‘Biological chorus’ beneath the waves of the Hauraki Gulf

‘Biological chorus’ beneath the waves of the Hauraki Gulf

The most comprehensive acoustic study of marine life in the Hauraki Gulf has recorded the whales, dolphins, snapping shrimp and sea urchins that create an ‘orchestra-like’ sound beneath the waves.

The most comprehensive acoustic study of marine life in the Hauraki Gulf has recorded the whales, dolphins, snapping shrimp and sea urchins that create an ‘orchestra-like’ sound beneath the waves.

University of Auckland PhD candidate Rosalyn Putland from the Institute of Marine Science gathered and analysed more than half a million minutes of sound from six hydrophone listening stations for the research, which was done over an eighteen month period.

Focusing on the coastal marine environment, this study is the largest and longest conducted to date in New Zealand waters.

“You could think of the sounds of the marine environment in the Gulf as a biological chorus, with each species contributing its own unique sound in the same way an individual instrument contributes to an orchestra,” Ms Putland says.

The study helps establish a baseline of data that can be used to measure changes and human impacts on the Gulf over time, which could contribute to policy and management decisions in years to come.

“What this study does show is that while we might think of life below the surface as relatively silent, it’s actually anything but.”

Some surprises from the data included the recording of a high number of earthquakes measuring 4 or more on the Richter scale - some from up to 750km away – as well as the detection of the sound of surface wind and rain on the seafloor.

The Gulf’s soundscape also changes over the course of the seasons, with higher sound levels during spring and summer and at dusk and dawn.

The types of sounds and frequency also differed between the six listening stations which were tens of kilometres apart. Dolphins were most commonly recorded at the outer Gulf stations of Horn Rock, Flat Rock and Jellicoe Channel, while Bryde’s whales were most frequently recorded at Flat Rock and Jellicoe Channel. Dolphin and whale recordings were rare at inner Gulf listening stations located at Waiheke, Bean Rock and Shearer Rock.

The study is published in Scientific Reports and was funded by a Rutherford Discovery Fellowship and a scholarship from the Royal Society of New Zealand.

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