• HOME
• COURSES
• DIVING
• DIVE SITES
• EQUIPMENT
• INJURIES
• LESSONS
• SEA LIFE

Home › Sea Life › Marine Species › Invertebrates › Sea Fans

Interesting Facts about Sea Fans

[Sea Fan Phylum: Cnidaria] [Class: Octocorallia] [Order: Malacalcyonacea] [Family: Gorgoniidae]

The genus Gorgonia contains around five hundred (500) different types of sea fans (known as gorgonians). Most of the soft coral sea fan classification is represented by a variety of fanlike formations.

This section contains information about sea fan corals, including where they are found, what they eat, and how the colonies of tiny polyps grow into huge fanned out structures.

Sea Fan Habitats and Geographical Range

Like most filter-feeding soft corals, the gorgonians also need a marine environment with current-rich, warm water.

Worldwide, the predominant regions to find sea fans are tropical and subtropical reefs, but especially:

• Eastern Pacific (e.g the coasts of Central and South America)
• Indo-Pacific Regions (Indonesia, Philippines, Great Barrier Reef, PNG)
• Some areas between Africa and Asia (e.g. The Red Sea)
• Western Atlantic (Florida, Caribbean Sea, Bahamas, Gulf of Mexico)

Despite being less common, some sea fan species also inhabit the deeper terrains of the transition zones in some temperate waters (many thousands of metres deep).

Nonetheless, they are strictly 'marine invertebrates' that would not survive in brackish or freshwater environments.

Instead, they thrive best when they can attach themselves to robust substrates, such as coral reefs, rocks, or even the skeletons of dead corals.

Here's the thing:

The optimum depth range for most types of sea fans is quite shallow, for strong sunlight penetration. As a result, the typical sea fan habitat will be between ten (10) and forty (40) metres (30 to 130 feet) below the surface.

Furthermore, the colonies of tiny filter-feeding polyps grow a lot faster in areas with strong water currents, due to a rich supply of plankton and other microscopic food particles.

Characteristics of the Sea Fan

So, what exactly is a sea fan? Using simplified sea life terminologies, the basic definition of a sea fan is a delicate lace-like soft coral that belongs with the Gorgonian group (e.g. order Alcyonacea).

Unlike many of the hard coral species that create rigid reef structures, such as staghorn coral, the basic shape and formation of sea fans is usually a fan-shaped whippy structure that shakes and sways (without breaking) if ocean currents are strong.

Moving on...

Flexible scleroprotein (known as gorgonin) creates the main structural strength of the skeleton. In most species, it provides strong support for the outer branches of the colony - along with any additional branching nets or tissues.

Sea fans grow in a variety of sizes and colours, especially those with subtle tones of red, purple, orange, and yellow.

The average size of a sea fan ranges between thirty (30) and 150 centimetres across.

Even so, the black sea fan (Iciligorgia schrammi) is one of the biggest of all living sea fans, measuring about two (2) metres tall (79 inches).

The Ecological Importance of Sea Fans

One of the little-known sea fan facts is that their branches provide essential shelter for a variety of marine organisms.

Not only do these elegant structures host brittle stars, pygmy seahorses, and shrimps, but they also help to filter sea water and contribute to the healthy biodiversity in coral reef ecosystems.

Interesting Fact: It's easy to think that common sea fan corals and sea whips are the same. Actually, both are types of gorgonians - and closely related - but they differ in several important ways.

What Do Sea Fans Eat?

As the tiny polyps grow, which may be as little as a few centimetres per year, they spread outwards and usually face the prevailing oceanic currents. This adaptation creates a large surface area for them to ensnare their prey and sift plankton particles from the water column.

Sea Fan Species List

How Do Sea Fans Reproduce?

Sea fan reproduction can occur in two distinctly different ways - sexually and asexual budding. Either way, both of these reproductive methods are vital for the long term survival of sea fan populations.

Sexual Reproduction

The primary method used by sea fans to create new colonies is "broadcast spawning". Most of the sea fan species have separate colonies of males and females (they are dioecious animals).

After releasing thousands of eggs and sperm into open water, usually aligned with temperature changes or moon phases, random fertilisation occurs.

Then...

Fertilised eggs develop into larval planulae before they eventually sink to the ocean floor and attach themselves to a suitable rigid surface (e.g. coral) and grow as a new colony. This is how sea fans can spread across large areas.

Asexual Reproduction

The process known as "asexual budding" is a way for damaged colonies to recover from fragmentation (e.g. pieces broken off by destructive storms).

Individual polyps, or fragments of the sea fan coral, reattach themselves to a substrate and begin to grow, thereby expanding the size of the colony.

Sea Fan Threats and Predators

Even though sea fan corals tend to be quite resilient, a number of natural and human-induced activities threaten the long term survival of healthy reef ecosystems.

For example, some of the natural predators of sea fans cause large amounts of destruction, especially:

• The flamingo tongue snail (Cyphoma gibbosum)
• Bearded fireworms (Hermodice carunculata)
• Fish species (e.g. butterflyfishes, angelfishes)
• Barnacles
• Sea sponges

Whereas, some of the most damaging human-caused threats include coral diseases (e.g. Aspergillosis), climate change (including ocean acidification), underwater garbage pollution, and overfishing.

Pro Tip: The IUCN Red List of Threatened Species assessed the pink sea fan (Eunicella verrucosa) in 1996 and cites their conservation status as "Vulnerable" (VU).

Divers also enjoyed reading about...