Nelms, S. E., Piniak, W. E. D., Weir, C. R., & Godley, B. J. (2016). Seismic surveys and marine turtles: An underestimated global threat? Biological Conservation, 193, 49–65. http://doi.org/10.1016/j.biocon.2015.10.020
Sometimes humans can be loud. Our new year’s fireworks scare our pets and when we make loud noises in the ocean the animals there might want to hide under the bed as well. Offshore oil and gas production requires exploration of the seafloor. Before a company invests in building a rig to drill for oil, they have a good idea of what they’ll find. We can explore the depths using reflected sound waves much like dolphins and bats echolocate. In a process known as ‘seismic surveys’, air guns shoot sound waves through the seafloor and create a picture of what lies beneath. As air is shot into the water it creates bubbles that expand and break, creating powerful sound waves. An average survey (though it varies a lot) involves 20-40 air guns firing bubbles from a boat moving throughout the area for several hours at a time.
Concerns about the threat of these surveys to ocean life grows as the use of seismic surveys increases. Marine mammals have been most widely considered in research and survey guidelines. This study focuses on sea turtles, giving an overview of research to date concerning the potential changes induced by seismic surveys to behavior, distribution, population dynamics, or other aspects of sea turtle health. Sea turtles throughout the world are on conservation watch lists; all populations within the United States are listed as endangered or threatened by the U.S. Fish and Wildlife Service.
The researchers employed a variety of methods to compile a story about what is known about sea turtles and seismic surveys, what lawmakers are doing with this information, and what ought to be done in the future.
Review of Previous Research
The literature was examined for studies concerning marine turtles, fish, and mammals and seismic surveys. The papers collected were categorized as relating to behavioral responses, physical impacts, or policy. Only 20 examples of research were found for turtles compared to 414 for marine mammals and 187 for fish. The number of studies per year is increasing for each animal group.
Multiple studies found behavior changes linked to seismic surveys such as staying near the surface or increasing swimming speed. The range of turtle hearing has been shown to overlap with the low frequency sounds of air guns. In the past turtles were thought to be deaf and therefore not as likely to be impacted by the big sounds created by air guns. No studies dealt with the potential for turtle entanglement in seismic survey equipment, something that was noted anecdotally during this study. Turtle entanglement is an issue with fishing gear such as commercial trawls and could be happening with air gun equipment as well but no one is recording the frequency. Also, no studies investigated the effectiveness of guidelines to protect turtles that are currently in place.
Seismic Survey Policy
Guidelines for seismic surveys including policies for protecting marine animals were reviewed for all areas in which sea turtles live. About 50 countries allow seismic surveying, only 7 of these have mandatory guidelines related to protecting marine life. Only three countries include turtles in their guidelines: Brazil, Canada and the U.S. The UK guidelines mention that current marine mammal rules could be used for turtles and basking sharks as well but does not make specific considerations for either.
All guidelines that include precautions for turtles recommend a visual search for turtles in the area and a 30-minute delay if one is spotted within 500-meters of an air gun. Surveys must start slowly and softly to give mobile animals a chance to leave. Responses vary if a turtle enters after a survey starts. Brazil requires immediate shutdown if a turtle enters the area. Canada outlines shutdowns in the case of the most endangered or threatened turtles. In the U.S. no shutdown is required for turtles, only marine mammals.
Lastly, a survey was sent to relevant stakeholders (including oil and gas industry, marine ecologists, and seismic operators) to determine the perceived state of the threat to turtles and what is being done in policy and research. Surveys were completed by 89 stakeholders from around the world, with most respondents from Europe and North America. The majority (86%) of people surveyed thought seismic activity could threaten turtles but most also agree that the research is lacking. Of respondents who work offshore 42% answered yes to seeing turtles impacted by the surveys including through behavioral changes, death, or entanglement/collision with equipment. Most people surveyed felt the industry generally complies to the guidelines when they are set. The top suggestions for areas of research were turtle distribution, behavior, hearing and population trends.
This paper shows the research bias that has led to a gap in our knowledge about sea turtles and how they may be impacted by seismic surveys. The research that does exist indicates there may be real threats that are not well understood and then not made into part of the guidelines of most countries. The researchers urge for more research and the surveys show that stakeholders, the people involved closely in a variety of capacities, agree with the push for more research. Everyone loves sea turtles and if the research directs us to protect them from the big scary sounds we make people will likely be moved to make the necessary changes. This paper is a good first step in identifying the holes in our knowledge and making a push for gathering more information. Sea turtles are already endangered and a sea without turtles is a sad thing to imagine!