Deep-Sea Discovery: Four New Algae Species Found Off Tanegashima Island
A team of researchers from Hiroshima University has identified four new species of coralline algae in the waters surrounding Tanegashima Island, Kagoshima Prefecture, Japan. The study also led to the revision of two genera and revealed a stark difference in species composition between shallow and deeper marine habitats.
Key Findings- Samples were collected by dredging the seafloor at depths of 30–40 meters at two locations roughly 10 km off Tanegashima Island’s western coast.
- DNA Analysis: Genes psbA, rbcL (chloroplast), and COI-5P (mitochondrial) were sequenced for identification.
- Microscopy: Morphological and anatomical observations were conducted using light and scanning electron microscopy.
- 12 species from five genera were identified.
- New species: Orientalilithon compactum, Roseolithon aggregatum, Roseolithon sparsituberculatum, and Sporolithon variotuberculatum.
- Habitat Gap: Only three of the 12 species found at depth were also present in a nearby shallow rhodolith bed at just 1 meter depth.
"Rhodoliths are unattached, pebble-like nodules, which are formed mainly by coralline algae." — Aki Kato, Associate Professor, Hiroshima University
Dr. Kato emphasized that these structures support marine biodiversity and contribute to long-term carbon storage.
A Striking Ecological Divide"A striking finding... is that completely different biological communities can exist at different depths within the same marine area." — Min Khant Kyaw, Postdoctoral Researcher
This contrasts sharply with other red algae studies, where approximately 80% of mesophotic (mid-depth) species also appear in shallow waters.
The researchers hypothesize that the unique diversity at depth may be driven by warmer near-bottom seawater and high sunlight penetration, enabled by the region’s exceptionally clear waters.
PublicationThe discoveries were published in the Journal of Phycology on May 13, 2026.