Red Sea is one of the most important repositories of the marine biodiversity in the world, it support populations for many species of marine mammals (about 15 species of dolphins and whales, and one dugong species). These marine resources have attracted the attention of tourists and increase tourism contribution to the Egyptian economy. At the same time, Red Sea oil and gas reserves are estimated to be around 100 billion barrel of oil equivalent. Kingdom of Saudi Arabia is planning to employ 200 drilling rigs in 2014 most of it will be in the Red Sea. Most of offshore drilling rigs and production platforms are found on group of large diameter piles which are driving into sea bed producing high amount of underwater noise. Underwater noise emitted during pile construction can mask biologically relevant signals for marine mammals which use sound as a mechanism to navigate and communicate. This noise might lead to behavioral reactions, harassment, and at very high levels can injure or even kill the mammal. The potential for underwater noise to affect marine mammals depends on how well the animal can hear the noise. Noises which can’t be heard well by the mammal are less likely to disturb or injure it except when it is associated with high sound pressure that can causes physical injury. Sound exposure level was used for evaluating noise effects on mammals because pile driving is an ongoing impulsive activity that will occur throughout the construction phase. Range-dependent Acoustic Model, Rogers Model, was used to assess underwater noise propagation of offshore pile driving taking into account seabed bathymetry, temperature, and salinity. It was found that an offshorepile driven with 235 kJ rated energy diesel hammer can cause behavioral disturbance to the marine mammal within a distance of 1000 m from the pile location; temporary threshold shift within a distance of 30 m; permanent threshold shift within a distance of 50 m;and injury, or even death, within a distance of 20 m. |
