NEW! In 2004, Acoustic Ecology Institute put together a concise, comprehensive Backgrounder on industrial seismic surveys. This 8-page Word document (designed for the media) gives a quick overview of the issue; detailed summaries of the scope, effects, and possible ways of addressing the issue; research of note; and links to online resources. [DOWNLOAD BACKGROUNDER(doc)]
The search for undersea reserves of oil and gas often begins with seismic exploration. Using sound waves generated by directed bursts of sound from airguns, typically used in multiple arrays of 4-24 airguns, the geology beneath the sea floor can be ascertained. Similar technology is often used for geological research into earthquakes or other earth-science topics. The effects of these sounds on sea creatures is a matter of increasing concern, given the many stresses at play on marine species populations.
Seismic airgun sounds typically peak at 200-230 decibels; scientists believe marine mammals and fish may be injured by sounds in the range of 190dB (generally considered to be the sound level at about 500m from the airgun). The physical impacts of seismic survey noise on marine mammals are usually assumed to be minimal, since the systems ramp up slowly enough and move slowly enough to allow animals to move away. However, auditory masking is quite likely at longer ranges, and confusion, temporary hearing loss, and perhaps long-term hearing damage are possible in the unlikely event of close exposure. In addition, there are a wide range of behavioral reponses, primarily avoidance and, in some cases, disruptions in foraging.
Energy-rich areas such as the North Sea and the Gulf of Mexico have been blanketed by surveys for many years, with little evidence of any die-offs of animals. The South China Sea, Indonesia, and West Africa are also areas of concentrated oil and gas exploration, with India and South America seeing increasing activity as well. There is increasing concern about the cumulative impacts of these especially loud sound sources on marine life, and there have been a few instances of coincidental strandings. Each survey (there have often been a hundred a year in the Gulf of Mexico) lasts for anywhere between a few days and a few weeks; the survey ship travels in a grid of parallel tracks, firing the guns every 10-60 seconds. Since 2005, in the face of these concerns, the oil and gas industry has more actively funded research into the sound profiles and effects of airgun sounds, in an effort to both increase their own understanding, and to provide data that might help them avoid what they consider excessively precautionary regulation of thier activities.
There are many factors to be aware of in considering the impacts of such sounds, including the different systems used to measure dB in the sea, the differing hearing ranges of various species and source frequencies of noise sources, the prevalance of high-volume shipping noise in the ambient noise of the ocean, and the many unknowns in our knowledge of the perception and use of sound by marine creatures. AEI's Ocean Acoustics section [GO THERE] is highly recommended reading to get up to speed on these complexities.
AEI Research Report - Seismic Surveys: What we Don't Know Can Hurt - Read executive summary and download full report: [GO THERE]
Greenpeace Overview of Seismic Exploration - [WEBSITE]
Living Oceans Society Literature Collection - Includes a sublist on seismic impacts, including comments submitted by researchers and research reports [WEBSITE]
Lamont-Dougherty Earth Observatory - Website of a leading geology research center run by Columbia University. Includes information on airguns used for academic research. [WEBSITE]
The value of marine seismic research [WEBPAGE]
Indian Ocean Sounds [WEBPAGE]
Oil and Gas Industry Reports and Initiatives Related to Biological Effects of Noise - Industry trade groups and coalitions have sponsored research into the effects of airguns for many years. A new Joint Industry Project (JIP) was initiated in early 2005. In the summer of 2006, this program moved to fruition, launched as the "E & P Sound and Marine Life Programme", and funded with donations from a consortium of oil and gas companies, all part of the OGP. Primary focus of the work is likely to be on marine mammals, with some emphasis also on fish, invertebrates, and other prey species.
E&P Sound and Marine Life Programme [WEBSITE] Summary presented at IWC in June 2006 [DOWNLOAD PAPER(doc)]
OGP (International Association of Oil and Gas Producers) Marine Mammal info, including JIP [WEBSITE]
IAGC (International Association of Geophysical Contractors) Position Paper on Marine Mammals and Sound, 2004 [DOWNLOAD REPORT(pdf)]
IAGC Task Force on Marine Mammals and Sound Goals Paper, 2001 [READ PAPER]
IAGC Marine Mammal info [WEBSITE]
Canadian Society of Exploration Geophysicists [WEBSITE]
Proceedings of the 1998 Seismic and Marine Mammals Workshop - From the Sea Mammal Research Unit at St. Andrews University. [WEBSITE]
Minerals Management Service Programmatic Environmental Assessment - Released in 2004, this EA covers geologic and geophysical activites in the Gulf of Mexico, including seismic surveys. The PEA sets a standard 500m safety radius, and lays the groundwork for MMS to request routine "incidental harassment authorizations" from NOAA for commercial surveys in the Gulf. See article from Petroleum News: [READ ARTICLE] Or, see MMS press release: [READ PRESS RELEASE] MMS PEA: [DOWNLOAD EA(pdf)]
Description of operations of Seismic Airguns - A detailed explanation of the physical operation of airguns, from the website of Robertson Research International, an oil and gas consulting firm. [WEBSITE]
New Zealand Department of Conservation Marine Mammal Action Plan - Covers all impacts on marine mammals; includes specific operations and monitoring objectives for seismic surveys. [DOWNLOAD REPORT(pdf)]
Canadian Department of Fisheries and Oceans Statment of Practice on Mitigation of Seismic Noise - A draft of the new Canadian operational and mitigation standards was released in February 2005. As of late 2005, DFO was still working on the final version. A copy of the peer-reviewed report, entitled “Review of Scientific Information on Impacts of Seismic Sound on Fish, Invertebrates, Marine Turtles and Marine Mammals” (Habitat Status Report 2004/002) is available. [DOWNLOAD REVIEW(pdf)] [WEBPAGE ON STATEMENT OF PRACTICE]
Industrial and academic Seismic Survey projects currently being planned or in operation [GO THERE]
Bridge Construction and Pile Driving
Pile driving to create solid foundations for bridges and, increasingly, wind turbines, creates loud noises that can, at relatively close ranges (a few hundred meters), cause temporary or permanent hearing loss in fish and marine mammals. AEI has, so far, not gathered detailed information on this issue.
Effects of Bridge Construction Noise on Resident Harbor Seals
In preparation for a multi-year renovation project on the Richmond Bridge (which spans an arm of San Francisco Bay ), CalTrans has commissioned San Francisco State University to do baseline studies of a colony of harbor seals that live on and around an island in the middle of the bridge's span. [WEBSITE]