Investigation of behavioural and acoustic responses of cetaceans to seismic surveys in Antarctica

Project description

Under the Act on the Implementation of the Protocol on Environmental Protection to the Antarctic Treaty (AUG), the Federal Environment Agency (UBA) is the national licensing authority for all activities in Antarctica that are organised from or emanate from Germany. As part of the licensing procedure under the AUG, an environmental assessment must be carried out by UBA as the implementing authority for all notified activities in the area covered by the Antarctic Treaty.
Seismic surveys using airguns are carried out to reliably determine the topography and geological composition of the seabed. These devices emit acoustic signals with high sound pressure levels. So far, the data basis is insufficient to assess possible impacts on marine fauna.
The aim of this project is to assess the effects of a geoscientific, seismic survey with airguns during the expedition "WAIS-BELL" (PS 134) in 2022/23 on cetaceans in the Antarctic. Here a behavioural response study will be carried out, which will include a multidisciplinary approach combining visual recording methods and passive acoustic monitoring (PAM).
The project aims to generate data on the distribution, habitat use and possible behavioural responses of cetaceans in their Antarctic feeding area in an undisturbed and acoustically disturbed situation. The work will be carried out during seismic surveys in the Amundsen and Bellingshausen Seas and will be carried out in close cooperation between TiHo, JASCO and the AWI geophysics group in their survey programme.
The noise exposure and vocalisations of cetaceans are recorded using an autonomous acoustic recording system (AMAR), which allows the identification, localisation and tracking of vocalizing individuals. Visual recording methods (helicopter, autonomous drone, possibly bridge or crow's nest of FS Polarstern) will be used to collect data on the distribution and behavioural responses during the seismic survey as well as habitat use of the cetaceans during transits to and from the study area.
The results will contribute significantly to assessing the potential effects of seismic surveys with airguns on whales and provide important information for the management of anthropogenic activities in the Antarctic Treaty Area.

Results: The project aimed at assessing the effects of seismic airgun surveys during the PS134 (WAIS-BELL) expedition on Antarctic cetaceans. A multidisciplinary monitoring concept combining visual observations and passive acoustic methods was developed to investigate behavioural responses, avoidance distances, and potential masking of whale vocalisations.

Ship-based observations by marine mammal observers (MMOs) and a validation team proved to be the most reliable mitigation measure. A comparison showed that teams of two MMOs achieved nearly the same detection performance as teams of three. Based on all shipboard sightings, a median avoidance radius of 3.4 km was determined when airguns were active, compared to 1.2 km when they were inactive. Limitations included weather, darkness, observer variability, and blind spots behind the vessel. The infrared (IR) camera provided some additional detections, but was constrained by technical issues, humidity, and a large blind sector. Nevertheless, system upgrades are recommended because of its utility during darkness. Helicopter aerial surveys significantly expanded the observation radius (up to 90 km) and gave insights into species distribution, but are not suitable for real-time mitigation. After initial technical issues, the drone showed potential for future real-time monitoring, though it could not yet be fully evaluated.

An Autonomous Long-Term Observatory (ALTO) system with an integrated AMAR was intended to record vocal activity before, during, and after seismic operations, but produced no data due to a technical malfunction, despite the general suitability of this technology. The PAM system QuietSea™ integrated into the streamer generated mostly false alarms. Among many detected events, only one single automatic detection was confirmed as a real baleen whale vocalisation. Possible reasons include masking by vessel noise, the bubble curtain behind the ship, and insufficient calibration or hardware issues.

No single method provided complete and reliable marine mammal monitoring under all conditions. Ship-based visual monitoring currently remains the most effective mitigation tool. IR systems, drones, and acoustic technologies require technical improvements, but could become valuable complementary tools, particularly in darkness, poor weather, or for underwater detection. A robust mitigation and protection strategy will require a combination of optimised monitoring approaches.