Ships to Reefs

Ships to Reefs HMCS Yukon in Mission Bay, San Diego
Photo Credit: California Ships to Reefs

Sinking old warships creates new habitats for marine species.


Old ships, new life. I'm Bob Hirshon and this is Science Update.

The HMCS Yukon lies 100 feet below the surface off of San Diego, California. But the Canadian warship wasn’t sunk in battle. Instead, it’s been turned into an ecologically friendly artificial reef, now home to thousands of animals. California Ships to Reefs vice president Dean Rewerts says that before sinking, all toxic materials are removed from a ship and then large holes are cut into it.

This is for access by divers and also by fish, where they can establish breeding populations. Almost immediately when the vessel hits the bottom of the ocean, a layer of calcium carbonate forms on the steel, that not only gives a foundation for the other things to latch on and start growing, it also protects the steel.

He says the Yukon and other ships are helping re-establish fish species that have been depleted across their natural range. I’m Bob Hirshon, for AAAS, the science society. 

Making Sense of the Research

Reefs are important and diverse marine ecosystems in which small organisms like algae and coral form complex structures that attract other fish and marine life. Humans have been creating artificial reefs accidentally for as long as we've been sailing ships (and occasionally sinking them). And we've been creating them deliberately to attact marine life for at least four hundred years: people in 17th-century Japan submerged rocks to grow a type of seaweed called kelp.

Over the past several decades, people all over the world have sunk ships, aircraft carriers, old tires, and even New York City subway cars to create artificial reefs. For a long time, the costs sometimes outweighed the benefits. Many structures sunk in the past weren't cleaned well and leached toxic chemicals into the ocean. Others, like the tires, broke apart and damaged natural coral reefs. 

As you heard, the California Ships to Reefs program is one of many artificial reef creation programs active today. Responsible organizations make sure that the ship (or other structure to be sunk) is thoroughly cleaned and stripped of all known toxic substances. They cut holes in the structure to make it more accessible to marine life. They also make sure to choose a location far from vulnerable marine ecosystems, and away from strong ocean currents that could carry parts of the structure to unwanted places. 

So far, the results for ships like the HMCS Yukon appear positive. Thirteen years after being sunk, the Yukon is home to a thriving reef ecosystem. It's also a popular spot for scuba divers. Time will tell if it continues to be a positive contributor to underwater life. But with so many human activities damaging marine ecosystems, it's a worthy effort to at least try to build some of them back up.

Now try and answer these questions:

  1. What is a reef?
  2. How can a sunken ship serve as an artificial reef?
  3. What have been some of the problems with past attempts at artificial reefs?
  4. What are some of the steps organizations currently take to prevent those problems from happening again?

You may want to check out the October 25, 2013, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: An ocean quadcopter gives researchers a sky-high view of the stormy North Atlantic, autonomous underwater vehicles that search for sunken treasure, and behind the untimely death of the octopus.

The California Ships to Reefs website has more information on the project.

Learn why coral reefs are important to people on land in the Science Update Tsunami Barriers.

Going Further

For Educators

The Last Reef blog post previews an informative new movie about coral reefs and the threats they face.

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