The Impact of Cyclone Gonu on Selected Coral Rich Areas of the Gulf of Oman Including Indications of Recovery at the Daymanyiat Islands

Abstract

The Gulf of Oman is located at the northwest end of the Indian Ocean, separating the Arabian Gulf from the Arabian Sea (Fig. 1), bordered by India, Oman, Pakistan, and Iran. This study summarizes the impacts of cyclone Gonu on coral communities within the Gulf of Oman and specifically those associated with the coast of the Sultanate of Oman (Fig. 2).

Upwelling and associated oceanographic features within the Gulf of Oman dominate marine ecosystems, preventing oligotrophic conditions favorable for true reef development by reducing water temperature, light attenuation, and bringing nutrients into the euphotic zone (Wilson 2007). The net result is the absence of the true coral reefs as defined in most tropical oceanic zones from much of the coastline (Wilson 2007). Instead, coral colonies grow on exposed rocky substrates or other dead coral colonies (e.g., Porites) and do not lay down a limestone-based reef matrix, subsequently forming incipient reefs. Very few true reefs have been identified in the Gulf of Oman, and where they do occur, they are limited in extent. True reefs are restricted to small areas, typically in shallow water embayments where light attenuation is high and the effects of upwelling events are limited (Wilson 2007). Examples of true reefs within the Gulf of Oman have been recorded at Barr Al Hikman (a large monospecific Montipora reef), Ras Sawadi, and Goat Island in Musandum (Sheppard and Salm 1988; Sheppard and Sheppard 1991; Salm 1992; Wilson 2007). However, coral communities of one form or another are widespread throughout the region typically comprising mixed hard and soft coral assemblages in surface waters at depths above 18 m. Hard coral cover is typically low in most areas ranging from 5-30% in mixed assemblages. Monospecific stands of Acropora and Pocillopora, however, can exceed 90% of the total coral cover over areas of 50 m² or more (personal observation).