National Geographic

Artificial Reefs

Source, Copyright and original article: R. J. Kern, National Geographic News

Shipwrecks may have redeeming ecological value. The ships often become artificial reefs and habitats, providing shelter for the very creatures threatened by humanitys original intrusion.

Red Sea researchers have found several shipwrecks have become thriving coral communities. These artificial reefs attract divers, easing human pressure on natural reefs.

"Coral reefs all around the world are experiencing substantial decline, partly due to human activities," says marine biology professor Yehuda Benayahu, who is studying how artificial reefs become part of the natural environment in the Red Sea. The University of Tel Aviv project is supported by the National Geographic Society's Committee for Research and Exploration.

The project is looking at how coral reef communities around ten Red Sea wrecks serve as models of artificial reefs. Benayahu is comparing the artificial reefs with adjacent natural reefs in the area.

"With time, the shipwreck becomes part of the natural environment," he says.

He hopes the study will provide information for future artificial reef projects aimed at the restoration and conservation of their natural counterparts.

New Habitats Utilized Quickly

When a ship sinks, it immediately becomes shelter for marine organisms. Such habitats provide new food sources, greater protection for juveniles, and more space for settlement, says Benayahu.

Space is at a premium in a coral reef environment. "The new habitat is utilized by fish very quickly," says Benayahu. Coral, which is composed of small and delicate polyps, develops more slowly, covering a shipwreck's surface over a period of many years.

The ships in Benayahu's study range in age from 16 to 130 years, representing various stages of reef development in the same locality. The ships close proximity to natural reefs allows scientists to make comparisons between the two environments. "It's a wonderful opportunity to study the rate of development and the potential of use of artificial reefs," says Benayahu.

What are the differences between a coral community that develops on a shipwreck and a natural reef?

"Orientation of space may play a role in determining what kind of corals and how fast they grow on horizontal or vertical features," says Benayahu. "We are able to predict, with quite a lot of success, what kind of corals will appear on various surfaces."

Most shipwrecks, especially those with intact masts, represent vertical structures that attract soft corals, such as the colorful dendronphya and scleronephthya, which add attractive framework to many reefs in the Red Sea and elsewhere in the Indian and Pacific oceans.

"Ships made of wood provide a different hosting environment than those built of steel," says Benayahu. "Steel is a very successful choice of reef as wood decays. Steel structures are also covered fast by calcareous algae, which provide an adequate surface for coral larvae to grow quickly."

Absolute Similarity

"With time, there is an absolute similarity between natural and artificial habitats," Benayahu says.

Another advantage of artificial reefs is that they can enhance the development of rare coral species that are not often found in natural reefs.

"The Red Sea is a paradise for discovering new species," says Benayahu. "It is one of the richest reef habitats in the world, in terms of density and diversity of species."

Perhaps the most unexpected advantage of shipwrecks that act as hosts for corals, is that they can ease human pressure on natural reefs.

"The presence of artificial reefs as an alternative dive site can reduce the stress placed on the natural reefs," says U.S. National Oceanic and Atmospheric Administration scientist Mark Eakin. "In many cases, artificial reefs will decrease the total dives on natural reefs."

Source, Copyright and original article: R. J. Kern, National Geographic News