Several papers have recently been published about fisheries, biodiversity, ecosystem health and sustainability of PG ecosystems (Khan and Al-Ajmi 1998; Nadim et al. 2008; Hamza and Munawar 2009; Sheppard et al. 2010; Feary et al. 2011; Sale et al. 2011; Burt 2013). Generally, the natural environment of the PG is very rich and a wide variety of marine habitats exists in the region (Fig. 1-6).
Despite the harsh environmental conditions resulting from a high salinity, high summer temperatures and large yearly temperature fluctuations, the PG supports a range of coastal and marine ecosystems which contribute to the biological and habitat diversity in the marine environment and provide valuable ecological sites for a variety of commercially and/or biologically important marine organisms. For example, Portonus segnis is the most
13 commercially important of all true crabs2 in the coastal habitat of Hormuzgan province
(Safaie et al. 2013). The coasts also provide the main nesting habitats of species of sea turtles, i.e. the hawksbill turtle (Eretmochelys imbricata) and the green turtle (Chelonia mydas) (Mobaraki 2004). Several marine protected areas in the Iranian part of the PG, such as the Hara Biosphere Reserve, are among the most visible management steps taken to conserve specific habitats and/or species. In addition, the Strait of Khuran is a Ramsar site, providing habitat to two globally threatened species: a wintering habitat for the Dalmatian pelican
Pelecanus crispus, and a regular feeding place for the green turtle Chelonia mydas.
The main marine coastal ecosystems of PG include rocky shores, coral reefs, seagrasses, mangrove habitats, estuaries, salt marshes, sandy beaches and mud flats (Sheppard et al. 2010) (see Fig. 1-6). In the following sections, we will briefly introduce those important coastal ecosystems of the PG.
- Rocky shores: Because of bed stability, presence of cracks and fissures in rocks and spaces available under stone fragments, rocky shores are considered as one of the most biologically rich environments in the PG (Sheppard et al. 2010). Rocky shores occur mostly in the north and have largely been formed as extensions of the Zagros mountains near the coastal areas. They are present mainly in the Oman Sea and the Strait of Hormuz (Nouri et al. 2010).
- Coral reefs: Although over the past two decades, research on coral reefs in the PG has grown exponentially, the PG’s reefs are in fast decline. Over 70 % of regional reefs have by now been effectively lost (Wilkinson 2008), and the prognosis for the future of the remaining PG reefs is not bright. Generally, due to the extreme temperature and salinity, diversity of corals in the PG is low and comprises only ca. 55-60 species or about 10 % of the coral species that occur in the wider Indo-Pacific region (Sheppard et al. 2010). According to Riegl and Purkis (2009), coral communities in the PG also experience bleaching and frequent temperature-related mass mortality events. For a recent comprehensive study of coral communities in PG, we refer to (Bauman et al. 2013; Burt 2013).
2 Among decapod crustaceans, true crabs (Brachyura) are by far represent the most species-
rich distinct decapod morphotype (with approximately 7,000 extant species). Because of their high nutritional value (proteins and minerals), they are used as a valuable food for livestock and poultry in the world (Naderlo et al. 2011)
14 - Estuaries: There are many definitions for estuaries (Mitra and Zaman 2016); one of the more commonly used states that an estuary is "a semi-enclosed coastal body of water which
has a free connection with the open sea at least intermittently and within which salinity of the water is measurably different from the salinity in the open ocean" (Pritchard 1967; Dyer
1997). In the Iranian part of the PG, most of the estuaries are riverine. The largest and the most important riverine estuarine system is the Arvand Rud delta located in Khuzestan province, where the Tigris and Euphrates enter the northern PG. Bahmanshir is another important estuary in the southwest of Iran (Khuzestan province), which supplies the agricultural, irrigation and drinking waters for the large cities of Abadan and Khorramshahr (Etemad-Shahidi et al. 2015).
- Seagrasses: Seagrasses perform a variety of functions within ecosystems and have both economic and ecological value (Costanza et al. 1997). As a habitat, seagrasses offer food, shelter and essential nursery areas to fish species and to the invertebrates that live within, or migrate to seagrasses. Seagrasses also play important roles in water flow, nutrient cycling, and food web structure. Only three species of seagrass occur in the PG, namely Halodule
uninervis, Halophila stipulacea and Halophila ovalis (Sheppard et al. 2010). These species
are generally tolerant to salinity and temperature extremes. They are particularly prevalent along southern and western shores (Price and Coles 1992). According to (Erftemeijer and Shuail 2012), around 7000 km2 of seagrass habitat have been mapped in the PG to date. However, seagrass habitats in the PG, like in other places in the world (Orth et al. 2006), are suffering a significant threat as a consequence of increasing anthropogenic stresses (Erftemeijer and Shuail 2012).
- Mangroves: Mangroves are coastal vegetations composed of shurbs and trees that grow mostly in saline or brackish water in tropical or subtropical areas. Mangrove habitats are ecologically important coastal ecosystems that provide food, shelter and nursery areas for a variety of terrestrial and marine fauna. The PG coastlines are mostly dominated by only one species of mangrove, Avicennia marina (13,000 ha). A second species, Rhizophora
mucronata, is also found at Sirik in the Strait of Hormuz. They occur principally in lagoons
and on leeward sides, islands and shoals along the Iranian coast as well as in Saudi Arabia, Bahrain, Oman, Qatar and the U.A.E. (Spalding et al. 2010). High salinity is believed to be responsible for the generally small stature of mangrove trees in the PG. Mangrove forests in Iran cover more than 15,000 ha distributed from the Oman Sea to the Mond protected area in the western part of the PG (Mehrabian et al. 2009).
15 - Sandy beaches: Sandy beaches are one of the dominant coastal habitats in the Iranian part of the PG. According to one estimate, the length of sandy shores in the Iranian part of the PG is about 577 km, 65 % of which are located in Hormuzgan province and the rest in Bushehr province (Naser 2014). Since we chose intertidal areas of sandy beaches in the northern part of the PG as the study area for this thesis, we will comprehensively introduce general features and more detailed information on sandy beach habitats in the following pages (§2 Intertidal
areas and sandy beaches).
- Mudflats: due to the sedimentary nature of the PG, sandy and muddy substrata are the most widespread habitats. Mudflats are especially dominant intertidal habitats along the coastline of the western Gulf, where water movements are less turbulent. For example, as a result of the discharge of silt from the Tigris and Euphrates rivers, 57 % of the Kuwait coastline is characterized by mudflats (Al-Zaidan et al. 2003). The total area of mudflats in the Iranian part of the PG is estimated to be about 7345 km2, 76 % of which in Khuzestan Province, 9.7 % in Bushehr province and the rest in Hormuzgan province (Etemad-Shahidi et al. 2015). In the Strait of Hormuz, three sites with a portion of intertidal mudflats occur, all being protected by the Ramsar convention (Matthews 1993).
16 Fig. 1-6. Habitat diversity along the Iranian coast of the Persian Gulf. a) "artificial" mangrove in Qeshm Island; b) pneumatophore zone of Avicennia mangroves in Mahshahr in Khuzestan; c) mangrove of Tiab Protected Area in Hormuzgan; d) a reflective sandy beach in Hormuzgan; e) mudflat in Khuzestan; f) a shore between Bandar Kangan and Asaluyeh in Bushehr; g) rocky/cobble shore between Bandar-Lengeh and Bandar Khamir in Hormuzgan; h) and j) rocky cliffs at the border of Hormuzgan and Bushehr. Adapted from (Naderloo and Tuerkay 2012).