Explorers marvel at 'Brittlestar City' on seamount in powerful current swirling around Antarctica

Millions of starfish-like creatures catch passing food in 4 km/h current; cod shelter from 'rattling' current in folds of huge bubblegum coral

Map showing the location of Macquarie Ridge Click here for more information.

Census of Marine Life-affiliated scientists, plumbing the secrets of a vast underwater mountain range south of New Zealand, captured the first images of a novel “Brittlestar City” established against daunting odds on the peak of a seamount – an underwater summit taller than the world’s tallest building.

Its cramped starfish-like inhabitants, tens of millions living arm tip to arm tip, owe their success to the seamount’s shape and to the swirling circumpolar current flowing over and around it at roughly four kilometers per hour. It allows Brittlestar City’s underwater denizens to capture passing food simply by raising their arms, and it sweeps away fish and other hovering would-be predators.

Discovery of this marine metropolis, announced today along with important new insights into seamount geology and physics, highlighted a month-long April expedition to survey the Macquarie Ridge aboard the Research Vessel Tangaroa of New Zealand’s National Institute of Water & Atmospheric Research, host of the Census of Marine Life seamount programme, CenSeam. The voyage was largely funded by the New Zealand Foundation for Research, Science and Technology.

Formed at least 12.5 million years ago, Macquarie Ridge stretches 1,400 km south from New Zealand to just above the Antarctic Circle. A multi-disciplinary scientific team from New Zealand and Australia extensively sampled this intriguing ecosystem deep beneath waves familiar to fishing trawlers but rarely reached by scientists.

Macquarie Ridge is one of a few places where the Antarctic Circumpolar Current is detoured in its endless clockwise churn at the globe’s southernmost latitudes – playing a vital part in the global ecosystem, merging and mixing waters of the Atlantic, Indian and Pacific Oceans.

Dense aggregation of brittlestars on rock with arms feeding in water current. Also soft corals, sponge and worms. Click here for more information.

Usually corals and sponges dominate seamount peaks, filtering food that arrives on the current. Biologists aboard the Tangaroa believe Brittlestar City is the first dense aggregation of another filter feeder, the brittlestar, ever found atop a seamount, and they credit the summit’s shape and extraordinary current circumstances there, 750-meters above the ocean floor.