GULF WAR OIL SPILL RECOVERY OF COASTAL AND MARINE PLANT AND ANIMAL COMMUNITIES

Transcription

1 GAOCMAO Silver Jubilee Conference Bahrain, 22 & 23 April 1997 GULF WAR OIL SPILL RECOVERY OF COASTAL AND MARINE PLANT AND ANIMAL COMMUNITIES BY DR. FRIEDHELM KRUPP NCWCD, JUBAIL MARINE WILDLIFE SANCTUARY ABSTRACT Following the Gulf War oil spill about 700 km of coastline from southern Kuwait to Abu Ali Island in Saudi Arabia were covered by a continuous band of oil and tar. The upper shores lost most of their typical plant and animal communities. About 50 % of the salt-marsh and mangrove vegetation was destroyed by the oil. A year after the spill, new mangrove seedlings started to re-colonise the oiled sediments. By 1995 most salt-marsh areas showed clear signs of recovery. However, in some isolated pockets of low-energy mudflats there is as yet hardly any indication of improvement. The oiled shores were first colonised by extensive cyanobacterial mats, followed by grazers. As of 1992 the original animal communities re-established populations on the affected shores. By 1993 most of the lower shores had re-gained normal species diversity. Between three and five years after the spill, 60 to 100 % of the original species had re-colonized the upper shores. Subtidal habitats with their seagrass beds and coral reefs had escaped oil contamination. However, fish and prawn populations were severely affected. Pelagic fish stocks and reef fish population densities reached their lowest level in After a decrease to 50 % of their normal levels, fish populations recovered in The decline in fish stocks also affected predators higher up in the food chain, such as sea birds. While the breeding success of terns at the Gulf offshore islands was still normal in 1991, it decreased to alarmingly low levels in the two following years. By 1994, however, it was back to normal. The nesting success of marine turtles was not affected. These are the results of a large international, multidisciplinary team of scientists who worked in the area continuously over a period of five years under the auspices of the European Commission and Saudi Arabia's National Commission for Wildlife Conservation and Development. One of the effects of the Gulf War is an increase in environmental awareness and several environmental initiatives have been launched after the crisis. The first marine habitat and wildlife sanctuary in the western Gulf has successfully been established in an area which was once most severely hit by the largest oil spill in history. INTRODUCTION The Arabian Gulf, a northern extension of the tropical Indian Ocean, is an almost landlocked, shallow sea. Its greatest depth does not exceed 120 m, and during the Pleistocene glacials, when the sea level of the world's oceans dropped below this value, the Gulf basin dried up, resulting in an eradication of its marine life. Recolonisation by plants and animals of Indo- Pacific origin started only some 17,000 years ago, which is rather recent in geological terms (KASSLER 1973). The Arabian Gulf is connected with the Indian Ocean through the narrow Strait of Hormuz. Exchange of water masses is restricted and turnover time has been estimated at 3 to 5.5 years (HUNTER 1986). Pollutants thus remain inside the Gulf for considerable periods of time. The region is characterized by an arid climate. Rainfall is scarce

2 2 and evaporation by far exceeds freshwater influx, resulting in high salinities. Water temperatures may drop to 11 C in winter while they climb to almost 40 C during summer. High sedimentation rates result in increased turbidity and limit light penetration. All these factors contribute to a naturally stressful environment for tropical marine biota and many species are living at the limit of their range. However, despite the fact that biological diversity is lower than in other parts of the tropical Indian Ocean, productivity is high and plant and animal communities are remarkable in their adaptation to an extreme environment. The Gulf is also characterized by a great variety of coastal and marine habitats (BASSON ET AL. 1977, SHEPPARD ET AL. 1992, ABUZINADA & KRUPP 1994). The largest oil spill in human history hit an environment which was already subjected to natural and man-induced stress. Between January through May 1991, millions of barrels of crude oil were intentionally released into the Gulf. The oil slick moved south along the Saudi Arabian coastline. When the wind direction suddenly changed, the oil was pushed onto the shore. Some 700 km of coast between southern Kuwait and Abu Ali Island, north of Jubail, were covered by a continuous band of oil. The islands of Batina and Abu Ali prevented the slicks from drifting further south. Most of the oil accumulated in the bays to the north of these islands. Part of the oil evaporated and another part was skimmed from the water surface. By mid-june 1991, the Kingdom of Saudi Arabia had recovered the record amount of over one million barrels of oil (TAWFIQ & OLSEN 1993). There was no evidence of largescale sinking of oil. Even in Kharlij Marduma, where heavy slicks persisted for more than three months, hardly any subtidal oiling was recorded. Low amounts of oil reached the seafloor after having been attached to suspended sediments, or after erosion of oiled intertidal sediments (MICHEL ET AL. 1993, RICHMOND 1996). Winds combined with high tides, however, carried the oil far inland, severely affecting the intertidal zone. The upper intertidal was completely inundated and lost most of its typical plant and animal communities. Depending on the substrate, the oil penetrated up to 30 cm deep into the ground. Animal burrows often conducted it even deeper into the sediment. The mid-intertidal was less severely affected and the lower beaches revealed a patchy pattern of oil contamination (JONES ET AL. 1994, 1996). The heads of sheltered bays were most severely affected. Large areas of salt-marshes and mangroves along with their associated fauna were eradicated. The circumstances and the magnitude of the spill required an international response. Among other international organisations, the European Union (EU) seconded a Task Force to the concerned authorities in Saudi Arabia. In conjunction with the National Commission for Wildlife Conservation and Development (NCWCD), the Meteorology and Environmental Protection Administration (MEPA) and the Research Institute of King Fahd University of Petroleum and Minerals (KFUPM), an environmental response plan was drafted, which has resulted in the development of a comprehensive environmental project. Objectives of this project included the assessment of the ecological damage caused by the oil spill, the development of environmentally friendly rehabilitation methods and the establishment of the first Marine Habitat and Wildlife Sanctuary for the Arabian Gulf in an area which was most severely affected by the oil spill. Under the auspices of the European Commission and the NCWCD, some 80 scientists from nine countries of the Gulf Cooperation Council and the European Union have been working in the area continuously for more than five years (KRUPP & JONES 1993). Their findings on the recovery of habitats and biota from an environmental disaster of unprecedented magnitude are summarized here below. RECOVERY OF INTERTIDAL HABITATS AND BIOTA

3 3 The intertidal zone was most heavily affected by the oil spill. Satellite images reveal that before the Gulf War, it was covered by microbial mats dominated by cyanobacteria (AL- THUKAIR & AL-HINAI 1993). Most of these mats were severely damaged or erased by the oil and in 1991 they were absent from the area. In early 1992, they rapidly recolonised the oilimpacted shores between the mean low and mean high water mark where they showed a distinct zonation. Microbial mats were usually the first colonisers of this zone, but they only occurred on oiled surfaces, which were covered by a sediment layer. No mats were observed on plain tar. One possible explanation for their luxuriant growth below the saltmarsh and mangrove zone was the absence of bioturbation and grazing as a result of the oil spill. It has not yet been determined whether cyanobacteria contribute directly to biological degradation of oil. Potential effects of their presence are discussed in SORKHOH ET AL. (1992), HÖPNER ET AL. (1996) and HOFFMANN (1996): When drying, polygonal mats curl up at their edges, exposing the tar layer below to oxygenation, an important prerequisite for biodegradation of hydrocarbons. The mats stabilize the sediment and prevent oil-degrading bacteria from being washed away. Additionally, several species are capable of nitrogen fixation, which could sustain the growth of oil-degrading bacteria. Extensive areas within the coastal zone of the Arabian Gulf are covered by intertidal salt marshes. In areas which are inundated by high tides, these highly productive habitats have been contaminated with oil and almost 50 % of the intertidal vegetation was extinguished. Species colonising the lower intertidal zone were most severely effected and one wide-spread species, Salicornia europaea, lost almost 99 % of its population. WARNKEN (1996) calculated the loss of above-ground plant biomass at more than 1000 tonnes. The tar layer on top of the sediments changed soil characteristics and inhibited the penetration of water and gases, causing severe stress to plants and animals. Recovery of salt march plants in sheltered, low energy areas was slow. It started only 4.5 to 5.5 years after the spill (BÖER 1994, JONES ET AL. 1996). Dwarf mangrove stands are a characteristic habitat found along the shores of the Arabian Gulf. A single species, Avicennia marina, occurs in the region. After the war many experts predicted that the mangroves in the oiled area would not survive the spill. The oldest shrubs, which had been killed by the oil, were 60 years old. About half of the mangroves survived and as of 1992, new seedlings successfully colonised areas which had either been artificially cleaned after the spill or which had not been completely covered by tar. Replantation experiments gave promising results (BÖER 1994, 1996). Between 1991 and 1995 recovery of intertidal macrobiota was studied by JONES ET AL. (1994, 1996) along 10 permanent transect lines (PTLs), each being characteristic of a specific habitat type. At these PTLs, quantitative data on the distribution of intertidal epi- and infauna at five tidal levels were collected. The oil rapidly disappeared from the lower shore while it severely contaminated the upper tidal levels. On rocky shores and high-energy sandy beaches it weathered and disappeared during the study period. On other soft sediment shores it reduced in extent. In 1991, between 50 and 100 % of key intertidal species were absent from the oil contaminated area, while they were present at normal population densities on control shores south of Abu Ali. By 1993, the species diversity of the lower shore was similar to that of the control sites while on the upper shore, tar mats prevented faunal resettlement. By 1995, however, species diversity in the upper eulittoral area ranged from 60 to 100 % of normal levels. At some sites abundances remained lower than normal for species without planktonic larvae. According to these authors, recovery rates of Gulf shores are within the time frame reported after other oil spills in other areas worldwide.

4 4 Located at the edge of two ecosystems, the marine and the terrestrial, the strandline is a small band of organic material which supports a diverse fauna. The oil was particularly washed onto the upper littoral fringe, extinguishing most organisms. Two years after the spill there were hardly any signs of recovery in the old strandline, but in most areas new strandlines had accumulated. By 1995 there was no longer any visible difference between strandlines in the polluted and unpolluted areas. Most organisms colonising the upper tidal fringe are r-strategists, producing more offspring than the environment would sustain under undisturbed conditions. They rapidly recolonise the upper littoral fringe from adjacent areas as soon as the habitat conditions are favourable (SCHNEIDER & KINZELBACH 1994). EFFECTS OF THE OIL SPILL ON SUBTIDAL BIOTA The oil slick floated on the water surface until it was washed ashore. Subtidal areas with their highly productive habitats, such as seagrass beds and coral reefs, escaped direct oil contamination. Nearshore subtidal habitats were found to be in reasonably healthy condition. The expected species composition and normal seasonality in diversity and abundance were observed. Except for very few tar balls at small, localised sites, which had probably been washed into these areas from the intertidal, no visible signs of oil pollution were found (KRUPP & ANEGAY 1993, RICHMOND 1996). Coral reefs surrounding the Saudi Arabian offshore islands are the most diverse of the entire Gulf. VOGT (1996) studied their condition along 10 transect lines in three nearshore and seven offshore reefs. Spatial distribution of the various coral species was recorded with an underwater video camera and analysed on a computer-based image processing system. The coral reefs were healthy without any visible sign of oil damage. Near Karan Island a few bleached Acropora were observed, but their number did not exceed normal levels. The coral reefs surrounding these offshore islands also host the largest number of reef fish species anywhere in the Arabian Gulf. Between 1992 and 1995, fish assemblages were monitored annually along the same transects. Counts taken in 1992 and 1993 resulted in an average of 34.6 species and individuals per 100 m² transect. In 1994, however, the average number of species increased by 11 % to 38.3, while the number of individuals almost doubled. Similarly high counts were obtained in 1995 (KRUPP & MÜLLER 1994, KRUPP & ALMARRI 1996). While juvenile and adult reef fishes had escaped direct oil contamination, the reduced counts after the crisis may probably be attributed to a reduction of planktonic eggs and larvae caused by the oil slick (MCCAIN & HASSAN 1993), resulting in lower levels of recruitment onto the reef in 1991 and By 1994, fish populations had recovered from the oil spill. During the spill only very localized fish mortalities were observed. The largest one occurred around Qurma, where about one to two dead fish were found per square metre of beach. Bottom, midwater and surface feeders were among the dead fish and their sizes ranged from 1 cm to 1 m (MEPA 1991). Saudi Arabian fisheries were heavily affected by the war. The war zone was closed to fishery for almost one year. Test fishing in inshore areas that were covered with oil for up to three months revealed apparently healthy, edible fish with no petroleum taste (CARPENTER 1992). While the oil spill had a limited effect on finfish stocks, prawn landings in Saudi Arabia fell markedly in 1991 and 1992, with a very low proportion of sexually mature specimens. According to MATHEWS et al. (1993) a man-induced recruitment collapse occurred. Recovery started in EFFECTS OF THE OIL ON MARINE TURTLES AND SEABIRDS

5 5 The Gulf offshore islands are important nesting sites of green and hawksbill turtles. Since 1991 the biology of these two species has been studied by the NCWCD on a regular basis. The oil spill contaminated the nesting sites, but by the time the females came ashore, the oil had been removed from the beaches. Marine turtles continue to nest in apparently normal numbers (AL-MERGHANI ET AL. 1996). Wintering seabirds were the first obvious victims of the Gulf War oil spill. SYMENS & SUHAIBANI (1994) reported more than 10,000 dead birds from 82 sited between Jubail and Khafji. An estimated 30,000 birds died as a direct result of oil-fouling. Of some species more than 50 % of the wintering populations north of Abu Ali may have been killed. The intertidal zone of the Gulf is one of the most important stop-over and feeding areas for migrant waders on the West Asian Flyway. Following the oil pollution in the intertidal zone, numbers of waders decreased to only about 2 % of the estimated pre-war levels. Before autumn 1992, no concentrations of waders were observed on the oil-impacted coastline. By the winter 1992/93, however, about 70 % of the waders were back to the area (SYMENS & SUHAIBANI 1994). The offshore islands are important breeding sites for several species of terns. When the oil spill occurred, they had not yet returned to their breeding grounds. By the time they arrived, there was no more oil floating on the water surface. Hence they escaped contamination during the spill and their breeding success was normal in However, in three species, which breed on these islands in internationally important numbers, it decreased dramatically in 1992 and again in In a fourth species, the white-cheeked tern, it failed completely, because swift terns preyed upon their chicks. This situation was a result of a reduced food availability following the decline in fish stocks. By 1994 the breeding success was back to normal, but chronic oil pollution continues to pose a threat to the bird populations (SYMENS & SUHAIBANI 1994). DISCUSSION AND CONCLUSIONS The 1991 environmental crisis severely disrupted the delicate ecological balance of the Arabian Gulf ecosystem. In most areas recovery started between one and three years after the oil spill, and five years after the disaster visual evidence of the ecological effects had largely disappeared. In exceptional cases, however, it will take decades until the environment has been fully restored to its pre-war condition. In general, recovery occurred within the expected time frame, despite the magnitude of the spill. Various experimental clean-up operations were conducted by MEPA in conjunction with the International Maritime Organization of the United Nations (IMO). The ecological effects are discussed in WATT (1996) and JONES ET AL. (1996). While after other major oil spills immediate large-scale clean-up operations often did more damage than good, clean-up techniques tested along the Saudi Arabian Gulf coast were carefully evaluated with regard to their ecological effects. Oil removal immediately after the spill was very successful, but clean-up operations more than a year after the crisis caused further mortalities among biota recolonising the area and are therefore not recommendable. The approach of supporting natural recovery and restricting artificial clean-up to the absolutely necessary minimum proved successful. A marine protected area of 2300 km², the Jubail Marine Wildlife Sanctuary, was successfully established in an area which had been most severely effected by the largest oil spill in history and an integrated network of marine protected areas, aimed at safeguarding the biological diversity of the entire Gulf ecosystem, has been proposed. These initiatives are

6 6 accompanied by extensive educational and public relations programmes. One of the effects of the 1991 ecological disaster is an increase in environmental awareness in the region. ACKNOWLEDGEMENTS The studies reported here were carried out under EC budget heading B with financial support from the European Commission and the NCWCD. The continuous support of the project by H.E. Prof. Dr. A.H. Abuzinada, Secretary General, and the staff of the NCWCD is gratefully acknowledged. REFERENCES ABUZINADA, A.H. & KRUPP, F The Arabian Gulf environment and the consequences of the 1991 oil spill. Courier Forschungsinstitut Senckenberg 166: AL-MERGHANI, M., MILLER, J.D., AL-MANSI, A. KHUSHAIM, O. & PILCHER, N.J The marine turtles of the Arabian Gulf. NCWCD studies In: A Marine Wildlife Sanctuary for the Arabian Gulf. Environmental Research and Conservation Following the 1991 Gulf War Oil Spill. F. Krupp, A.H. Abuzinada & I.A. Nader (eds). Riyadh & Frankfurt: AL-THUKAIR, A.A. & AL-HINAI, KH Preliminary damage assessment of algal mats sites located in the western Gulf following the 1991 oil spill. Marine Pollution Bulletin 27: BASSON, P.W., BURCHARD, J.E., HARDY, J.T. & PRICE, A.R.G Biotopes of the Western Arabian Gulf. 284 pp. ARAMCO, Dhahran. BÖER, B Status and recovery of the intertidal vegetation after the 1991 Gulf War oil spill. Courier Forschungsinstitut Senckenberg 166: BÖER, B Trial planting of mangroves (Avicennia marina) and salt-marsh plants (Salicornia europaea) in oilcontaminated soil in the Jubail area, Saudi Arabia. In: A Marine Wildlife Sanctuary for the Arabian Gulf. Environmental Research and Conservation Following the 1991 Gulf War Oil Spill. F. Krupp, A.H. Abuzinada & I.A. Nader (eds). Riyadh & Frankfurt: CARPENTER, K.E Preliminary observations on the effects of the 1991 Gulf War on fisheries. Marine Pollution Bulletin 24: HOFFMANN, L Recolonization of intertidal flats by microbial mats after the Gulf War oil spill. In: A Marine Wildlife Sanctuary for the Arabian Gulf. Environmental Research and Conservation Following the 1991 Gulf War Oil Spill. F. Krupp, A.H. Abuzinada & I.A. Nader (eds). Riyadh & Frankfurt: HÖPNER, T., YOUSEF, M., BERTHE-CORTI, L., FELZMANN, H., STRUCK, H. & AL-THUKAIR, A Cyanobacterial mats on oil-polluted sediments - start of a promising self-remediation process? In: A Marine Wildlife Sanctuary for the Arabian Gulf. Environmental Research and Conservation Following the 1991 Gulf War Oil Spill. F. Krupp, A.H. Abuzinada & I.A. Nader (eds). Riyadh & Frankfurt: HUNTER, J.R The physical oceanography of the Arabian Gulf: a review and theoretical interpretation of previous observations. In: Marine Environment and Pollution. Proceedings of the Arabian Gulf Conference on Environment and Pollution. Halwagy, R., Clayton, D. & Bahbehani, M. (eds). Kuwait: JONES, D.A., WATT, I., PLAZA, J., WOODHOUSE, T.D. & AL-SANEI, M Natural recovery of the intertidal biota within the Jubail Marine Wildlife Sanctuary after the 1991 Gulf War oil spill. In: A Marine Wildlife Sanctuary for the Arabian Gulf. Environmental Research and Conservation Following the 1991 Gulf War Oil Spill. F. Krupp, A.H. Abuzinada & I.A. Nader (eds). Riyadh & Frankfurt: JONES, D.A., WATT, I., WOODHOUSE, T.D. & RICHMOND, M.D Intertidal recovery in the Dawhat ad-dafi and Dawhat al-musallamiya region (Saudi Arabia) after the Gulf War oil spill. Courier Forschungsinstitut Senckenberg 166: KASSLER, P The structural and geomorphic evolution of the Persian Gulf. In: The Persian Gulf. Purser, B.H. (ed.). Berlin, Springer:

7 7 KRUPP, F. & ALMARRI, M Fishes and fish assemblages of the Jubail Marine Wildlife Sanctuary. In: A Marine Wildlife Sanctuary for the Arabian Gulf. Environmental Research and Conservation Following the 1991 Gulf War Oil Spill. F. Krupp, A.H. Abuzinada & I.A. Nader (eds). Riyadh & Frankfurt: KRUPP, F. & ANEGAY, K Habitats and species composition in subtidal areas north of Abu Ali, Saudi Arabia. Final Report of the Scientific Workshop on Results of the R/V Mt. Mitchell Cruise in the ROPME Sea Area, Kuwait 1993, 2: KRUPP, F. & JONES, D.A The creation of a marine sanctuary after the Gulf War oil spill. Marine Pollution Bulletin 27: KRUPP, F. & MÜLLER, T The status of fish populations in the northern Arabian Gulf two years after the 1991 Gulf War oil spill. Courier Forschungsinstitut Senckenberg 166: MATHEWS, C.P., KEDIDI, S., FITA, N.I., AL-YAHYA, A. & AL-RASHEED, K Preliminary assessment of the effects of the 1991 Gulf War on Saudi Arabian prawn stocks. Marine Pollution Bulletin 27: MCCAIN, J.C. & HASSAN, M Assessment of ichthyoplankton in Saudi Arabian Gulf waters before and after the 1991 Gulf oil spill. The Arabian Journal of Science and Engeneering 18 (2): MICHEL, J., HAYES, MO., KEENAN, R.S., SAUER, T.C., JENSEN, J.R. & NARUMALANI, S Contamination of nearshore subtidal sediments of Saudi Arabia from the Gulf War oil spill. Marine Pollution Bulletin 27: RICHMOND, M Status of subtidal biotopes in the Jubail Marine Wildlife Sanctuary, with special reference to softsubstrata communities. In: A Marine Wildlife Sanctuary for the Arabian Gulf. Environmental Research and Conservation Following the 1991 Gulf War Oil Spill. F. Krupp, A.H. Abuzinada & I.A. Nader (eds). Riyadh & Frankfurt: SCHNEIDER, W. & KINZELBACH, R Effects of the 1991 oil spill on the supratidal fringe. Courier Forschungsinstitut Senckenberg 166: SHEPPARD, C., PRICE, A. & ROBERTS, C Marine Ecology of the Arabian Region: Patterns and Processes in Extreme Tropical Environments. Academic Press, London, 359 pp. SORKHOH, N.A., AL-HASSAN, R.H., RADWAN, S.S. & HÖPNER, T Self-cleaning of the Gulf. Nature 359: 109. SYMENS, P. & SUHAIBANI, A The Impact of the 1991 Gulf War oil spill on bird populations in the northern Arabian Gulf - a review. Courier Forschungsinstitut Senckenberg 166: TAWFIQ, N.I. & OLSEN, D.A Saudi Arabia's response to the 1991 Gulf Oil spill. Marine Pollution Bulletin 27: VOGT, H Investigations on coral reefs in the Jubail Marine Wildlife Sanctuary using underwater video recordings and digital image analysis. In: A Marine Wildlife Sanctuary for the Arabian Gulf. Environmental Research and Conservation Following the 1991 Gulf War Oil Spill. F. Krupp, A.H. Abuzinada & I.A. Nader (eds). Riyadh & Frankfurt: WATT, I A summary of the clean-up techniques used in the Jubail Marine Wildlife Sanctuary after the Gulf War oil spill and an assessment of their benefit to intertidal recovery. In: A Marine Wildlife Sanctuary for the Arabian Gulf. Environmental Research and Conservation Following the 1991 Gulf War Oil Spill. F. Krupp, A.H. Abuzinada & I.A. Nader (eds). Riyadh & Frankfurt: