are the most important habitats for small crustaceans that dwell in them. They are as crucial an indicator of biological health on the surface of the water, as the corals are to biological health of the Persian Gulf in deeper waters. Mangroves' ability to survive the salt water through intricate molecular mechanisms, their unique reproductive cycle, and their ability to grow in the most oxygen-deprived waters have allowed them extensive growth in hostile areas of the Persian Gulf. However, with the advent of artificial island development, most of their habitat is destroyed, or occupied by man-made structures. This has had a negative impact on the crustaceans that rely on the mangrove, and in turn on the species that feed on them. Gallery Oil and gas The Persian Gulf and its coastal areas are the world's largest single source of petroleum, and related industries dominate the region. Safaniya Oil Field, the world's largest offshore oilfield, is located in the Persian Gulf. Large gas finds have also been made, with Qatar and Iran sharing a giant field across the territorial median line (North Field in the Qatari sector; South Pars Field in the Iranian sector). Using this gas, Qatar has built up a substantial liquefied natural gas (LNG) and petrochemical industry. In 2002, the Persian Gulf nations of Bahrain, Iran, Iraq, Kuwait, Qatar, Saudi Arabia, and the UAE produced about 25% of the world's oil, held nearly two-thirds of the world's crude oil reserves, and about 35% of the world's natural gas reserves. The oil-rich countries (excluding Iraq) that have a coastline on the Persian Gulf are referred to as the Persian Gulf States. Iraq's egress to the Persian gulf is narrow and easily blockaded consisting of the marshy river delta of the Shatt al-Arab, which carries the waters of the Euphrates and the Tigris rivers, where the east bank is held by Iran. See also Eastern Arabia Eastern Arabian cuisine Cradle of civilization Deluge (prehistoric) Musandam Peninsula History of the United Arab Emirates#The pearling industry and the Portuguese empire: 16th - 18th century Saeed bin Butti#Perpetual Maritime Truce Trucial States Sultan bin Saqr Al Qasimi#Perpetual Maritime Truce of 1853 Persian Gulf campaign of 1809 Persian Gulf campaign of 1819 General Maritime Treaty of 1820 Geography of Iran Geography of Saudi Arabia Geography of Oman Geography of United Arab Emirates Geography of Qatar Geography of Bahrain Geography of Kuwait Geography of Iraq