A tiny red seaweed confirmed as completely new to science has been identified off Cornwall by the British public body Natural England. Underwater surveys of maerl beds off the south coast of Cornwall have uncovered a “remarkable array of rare and scientifically important seaweeds, including species never before recorded in the UK”, it says.
Among the findings are species last seen centuries ago and the newly identified Ceramium (pincer weed), which is said to be so small that it has never been possible to identify before.
“Divers brought up living fragments to the surface, allowing scientists to grow it in the lab and sequence its DNA for the first time,” Natural England, the British government’s advisory body for the environment, says.
The vast majority of England’s maerl beds are in Cornwall, and are formed by slow‑growing, coral‑like red seaweed. They are described by scientists as among the most biodiverse shallow‑water habitats in the north‑east Atlantic, providing nursery grounds and shelter for a wide range of marine life and locking away carbon which becomes trapped in the sediments.
Seaweed expert Francis Bunker, who discovered the minute Ceramium in these surveys, said that “finding species new to science in our waters is thrilling”. “But it also shows how much biodiversity is still hidden in these beds and what we stand to lose if these habitats are damaged before we’ve fully understood them.”
Tiny Wonder — The newly identified Ceramium species, a minute red seaweed discovered in Cornwall's maerl beds and confirmed as completely new to science through laboratory DNA analysis. Photo: Natural England
“Physical disturbance, for example through scallop dredging, pollution and climate change, poses ongoing threats to maerl beds,” Bunker said.
Natural England Senior Marine Officer Angie Gall said that more than 350 species living on the surface of the maerl beds have been recorded, and “that’s only the beginning”. “Many more species live hidden within the maerl or appear at different times of year. There is still so much to uncover. Maerl beds are living archives of our natural history. Protecting them is essential if we are to safeguard marine biodiversity for future generations,” she said.
World-leading seaweed taxonomy authority Professor Christine Maggs said she had first encountered the tiny Ceramium in the early 1980s, and had “been wondering about it ever since”. “It’s so minute that you can only study it if divers bring it up alive, and even then it takes careful cultivation to get enough material to work with. Natural England’s surveys finally provided the missing piece of a scientific puzzle I’ve been trying to solve for most of my career,” she said.
The surveys also recorded Ulva rigida, a green sea lettuce never previously confirmed in the UK, Neofolia rosea (little rosy tongue weed) only found once before in the UK, at this site, and Bonnemaisonia clavata, a delicate red seaweed last seen in British waters in the 18th century, Natural England said.
Following initial reports from citizen scientist divers on the Seasearch project, Natural England’s work in 2023 and 2024 led to the discovery of extensive areas of previously unknown maerl beds off England’s south coast, “a reminder that even in well-studied waters, significant ecosystems remain hidden”, it said.
