IN THE KNOW

BLACK CORALS belong to a thorny group under the order Antipatharia with over 150 species.

These creatures are found in seas all over the world in varying depths. They are, however, common in depths reaching 300 meters and even deeper, as they do not need too much light.

Black corals grow in tree- or bush-like forms. Despite the name, they vary in color from white to red, green, yellow, or brown and is seldom black.

Feeding on organic matter that sinks rapidly into the sea, black corals do not have a symbiotic algae associated with them. Instead, they are highly dependent on strong currents for food to reach them.

Growing at a rate of 8-22 micrometers per year, the black corals are the slowest growing deep-sea corals.

Other types of corals in shallow waters grow at a rate of 1 mm per year, or 65 times faster than black corals. Human fingernails grow about 3 mm per year, or 200 times faster.

Owing to their luster and flexibility, black corals have been harvested for centuries to make jewelry, handicrafts and ornaments.

In recent years, the diminishing population of black corals in Mexico and Hawaii has been a cause of concern.

Sensitive to natural or manmade disturbances in the surface ocean and sea floor, black corals may take decades to centuries to recover.

In April, the US Geological Survey Pacific Coastal and Marine Science Center announced the discovery of 2,000-year-old deep-sea black corals, most only two feet tall, in the Gulf of Mexico. Inquirer Research

Sources: US Geological Survey Pacific Coastal and Marine Science Center; aquaticcommunity.com; Hawaii Division of Aquatic Resources; National Geographic Society