Gorgonia

Sea Fans, members of the Gorgonian family, are a group of soft corals that can grow to enormous sizes with mesmerizing colors.

With over 3,400 different species of sea fan, it would be difficult to dive into them all, so let’s look at Gorgonia as a whole, their general characteristics, where to find them, and what makes them so special.

Gorgonia Coral Categorization

Kingdom: Animalia
Phylum: Cnidaria
Class: Octocorallia
Order: Alcyonacea
Family: Gorgoniidae
Genus: Gorgonia

Identification

Sea fans are magnificent to see, and trust us; you’ll know when you have seen one.

Sea Fans closely represent a flattering leafless tree, with its branches fanning out from the trunk in all directions.

These soft corals can often be seen with a thicker “stem” or central skeletal structures running through the center of the branches, consisting of gorgonin with smaller nodes expanding from them.

This central skeleton supports all the branches of the coral. Once again, similar to the trunk and branching system of a tree.

Credit: Sean Nash – Flickr

As the coral grows new polyps, the branches of the coral further expand.

This, and their tendency to sway in the currents, is what gives these invertebrates their fan life features, as well as their name.

Gorgonians can be found in a variety of colors, including pink, purple, yellow, red, orange, and white.

Although the branching systems of different sea fan species differ, in ideal conditions, all species tend to grow to a similar max height – approximately 60cm (2 feet).

That said, some species of sea fan, such as the Gorgonia ventalina (Purple Sea Fan), can grow up to 180cm tall and 150cm wide.

Habitat and Distribution

Sea fans can be found growing in colonies from shallow reefs to depths as deep as 1000m. Because of the many species, the Gorgonia can be found in all the seas, particularly in tropical regions.

These locations include:

• South Atlantic
• Indo-Pacific
• West Indies
• Malay Archipelago
• Bermuda
• Bahamas

Sea fans can be found attached to coral reef beds, bedrock, or in large forests spread along rock shelves.

Although sea fans can be found in most waters, they thrive in areas with stronger currents, which increases their feeding abilities.

Feeding

Similar to most soft corals, sea fans expand their polyps out from the skeletal structure, which allows them to filter out the water for necessary nutrients, which in the sea fans’ case, is plankton.

Credit: Chaloklum Diving

Sea fans will spread out their polyps to form a net-like structure that filters passing water (hence the advantage of steady currents).

Reproduction

Some, but not all, Sea Fan species reproduce sexually. Like many corals, Gorgonians grow in colonies comprising either males or females, although, in some cases, both male and female sea fans can be seen grouped in large coral reefs such as sea fan forests.

During reproduction, sea fans release their respective gametes (eggs and sperm) into the water, where they are externally fertilized.

Because they are freely released into the ocean, gametes or fertilized eggs can drift far distances from their parent corals, landing and forming new colonies in new locations.

Once eggs are fertilized, they begin transforming into a planula larva. These larvae swim for a time before settling and metamorphosing into a polyp.

From the first polyp, additional buds and polyps will grow, eventually forming a majestic sea fan colony.

Credit: Rawpixel

It’s also possible for sea fans to reproduce asexually (where offspring are produced from a single parent).

This can occur in two ways – fragmentation or budding.

When coral “buds” it forms new polyps from the parent coral, later separating and forming a new colony.

Fragmentation, whether it be intentional or accidental, occurs when a piece of coral has been removed from the parent and begins to form a new colony in the area in which it lands.

This commonly occurs during rough sea conditions or through predators and larger sea species disrupting reefs.

Predators and Threats

Like many soft corals, sea fans are a favorite for the small ocean slugs known as nudibranchs.

These colorful sea slugs, among others such as species that fall into the Ovulidae family (false cowries), particularly the Flamingo tongues snail (Cyphoma gibbosum), are specialized feeders of Gorgonians, sliding along the corals surface, feeding periodically on the invertebrate.

Credit: Laszlo Ilyes

Apart from sea snails and slugs, some fish, crustaceans, and humans all pose a risk to these soft corals.

Similar to most of the ocean’s coral, Sea fans are threatened by climate change and increasing ocean temperatures. However, some researchers suggest that they may be more resilient than they think.

Defenses and Adaptability

Although many coral species are currently suffering due to changing global climates, some researchers, such as those from the University of Exeter, believed that as these corals sway towards warmer waters, they are likely to migrate further North to balance out the water temperature.

Although this has not been demonstrated yet, it’s believed that this could make Sea fans, along with other warm water corals, more resilient to the increasingly warmer ocean waters.

According to Dr. Jenkins, this could keep waters suitable for these species for the next 100 years.

Migration, however, is not this animal’s only line of protection. As these corals cannot move, they rely on chemical defenses to protect them from common predators such as the previously mentioned sea slugs.

Credit: Jill Lenoble – Flickr

Secondary metabolites and calcified sclerites are formed by the sea fans which are used to deter such predators.

In one study, the effectiveness of sea fans’ chemical and structural defenses was tested.

This study showed that with the presence of sclerites, feeding by the Flamingo-tongue snail was reduced by 49%.

This deterrent also saw an 87% drop in feeding from tropical fish.

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