Whales, dolphins, squid and fish
are among the many marine species that rely on underwater sounds for everything
from foraging to communication. By listening to what's happening in the water
around them they able to orientate themselves, locate prey, avoid predators or
even select a mate.
But the underwater sonic
landscape is changing. It's being affected by commercial shipping, sonar
systems used by the navy, for example, or by fishing industries to locate fish
schools and blasting for construction. Marine seismic surveys – which explore
subterranean geological features for petroleum, natural gas and mineral
deposits – are also becoming more common in response to the world's growing energy
demands.
These extremely loud man made
underwater noises can harm marine animals. Seismic surveys can cause barotrauma
in fish, which is the damage of tissues due to rapid changes of pressure
following the loud sounds wave travelling through the water. Fish eggs that are
laid in the vicinity of seismic surveys are also more likely to die off. And
recent research has shown that more zooplankton dies near seismic surveys.
These are the tiny animals that form the base of the marine food chain,
underpinning entire oceans' productivity. All of this means that seismic
surveys can have serious consequences on marine ecosystems.
Until now there's been no
evidence about the potential effects of seismic surveys on seabirds. My
colleagues and I recently published a study that assessed the foraging
behaviour of African penguins before, during and after seismic operations
conducted within 100 km of their two largest breeding colonies.
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