The Influence of Gas Flares on the Orientation of Green Turtle Hatchlings at Thevenard Island http://www.arbec.com.my/sea-turtles/art14julysept01.htm[11/5/2009 2:54:11 PM] The Influence of Gas Flares on the Orientation of Green Turtle Hatchlings at Thevenard Island, Western Australia Kellie Pendoley Abstract Thevenard Island, situated 10 nm off the coast of north western Australia, is a known nesting site for Green turtles (Chelonia mydas), and also supports an oil production facility. A condition of the Government approval to develop the facility was to minimize light impact on sea turtles. The original gas flare was purpose-built to shield the flame from nearby nesting beaches. A second pit flare was installed in the early 1990 sfor short term use while the primary shieldedflare was undergoing maintenance. Post commissioning surveys and routine inspections indicated that both the flares and the facility lights were potential sources of impact on the sea finding success of C. mydas hatchlings. In September 1995, the spectral characteristics of the two flares were measured, and results suggested the flares emitted light in a spectral range outside of that visibk to C. mydas. Arena experiments were subsequently carried out to determine ~/ the light sources were disorienting hatchlings emerging in the vicinity of the ft ares and over what distance the influence might extend The results suggested that the flares caused disorientation of hatchlings during nights of new moon, however this impact was reduced with distance from the source and as the moon phase progressed towards full moon. Introduction Government approval to develop an oil and gas processing facility on Thevenard Island, 20 nm off the coast of north west Western Australia (Fig. 1), was contingent on the ability to minimise impacts on sea turtles breeding on the island. Specifically, the company was required to shield a proposed gas flare. A state-of-the-art flare tower was installed, but ongoing operational problems resulted in the construction of a backup pit flare adjacent to the flare tower. Subsequent company and Government environmental inspections indicated the light from both the shielded flare and the pit flare had the potential to impact hatchling sea turtles. Flames were generally not visible from either flare at beach level, but both flares produced a highly visible sky glow. A two-stage study to characterise the flares and to test the impact of the flares on hatchling sea turtles was carried out between September 1995 and March 1996. The objectives of the study were to determine whether there was a spectral difference between the tower and the pit flare, whether the spectral differences altered by changing gas flow rates, the magnitude of luminous loss with distance away from the flares, and what other sources of illumination occurred on the island. At the same time we investigated if the flares affected hatching orientation, over what distance, and did any other light sources on the island attract hatchlings.