Abstract
The Persian Gulf represents an extremely important economic, political, and strategic aquatic resource. Although the Gulf region is known worldwide for its oil and gas deposits and production, very little is known about its ecosystem health, food web dynamics, fisheries, biodiversity, and sustainability. The present study reviews and highlights the major anthropogenic stressors that threaten the marine and coastal ecosystems of the Gulf. The Persian Gulf environment lacks the holistic, ecosystem-based research and monitoring that have been conducted in other marine ecosystems. There is a need for multi-disciplinary, multi-trophic, and multi-agency international investigations, including the application of emerging technology. Such an integrated strategy is urgently needed to save the rapidly changing marine ecosystems from the impact of rapid and vigorous coastal development across the entire Gulf region. The necessity of developing and implementing ecosystem health agreements between the various riparian countries is emphasized for expeditious protection, conservation, and management of this precious but threatened natural heritage.
Keywords: Persian Gulf, human impact, coastal management, ecosystem protection
An overview of the Persian Gulf environmental features
The Persian Gulf was given another designation in 1978 as the ROPME Sea. ROPME refers to the Regional Organization for Protection of the Marine Environment agreement signed by Bahrain, I.R. Iran, Iraq, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates. This organization was established as an outcome of the conference held in Kuwait on 15–23 April 1978, which adopted the Kuwait Action plan for the protection and development of the marine environment and the coastal areas. According to Article II of the Kuwait Regional Convention, the ROPME Sea Area is defined as extending between the following geographic latitudes and longitudes, respectively: 16° 39′ N, 53° 30′ 30″ E; 16° 00′ N 53° 25′ E, 17° 00N, 56° 30′ E; 20° 30′ N, 60° 00′ E; 25° 04′ N, 61° 25′ E (ROPME, 2000). While we acknowledge the various names for the Gulf, in this study we will refer to it as the Persian Gulf since this name has been adopted by 7 of the 8 members of the Kuwait convention.
The Persian Gulf has been the most important area in the Middle East during the last two decades. This importance is not only because of wars and political conflicts which have devastated many of the countries surrounding the Gulf, but also because of its huge reserves of oil and gas. Reserves of 76 billion metric tons of recoverable oil and 32.4 trillion cubic meters of natural gas are distributed between the 8 gulf countries (United Arab Emirates, Qatar, Bahrain, Saudi Arabia, Kuwait, Iraq, Iran, and Oman).
The Persian Gulf is located between latitudes 24° and 30°N and longitudes 48° and 57°E (Figure 1). It is a semi-enclosed sea, stretching 1,000 km from the Shatt Al-Arab waterway in southern Iraq to the Strait of Hormuz, and varies in width from 75 to 350 km. It is bordered by the Arab Peninsula in the south (United Arab Emirates, Qatar, Saudi Arabia, and Kuwait), by Iraq in the north, and by Iran on the east. The Gulf extends over an area of about 239,000 km2 with an average depth of about 36 m. The maximum depth is about 100 m along its axis, and the average volume is about 8630 km3 (Reynolds, 1993). The Persian Gulf bathymetry is characterized by an increasing inclination from south to north. A shallower shelf extends in front of the United Arab Emirates coast, where the average depth is about 20 m. The depth increases toward the Iranian coast where the maximum depth is about 80 m. The shallowest zone of the Gulf (<20 m) is in the Shatt Al-Arab delta in the northwest, it deepens towards the south in a gradual trend (Figure 1). According to the European Geosciences Union report, 14,000 years ago the Persian Gulf was free from marine influence out to the edge of the Biaban shelf, but the potential existed for extensive shallow lakes and swamps on the Gulf floor along the ancient bed of the Euphrates-Tigris river system through late glacial time. By about 12,000 years ago, the marine water incursion into the central basin had started, and the western basin flooded about 1000 years later.
From a hydrological point of view, it is a unique stream for water exchange between the Persian Gulf and the Gulf of Oman. This process keeps the salinity level of the gulf almost constant over the years. Several scientists, including Hughes and Hunter (1979), studied this phenomenon. Hunter (1983) estimated the residence time of the Persian Gulf basin to be 2 to 5 years while Johns and Olson (1998) proved by their measurements that the residence time ranges only between 350 to 500 days.
Most of the river discharges into the Persian Gulf are concentrated in the north, primarily from Iraq and Iran. Shatt Al-Arab is considered a confluence of three major rivers: the Tigris, Euphrates, and Karun. The annual average flow of the Tigris and Euphrates is 708 m3s−1, and the Karun outflow is 748 m3 s−1. Ninety percent of the Tigris and Euphrates rivers’ flow is lost in evaporation and agricultural activities. Hence, the main discharge into the Gulf comes from the Karun River. Some recent investigations estimated the outfall into the Shatt Al-Arab at approximately 1000 m3y−1. Other major rivers, which discharge into the Persian Gulf, are the Hendijan (203 m3 s−1), the Hilleh (444 m3 s−1), and the Mand (1387 m3 s−1). The sum of these averages amounts to an annual runoff of 110 km3y−1 (Reynolds, 2002). Although the freshwater discharges add 10–46 cm to the water level of the Gulf, it was calculated that the freshwater deficit in the Persian Gulf is about 10 times the annual river discharge, due to evaporation, which is estimated to be 140–500 cm per year.
The Gulf region and the Arabian Peninsula are known to be one of the hottest areas in the world. The main reason for the dryness of the area is the coastal mountains that separate the Arab Peninsula from the sea. The eastern zones of the Gulf are an exception to these conditions, where they are affected by the Indian Ocean monsoon causing some sparse rainfalls (ROPME, 1999). The air temperature in the Gulf area varies between 0°C during winter and 50°C during summer months, while the water temperature is varied between 10°C in winter and 39°C during summer (Reynolds, 1993). Such dryness causes high evaporation, which influences the water salinity of the Gulf, which ranges between 40–50 ppt, with extreme values between 70–200 ppt at semi-enclosed coastal basins (e.g., Gulf of Salwa-Qatar).
Before the oil discovery in the region “sometime after the Second World War,” the Persian Gulf was an important trading basin between the Middle East and the Far East countries. It was also the source of food for many of the gulf populations, who were mainly fishermen and pearl divers. Since the oil discovery in the early 1950s, the economic situation of the surrounding populations has improved significantly. However, such development has negatively influenced the Persian Gulf ecosystems where, in the absence of legislation and environmental laws, all types of wastes from human activities were dumped in the Persian Gulf (Khan and Price, 2002). This is in addition to intensive shipping and oil industrialization, which resulted in many oil spills either from ship accidents or from the destruction of oil wells, especially during the Gulf War of 1991 (Khan et al., 2002). After the Gulf War, many local and international scientific and environmental bodies were interested in evaluating.
Major stressors of the Persian Gulf Ecosystems
Although there are harsh natural stressors of high temperature and high water salinity which have to be tolerated by living organisms in the Gulf, various man-made stressors have been added during the last few decades, which have influenced the marine coastal life and consequently the whole ecosystem of the Gulf. Such anthropogenic stressors resulted mainly from economic activities within the Persian Gulf countries after the oil discoveries in their territories during the 20th century. This article identifies the major stressors including: oil reserves and oil industry; population density increases; desalination plants; accidental and intentional oil spills; oil transportation and exotic species invasions; sea constructions and coastline alteration; modifications of coastal hydrodynamics; water quality deterioration and declining fisheries. Each of these will be discussed in the following sections.
Oil reserves and oil industry
Oil reserves and oil industry are one of the major stressors on the Persian Gulf ecosystem. In fact, without the discovery of oil, many of the negative human impacts on its ecosystem would not exist. According to actual estimates, Gulf countries own more than 50% of the world’s oil and natural gas reserves, especially after the recent discovery of a huge gas reserve in Qatar, which is estimated by the U.S. Energy Information Administration to be >911 trillion Cubic feet (Oil and Gas Journal, 2005). Such an energy source has stimulated many countries, especially the most industrialized ones, to build economic relationships with the Gulf countries. On the other hand, the competition between industrialized countries to guarantee the maximum control of future energy has resulted in political conflicts in the area, which lead to military wars between oil producing countries themselves as well as between producing and industrialized countries. Oil production, and its related industries, is considered the basis of various human impacts on the Gulf ecosystems, from increasing population densities in the gulf countries through enlargement of infrastructure to satisfy the population increase, leading to oil spills either through accidental or intentional events (e.g. Gulf War in 1991).
Population growth
Although there have been no recent census of the different Gulf countries, partly due to current economic instabilities of certain countries, the estimated figures given by ROPME (1998) (Figure 2) may be considered representative of the relative densities and coastal distributions. That being said, in 2007 the census of the United Arab Emirates (UAE) indicated 4.5 million inhabitants, up from 2.7 million given by ROPME in 1998. This means that during the 9-year interval, the UAE population increased by >65%, with an annual rate of >7%. This is not a natural increase in the local population but is a result of the economic boom, which required the import of expatriate workers to satisfy infrastructure development. The rate of increase in population in the UAE can be applied to the other Gulf countries, especially when they are applying similar policies through their Gulf Cooperative Council (GCC) agreement. The first demand of a fast-growing population is the availability of freshwater for human use. But since the Gulf countries are suffering from a shortage of natural freshwater, desalination plants are becoming the fast and easy solution to overcome the freshwater shortage. Desalination plants, with their negative effects on the Gulf ecosystem, can be considered the next man-made stressor.
Desalination plants
The high living standards in the Persian Gulf countries coupled with their demographic growth have led to the evolution of desalination technology. Desalinated water has the highest contribution to the water budget of the area where desalination plants are supplying water for domestic use in addition to industrial and agricultural purposes. In certain countries such as the UAE, desalination plants supply 98% of the freshwater demand of the country. In spite of natural freshwater scarcity in the UAE, Abu Dhabi Emirate has one of the highest per capita water consumptions in the world due to the high standard of living and lifestyle (Sommariva and Syambabu, 2001). According to Abu Dhabi Water and Electricity Authority reports (ADWEA, 2006 www.adwea.ae), the consumption per capita exceeds 500 l d−1. There are many desalination plants along the coastal area of the Persian Gulf countries. All of these plants are discharging their effluents, after limited treatment processes, into the marine water. These effluents contain some chemicals, heated water, and high concentrations of brine. Continuous dumping of such effluents may threaten coastal ecosystems and may have implications on marine water quality in general and eventually on marine life.
Accidental and Intentional oil spills
By definition, oil spills or oil slicks are the unintentional release of liquid petroleum hydrocarbons into the environment because of human activity. The terms often refer to marine oil spills, where oil is released into the ocean or coastal waters. Oil can refer to many different materials, including crude oil, refined petroleum products (such as gasoline or diesel fuel) or by-products, ships’ bunkers, oily refuse or oil mixed in wastes (Einarsson, 2009). The increase of oil tanker activity for oil transportation is responsible for the oil and waste releases into the Gulf environment. The normal release from ships and refineries is minimal compared with oil spills resulting from oil well explosions or oil tanker accidents. Prior to the Gulf War, five oil spills occurred in the Gulf water each being larger than the 1989 Exxon Valdez spill.
The Gulf War oil spill was the largest in history, where a huge amount of oil (2.5–4.0 million barrels) was dumped into the Persian Gulf intentionally. The oil covered about 600 square miles of the sea surface and blackened about 300 miles of the coastline between Kuwait and Saudi Arabia. It was a severe environmental disaster. In fact, in addition to the apparent environmental damage which affected Kuwait and Saudi desalination plants, fouled coastline, inundated salt marshes and mangrove coastal forests, and killed wildlife, it has been estimated that the black oily rain from burned oil had doubled the amount of oil spilled directly into the Gulf (Ackleson et al., 1992).
Although international and local authorities have made efforts in cleaning the Gulf environment from the Gulf War oil spill, it is well known that removing oil from the sea surface does not mean that a complete recovery has been reached. The main problem remains in the bottom sediments where heavy oil covers bottom life and may destroy many habitats by killing sessile living fauna and flora, consequently disturbing the whole ecosystem. Natural environmental purification where biodegradation by the existing microorganisms acclimatized to oil pollution may need many years. According to a specialized study of oil biodegradation in the Persian Gulf, the Gulf is considered as a unique marine environment in its capacity for self-purification from oil spills. This self-purification process is based on the existence of well-adapted microorganisms capable of degrading oil, and the high rate of photo-oxidation due to the long duration of daylight.
Oil transportation and exotic species invasion
The discharge of ballast water from oil tankers into coastal areas has universal impact but is much accentuated in the Persian Gulf marine ecosystems. The discharging of ballast water releases organisms and sediments that have been carried by returning tankers from ports around the world. It has been recognized that one of the most devastating impacts of human activity on marine environments, particularly coastal, is the introduction of foreign species which may severely alter the biodiversity (Viard, 2003). According to Linden et al. (1990), about 20,000 to 35,000 tankers discharge ballast water while passing through the gulf area annually. These discharges can reach a volume of 5 to 9 million metric tons per year. Hamza (2006) collected water samples from the ballast water tanks of a gas tanker stopped along the UAE coastal area and compared the plankton therein with the plankton samples collected from the Gulf water outside the ship. Twelve phytoplankton species and 6 zooplankton species were identified within the ballast water. Of these, only two phytoplankton species (Navicula minutum and Ceratium furca), were also found living in the seawater at the tanker stop (Table 2), in addition to fish eggs and naulpii. This suggests that in each trip, several exotic species may be transported as living organisms to the Gulf ecosystem. These findings may explain to a certain extent the different environmental phenomena appearing in the coastal area of the UAE during the last few years such as red tide and fish kill. Both red tide and fish kill are new to the Gulf area and recently recorded in Kuwait, Oman, Saudi Arabia, and UAE (ROPME, 2000). In fact, many investigations in these countries have shown that irregular blooming of certain dinoflagellate organisms in their coastal areas prior to the fish kill phenomenon.
Sea constructions and coast line alteration
The Persian Gulf and the coasts surrounding various Gulf countries are undergoing massive construction activities. With intensive dredging and reclamation of coastal areas, marine habitats and coastal ecosystems are facing serious environmental challenges. This is the second most critical stressor affecting the marine ecosystem of the Persian Gulf. It has been estimated that oil reserves in the Gulf area will expire within the next 30–50 years, which has prompted oil-producing Arab countries to search for alternate sources of future income. This has stimulated the governments of these countries to use oil income for future investments, to transform the area into the biggest trading and commercial center of the Middle East. To that end, the Gulf countries have developed more than 40% of the coastline during the last 20 years. For instance, 10 km of the Omani coastline has been altered with quarry and sand beach materials. In Bahrain, the total area dredged is about 1350 ha and the area reclaimed is about 900 ha, which resulted in adding 39 km2 of new land mass in less than 20 years. Nearly 60 million m−3 of sediments were dredged during the construction of the Saudi Bahrain causeway. In Kuwait, considerable parts of the intertidal area in front of Kuwait city and areas in the southern coast have been reclaimed. As a consequence, significant erosion problems have developed along most of the fill edges of the reclaimed areas (Kana, 2002; Salahuddin, 2006). In Saudi Arabia, approximately 40% of the coastal Gulf area has been developed. Residential and commercial developments have been made along the coast, particularly in Jubail, Tarut Bay, Dammam, and Khobar. These areas of shallow sub-tidal coast are highly productive and form nursery and feeding grounds for most commercial fish and shrimp species
Modifications of coastal hydrodynamics
The construction of such huge artificial islands within coastal areas will certainly alter water circulation along the coasts. Such deviations could formulate new hydrodynamic patterns that can initiate phenomena such as strong eddies, slowing water circulation and/or stagnation. That is in addition to erosion and accretion processes, which may represent the main problem facing such sea construction activities. Such processes have started to reveal their negative impacts on coastal habitats. Despite the absence of accurate records, accretion of sediments in certain coastal areas along the UAE has resulted in the death of thousands of mangrove trees. In spite of the efforts of the UAE government to conserve and maintain the unique mangrove population of Avicenna marina trees, which covers about 30 km2 (Dodd et al., 1999), the population has perished. It is strongly suspected that this is due to the side effect of coastal hydrodynamic modifications.
Water quality deterioration
The increase in population density along the Persian Gulf coastal areas as a consequence of artificial island occupation will increase the discharge of many industrial and domestic effluents into the Gulf water. Although the source of the water was desalinated Gulf water, its use for both industrial and domestic purposes will add many pollutants. Such components will be at least partially discharged, even through the common sewage treatment processes, to the Gulf environment. The increase of nutrient salts will enhance algal growth and could be responsible for eutrophication and the fish kills which recently appeared along the coasts of several gulf countries (ROPME, 2000; Hamza, 2006). The massive dredging of the bottom sediments of coastal areas has also created significant turbidity in the water column. This reduces the water transparency and damages sea-grass beds by preventing or reducing their photosynthetic activities (Al-Jamali et al., 2005). Furthermore, such turbidity is responsible for the coral bleaching phenomenon observed in the Persian Gulf.
Declining fisheries
In addition to the negative effects of oil spills on the marine life in the Persian Gulf, the coastal constructions have damaged and removed a significant percentage of nursery and feeding grounds for commercial fish and shrimp species (Al-Jamali, 2006). The Gulf countries have always maintained a self-sufficient fisheries industry. Recently many fishery authorities of Gulf countries have indicated a loss of fisheries potential due to human activities along coastal areas. Such activities have negatively influenced biodiversity, habitats, and fish stocks. One of the major problems facing these authorities is the lack of a complete fish stock assessment covering the whole Gulf ecosystem. Although many countries have made efforts, such assessments need the full support and cooperation of all countries surrounding the Persian Gulf. On the other hand, many efforts have been made to restore the Gulf fisheries, including the development of aquaculture of commercial species, with the aim to substitute the loss of nursery and spawning grounds of native species.
Managing and protecting the Gulf
Topics covered in the monograph “The Persian Gulf Ecosystem: Health and Sustainability” Khan, Munawar & Price, 2002.
A previous review of the ecosystemic health of the Persian Gulf called for the establishment of an integrated, multi-trophic, and multi-disciplinary research program that would include structural and functional assessments of the Gulf environment as well as ecosystem modeling (Munawar et al., 2002). Such a program is mandatory to ensure the holistic management and sustainable development of the Gulf. The overriding goal should be to strike a balance between necessary exploitation and preservation of the natural features of the coastal zone (Kana, 2002). Within the Gulf countries, a lack of cooperation and information exchange means that holistic ecosystem protection and management are still beyond the priorities of the economic agenda of many governments.
There have been some recent scientific initiatives in the Persian Gulf, which have resulted in the compilation and sharing of important research findings. The Kuwait Institute for Scientific Research and the Aquatic Ecosystem Health and Management Society (AEHMS) brought together some of the leading scholars working on the Gulf and produced a monograph, The Persian Gulf Ecosystem: Health and Sustainability, as part of the Ecovision World Monograph Series (Khan et al., 2002). The monograph also provided a general conceptual plan for the management stressors affecting the Persian Gulf (Figure 3). In 2006, the United Arab Emirates University at Al-Ain and the AEHMS jointly organized the First International Conference on The State of the Persian Gulf Ecosystems: Future and Threats, inviting scientists in Gulf countries and from abroad to present their research with the aim of maintaining continuous and updated records of any ecosystem changes and/or impacts. Many of the papers originating from this conference were published in a special issue of Aquatic Ecosystem Health and Management (AEHMS, 2007). Following the 2006 conference, a Middle East chapter of the AEHMS was established to organize a future series of conferences on the Persian Gulf at regular intervals.
Although ROPME (Regional Organization for the Protection of the Marine Environment) has made recent efforts to organize different cruises with the aim of sampling and analyzing, the stressors listed below still have major ecological effects on the Persian Gulf:
- Salinity (as an ecological factor): Restricts the Gulf’s biota, mainly due to osmotic/physiological stresses, resulting in stunting of some species and enhanced growth of others (e.g., Tilapia fish). Species richness decreases with increasing salinity, although abundances may be high.
- Temperature extremes: Low water temperatures (13-14°C) and duration of low values limit species richness and cause mortality to reef corals. Temperature extremes also stress intertidal and shallow subtidal fauna: about 13 coral species survive temperature fluctuations of 29-28°C.
- Habitat loss, sedimentation, and turbidity: Habitat loss is possibly the most serious stressor in the Persian Gulf; effects are ultimately linked to the degree of dependence of species on particular habitats; coral biota is very distinctive, and many species are not adapted to other ecosystems. Sedimentation and turbidity are caused by natural factors and human activities.
- Pollution: High “contaminant” concentrations of petroleum hydrocarbons and heavy metals are recorded in sediments, seawater, and biota at several locations in the Persian Gulf. Eutrophication is a problem in localized areas. Understanding of effects (“pollution”) increased as a result of the 1991 Gulf War; e.g., sediments at 5 of 11 sites studied in 1993 exhibited high toxicity and contained high petroleum levels.
Conclusions
An ecosystem-based multi-disciplinary, multi-trophic, and multi-national strategy is badly needed for establishing a consistent database of ecological parameters for the Persian Gulf. The application of standardized techniques for sampling and processing by riparian countries should be a top priority. Consequently, multi-national training programs will be required for scientists and managers so that data quality is sustained. Needless to say, international agreements for the management and sustainable development of the Gulf are essential to provide guiding principles for its protection and conservation. Emerging stressors such as climate change, expansion of exotics, sediment quality, and algal blooms will need the immediate attention of the Persian Gulf research community.