Antarctica's the Weddell Sea has its largest fish nursery ever discovered beneath it.

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They discovered 60 million icefish nests.

Researchers on a Weddell Sea icebreaker were amazed to see 60 million icefish nests scattered across the icy surface. Every nursery is watched after by a ghostly parent, making this the world's largest known breeding colony.

When his graduate student Lilian Böhringer, watching the camera feed on the German icebreaker RV Polarstern, called up to the bridge, Autun Purser of the Alfred Wegener Institute was on the bridge keeping watch for whales. On one of the ship's operations, the Ocean Floor Observation and Bathymetry System (OFOBS), a one-ton camera towed behind the boat, provided a live feed to Böhringer, who was monitoring the seabed.

At a distance of roughly 10 inches (25 cm), Böhringer could view fish nests poking out of the seafloor in all directions and covering an area of 93 square miles (240 square kilometers). "The camera kept panning [over the ocean floor]. They may be found all over the place. "According to Böhringer, he spoke with Live Science.

A species of icefish native to the cold southern oceans, the notothenioid icefish (Neopagetopsis ionah), cut the nests out of the muck on the seafloor. They are the only animals known to date whose blood contains no hemoglobin. They are referred to as "white-blooded" because of this.

"We felt we had found something wonderful after calling the home institute the next day," Purser added.

After the first discovery, the team performed several passes over the spot, towing the camera at a deeper depth to obtain a complete picture of the colony.

Icefish usually nest in large groups, but Purser said the most he's ever seen was forty nests. After a thorough investigation, this nesting place is expected to have 60 million nests. Purser remarked, "We've never seen anything like this."

One adult fish kept an eye on an average of 1,700 eggs in each of these nests.

A 3.6-degree Fahrenheit (2-degree Celsius) upwelling was the research subject, bringing them to the general area. "Our goal was to understand how carbon moves from the ocean's surface to the seafloor and what communities are in the water column," Purser added.

As the water rises, scientists discovered minute zooplankton near the surface among the icefish larvae that swim to the banquet before returning to the seafloor, where they breed after hatching. Icefish were expected to be found in the upwelling due to the abundance of food. However, a reproductive colony several orders of magnitude larger than previously seen was not.

These large icefish colonies appear to be an important element of the local ecosystem because of the abundance of fish carcasses found nearby, which suggests that they serve as food for the nearby Weddell seal population and protect nests.

Under the worldwide Commission for the Conservation of Antarctic Marine Living Resources, an initiative is underway to establish the colony as a Marine Protected Area.

A strange thing about the icefish colony is that it appears to have a clearly defined boundary. Like penguin colonies, Purser said: "[The colony] went from dense to nothing, much like penguin colonies." "It was like a line in the sand," he said.

They discovered that the "line in the sand" they were referring to was the outside edge of a warm upwelling. Regardless of whether or not this is a coincidence, the upwelling appears to provide a suitable breeding ground for the icefish.

The crew of the Polarstern left behind two cameras before they left the area to investigate the unique environment. As of April 2022, Purser intends to return to the Weddell Sea.

Purser stated, "I'm sure there's much more to discover."

Current Biology released this study on January 13th.

Reference : https://www.livescience.com/largest-icefish-breeding-colony-discovered-antarctica

Image source : https://pixabay.com/id/photos/antartica-es-alam-patung-es-3427141/

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