Unveiling Uruguay’s Hidden Coral Reefs
Post-Cruise Impact - Visualizing the Deep off Uruguay, 2025
During the 2025 Visualizing the Deep off Uruguay expedition, scientists aboard the Schmidt Ocean Institute’s R/V Falkor (too) revealed thriving deep-water coral reefs and newly documented habitats across Uruguay’s continental margin – one of the least explored regions of the South Atlantic. Through a combination of advanced mapping, ROV surveys, and biological sampling, the mission provided the first detailed glimpse into ecosystems that had previously existed only on maps and in theory.
Led by Dr. Alvar Carranza of the Centro Universitario Regional del Este (CURE), Universidad de la República, Uruguay, the mission set out to study the biodiversity of the region – a critical gap in modern ocean exploration – and to identify, categorise, and assess the health of Vulnerable Marine Ecosystems (VMEs) in the deep waters off Uruguay. This included investigations of deep-water coral reefs, chemosynthetic ecosystems linked to potentially active cold seeps, and the upper abyssal plain, an area largely unknown to science.
The discoveries exceeded expectations. The team found that deep-sea coral reefs off Uruguay are in surprisingly good condition, despite signs of human impact such as derelict fishing gear. These vibrant reef systems are predominantly built by Desmophyllum pertusum, a slow-growing cold-water coral species recently classified as vulnerable to extinction. Among the most striking findings was Mound “L”, a coral structure located at 300 metres depth and spanning 1.3 square kilometres – equivalent to more than 180 football fields – with the tallest mound rising 40 metres from the seabed.
“The project benefits from extensive international and regional collaborations involving a diverse range of institutions,” said Alvar. “These collaborations enrich the project’s scope, enhance its scientific impact, and facilitate the exchange of knowledge and expertise, thereby contributing to capacity building at a national level.”
Professor Angelika Brandt of the Senckenberg Research Institute and Natural History Museum Frankfurt and Sylvie Gaudron of the Université de la Sorbonne joined the cruise, helping to build new partnerships and future plans.
“It was fascinating to see how many species were collected – even new ones among the macro- and megafauna. I was especially impressed by the precision of the ROV’s fine manipulation,” Angelika reflected.
Angelika hopes to continue work on the collected material in Montevideo and Buenos Aires, and to contribute to review papers, while also promoting Challenger 150 research alongside colleagues across Europe and South America.
The expedition also sparked wider collaborations with institutions in Brazil (UFRJ, UFRGS, MZUSP, IO/USP), Argentina (UBA, CONICET), and Chile (UCN) – partnerships that are essential for advancing taxonomy, standardising species identification, and informing policy related to deep-sea VMEs.
“Being part of Challenger 150 has been incredibly valuable for our team,” Alvar added. “It helped us secure support for our Schmidt Ocean Institute proposal, connect with new collaborators, and incorporate additional expertise into our scientific crew.”
Angelika summed up the spirit of the expedition:
“It’s always a pleasure to be part of this important international venture. We’re happy to fill in small pieces of the biodiversity puzzle.”
These discoveries and collaborations reflect the growing capacity for deep-sea research in the South Atlantic and reinforce the shared goals of Challenger 150 and the UN Ocean Decade – to explore, understand, and protect the deep ocean.
This story forms part of the Challenger 150 Post-Cruise Impact series, sharing reflections and discoveries from expeditions contributing to the goals of the UN Ocean Decade.