Snowflake Coral

Overview

Carijoa riisei, commonly known as the snowflake coral, is a colonial soft coral recognized for its tangled, branching growth form and prominent white polyps. Unlike many other corals, it lacks symbiotic algae and functions as an obligate predator, relying entirely on capturing food from the water column.

Appearance

This species forms dense, bushy clusters of hollow, branching stems that can reach up to 30 cm in length. Each stem is typically white to pale pink and features eight longitudinal grooves. When extended, the polyps display eight white, pinnate tentacles that resemble the delicate rays of a snowflake, giving the coral its common name.

Distribution & habitat

While originally described from the Virgin Islands, this coral is now considered a widespread, invasive species in many tropical and subtropical marine regions, including the Pacific and Atlantic Oceans. It thrives in shaded environments such as crevices, ledges, lava tubes, and the undersides of coral heads. It is also frequently found on artificial structures like ship hulls, piers, and oil platforms, which facilitate its dispersal via biofouling.

Biology & behavior

Carijoa riisei is a highly adaptable and aggressive competitor that can rapidly colonize hard substrates. It reproduces both sexually and asexually, releasing free-floating planula larvae that settle on new surfaces. Because it does not require sunlight, it often outcompetes slower-growing native species, such as black corals, by overgrowing them and monopolizing available space and food resources.

Feeding

As a passive suspension feeder, it captures a variety of prey, including zooplankton, phytoplankton, and diatoms. Its ability to thrive in turbid, nutrient-rich waters allows it to maintain high levels of productivity even in areas where other corals might struggle.