World Ocean Day wrap: five ocean stories

Happy World Ocean Day! To celebrate, Cosmos is looking back over what we have written about our oceans and seas in the past six months.

Here is a tribute to our big blue bodies of water.

Mapping the undersea landscape of the reef

Four researchers on a boat, despite the pandemic.

About 160 kilometres off the Queensland coast, the RV Falkor is exploring the deep blue waters of the southern Great Barrier Reef in search of drowned worlds

The research vessel – operated by the Schmidt Ocean Institute – is nearing the end of a month-long expedition to map undersea features that formed during the last Ice Age, to help us better understand today’s rapidly changing reef environment.

Energetic ocean eddies on the rise

As the ocean heats up, swirling eddies are getting more active.

A team of Australian researchers has found that climate change has made ocean eddies, which are drivers of ocean currents and weather, increase in activity over the past few decades.

Ice floes displaying ocean eddies off the kamchatka peninsula.
Ice floes displaying ocean eddies off the Kamchatka Peninsula. Credit: NASA / Wikimedia Commons

“The changes we found suggest that regions that were already rich in eddies are becoming even richer. This includes the eddy-rich Southern Ocean around Antarctica, as well as some of the world’s major boundary currents like the East Australian Current,” says lead researcher Josué  Martínez Moreno.

Dazzle to survive

Diversification of the stunningly colourful fairy wrasses was propelled by sea-level changes during the last ice age, according to an Australian study published in the journal Systematic Biology.

The resplendent coral fish, from the species-rich Cirrhilabrus genus of the Labridae family, emerged about 10 million years ago. But the genomic study found they diversified just 3–5 million years ago, during the Pliocene/Pleistocene when sea levels were in constant flux.

Wrasse1 1 jpg
Credit: Yi-Kai Tea

“The rise and fall of sea levels allowed for populations to mix, while also isolating populations,” says lead author Yi-Kai Tea, from the University of Sydney. “These repeated events promoted speciation by acting as a ‘species pump’.”

Maybe more importantly, there are some EXCELLENT looking fish in this article.

Anthropocene: the musical

In sonic terms, Earth’s waters have segued from classical to heavy metal.

Since the (first) Industrial Revolution, the soundscape of the ocean has been undergoing a drastic revolution too. No longer do whale calls or pounding surf dominate – instead, sounds generated by human activity ring through the water, from fishing, shipping and resource exploration, to infrastructure development and more.

An international team of scientists has now released the biggest review of marine noise pollution yet, finding significant evidence that anthropogenic noise is affecting marine wildlife, from whales to invertebrates, as well as their ecosystems.

They document how human-generated noise disrupts animals’ behaviour, physiology and reproduction, and in extreme cases even causes death.

Year of the quiet ocean

Despite the ocean getting noisier with human activities, last year, as pandemic-related lockdowns enveloped the world, our oceans – just like our cities – fell more silent than they likely have been since the onset of globalisation. Now, scientists hope to study exactly how the resultant quiet has affected marine species usually besieged by the sound pollution from shipping, fishing and other anthropogenic ocean traffic.

The study marks the first time the poorly understood relationship between artificial sound and ocean creatures will be thoroughly examined at a global scale.

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