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Colin Bursey and Christa Lee Spurrell

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Seismic Oil Explorationy Seismic reflection = a process used to determine

shape, thickness, composition, and other

characteristics of the sediment layers underlying theocean floor (the subbottom).

y uses strong pulses produced by an airgun (positionedunder a ship) to penetrate the sea floor. When reflectedback to a surface sensor called a hydrophone,information can be gathered about the subbottom.

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Seismic Oil Exploration

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Seismic Oil Explorationy seismic reflection profile = an

image produced from thereflection displaying the

subbottom geologic structure.This allows oil companies tosurvey the open oceansubbottom to help predict

where oil fields may be located.y uses low frequency sounds (10-

300Hz) at approximately 200-230db.

y A seismic survey can usually lastup to 2-3 weeks and covers arange of 300 to 600 miles.

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Potential Impactsy Seismic oil exploration has been hypothesized to have potential

detrimental effects on marine life.y Many marine animals, especially cetaceans (including whales

and dolphins) have very sensitive hearing and the loud noisesproduced can cause ear damage, as well as other behavioural,physiological and physical harm

y Different marine species are affected in different ways by thisexploration technique

y There is much debate over the magnitude of the impacts; as you

would expect, environmentalists may exaggerate the impactswhile oil companies may downplay them.y Much research has already been done, however it is difficult to

asses the true impacts as so many organisms and parametersmust be measured. Much research is still required.

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Impacts on Marine Mammalsy Physical (including physiological)

y Damage to body tissue

y

Gross damage to ears causing permanent and/or temporarythreshold shift

y PTS (Permanent Threshold Shift): Reduction in auditory sensitivity

y After exposing belugas and whales to one second tones at 0.4, 3,10, 20, and 75 Hz, it was found that levels between 192 and 201 dBcaused a 6 dB reduction in sensitivity, but tones at 400 Hz had noeffect on sensitivity.

y TTS (Temporary Threshold Shift): Reduction in auditory sensitivitywith eventual recovery

y Chronic stress effects that reduce viability

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Impacts on Marine Mammalsy Perceptual

y Masking of biologically significant soundsy communication signals, echolocation, sounds associated with

orientation, finding prey, or avoiding natural or manmade threatsy Behavioural

y Disruption of foragingy Avoidance of particular areas

y May play a major role in whales swimming aground

y

Altered dive and respiratory problemsy Disruption of mating systems

y Indirecty Reduced prey availability which results in reduced feeding

rates

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Impacts on Fishy No documented cases of mortalityy Lab studies show low proportions of lethal effects from low

frequency sounds

y There are possible effects on hearing when exposed atclose range

y There is a high likelihood that distribution/swimming

patterns are affectedy Possible dispersion of spawning aggregations or

deflection from migration paths

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Impacts on Invertsy No documented cases of mortality

y However there have been beachings of giant squid

y Possible effects on growth and reproduction rates

y Possible stress in gastropods

y Possible change in swimming patterns

y Seismic impacts on zooplankton, eggs, and fish larvaey May arrest development of eggs

y And developmental anomalies are known to occur in smallproportions

y Also seismic activity has been known to damagereproductive processes, auditory functions, and have othereffects on benthic invertebrates such as crab and lobster.

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Impacts on Turtlesy The impact of seismic activity on sea turtles has been

observed to cause an increase in swimming speed and

in avoidance activity resulting in changes in migratorydirection

yAlso a loss in hearing sensitivity has also beenobserved.

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Referencesy DFO (2004). Review of Scientific information on

impacts of seismic sound on fish, invertebrates,marine turtles and marine mammals. DFO Can. Sci.

Advis. Sec. Habitat Status Report. 2004/002.

y Gordon et al. (2003). A Review of the Effects ofSeismic Surveys on Marine Mammals.Marine

Technology Society Journal. 37-4.

y Pinet, P. R. (2009). Invitation to Oceanography (5th ed).Jones and Bartlett Publishers; Sudbury, MA.