A team of scientists from the Center for Genomic Regulation (CRG) in Barcelona discovered that the coral Oculina patagonica, a species of hard coral from the Mediterranean Sea, possesses a dual feeding strategy that allows it to adapt to extreme environments and survive marine heatwaves.
The results were published in the journal Nature, and provide new insights into the resilience of marine species in the face of climate change.
Dual Feeding: Symbiosis and External Capture
The metabolic flexibility of Oculina patagonica is based on its ability to obtain nutrients from two sources:
- Symbiosis with dinoflagellate algae: when conditions are optimal, the coral associates with photosynthetic algae
- Capture of external particles: in hostile environments, it can feed directly on suspended organic matter
This dual strategy allows it to remain active even in turbid or deep waters, where light is scarce and other species collapse.
“The ability of Oculina to live without a photosynthetic partner allows it to colonize areas with low light or intense sedimentation,” explained researcher Xavier Grau Bové, co-author of the study.
From Discreet Species to Resilient Colonizer
Although it was first identified in the Gulf of Genoa in 1966, for years it was thought to be an invasive species from the Atlantic. Recent research confirmed its Mediterranean origin and its millennia-long presence in small populations.
The increase in temperatures and the change in environmental conditions favored its expansion through shallow coastal areas, where temperatures range from 10°C in winter to more than 30°C in summer.
Reversible Bleaching and Survival Without Algae
Unlike other stony corals, Oculina patagonica can expel its symbiotic algae when the water exceeds 29°C, losing its color in a process of bleaching. However, it does not die: it survives until conditions improve and it can reincorporate the algae.
There are even populations that live completely without them, in caves or depths of 30 to 40 meters, where sunlight does not reach.
“When it was first documented in Levantine waters, it was thought it would not survive. But against all odds, it established itself and its populations are growing,” noted Dr. Shani Levy, first author of the study.
Genetics, Evolution, and Comparison with Tropical Corals
The CRG team approached Oculina’s resilience from a genetic and cellular perspective. They sequenced its entire genome, analyzed thousands of individual cells, and developed comparative cellular atlases with algae-dependent tropical corals.
“Oculina is resilient because it does not strictly depend on the photosynthetic products of algae,” highlighted researcher Arnau Sebé Pedrós, lead author of the study.
The Mediterranean as a Natural Climate Laboratory
The Mediterranean Sea, being a semi-enclosed ecosystem, presents extreme variations in temperature, salinity, and nutrients, making it an ideal scenario for studying marine adaptation.
“It functions as a natural stress test. The organisms living here already face extreme fluctuations, giving us clues about how marine life might evolve under accelerated warming,” concluded Levy.
Can Oculina Replace Reefs?
Although this species shows remarkable adaptability, scientists warn that it is not a reef-building coral. Therefore, it cannot compensate for the loss of tropical reefs, which cover less than 1% of the ocean floor, but host a quarter of all marine species.
“The best way to help any marine ecosystem will always be to prevent warming from its source,” emphasized Grau Bové.
