Hermannsen Line, Tougaard Jakob, Beedholm Kristian, Nabe-Nielsen Jacob, Madsen Peter Teglberg
Section for Marine Mammal Research, Department of Bioscience, Aarhus University, Roskilde, Denmark; Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.
Section for Marine Mammal Research, Department of Bioscience, Aarhus University, Roskilde, Denmark.
PLoS One. 2015 Jul 27;10(7):e0133436. doi: 10.1371/journal.pone.0133436. eCollection 2015.
Airguns used in seismic surveys are among the most prevalent and powerful anthropogenic noise sources in marine habitats. They are designed to produce most energy below 100 Hz, but the pulses have also been reported to contain medium-to-high frequency components with the potential to affect small marine mammals, which have their best hearing sensitivity at higher frequencies. In shallow water environments, inhabited by many of such species, the impact of airgun noise may be particularly challenging to assess due to complex propagation conditions. To alleviate the current lack of knowledge on the characteristics and propagation of airgun pulses in shallow water with implications for effects on small marine mammals, we recorded pulses from a single airgun with three operating volumes (10 in3, 25 in3 and 40 in3) at six ranges (6, 120, 200, 400, 800 and 1300 m) in a uniform shallow water habitat using two calibrated Reson 4014 hydrophones and four DSG-Ocean acoustic data recorders. We show that airgun pulses in this shallow habitat propagated out to 1300 meters in a way that can be approximated by a 18log(r) geometric transmission loss model, but with a high pass filter effect from the shallow water depth. Source levels were back-calculated to 192 dB re µPa2s (sound exposure level) and 200 dB re 1 µPa dB Leq-fast (rms over 125 ms duration), and the pulses contained substantial energy up to 10 kHz, even at the furthest recording station at 1300 meters. We conclude that the risk of causing hearing damage when using single airguns in shallow waters is small for both pinnipeds and porpoises. However, there is substantial potential for significant behavioral responses out to several km from the airgun, well beyond the commonly used shut-down zone of 500 meters.
地震勘探中使用的气枪是海洋栖息地中最普遍、最强大的人为噪声源之一。它们被设计为在100赫兹以下产生大部分能量，但据报道，这些脉冲还包含中高频成分，有可能影响小型海洋哺乳动物，而小型海洋哺乳动物在较高频率下具有最佳听力敏感度。在许多此类物种栖息的浅水环境中，由于传播条件复杂，气枪噪声的影响可能特别难以评估。为了缓解目前对浅水中气枪脉冲特性和传播缺乏了解的状况，以及其对小型海洋哺乳动物影响的相关知识，我们在一个均匀的浅海栖息地，使用两个校准过的Reson 4014水听器和四个DSG - 海洋声学数据记录仪，在六个距离（6米、120米、200米、400米、800米和1300米）处记录了单个气枪在三种工作容积（10立方英寸、25立方英寸和40立方英寸）下的脉冲。我们发现，在这个浅海栖息地，气枪脉冲以一种可以用18log(r)几何传输损耗模型近似的方式传播到1300米，但受到浅水深度的高通滤波效应影响。源级经反算为192分贝（参考微帕斯卡平方秒，声暴露级）和200分贝（参考1微帕斯卡，等效连续A声级 - 快速，125毫秒持续时间内的均方根），即使在1300米处最远的记录站，脉冲在高达10千赫兹时仍包含大量能量。我们得出结论，在浅水中使用单个气枪时，对海豹和鼠海豚造成听力损伤的风险较小。然而，在距气枪数公里范围内，存在引发显著行为反应的巨大可能性，远远超出了常用的500米关闭区。
