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Deadly silence threatens marine environments

Environment

URBANISATION and nutrient pollution are silencing wildlife and causing marine ecosystems to fade.

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Researchers from the University of Adelaide in South Australia have found that “eutrophication” caused by run-off from adjacent land and sewage are disrupting nearby ocean life.

The natural ambience and sounds of the ocean are essential for helping fish navigate waters and locate ideal breeding grounds.

The marine “soundscape” comes largely from the snapping of shrimps, but also the rasping of sea urchins and fish vocalisations.

The study investigated kelp forests and seagrass beds in St Vincent’s Gulf off the coast of the South Australian capital Adelaide.

Research leader Ivan Nagelkerken said sound was very important for some species of fish and invertebrates to find sheltering habitats in reefs and seagrass beds.

“The nutrient pollution causes different animals in the ocean to find it harder to find these habitats because it is quieter,” he said.

“If this is affected you can immediately infer that without replenishment of the species there will be no sustainable population of animals in the sea.”

The researchers used a cost-effective monitoring underwater microphone known as a hydrophone to measure the sounds and ordinary audio recorders to analyse the readings.

They compared audio recordings of these polluted waters with audio recordings at natural high-CO2 underwater volcanic vents, which show what water conditions are predicted to be like at the end of the century under global ocean acidification.

The results showed a similar pattern of sound reduction in both the degraded ecosystems and the potential ecosystem soundscapes affected by climate change.

Associate Professor Nagelkerken said the results were applicable to areas affected by nutrients coming from nearby agriculture worldwide and could be happening in diverse habitats such as the Great Barrier Reef off the east coast of Australia – the world's largest coral reef system.

“With ocean systems, they can usually deal with some sort of stress as long as it is not too much and too frequent,” he said.

“But if you add too many stressors like the acidification of oceans, warmer oceans, nutrients on top of that, over fishing, then these habitats degrade very rapidly.”

Associate Professor Nagelkerken said the best course of action would be to tackle the issues in local areas by reducing some of the manageable stressors, which would buy time for ecosystems to battle climate change naturally.

The study titled The sounds of silence: regime shifts impoverish marine soundscapes was published in the journal Landscape Ecology.

Adelaide has three long-standing universities, Flinders UniversityUniversity of South Australia, and the University of Adelaide, each of which are consistently rated highly in the international higher education rankings.

This is a Creative Commons story from The Lead South Australia, a news service providing stories about innovation in South Australia. Please feel free to use the story in any form of media. The story sources are linked in with the copy and all contacts are willing to talk further about the story.

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