**1. Introduction**

The Arabian Gulf is a marginal and semi-enclosed sea situated in the subtropical region of the Middle East between latitudes 24o and 30o N and longitudes 48o and 57o E (Figure 1). The Arabian Gulf constitutes part of the Arabian Sea Ecoregion, and represents a realm of the tropical Indo-Pacific Ocean (Spalding et al., 2007). It is a shallow sedimentary basin with an average depth of 35 m and a total area of approximately 240,000 km2 (Barth and Khan, 2008).

Due to the high-latitude geographical position, the relative shallowness and the high evapo‐ ration rates, the Arabian Gulf is characterized by extreme environmental conditions. Sea temperatures are markedly fluctuated between winter and summer seasons (15 - 36°C). Salinity can exceed 43 psu and may reach 70-80 psu in tidal pools and lagoons. Therefore, marine organisms in the Arabian Gulf are living close to the limits of their environmental tolerance (Price et al., 1993).

Despite these harsh environmental conditions, the Arabian Gulf supports a range of coastal and marine ecosystems such as mangrove swamps, seagrass beds, coral reefs, and mud and sand flats (Naser, 2011a). These ecosystems contribute to the maintenance of genetic and biological diversity in the marine environment and provide valuable ecological and economic functions as they form feeding and nursery grounds for a variety of commercially important marine organisms.

However, these ecosystems are under ever-increasing pressure from anthropogenic activities that are associated with the rapid economic, social and industrial developments in the Arabian Gulf countries. The Arabian Gulf is considered among the highest anthropogenically impacted regions in the world (Halpern et al., 2008). The coasts of the Arabian Gulf are witnessing rapid industrialization and urbanization that contribute to the degradation of naturally stressed marine ecosystems. Coastal and marine environments are affected by intensive dredging and

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reclamation activities, and several sources of pollution, including industrial waste, brine waste waters, ports and refiners, oil spills, and domestic sewage (Sheppard et al., 2010). These threats warrant the designation of the Arabian Sea Ecoregion, including the Arabian Gulf as 'critically endangered' by the International Union for the Conservation of Nature (IUCN) and the World Wildlife Fund (WWF) (http://wwf.panda.org).

ecosystems are considered Valued Ecosystem Components (VECs) because they provide important ecological goods and services (Treweek 1999). Most of these habitats are rich in varieties of fish, which are a major source of food for people in the Arabian Gulf. Ecosystem benefits in the Arabian Gulf are not limited to the direct consumptive value of seafood, but extend to other services ranging from primary production and nutrient cycling to erosion and

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Seagrass beds are highly productive ecosystems that provide important ecological functions and economic services (Sheppard et al., 1992). Ecologically, seagrass ecosystems provide food sources and feeding grounds for several threatened species in the Arabian Gulf such as turtles and dugongs (Abdulqader and Miller, 2012; Preen et al., 2012). They can also improve water quality by stabilizing loose sediment and by filtering some pollutants out of the water (Duffy, 2006). Economically, they serve as important nursery grounds for penaeid shrimps, pearl oysters and other organisms of importance to the Arabian Gulf's commercial fisheries

Three species of seagrass occur in the Arabian Gulf; namely, *Halodule uninervis*, *Halophila stipulacea* and *Halophila ovalis* (Phillips, 2003). These species are generally tolerant to salinity and temperature extremes of the Arabian Gulf. For instance, seagrasses are thriving in the extreme thermosaline conditions of Salwa Bay, south of Bahrain, where sea temperature

Seagrass beds are distributed along most of the shores of the Arabian Gulf. According to Erftemeijer and Shuail (2012), around 7000 km2 of seagrass habitat have been mapped in the Arabian Gulf to date. Extensive growth of seagrass is typically associated with sandy and muddy substrates in nearshores and shallow waters (less than 10 m). The largest areas of seagrass beds occur off the coasts of United Arab Emirates and between Bahrain and Qatar

seagrass habitats are of critical importance as they support the largest population of dugongs

Coral reefs ecosystems provide a variety of ecological services such as renewable sources of seafood, maintenance of genetic, biological and habitat diversity, recreational values, and economic benefits such as utilizing reefs for creating land. Numerous nearshore reefs have been reclaimed along the coastline of the Arabian Gulf. Coral reefs are featured by both biological diversity and high levels of productivity. The high diversity of coral reefs provides a wide range of habitats for other reef species and fish. Coral reefs in the Arabian Gulf have

Coral growth occurs in most of the Arabian Gulf with best development on offshore shoals. Additionally, fringing corals occur along the coastlines of United Arab Emirates, Qatar, Saudi Arabia and Bahrain (Riegl and Purkis, 2012). Extremes in temperature, salinity and other

, respectively (Erftemeijer and Shuail, 2012). These

C and salinity may reach 70 psu in summer.

sedimentation control.

(Erftemeijer and Shuail, 2012).

with estimated areas of 5500 and 1000 km2

traditionally been important habitats for fisheries.

known outside Australia (Preen, 2004).

**2.1. Seagrass beds**

exceeds 31 o

**2.2. Coral reefs**

Due to its unique environmental setting, the Arabian Gulf is increasingly receiving interna‐ tional scientific interest to study the effects of environmental extremes on marine organisms, and to investigate the potential impacts of future climate change on the ecological integrity of marine ecosystems (Riegl and Purkis, 2012; Feary et al., 2013). This chapter identifies valued ecosystem components in the Arabian Gulf, characterizes natural and anthropogenic impacts on these ecosystems, and suggests measures for conservation that might contribute to the protection of the fragile marine ecosystems in the Arabian Gulf.

**Figure 1.** Map of the Arabian Gulf.

#### **2. Valued ecosystem components**

People of the Arabian Gulf are related economically, culturally and socially to the sea. Several ecosystems, including seagrass beds, coral reefs, mangroves, and mudflats contribute signifi‐ cantly to the productivity of marine resources in the Arabian Gulf (Khan et al., 2002). These ecosystems are considered Valued Ecosystem Components (VECs) because they provide important ecological goods and services (Treweek 1999). Most of these habitats are rich in varieties of fish, which are a major source of food for people in the Arabian Gulf. Ecosystem benefits in the Arabian Gulf are not limited to the direct consumptive value of seafood, but extend to other services ranging from primary production and nutrient cycling to erosion and sedimentation control.

#### **2.1. Seagrass beds**

reclamation activities, and several sources of pollution, including industrial waste, brine waste waters, ports and refiners, oil spills, and domestic sewage (Sheppard et al., 2010). These threats warrant the designation of the Arabian Sea Ecoregion, including the Arabian Gulf as 'critically endangered' by the International Union for the Conservation of Nature (IUCN) and the World

Due to its unique environmental setting, the Arabian Gulf is increasingly receiving interna‐ tional scientific interest to study the effects of environmental extremes on marine organisms, and to investigate the potential impacts of future climate change on the ecological integrity of marine ecosystems (Riegl and Purkis, 2012; Feary et al., 2013). This chapter identifies valued ecosystem components in the Arabian Gulf, characterizes natural and anthropogenic impacts on these ecosystems, and suggests measures for conservation that might contribute to the

People of the Arabian Gulf are related economically, culturally and socially to the sea. Several ecosystems, including seagrass beds, coral reefs, mangroves, and mudflats contribute signifi‐ cantly to the productivity of marine resources in the Arabian Gulf (Khan et al., 2002). These

Wildlife Fund (WWF) (http://wwf.panda.org).

298 Biodiversity - The Dynamic Balance of the Planet

**Figure 1.** Map of the Arabian Gulf.

**2. Valued ecosystem components**

protection of the fragile marine ecosystems in the Arabian Gulf.

Seagrass beds are highly productive ecosystems that provide important ecological functions and economic services (Sheppard et al., 1992). Ecologically, seagrass ecosystems provide food sources and feeding grounds for several threatened species in the Arabian Gulf such as turtles and dugongs (Abdulqader and Miller, 2012; Preen et al., 2012). They can also improve water quality by stabilizing loose sediment and by filtering some pollutants out of the water (Duffy, 2006). Economically, they serve as important nursery grounds for penaeid shrimps, pearl oysters and other organisms of importance to the Arabian Gulf's commercial fisheries (Erftemeijer and Shuail, 2012).

Three species of seagrass occur in the Arabian Gulf; namely, *Halodule uninervis*, *Halophila stipulacea* and *Halophila ovalis* (Phillips, 2003). These species are generally tolerant to salinity and temperature extremes of the Arabian Gulf. For instance, seagrasses are thriving in the extreme thermosaline conditions of Salwa Bay, south of Bahrain, where sea temperature exceeds 31 o C and salinity may reach 70 psu in summer.

Seagrass beds are distributed along most of the shores of the Arabian Gulf. According to Erftemeijer and Shuail (2012), around 7000 km2 of seagrass habitat have been mapped in the Arabian Gulf to date. Extensive growth of seagrass is typically associated with sandy and muddy substrates in nearshores and shallow waters (less than 10 m). The largest areas of seagrass beds occur off the coasts of United Arab Emirates and between Bahrain and Qatar with estimated areas of 5500 and 1000 km2 , respectively (Erftemeijer and Shuail, 2012). These seagrass habitats are of critical importance as they support the largest population of dugongs known outside Australia (Preen, 2004).

#### **2.2. Coral reefs**

Coral reefs ecosystems provide a variety of ecological services such as renewable sources of seafood, maintenance of genetic, biological and habitat diversity, recreational values, and economic benefits such as utilizing reefs for creating land. Numerous nearshore reefs have been reclaimed along the coastline of the Arabian Gulf. Coral reefs are featured by both biological diversity and high levels of productivity. The high diversity of coral reefs provides a wide range of habitats for other reef species and fish. Coral reefs in the Arabian Gulf have traditionally been important habitats for fisheries.

Coral growth occurs in most of the Arabian Gulf with best development on offshore shoals. Additionally, fringing corals occur along the coastlines of United Arab Emirates, Qatar, Saudi Arabia and Bahrain (Riegl and Purkis, 2012). Extremes in temperature, salinity and other physical factors in the Arabian Gulf restrict the growth and development of corals to patchy forms (Sheppard et al., 2010). However, despite these harsh environmental conditions, corals in the Arabian Gulf exhibit remarkable resilience and vitality.

countries in the Arabian Gulf, particularly Bahrain. It is recognized that the IUCN Red List categories and criteria provide objective framework for the classification of studied species. However, these categories and criteria are primarily designed for global taxon assessments

Bahrain is a good example to demonstrate the effect of rough resolution assessment (i.e. globally or regionally rather than locally). Based on the Red List, mangroves in Bahrain are classified as 'Least Concern'. However, mangrove stands in Bahrain are severely subjected to human impacts that might affect the existence of this important ecosystem. The marine area of Tubli Bay, which hosts the last remaining mangroves in Bahrain, has been reduced from to

destroyed mangrove stands and reduced their spatial distribution in Bahrain. Due to the severe reduction in mangroves distribution accompanied by continuous anthropogenic threats, mangroves in Bahrain should arguably be classified within the threatened categories (i.e. Critically Endangered, Endangered or Vulnerable). Consequently, urgent conservation measures, including rehabilitation and restoration should be carried out to sustain the

Due to the sedimentary nature of the Arabian Gulf, sand and mud substrata are the most widespread habitats. They extend from intertidal salt marshes to the maximum depth and account for more than 97% of the bottom substrate of the Arabian Gulf (Al-Ghadban, 2002). Tidal mudflats are generally restricted to low energy environment associated with low water movement mainly along the coastlines of Kuwait, Saudi Arabia and United Arab Emirates. These habitats are favorable areas for the colonization by mangroves, algal and cyanobacterial mats, which play important roles in primary productions and food chains. Subtidal and tidal muddy habitats are extremely rich in macrobenthic assemblages, which form the largest and

Generally, biodiversity and distribution of macrobenthos in the Arabian Gulf are primarily governed by sediment type, temperature, salinity, primary productivity, depth and physical disturbance (Coles and MacCain, 1990). Macrobenthic assemblages through their high secondary productivity contribute significantly to the overall fisheries and marine productiv‐ ity. Additionally, mudflat habitats provide feeding and roosting grounds for important shorebird populations. Some of these important bird areas are declared as wetlands of international importance (Ramsar Convention of Wetlands). Tubli Bay in Bahrain is an example of a Ramsar site that supports large numbers of wintering and migratory shorebirds

The Arabian Gulf is facing multiple natural and anthropogenic environmental stressors. The unique physical and chemical settings represented by extremes in temperature and salinity

in 2008 due to intensive reclamation activities. These activities significantly

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301

(IUCN, 2012).

25 to 12 km2

**2.4. Mudflats**

(Al-Sayed et al., 2008).

**3. Environmental stressors**

remaining of mangrove ecosystem in Bahrain.

most diverse marine ecosystem in the Arabian Gulf.

Recently, corals in the Arabian Gulf have been exposed to severe temperature anomalies at a recurrence faster than in any other coral regions in the world. Therefore, it is argued that corals in the Arabian Gulf already exist in a thermal environment that is equal to the 2099 projections of the Intergovernmental Panel on Climate Change (IPPC) in tropical oceans (Riegl and Purkis, 2012). This embarked regional and international interest in using the Arabian Gulf as a model ecosystem to understand the potential impact for future climate change (Burt, 2013). One aspect of that interest is the establishment the Mideast Coral Reef Society (MCRS) in 2013, with the aim of generating a deep understanding of these unique ecosystems and promoting their conservation and sustainable use.

Unfortunately, coral reefs in the Arabian Gulf have been severely affected by recent bleaching events as well as human impacts such as sediment runoff from dredging and reclamation activities and pollution from different land-based sources. Large-scale decline in coral reef has been observed. It is estimated that almost 70% of original reef cover in the Arabian Gulf may be considered lost and a further 27% threatened or at critical stages of degradation (Wilkinson, 2008).

#### **2.3. Mangrove swamps**

Mangrove habitats are ecologically important coastal ecosystems that provide food, shelter and nursery areas for a variety of terrestrial and marine fauna. Mangrove habitats of the Arabian Gulf support a variety of important species of fish, shrimps, turtles, and birds, and significantly contribute to the coastal productivity (Al-Maslamani et al., 2013). The Arabian Gulf coastlines are dominated by only one species of mangroves, *Avicennia marina.* The processes of osmoregulation and salt secretion allow *Avicennia marina* to cope with hypersa‐ linity conditions in the Arabian Gulf (Dodd et al., 1999). Naser and Hoad (2011) investigated salinity tolerance and salt secretion in Bahrain and found that successful establishment of mangroves depends critically on the tolerance of these plants to salinity at the early stages of development.

Mangroves are largely distributed along the southern shores of the Arabian Gulf. Dense growth of mangroves is particularly confined to low-energy and sheltered coastal areas along the coastlines of United Arab Emirates, Saudi Arabia and Qatar. While mangroves are relatively widespread throughout the Arabian Gulf countries, there are variations in their distributions from one country to another. For instance, the total extent of mangroves in United Arab Emirates is estimated to be 38 km2 (Dodd et al., 1999) compared with only 0.31 km2 in Bahrain (Abido et al., 2011).

According to the IUCN Red List of threatened species, mangroves in the Arabian Gulf are classified as 'Least Concern'. The Red List assessment concluded that although there are overall range declines in many areas, they are not enough to reach any of the threatened category thresholds. However, it can be argued that this classification might not be applicable to certain countries in the Arabian Gulf, particularly Bahrain. It is recognized that the IUCN Red List categories and criteria provide objective framework for the classification of studied species. However, these categories and criteria are primarily designed for global taxon assessments (IUCN, 2012).

Bahrain is a good example to demonstrate the effect of rough resolution assessment (i.e. globally or regionally rather than locally). Based on the Red List, mangroves in Bahrain are classified as 'Least Concern'. However, mangrove stands in Bahrain are severely subjected to human impacts that might affect the existence of this important ecosystem. The marine area of Tubli Bay, which hosts the last remaining mangroves in Bahrain, has been reduced from to 25 to 12 km2 in 2008 due to intensive reclamation activities. These activities significantly destroyed mangrove stands and reduced their spatial distribution in Bahrain. Due to the severe reduction in mangroves distribution accompanied by continuous anthropogenic threats, mangroves in Bahrain should arguably be classified within the threatened categories (i.e. Critically Endangered, Endangered or Vulnerable). Consequently, urgent conservation measures, including rehabilitation and restoration should be carried out to sustain the remaining of mangrove ecosystem in Bahrain.

#### **2.4. Mudflats**

physical factors in the Arabian Gulf restrict the growth and development of corals to patchy forms (Sheppard et al., 2010). However, despite these harsh environmental conditions, corals

Recently, corals in the Arabian Gulf have been exposed to severe temperature anomalies at a recurrence faster than in any other coral regions in the world. Therefore, it is argued that corals in the Arabian Gulf already exist in a thermal environment that is equal to the 2099 projections of the Intergovernmental Panel on Climate Change (IPPC) in tropical oceans (Riegl and Purkis, 2012). This embarked regional and international interest in using the Arabian Gulf as a model ecosystem to understand the potential impact for future climate change (Burt, 2013). One aspect of that interest is the establishment the Mideast Coral Reef Society (MCRS) in 2013, with the aim of generating a deep understanding of these unique ecosystems and promoting their

Unfortunately, coral reefs in the Arabian Gulf have been severely affected by recent bleaching events as well as human impacts such as sediment runoff from dredging and reclamation activities and pollution from different land-based sources. Large-scale decline in coral reef has been observed. It is estimated that almost 70% of original reef cover in the Arabian Gulf may be considered lost and a further 27% threatened or at critical stages of

Mangrove habitats are ecologically important coastal ecosystems that provide food, shelter and nursery areas for a variety of terrestrial and marine fauna. Mangrove habitats of the Arabian Gulf support a variety of important species of fish, shrimps, turtles, and birds, and significantly contribute to the coastal productivity (Al-Maslamani et al., 2013). The Arabian Gulf coastlines are dominated by only one species of mangroves, *Avicennia marina.* The processes of osmoregulation and salt secretion allow *Avicennia marina* to cope with hypersa‐ linity conditions in the Arabian Gulf (Dodd et al., 1999). Naser and Hoad (2011) investigated salinity tolerance and salt secretion in Bahrain and found that successful establishment of mangroves depends critically on the tolerance of these plants to salinity at the early stages of

Mangroves are largely distributed along the southern shores of the Arabian Gulf. Dense growth of mangroves is particularly confined to low-energy and sheltered coastal areas along the coastlines of United Arab Emirates, Saudi Arabia and Qatar. While mangroves are relatively widespread throughout the Arabian Gulf countries, there are variations in their distributions from one country to another. For instance, the total extent of mangroves in United Arab Emirates is estimated to be 38 km2 (Dodd et al., 1999) compared with only 0.31 km2 in

According to the IUCN Red List of threatened species, mangroves in the Arabian Gulf are classified as 'Least Concern'. The Red List assessment concluded that although there are overall range declines in many areas, they are not enough to reach any of the threatened category thresholds. However, it can be argued that this classification might not be applicable to certain

in the Arabian Gulf exhibit remarkable resilience and vitality.

conservation and sustainable use.

300 Biodiversity - The Dynamic Balance of the Planet

degradation (Wilkinson, 2008).

**2.3. Mangrove swamps**

development.

Bahrain (Abido et al., 2011).

Due to the sedimentary nature of the Arabian Gulf, sand and mud substrata are the most widespread habitats. They extend from intertidal salt marshes to the maximum depth and account for more than 97% of the bottom substrate of the Arabian Gulf (Al-Ghadban, 2002). Tidal mudflats are generally restricted to low energy environment associated with low water movement mainly along the coastlines of Kuwait, Saudi Arabia and United Arab Emirates. These habitats are favorable areas for the colonization by mangroves, algal and cyanobacterial mats, which play important roles in primary productions and food chains. Subtidal and tidal muddy habitats are extremely rich in macrobenthic assemblages, which form the largest and most diverse marine ecosystem in the Arabian Gulf.

Generally, biodiversity and distribution of macrobenthos in the Arabian Gulf are primarily governed by sediment type, temperature, salinity, primary productivity, depth and physical disturbance (Coles and MacCain, 1990). Macrobenthic assemblages through their high secondary productivity contribute significantly to the overall fisheries and marine productiv‐ ity. Additionally, mudflat habitats provide feeding and roosting grounds for important shorebird populations. Some of these important bird areas are declared as wetlands of international importance (Ramsar Convention of Wetlands). Tubli Bay in Bahrain is an example of a Ramsar site that supports large numbers of wintering and migratory shorebirds (Al-Sayed et al., 2008).
