Marine ecology: It’s getting too noisy for the oysters

Shipping, seismic surveys, military activities, wind turbines or deep-sea mining – things are getting louder in the ocean. This man-made noise in the water has been increasing for years. According to the Federal Environment Agency, in some regions it has even doubled or tripled in the last 50 years.

What is barely noticeable to humans significantly disturbs creatures such as whales, seals, birds, many fish and even some invertebrates such as squid. Because they use sound for a variety of vital activities such as communication, finding mates and food, avoiding enemies and navigation. “A change in the background noise caused by humans can have a negative impact on the biological fitness of individual animals and entire populations,” says the German environmental authority.

Sound of the ocean obscured

Research from the University of Adelaide now shows that noise from human activities also has a significant impact on shellfish such as oysters. The noise created by humans disturbs the animals during a critical process, namely when they settle in certain regions. The ocean’s natural sound is being drowned out by the increase in human-made noise pollution, said Brittany Williams, lead author of the study, published in the journal »Proceedings of the Royal Society B” has been published.

“Many marine larvae rely on natural sounds to navigate and select their homes,” explained the researcher. This process is disrupted by human-generated noise. In addition, the disturbance poses a problem for conservationists who want to use natural sounds to attract oysters to restored reefs to recultivate marine ecosystems, they said. According to the researchers, this acoustic enrichment is less effective on noisy coastal strips near large cities and urbanized waterways.

Marine ecosystem suffers

This is indicated, for example, by the fact that in their study the scientists were unable to increase larval recruitment in environments with strong human noise pollution. This suggests that the noise pollution is masking the actual sounds of the ocean. This situation has potentially profound implications for the vitality and resilience of the marine ecosystem, warned study co-author Sean Connell.

Because oysters play an essential role as “water filters” in the health of rivers and coastal waters. The shellfish filter the water – the Sydney Rock Oyster, for example, manages four liters per hour, the Japanese Pacific oyster even 24 liters. Multiply that by the millions of oysters that live in some river systems and the animals become the “kidneys” of a river, said oyster farmer Sheridan Beaumont, who farms on the Hawkesbury River, a 45-minute drive north of Sydney.

Alternative to sewage treatment plants

While they filter the water, the shellfish not only absorb their own nutrients, they also suck in particles at the same time. These are then transported to the seabed. In this way, the water quality as well as the clarity of the water is improved. Clearer water allows more sunlight to pass through. At the same time, in regions where oysters live, the deposition of oyster droppings creates a nutrient-rich seabed. This combination allows seaweed to thrive, as a group of Australian researchers report in the academic magazine »The Conversation« once explained. And that in turn promotes mussel species, worms and crabs and ultimately forms “the basis for the entire food web on the coast.”

Oysters are so efficient that Swedish researchers put them in one Study from 2011 once rated as a cost-effective alternative to sewage treatment plants. The importance of oysters was once demonstrated in the Chesapeake Bay, the largest estuary on the East Coast of North America, where the loss of oyster reefs turned an ecosystem of previously clear, fish-rich water into a murky, algae-strewn broth. Oysters also provide a safe haven for young fish and small marine invertebrates. The small sea animals can even help in the fight against global warming – because they absorb carbon.

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