The Corals of Saint Brandon
The corals deserve a careful introduction — they are the architects of Saint Brandon, the reason the atoll exists at all, and they are also the most vulnerable of its living systems.
Saint Brandon exists because of coral. Strip the living reef away, and the islands disappear within a single human lifetime — the sand cays would erode, the lagoons would silt, the structural integrity of the place would unravel. The reef is the floor on which everything else stands, and it is built, atom by atom, by colonies of small, slow, soft-bodied animals that secrete calcium carbonate around themselves to make a home. A single coral colony is thousands of individuals working in concert. A single reef is millions of such colonies, layered on top of one another across thousands of years.
The reef at Saint Brandon is one of the more remarkable in the western Indian Ocean. It is largely intact. It is structurally complex. It supports — by the most recent surveys — at least thirty-six documented species of hard coral across eight families, six species of soft coral, and the longest algal ridge in the Indian Ocean. Live coral cover ranges from around 3 to 35 percent across the surveyed sites, with the highest coverage on the western reef wall where the Acropora table corals form their characteristic thickets. The 2024 surveys recorded fish biomass at five of eight sampled sites that exceeded the western Indian Ocean regional benchmark — a measure of how productive an intact reef can still be when it has been spared the pressures that have flattened most others.
What kept Saint Brandon’s reef in this condition is partly its remoteness, partly the long-term fishery management of the Raphael Fishing Company, and partly the quiet good fortune that it has never been heavily exploited for the aquarium trade or the live reef-fish trade that has destroyed reefs across South-East Asia. It is one of the last reefs in the Indian Ocean where a careful snorkeller, drifting with the current, can still see what a healthy coral community is supposed to look like.
The list below covers the species I would have moved through during the nineteen days I was in the water — on the reef terrace and lagoon-patch reefs of L’île du Sud, in the back-reef and reef-flat habitats off Coco, on the eastern reef of Raphael, and at the spur-and-groove zone known to the fishermen as Sharks Point. Not all of Saint Brandon’s coral fauna lives in these habitats; the deepest reef-slope species, the rare cold-water associates of the outer wall, and the species restricted to the northern Guano Islands are not included here. What I have listed is what was around me, in the water, the days I was looking down.
THE HARD CORALS
Acropora hyacinthus — the great pale-blue table coral.
The signature coral of the western reef wall. Forms broad, flat, plate-like tables sometimes more than a metre across, often growing in tiered colonies that look from above like a stack of dinner plates. Fast-growing for a coral — a single colony can add a centimetre of new growth a year. Pale blue, sometimes green or gold-tinged. Visible to drone footage at low tide. See the note on table corals below for a recent scientific revision of this species.Acropora digitifera — finger coral
Stubby, finger-thick branching coral that forms small dense clumps on the reef-flat and back-reef. Often pale brown, sometimes electric blue at the tips. One of the most common branching corals in the lagoon-patch communities.
Acropora humilis. Compact, hand-sized colonies of short thick branches. Common in the spur-and-groove zone and the higher-energy parts of the reef terrace.
Acropora humilis.
Compact, hand-sized colonies of short thick branches. Common in the spur-and-groove zone and the higher-energy parts of the reef terrace.Acropora nasuta
A branching Acropora with characteristically pointed branch tips. Documented in the 1997 transect surveys.Acropora cytherea, A. selago, A. lutkeni
Three additional Acropora species documented at Saint Brandon, all forming branching or tabular colonies on the reef-terrace and reef-crest habitats.Acropora palifera (Isopora palifera) — the back-reef Acropora
A robust, columnar form of Acropora found particularly in the back-reef habitat, where wave energy is lower and the coral can grow in stout vertical columns rather than the broad plates of the open reef.Porites lutea — yellow pumpkin coral
A massive, dome-shaped coral. The bright yellow individuals that grow to the size of small cars on the reef-flat. P. lutea is one of the great reef-builders — slow-growing but long-lived, with single colonies estimated at hundreds of years old. The coral I observed regrowing around the Yu Feng wreck site was Porites lutea.Porites rus, Porites cylindrica
The other Saint Brandon Porites species. P. rus forms massive irregular mounds on the back-reef and lagoon floor. P. cylindrica forms branching columns that grow in regularly spaced patches across the back-reef in 0.5 to 1 metre of water.Pocillopora damicornis — common cauliflower coral
A small, delicate, finely branched coral that dominates the reef-crest and the higher-energy parts of the back-reef. Pink to cream to brown, depending on light and depth. One of the fastest colonisers after cyclonic damage.Pocillopora verrucosa — knob-horned coral
Similar to P. damicornis but with thicker, knobbier branches. Common in the lagoon-patch reefs.Stylophora pistillata — finger coral, club-finger coral
A delicately branched coral with characteristic blunt-tipped branches. Pink, lilac, or pale brown. Common across the back-reef and on the protected sides of the lagoon-patch reefs.Pavona — leaf coral, plate coral
Several Pavona species are documented at Saint Brandon, forming enormous hillocks on the lagoon-patch reefs in a way that is described in the scientific literature as unusual for Mauritius. The colonies grow in convoluted plate-like or vase-like shapes. P. minuta and P. cactus are among the species recorded.Hydnophora microconos — horn coral
A massive coral with characteristic small horn-like projections across its surface. Common on the back-reef habitats.Heliopora coerulea — the blue coral
One of the more unusual corals at Saint Brandon. Heliopora is the only living member of a coral order whose other members went extinct in the Cretaceous. Its skeleton, beneath the brown living tissue, is genuinely blue — a striking colour visible when a fragment is held to the light. Rare but documented in the 1997 surveys.Favia, Favites, Goniopora, Lobophyllia
Smaller massive and brain-style corals that fill the spaces between the larger reef-builders. Favia — the moon corals — are particularly distinctive, with regularly spaced circular corallites that give the colony surface the appearance of a stone wall.Cyphastrea
A smaller massive coral, often forming irregular cushion-like colonies on the back-reef.Platygyra — brain coral
The classic convoluted brain-coral colonies of the lagoon-patch reefs. Platygyra daedalea is the most common species at Saint Brandon.Astreopora myriophthalma
A massive coral with a finely pitted surface, found across the reef-terrace.Galaxea fascicularis
A particularly beautiful coral, with delicate green or fluorescent tentacles extended during the day. Less common at Saint Brandon than at some Indian Ocean reefs but documented in the surveys.Millepora — fire coral
Not a true coral — biologically closer to a jellyfish, and equipped with stinging cells that produce a painful burning rash on bare skin contact. Yellow-tan, finely branched, often growing on the reef-crest and in shallow back-reef habitat. Best photographed, not touched.A NOTE ON THE TABLE CORALS
The signature coral of Saint Brandon’s western reef wall — and almost certainly the most photographed coral at the atoll — is what scientists have, for over a century, called Acropora hyacinthus: the great pale-blue tabular coral that grows in stacked plate-like colonies sometimes more than a metre across.
In August 2025, a landmark genomic study led by Dr Sage Rasmussen of the University of Technology Sydney and Queensland Museum’s CoralBank project, working with an international team across the Indo-Pacific, revealed that Acropora hyacinthus is not, in fact, a single widespread species. It is a complex of at least sixteen distinct species, five of which had been previously unknown to science. The study, published in the journal Invertebrate Systematics, applied genomic-scale DNA analysis to over a hundred and thirty specimens from twenty-two Indo-Pacific regions and revealed what the lead authors called a hidden world of coral diversity that’s been right in front of us all along.
What this means for Saint Brandon is not yet known. Specimens from the atoll were not, as far as I can determine, included in the Rasmussen et al. dataset. The table corals I photographed on the western reef wall, the ones that drone footage skimmed across at low tide, may turn out — when someone finally collects and sequences them — to be one of the newly described species, an existing one with a smaller-than-assumed range, or potentially something not yet recognised at all. The 2013 discovery of Novaculops alvheimi at Saint Brandon suggested that the atoll harbours undescribed fish species. The Rasmussen et al. work suggests that the corals may be hiding their own secrets.
The conservation consequence is significant. If what was assumed to be a single widespread species at Saint Brandon turns out to be a regional endemic with a small range, the urgency of protecting the reef becomes much greater than it currently is. Species with small ranges are more vulnerable to extinction, as the study’s authors note, especially as coral bleaching and climate effects intensify across the Indo-Pacific. Saint Brandon’s reef has remained more intact than most. It may, on closer scientific examination, also turn out to be more uniquely valuable than most.
THE SOFT CORALS
Sarcophyton — leather coral
The large, fleshy, mushroom-shaped soft corals that grow in scattered patches across the reef-terrace and lagoon floor. Cream, gold, or pale brown. They sway in the current. They retract their polyps when disturbed.Sinularia
Smaller, branched soft corals with finger-like lobes. Common across the back-reef and the lagoon-patch reefs.Lobophyton, Nephtys, Cladiella, and others
Several other soft coral genera are documented at Saint Brandon, contributing to the six species recorded in the 1997 transect surveys. Soft corals are particularly abundant on the reef-terrace habitat.Your content goes here. Edit or remove this text inline or in the module Content settings. You can also style every aspect of this content in the module Design settings and even apply custom CSS to this text in the module Advanced settings.
A NOTE ON CURRENT CORAL RESEARCH AT SAINT BRANDON
The 1998 World Bank surveys produced the first systematic baseline for Saint Brandon’s coral fauna. The work has, in the years since, been built on by a series of expeditions — some sustained, some brief — that together represent the slow accumulation of what we know about the reef. The corals at Saint Brandon are still being learned.
The Monaco Explorations Indian Ocean Mission, 2022
In October and November of 2022, the Société des Explorations de Monaco — the modern continuation of the oceanographic society founded by Prince Albert I more than a century ago — chartered the South African polar research vessel S.A. Agulhas II for a two-month, ten-thousand-nautical-mile circumnavigation of the south-western Indian Ocean. The expedition mobilised one hundred and seventy participants of twenty nationalities, including marine biologists, oceanographers, photographers, and artists. After working extensively at the Saya de Malha Bank — the largest seagrass meadow on the planet, jointly managed by Mauritius and Seychelles — the Agulhas II sailed south to Saint Brandon to conduct a dedicated research station around the atoll. The Saint Brandon component was part of a wider study coordinated under the United Nations Decade of Ocean Science. The expedition’s scientific reports are still being processed, but the work fed directly into research projects led by Professor Ranjeet Bhagooli and Dr Deepeeka Kaullysing of the University of Mauritius on phytoplankton biomass, water mass dynamics, and biodiversity along the Mascarene Plateau.
The Couëdel et al. 2023 reef-fish biodiversity study
A peer-reviewed paper published in Ecology and Evolution in May 2023 by Couëdel and colleagues compared the reef-fish biodiversity of the Mascarene region — Mauritius, Reunion, Rodrigues, Agalega, and Saint Brandon. The study used a combination of morphometric analysis, visual surveys, and molecular identification techniques to resolve long-standing taxonomic confusions in the region’s reef-fish community, particularly in the blenny family. Several species names previously thought to apply across the Indian Ocean were confirmed or revised, including Cirripectes randalli, originally described in 1988 from a coral surge channel on the western side of Île Raphael at Saint Brandon — a species whose type specimen is held at the Smithsonian Institution in Washington and whose holotype reads, on the catalogue, simply: Cargados Carajos Shoal, southwestern Indian Ocean, 16°26’S, 59°36’E. The reef around Raphael, where I caught fish from a pirogue, is the spot from which a small species of blenny was first scientifically described.
The Odysseo Foundation and the Saint Brandon Conservation Trust, 2023 onwards
In 2023 the Saint Brandon Conservation Trust was established as the principal non-governmental conservation body for the archipelago. Its founding partners include Odysseo Mauritius — the Mascarene region’s largest oceanarium, located at Pointe aux Piments on the main island — operating through its dedicated conservation arm, the Odysseo Foundation. Odysseo’s Coral Project, run in collaboration with Secore International, the University of Mauritius, and Eco Sud, is pioneering coral restoration by sexual reproduction in the western Indian Ocean — a technique in which coral spawn is collected during synchronous mass-spawning events, the larvae raised in laboratory conditions, and the resulting recruits returned to degraded reef areas. The technique is at the frontier of coral restoration science. Saint Brandon is one of the sites identified for future application of the methodology, with sample collection and ecosystem assessment already underway. A joint expedition between Odysseo, the Saint Brandon Conservation Trust, National Geographic Explorers, and the University of Mauritius reached the atoll in 2024 to begin baseline data collection — a continuation of the work the World Bank began in 1997 and the Mauritian Wildlife Foundation expanded in 2016.The Rasmussen et al. 2025 Acropora hyacinthus study
The most recent and most provocative finding for Saint Brandon’s coral fauna comes from outside the atoll — the landmark genomic study described in the note on table corals above. Applying genomic-scale DNA analysis to Acropora specimens from twenty-two Indo-Pacific regions, the study revealed that what was thought to be a single widespread table coral is in fact a complex of at least sixteen species. Specimens from Saint Brandon have not yet been included in the genetic analysis. The table corals at the atoll await proper sequencing — and may, when sequenced, prove to be among the more biologically distinctive corals in the western Indian Ocean.The University of Mauritius reef-endemism work
A 2021 study published in Conservation Science and Practice by Bhagooli, Naggea, and colleagues established that Mauritius — including its outer islands — has the highest level of marine species endemism in the Western Indian Ocean Faunal Province. The status of these endemic species has, the authors noted, not been comprehensively evaluated. For Saint Brandon, which sits at the heart of the Mauritian outer-island system, the conservation argument is unambiguous: the atoll likely supports species found nowhere else, and the absence of formal status assessment is itself a research priority.Editorial & Commissioned Work
If you would like to be in touch — for editorial commissions, place writing, long-form journalism, or design and brand work — write to me at river@welovethesea.co
I am available to be sent to places. I take a small number of commissions a year, for editors, publications, and brands who want a particular kind of attention paid to a particular place. Travel writing in the conventional sense is not what I do. My work is written from inside a place rather than across the surface of it, paired with original research and field notes from the ground.
A note on this site
The pages here are observational, not authoritative. Where I have drawn on the scientific record and research, I have cited it. Where I have written from my own watching, I have said so. For the formal conservation work being done at Saint Brandon — and there is good work being done — please visit the Saint Brandon Conservation Trust.
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