Research Article
Coral Reefs in the Persian Gulf and Oman Sea: An Integrated Perspective on Some Important Stressors
Iranian National Institute for Oceanography, No. 3, Etemadzadeh St., Fatmei Ave., Tehran, 1411813389, Iran
Coral reefs are important constituents of marine ecosystems (Perkol-Finkel and Benayahu, 2007) and is getting an important place in search for new drugs also (Anbuselvi et al., 2009; Sukarmi and Radjasa, 2007). But they are suffering significant changes in diversity; species abundance and habitat structure worldwide (Hughes et al., 2007). Over the last few decades, they have been rapidly deteriorating because of a variety of environmental and anthropogenic pressures, such as elevated seawater temperature (Abram et al., 2003; Brown et al., 2000; Weber et al., 2006), sedimentation (Rees et al., 2005; Weber et al., 2006) fishing with cyanide (Cervino et al., 2003), pollution and over fishing (Eghtesadi-Araghi, 2005; Eghtesadi et al., 2002; Vestergaard et al., 2003; WWF, 2007b) that lead to a loss of coral diversity, increased incidence of disease, reduced growth, reduced reproduction and mass mortality (Heilman et al., 2008). Temperature, irradiance, turbidity, sedimentation, salinity, pH and nutrients affect survival of corals. These parameters control the physiological processes of photosynthesis and calcification as well as coral survival and consequently, coral reefs arise only in select areas of the worlds oceans.
Generally, coral reefs diversity in the Persian Gulf and parts of the Oman Sea (also called ROPME Sea Area (RSA)) is typically low (100-130 species) (Maghsoudlou, 2008) comparing to Indian Ocean (quarter the number of Indian Ocean) (Mohammadi, 2005). This is due to extremes of water temperature and salinity that are close to the physiological tolerance limits of many species. Coral Species composition in this area is typically Indo-Pacific and hard corals species richness in the Oman Sea (which is about 70 species) is more than the entire Persian Gulf (Sheppard and Salm, 1988). The increasing trend of temperature and salinity in the Persian Gulf and Oman Sea (Heilman et al., 2008) adds significance of the articles in this regard.
Stressors environmental conditions and their biomarkers in the persian gulf: Coral reefs in the Northern Persian Gulf live under unique temperature conditions and the seawater temperature ranges are between 14 to 34°C (Coles and Fadlallah, 1991). This sharp ten degrees centigrade change (which is an intense decrease in sea water temperature) occurs in warm to cold season transition in December and might cause a cold stress in the corals (Fadlallah et al., 1995). The physiological and biochemical responses to these stressors can be used as the biomarkers for understanding of caveat in coral reefs (Eghtesadi-Araghi et al., 1999) which will be reviewed in this article with emphasis on temperature, salinity and ultraviolet radiation.
Seasonal changes in environment of the coral reefs may exert a physiological effect on this organism. Branching and massive coral species show different responses to temperature stress which might affect their growth and metabolic rates (Gates and Edmunds, 1999), i.e., their resistance toward stressful environmental conditions. Slow-growing massive coral species live longer when compared to branching ones. Branching corals have thinner tissue layers which provide less photosynthetic products and energy-rich compounds, resulting in lower adaptability to sudden environmental changes (Gates and Edmunds, 1999).
Total protein concentration as biomarker of temperature in coral reefs: Schlder and DCroz (2004) reported previously that tissue concentration of total soluble proteins is an indicator of the health condition of the coral host. For example, protein metabolism is a key factor for the stabilization of the physiological condition in corals and variation is reported to result from environmental disturbances. This was observed in the Caribbean corals Acropora cervicornis and Montastraea franksi, which showed up to 43% variation in protein concentration within a day period, when exposed to elevated water temperatures. Corals with high resistance to bleaching have high concentrations of symbionts, chlorophyll and soluble proteins.
They also suggested that massive corals are better able to survive with changing environmental conditions compared to branching corals. Present studies also revealed that massive (Favia sp.) and branching (Acropora sp.) corals have different behaviors in similar environmental conditions (Eghtesadi-Araghi, 2005).
Schlder and DCroz (2004) used 23.8, 29.1 and 29.3°C as low, ambient and high temperatures on their studies, respectively. Their results showed that total protein concentration of massive corals exhibited highest amount in 29.1°C and a moderate amount in 23.8 °C which is in agreement with our results in 27.0 and 22.0°C, respectively (Eghtesadi-Araghi, 2005).
Coral reefs in the Persian Gulf are usually exposed to annual ranges of temperatures that exceed the extremes reported for any other reef area in the world. Normal winter water temperatures in the Persian Gulf rank among the lowest recorded on coral reefs (Coles and Fadlallah, 1991). A sharp ten degrees centigrade change which is an intense decrease in sea water temperature occurs in warm to cold season transition in December and might cause a cold stress in the corals of this region (Fadlallah et al., 1995).
Zooxanthellae are the main primary producers on coral reefs (Van Oppen and Gates, 2006). Low temperature stress usually results in mortality of these algae and reduction in coloration to pale in coral species and finally decadence of corals. Investigations indicated that only 1- 2 weeks of continuous exposure to 18°C or less might result in low survival rate and change of metabolic activity of corals which eventually leads to their degradation. Low temperature also could limit distribution of corals in the marine and oceans; Some reef corals can live and survive in cold water as low as 10.5°C but they cannot create reefs but the duration of exposure to such low temperature has not been determined. In our study, field studies confirm that the Acropora spp. in the Persian Gulf is sensitive to low range of temperature from 15-27°C (Eghtesadi-Araghi, 2005).
UV radiation and coral biomarkers: The most important prerequisite for photosynthesis is solar radiation. Photoautotrophic organisms convert light energy into chemically bound energy in the process of photosynthesis, which is used for biomass production. But many biological processes may be deceased by excessive light quality and UV irradiance (Barber and Andersson, 1992), or if short wavelength radiation with high energy content, such as UV radiation, is absorbed by biomolecules. Therefore, reduced photosynthetic and general metabolic activity is expected to occur when important components in plant metabolism are damaged. It has also been reported that UV radiation independently increase the activities of different enzymes (e.g., ascorbate peroxidase, catalase and superoxide dismutase) within the zooxanthellae of the zoanthid Palythoa caribaeorum. When coral reefs are exposed to UV, H2O2 and Sodium arsenite, an increase in oxidative stress proteins production occurs. Reports have been indicating that UV couple to high temperature primarily stimulates in situ photo-bleaching of photosynthetic pigments in Acrpora digitifera. It is shown that acclimation to moderate or low light in corals occurs mostly via two mechanisms: accumulation of photosynthetic pigments in zooxanthellae and increasing the population density of zooxanthellae. Present result showed that a negative significant correlations were observed between chlorophyll-a and water temperatures as well as chlorophyll-a and UV radiation index in Favia sp. and Acropora sp. Present result also revealed that minimum value of chlorophyll-a for coral reefs was observed in Summer, whilst maximum value was recorded in winter (Eghtesadi-Araghi, 2005). Present studies (Eghtesadi-Araghi, 2005) also confirmed that acclimation in Favia sp. and Acropora sp. to low light in winter was accompanied by a significant increase in accumulation of chlorophyll-a. The increase of chlorophyll-a of corals with lowering light intensity in habitat was detected by us and by other authors on different coral species (Brown et al., 1999).
Stress protein concentration as biomarker of temperature in coral reefs: Health assessment of scleractinian corals, which are major components of the coral reef ecosystem, is an important issue for the conservation of coral reefs. During the last decade, molecular biomarkers have become useful tools to evaluate the health of organisms (Eghtesadi-Araghi et al., 1999). Several studies have investigated the relationship between stressors and gene expression of cnidarians (Morgan et al., 2001). These studies used heat shock proteins (HSP) as indicators and demonstrated the induction of these proteins by stressors (Wiens et al., 2000). In response to cellular stress such as heat, cold, anoxia, cyanide and heavy metal a set of proteins, called stress proteins or Heat Shock Proteins (HSPs) is induced. Under environmental stressors, most HSPs provide various mechanisms that protect and recover stress damaged proteins. Determination of heat shock proteins (e.g., HSP 70) has been reported to be a suitable marker for environmental stress in the tissues of corals and their symbioants.
Thermal stress is suggested to play a role as a stressor for corals and their symbioants. Changes at the cellular and biochemical level are usually the first detectable response to an environmental stress and can be observed before the morphological signs of stress are evident (Bierkens, 2000). Organisms respond to cellular stress by synthesizing several stress proteins (e.g,. heat-shock proteins (HSPs)) (Dunn et al., 2004). Members of the 70 kDa heat shock proteins (HSP70s) play an essential role in protein folding, transport of proteins into different cellular compartments, regulation of apoptosis and regulation of the heat-shock response (Brown, 1997). Seasonal changes in the environment may exert a physiological effect on coral reefs. Sharp et al. (1997) reported the presence of an HSPs70 in Goniopora djiboutiensis detected by immunoblotting. Fang et al. (1997) reported the appearance of a newly synthesized 35 kDa protein both in Acropora grandis and in its symbiotic algae after heat exposure. In our studies, we have found significant higher levels 70 kDa protein densities occurs in winter coinciding with decreased temperature when compared to warm season. Present results also revealed that average numbers of colony decreased in Winter which high levels of 70 kDa protein in Porites sp. were observed. We found that a significant negative correlation was existed between 70 kDa protein density (%) and water temperatures. Therefore, we suggest that 70 kDa protein densities can be applied as a useful tool for determination of cold stress in Porites sp. (Eghtesadi-Araghi, 2005).
Kendall et al. (1983) reported previously that tissue concentration of total soluble proteins is an indicator of the health condition of the coral host. For example, protein metabolism is a key factor for the stabilization of the physiological condition in corals and variation is reported to result from environmental disturbances. This was observed in the Caribbean corals Acropora cervicornis and Montastraea franksi, which showed up to 43% variation in protein concentration within a day period, when exposed to elevated water temperature (Kendall et al., 1983).
All organisms have lethal limits to their temperature range and yet within this range they also have optimal temperatures for development of structure and function (Rombough, 1976). Within an ectotherms tolerance limit, variation in temperature will influence metabolism and therefore related physiological processes, affecting growth and development. Coral reefs in the Persian Gulf are usually exposed to annual ranges of temperatures that exceed the extremes reported for any other reef area in the world. Normal winter water temperatures in the Persian Gulf rank among the lowest recorded on coral reefs (Coles and Fadlallah, 1991). Zooxanthellae are the main primary producers on coral reefs (Van Oppen and Gates, 2006). Low temperature stress usually results in mortality of these algae and reduction in coloration to pale in coral species and finally decadence of corals. Investigations indicated that only 1-2 weeks of continuous exposure to 18°C or less might result in low survival rate and change of metabolic activity of corals which eventually leads to their degradation.
The coral reefs of the Persian Gulf and Oman Sea are critical habitats of cultural, socioeconomic and scientific value. However, their development is constrained by a variety of oceanographic factors including: extreme temperatures and salinity, high levels of suspended sediments, limited surface area of substratum suitable for the settlement of recruits and the scoring action of mobile sediments. Disease and outbreaks of Crown-of-Thorns starfish represent naturally occurring threats to coral reefs though the former may be aggravate by stressor derived from human activities. The diversity of coral reefs as indicated by the number of recognized species in each of the regions littoral countries are mentioned in Table 1. The threats on Coral Reefs in the region are shown in Table 2 which has been recognized by regional experts during meetings from 2003 to 2007.
Table 1: | The diversity of coral reefs as indicated by the number of recognized species in each of the regions littoral countries |
Table 2: | The threats on Coral Reefs in the region |
According to these information and the capacities (mentioned below) in each of the countries a series of needs are informed for conservation and management coral reefs in the Persian Gulf and Oman Sea.
Existing capabilities of region:
Littoral countries capacities: During the above mentioned meeting all participants agreed that there are a few capabilities for coral conservation and research in the region. Some of these capacities include:
• | Local diving facilities in each country |
• | Private professionals divers |
• | Universities and marine colleges along the coast |
• | National data centers in some Persian Gulf and Oman Sea countries in the framework of ODINCINDIO project |
GCRMN-RSA node (INCO) existing capabilities: The Responsible National Oceanographic Data Center (RNODC-PG) in the Persian Gulf was established in April 2004 at INCO and there is enough capability in this section to establish a Regional Coral Reef Data Center (RCRDC) for the RSA if a small budget would be allocated for equipment and training of coral reef database operators (for data entry, verification, analysis and preparing regional summaries). In addition of RNODC responsibility, INCO has participated in Ocean Data and Information Network for Central Indian Ocean (ODINCINDIO) Project in October 2004.
Regional needs for coral reefs conservation and management:
• | There is a need to reduce diver and boat anchor damage. In all countries, mooring buoys should be installed at the major reef sites to prevent further anchor damage to corals. Additionally, spear fishing should be banned (and the ban enforced) to allow reef fish populations to recover |
• | Solid waste cleanup projects need to be organized in each country to remove accumulated debris from the reefs, including plastics, metals, glass and discarded fishing equipment |
• | Public education campaigns are needed to increase understanding of the importance of coral reefs and their sensitivity to damage and pollution. These should highlight the use of moorings to prevent damage to corals, the need for restrictions on fishing on these reefs, the problems caused by littering and refuse and the need for public and private participation in the management of coral reefs |
• | There is a need to develop and expand local capacity to monitor and carry out research on coral reefs. This must also include the designation, where applicable, of competent authorities to manage and conserve coral reefs and preparation of detailed management plans to promote the sustainable and wise use of reef resources |
• | There is a need to designate additional Marine National Parks and Marine Protected Areas (MPA) in the context of integrated management plans. Only within these protected areas will the countries be able to fully protect coral reefs |
• | Coastal development and in particular dredging and land filling, should be curtailed and properly managed. The use of silt curtains should be mandatory in landfill operations and only after stringent Environmental Impact Analyses. Given the limited extent of coral reefs, coral reef areas should never be approved for land filling |
• | There is a need to improve navigational aids and radio communication in RSA waters, especially on major shipping channels and implement current Oil Spill Contingency Plan, including the development of site specific plans, improve capacity to respond to spills of oil and other hazardous materials, including a review and upgrading of port reception facilities for solid and liquid waste |
Recommendations for development of GCRMN activities: It is believed that the following actions are useful for each littoral Persian Gulf and Oman Sea countries to build and increase its capacities on coral reefs:
• | Technology transfer, training and monitoring to communities: establishment of trainer teams in each country through training courses etc |
• | Designation and implementation of Strategic Capacity Building Programs according to the needs of each country and region |
• | Recognition of the national monitoring networks in each Persian Gulf and Oman Sea countries to collaborate with regional node and facilitate interaction among the institutions and the agencies which form the core of the network in each country and region |
• | Establishment and equipment of a regional database center as well as establishment of a National Database Center in each country that interacts closely with the regional/sub-regional Network Node Database |
• | Public awareness through: annual reporting, updating of the web site, regular working/networking and information workshops, poster and media (a tentative website has been develop by INCO through following http://www.inco.ac.ir/coralreefs/home.htm) |
• | Designing and implementation of Coral Reefs Action Plan according to the needs of each country and region |
After eight years of establishment GCRMN node in the Persian Gulf and Oman Sea and conducting many essential actions in the region, we need to shift to field training and monitoring actions that should be conducted at three selected GCRMN sites of the region. Then the needs and equipments are to be assessed through training workshops, for each country and regional node. In this way, the results could be incorporated into the capacity building strategies. The Global Coordinator of GCRMN assist the regions and countries to identify existing national and regional monitoring capabilities and activities and determine capacity for monitoring network development and requirements for training and equipment. We believe that application of successful earlier experiences in this regard such as South East Asia node and also ICRI Middle East Strategy can lead us to act rapidly for development of a cost-effective plan for conservation and management of coral reefs in the region.
Authors thank the Iranian national Center for Oceanography (INCO) and the Regional Organization for Protection of Marine Environment (ROPME) for their supports on regional workshops of Coral Reefs in the region.