“We were not expecting to see this level of biodiversity in the Argentine deep sea, and are so excited to see it teeming with life,” said the expedition’s chief scientist, Dr. María Emilia Bravo of the University of Buenos Aires and CONICET. “Seeing all the biodiversity, ecosystem functions, and connectivity unfolding together was incredible. We opened a window into our country’s biodiversity only to find there are so many more windows left to be opened.”
Covering at least 0.4 square kilometers, the Bathelia reef is nearly the size of Vatican City. This stony cold-water coral provides habitat for other organisms, such as fish, crustaceans, and octopuses. Recognized as a Vulnerable Marine Ecosystem (VME) indicator species, Bathelia candida has been documented throughout the Southwestern Atlantic Ocean, with the largest patches off the coast of Argentina, but scientists hadn’t understood its extent until this expedition. The team found Bathelia reefs 600 kilometers (373 miles) further south than its known range, at 43.5° latitude.
The team also documented Argentina’s first deep-water whale fall at 3,890-meters-depth and a rare phantom jellyfish—a deep-sea jelly that can grow as long as a school bus. Whale falls—places on the seafloor where a whale’s body lands after the animal dies—serve as temporary ecosystems, providing food for animals, including octopuses, sharks, and crabs. In addition, the scientists observed ancient Bubblegum coral gardens (Paragorgia arborea) nestled among large sponges in the 3,000-meter-deep Malvinas Trough near Tierra del Fuego.
“We collected an unprecedented number of chemical, physical, and biological samples that will be used to understand connections in our waters for years to come,” said Dr. Melisa Fernández Severini of Instituto Argentino de Oceanografía and CONICET. “These samples represent a unique opportunity to understand not only how extraordinary these extreme ecosystems are, but also how vulnerable they can be.”
The team’s primary goal was to locate cold seeps, deep-sea environments where methane and other chemicals released from the seafloor serve as energy for microbes, which provide sustenance for animals like clams, mussels, and tube worms. They found one active seep measuring 1 square kilometer—twice the size of the Bathelia reef—which included a large patch of chemosynthetic clams.
Scientific understanding of how cold seeps and deep-sea coral reefs interact is still in its adolescence, said Bravo.
The team observed trash in some areas, including fishing nets, garbage bags, and a VHS tape in near-pristine condition, owing to the durability of plastics. The sticker on the side of the tape is in Korean, but the team is not sure how it arrived off the Argentinian coast or how old it is.
“With every expedition to the deep sea, we find the Ocean is full of life—as much as we see on land, and perhaps more because the Ocean contains 98% of the living space on this planet,” said Schmidt Ocean Institute’s executive director, Dr. Jyotika Virmani. “We have been privileged to work with outstanding scientists across three expeditions in Argentinian waters, and look forward to seeing their research continue to unfold, unlocking new understanding and inspiration.”
