Protected species observation is a regulatory requirement for seismic surveys carried out in the Gulf of México. The Bureau of Ocean Energy Management (BOEM; www.boem.gov) and the Bureau of Safety and Environmental Enforcement (BSEE; www.bsee.gov) are the main governing bodies accountable for mitigation guidelines to protect marine mammals and turtles during offshore works in the Gulf of México.
THE ROLE OF PROTECTED SPECIES OBSERVERS AND GUIDELINES
It is the duty of the Protected Species Observer (PSO) to ensure that no marine mammals and/or turtles are in the immediate vicinity (known as the exclusion zone) of the seismic source. After a 30 minute period of observations with no marine mammal or turtle sightings, the ramp-up or ‘soft start’ procedure can commence. A soft start is a gradual increase in sound source level over a period of 20 – 40 minutes. During seismic surveys, the ramp-up procedure commences generally by firing the smallest airgun in the array, and introducing larger airguns (i.e. airguns with a greater energy output (dB) and volume (in³)). A ramp-up procedure is intended to warn marine mammals and turtles of imminent seismic operations, and to allow adequate time for those animals to leave the immediate area around the source before it reaches full source level.
In the Gulf of México, at least two PSO’s are required on-board vessels conducting seismic operations.
Acoustic analysis of noise produced by airgun arrays during seismic surveys is low frequency in general (e.g. JASA 83: 2246-54 and 103:2177-84 and JASA express 128, 181-7), overlapping with those frequencies used by baleen whales (non-toothed whales). For more information on marine mammals and seismic surveys please see www.marinemammalseismic.co.uk.
Over the last few decades, low frequency ocean noise has increased significantly. This has raised concerns that increased noise could affect marine mammals at an individual, and potentially population level. In areas such as the Gulf of México, where numerous marine mammal species are found, including baleen whales, additional measures have been put in place to help minimise any potential impact. Thus, if a whale is observed within the 500 m exclusion zone during operations, the PSO on-board can call for an immediate shut-down of the seismic source.
MARINE MAMMALS IN THE GULF OF MÉXICO
The Gulf of México has a rich and diverse marine life, with 28 species of marine mammal known to frequent the area. While all marine mammal species are protected in accordance with the Marine Mammal Protection Act, MMPA (http://www.nmfs.noaa.gov/pr/laws/mmpa/), six of these marine mammals are listed as endangered under the Endangered Species Act, ESA, (http://www.nmfs.noaa.gov/pr/laws/esa/), including: sperm (Physeter macrocephalus), sei (Balaenoptera borealis), fin (Balaenoptera physalus), blue (Balaenoptera musculus), humpback (Megaptera novaeangliae), and North Atlantic right whales (Eubalaena glacialis).
Marine mammals are reliant acoustically on sound for navigating, foraging and communicating underwater. In order to minimise potential anthropogenic impacts on marine mammal species, Passive Acoustic Monitoring (PAM) has become a popular and reliable mitigation tool that compliments visual monitoring during protect species observation. Passive Acoustic Monitoring involves listening for vocalising marine mammals with a hydrophone. For more information please see www.passiveacousticmonitoring.com
Not only can PAM (www.passiveacousticmonitoring.co.uk) be used during poor visibility, but it is very effective at detecting vocal submerged or diving animals. Sperm whales, recorded frequently in the Gulf of México, are highly vocal animals with sound recorded as loud as 230 dB re 1 µPa @ 1 m, the loudest sound produced by any animal. Sperm whales are also deep divers; it is thought they can reach depths of up to 3 km, and spend around 70% of their time on foraging (i.e. feeding) dives. Sperm whales are thought to spend around only 14% of their time at the surface (i.e. allowing only for a small portion of time where they can be detected visually).
OCEAN SCIENCE CONSULTING
Ocean Science Consulting personnel are all qualified highly and possess a wealth of knowledge in marine biology, oceanography, and bioacoustics. At OSC, we strive to provide a service at a standard high above the rest, which to date has led to rolling contracts from repeat clients. We offer our clients a unique service, providing advice in project/mitigation planning (www.marinemammalmitigationplan.co.uk) for offshore operations, as well as PSO, Marine Mammal Observers (www.marinemammalobservers.co.uk) and PAM operators (www.pamoperator.co.uk) and systems (www.passiveacousticmonitoringsystem.co.uk).
For more information about Ocean Science Consulting Ltd, our current research (www.osc.co.uk/publications.php) and latest news, or to find out information on how we can help with your project see our main site www.osc.co.uk.