavy aromatics (fraction 3, 20% methylene chloride/80% hoxanc); 18.9% polar fraction (fraction 4, mcthylene
chlonde); and 22.5% unrecovered. 13. C. D. Getter, G. I. Scott, J. Michel, in 1981 Od Spill Conference (Publ. 75-4161.
American Petroleum Institute, Washington, DC. 1981), pp. 535-540. 14. Rcfincrv ofhcials estimated that <21.000 liters of Corcu 9527 (Epions Chemicals
America) were spraved from aircraft (6). STRI personnel observed thus spraving
berween Acana Chiquita and Punta Galeta. 15. J. D. Woodlev et al., Science 214, 749 (1981); J. H. Connell, ibid. 199, 1302
(1978). 16. Surveys beyond Punta Galeta began the first week of June 1986 and lasted 1
month. Vidcotapes were made of the coast berween Rio Chagres and Islas Naranjos. and scill photographs were made all along the coast. Visual assessments were made of degree of oiling (heavy, moderate, light, or absent) and the habitats
and types of organisms obvious affected. 17. J. D. Cubit, G. Batista de Yee, A. Roman, V. Batista, in Agonia de la Naturaleza, S.
Hackadon Moreno and ). Espinosa Gonzalez, Eds. (Impretes, Panama, 1985), pp.
183-199, Revista Medica Panama 9, 56 (1984). 18. Oil was observed commonly until the time of manuscripe revision (July 1988)
around Isla Pavardi, where it emerged directly from the coral landhu on which the refinery is built, and Punta Muerto, Bahia Cativa, castern Isla Largo Remo, and
Punta Galeta. 19. Within this area oil commonly escaped from sediments when we walked among
mangroves or cored into shallow subtidal scagrass beds. Interudal surfaces were
heavily coated with ou. 20. Most of the ow that escaped from Bahua Cativa was driven west. Coasts facing north
to northeast were heavily oued, whereas adjacent areas facing west or south received Littk oul. The best studied example is at the northwestern side of Isla Largo
Romo (Table 2). 21. These low tides occur annually at this time of year (8,9). Sea levels during most of
this time were as much as 10 cm below the 9-year average for this period of
normally low sea level. 22. Corals were collected by divers on davs when on surface slicks were visible, placed
in solvent rinsed aluminum foil, and frozen. Tissues were removed from skeletons with an air pick and homogenized with a tissue grinder. To minimize vanations due to water or carbonate inclusions, standard Lowrey protein determinations were used as one measure of tissue mass. After solvent atraction, total lipid weights were determined microgravimetrically. Extracts were fractionated by adsorption chromatography. Hydrocarbons were analyzed with a capillary gas chromatograph cqmpped with a flamc ionizabon detector and 25-m SÉ 52 fused
silica columns 23. R H Green, Sampling Design and Statistical Methods for Environmental Biologists
(Wiley, New York, 1979). 24. J. B. C. Jackson, Bull. Mer. Sci. 23, (1973); K. L. Heck. Mer. Biol. 41, 335 (1977);
R Vasquez-Montoya, An. Inst. Cienc. Mar. Limnol. Univ. Nac. Auton. Mex. 10,1
(1983) 25. This estimate was extrapolated from acrial photographs of 36 km of the 82-km
shorelinc, of which 76 km contains mangroves. Of the photographed shorelinc,
36% contained a band of dead mangroves. 26. Sprouting success was measured for seedlings collected from an unoiled site, and
planted in one unoiled and two oiled sites. Of 25 scodlings transplanted into cach
site, 16 (64%) sprouted at the unoiled site and 1 (2%) sprouted at the oiled sites. 27. J. P. Sutherland. Mar. Biol. 58, 75 (1980); W. E. Odum, C. C. McIvor, T. J. Smith
HI, The Ecology of the Mangroves of South Florida: A Community Profile (Publ. 81/24,
U.S. Fish Wildlife Service, Washington, DC, 1982). 28. Roots were sampled three times before the spill in rivers and channels (September
to October 1981, January 1982, and Junc 1982) and twice in open habitats (September to October 1981 and January 1982). Several areas of shore within cach habitat were chosen haphazardly. Fifteen to 25 intertdal roots 2 20 cm long that had not become firmly attached to the mud were lifted from the water, and cover of attached organisms was measured for cach root by 100 random point counts after the oil spill or was estimated visually before the spill. Afte the spill previously sampled riverinc and channel habitats included both oiled and unoiled sites but all open sites were oiled. Thus it was necessary to choose sites near Portobelo (Fig. 2),
Amount of olling
Fig. 8. Frequency of injury for the three most common species of massive corals in relation to the amount of oiling a 12 reefs (4 unoiled, 3 lightly to moderately oiled, and 5 heavily oiled). Open bars represent coral colonies with injuncs that did not exceed 10% of the surface area of the coral; filled bars represent injuries greater than 10% (maximum observed, 100%). Sample sizes are shown above cach category of oiling. Abbreviations; Dip, Diplona divosa; Por, Pontes astreoides; Sid, Siderastrea siderea; s, shallow (0 to 1 m), and d, deep (1 to 2 m).
natural populations from laboratory-based physiological data or small-scale, short-term press perturbation experiments in the field (2, 3, 48, 52, 53).
Third, sublethal effects are extensive and may be more important in the long term than initial mortality (3, 48). Changes in stomato pod behavior and population structure were more pronounced than might be expected from a simple reduction in numbers. Likewise, injury of corals has allowed colonization of their bare skeleton by algae and other sessile organisms that may overgrow parts of colonies that survived the initial effects of oil (3, 54). Corals stressed by oil are probably also more susceptible to cpidemic discasc and likely to grow and reproduce more slowly than unaffected colonics (3, 5, 52). Any combination these effects may further reduce overall abundance of corals as much as the initial spill (54). Such a chain reaction could continue long after any petroleum hydrocarbons are present in the environment or coral issues, just as staghom coral continued to decline precipitously following a severe hurricane in Jamaica (55)
The response of organisms to an oil spill, or any other major disturbance, will depend on the conditions in which they normally live (15, 48, 56). Moreover, the suite of organisms able to survive under conditions of chronic pollution, and their resistance to further stress, is typically different from that in similar unpolluted habitats (48, 57). Much of Bahia las Minas has been subjected to human disturbance, beginning with decades of excavation, dredging, and landfilling for the construction of the Panama Canal and the City of Colon, drainage and spraying of mangroves for mosquito control, construction of the refinery and a large cement plant on landfill, a major oil spill in 1968, and unknown amounts of chronic oil pollution from the refinery and ships passing to and from the Canal (4, 5, 17, 58). It is a mcasure of the severity of the 1986 oil spill that the biological consequences were so detectable despite this history of environmental abuse.
REFERENCES AND NOTES
1. National Research Council, Oil in the Sea: Inputs, Fetes, & Efas (National Academy
Press, Washington, DC, 1985). 2. R. B. Clark, Philos. Trans. R. Soc. London Ser. B 297, 185 (1982); R S. Carney,
Am. Sa 74, 298 (1986). 3. Y. Loya and B. Rinkevich, Mar Ecol. Prog. Ser. 3, 167 (1980).
6 JANUARY 1989