Snowflake Coral, Carijoa riisei

Snowflake Coral, Carijoa riisei. Underwater photographs taken in Bahía de Banderas, Puerta Vallarta, Jalisco, July 2026. Photographs and identifications courtesy of Greg Timms, youtube.com/@CoralmasterdivesPuertoVallarta/videos. Note: the photo just above shows a Snowflake Coral covered with Cyanobacteria bacterial blooms.

Morphology: Snowflake Coral forms an erect, branching colony. The polyps are cylindrical and have eight pinnate tentacles that resemble snowflakes. The polyps are connected by a living tissue (coenenchyme), which covers the internal skeleton. The skeleton is made up of calcareous particles called sclerites, which provide rigidity to the branches. The branches arise from a single stem, and grow densely enough to have a bushy appearance.  The stem starts out smooth near the base, but has eight ridges higher up.   The branches may be reddish-brown, orange, or whitish in color. The polyps are white, and can withdraw within the coenenchyme if disturbed. Snowflake Coral colonies reach a maximum of 35.5 cm (14 inches) in height.

Habitat and Distribution: Snowflake Coral is found attached to rock, coral, and oyster shell reefs, pilings, ship hulls, other infrastructure, mangroves, in caves, and on other hard substrates. They are azooxanthellate and can grow in shaded or deep water areas. They live subtidally to depths in excess of 700 m (2,296 feet). Snowflake Coral is native to the Indo-Pacific. They have been introduced, and are now established, in the subtropical to tropical Eastern Pacific, Western Atlantic, and Eastern Atlantic oceans. They arrived in the tropical Western Atlantic prior to 1860. They were first discovered in the Tropical Eastern Pacific around 2000. The Snowflake Coral is now found in all Mexican waters of the Gulf of Mexico in the Atlantic Ocean and along the southwest coast of Mexico from, Puerto Vallarta, Jalisco to Guatemala in the Pacific Ocean.

Diet: Snowflake Coral is a suspension feeder. The polyps use their  tentacles to capture phytoplankton, like diatoms and cyanobacteria, and zooplankton, such as amphipods and fish larva, from the surrounding water.

Predators: In the Indo-Pacific, Snowflake Coral is preyed upon by the Spun-of-Light Nudibranch, Phyllodesmium poindimiei, and the Elegant Tritoniopsis Nudibranch, Tritoniopsis elegans. They seem to have few predators in other regions.

Reproduction: Snowflake Coral colonies are almost always gonochoric (male or female for life), but some (1-2%) are hermaphroditic (having both male and female reproductive organs). They reproduce  sexually through broadcast spawning with external fertilization. Unlike many corals, the eggs are heavy, and sink to the bottom, instead of drifting as plankton.  This causes the new colonies to remain near their parents, forming dense bushy clusters. The zygotes develop into planula larva and then metamorphose into polyps. These new polyps reproduce asexually through budding to grow new colonies.  Snowflake Coral can also reproduce asexually, either by  sending out runners (stolens), which send up new stalks, or by fragmentation.

Ecosystem Interactions: Snowflake Coral can form dense colonies that provide shelter and structural complexity for a variety of fishes and invertebrates. However, outside its native Indo-Pacific range, it may have veryfew effective natural predators or other biological controls. Its rapid growth and reproduction can allow it to spread quickly and compete aggressively with native corals and other sessile invertebrates. Snowflake Coral can overgrow neighboring organisms, eventually smothering the underlying host and preventing it from feeding and functioning normally. It is also an efficient suspension feeder, potentially competing with native species for food suspended in the water column. In Hawaii, Snowflake Coral has caused severe damage to black coral forests and has become a significant ecological and economic concern. Because Snowflake Coral has been present in the Gulf of Mexico for more than a century, much of its early ecological impact occurred before modern, long-term ecosystem monitoring was available. As a result, the full extent of its historical effects is difficult to determine. Its more recent expansion into the Eastern Tropical Pacific, however, has attracted considerable scientific attention. Studies have documented serious impacts on native octocorals, including high mortality rates and local losses of some species. One study from Colombia reported mortality rates of up to 87% among affected native octocorals. Interestingly, Snowflake Coral itself appears vulnerable to heavy cyanobacterial overgrowth in the Eastern Tropical Pacific. Dense cyanobacterial growth can cover the colonies, smother the polyps, and interfere with feeding and other normal functions. During the El Niño conditions of the summer of 2026, observations in the Banderas Bay region showed cyanobacterial overgrowth eliminating nearly an entire reef patch that had previously been dominated by Snowflake Coral. Despite this setback, the coral’s rapid growth and reproductive ability allowed new colonies to begin re-establishing themselves.Although cyanobacterial overgrowth may temporarily slow the expansion of Snowflake Coral, it does not appear to provide a reliable long-term control, particularly because the species is capable of recovering and recolonizing affected areas rapidly.

Synonyms: Carijoa rupicola, Carijoa rusei, Clavularia riisei, Clavularia rusei, Paratelesto riisei, Telesto africana, Telesto riisei, Telesto rupicola, and Telesto rusei.