By Coral Reefs Blog From Rice University

“Fake it till you make it: Artificial reefs can provide realistic habitat for reef organisms”

A couple of summers ago, I went on a scuba diving trip to Grand Cayman in the Cayman Islands. One of the sites that I dove was the sunken USS Kittiwake, a hence decommissioned Navy submarine rescue ship, which now sits on Seven Mile Beach’s sandy bottom 60 feet below the surface, adjacent to surrounding reefs.

Dive sites in the Cayman Islands. Kittiwake is on the left, located on the west side of Grand Cayman.

Dubbed as the “…single most significant occurrence in a decade for Cayman’s dive industry,” the sinking of the USS Kittiwake in 2011 served not only as a recovery measure to combat recent losses in coral cover, but also as a new diving attraction for ecotourism.

But what purpose does a sunken ship have at the bottom of an ocean?

Specifically, USS Kittiwake serves as an artificial reef. Artificial reefs provide an alternate home for fish and other marine organisms, as well as antecedent topography for coral larvae to settle on, because the natural reef may be damaged and/or organisms may not be present on the natural reef.

Once the USS Kittiwake was placed on the ocean floor, encrusting organisms such as sponges and corals could begin to settle. Soon, small fish were attracted, and larger animals will then be attracted. Ideally, the artificial reef will be almost identical to a natural reef.

Why do we need an artificial reef in Grand Cayman?

As I mentioned previously, the sinking of USS Kittiwake is a recovery measure for recent losses in Grand Cayman coral cover. For the Caribbean as a whole, coral cover has declined 80% since the early 1980’s.

Prior to 2005, Grand Cayman mean coral cover declined from 25.7% in 1997 to 15.4% in 2001, most likely due to bleaching events, lethal coral diseases, and algal overgrowth, according to Jones et al. (2008).

The Cayman Islands were affected by the Caribbean-wide bleaching event in 2005, but were even more affected by a mass bleaching event in summer 2009.

This 2009 bleaching event was a response to a “hot deep water gyre” and unusually high solar radiation due to a periodic lack of cloud cover (Campbell, 2010). Grand Cayman had the most severe impact from this event than on the other two Cayman Islands (Campbell, 2010). In addition, the Caymans fall victim to physical damage from tropical storms and hurricanes, which strips soft corals and sand from shallow reefs, as well as causes breakage of hard corals (Jones et al., 2008).

As mentioned above, artificial reefs provide an alternate shelter to organisms, and sufficient antecedent topography for corals to settle on. Because of these recent coral losses in Grand Cayman, it is paramount that the ecosystem is preserved.

Having an artificial reef in Grand Cayman is especially important to maintain high marine biodiversity, since the island is home to 36 different coral species, and 350 types of fish.

How effective is this artificial reef, anyway??

For the Kittiwake reef specifically, the effects are beginning to show. 8 months after its sinking, the effectiveness was evaluated. According to blogger smeltst, corals and sponges had already begun to be form.

I can vouch for this observation, too: I saw small corals forming, some algae, and lots of fish swimming through the ship.

More studies will need to be conducted in the future to see the long-term effectiveness of the wreck.

Disadvantages to Artificial Reefs

However, there are some disadvantages to artificial reefs. For example, USS Kittiwake is an old, rusty ship that poses a risk of contamination. Heavy metals intrinsic to the ship’s construction contain toxic materials that may gradually affect the wildlife that settles there.

Because the artificial reefs tweak the physical architecture and complexity of reef structure, another disadvantage to artificial reefs is the stability. Natural coral reefs are secure in the benthos, but artificial reefs, if not designed properly, may not be stable. The Kittiwake is sturdy and weighed down, but other artificial reefs may not be this way.

Currently, there are multiple options for reef conservation. Such options include a shade cloth for shield corals from UV exposure, reef balls, and Ecoreefs. The effectiveness of these options are limited, as most are recent developments in conservation.

Citations:

Bowerman, Todd. “The Disadvantages of Artificial Coral Reefs.” Animals. Demand Media, n.d. Web. 25 Apr. 2015.

Campbell, Jessica. Recovery of Caymanian Reefs after a coral bleaching event; can Marine Parks help? Diss. Bangor University, 2010. Print.

Jones, Loureene, Pedro M. Alcolado, Yuself Cala, Dorka Cobián, Vania Coelho, Aylem Hernández, Ross Jones, Jennie Mallela, and Carrie Manfrino. “The Effects of Coral Bleaching in the Northern Caribbean and Western Atlantic.” Status of Caribbean Coral Reefs after Bleaching and Hurricanes in 2005. By Clive R. Wilkinson and David Souter. Townsville, Australia: Global Coral Reef Monitoring Network, 2008. 73-83. Print.

“Kittiwake Sites in Cayman, Kittiwake Wreck Dive – Kittiwake Cayman.” Kittiwake Sites in Cayman, Kittiwake Wreck Dive – Kittiwake Cayman. Dive 365 Cayman Islands, 2015. Web. 24 Apr. 2015.

Lindberg, Bill, and Mark Schrope. “Understanding the Ecology of Artificial Reefs: No Simple Answers.” EDIS New Publications RSS. Sea Grant Florida, Jan. 2010. Web. 25 Apr. 2015.

McDonnell, Tim. “Watch: These Reefs Are Beautiful-but Most of the Coral Is Dead.” Mother Jones. N.p., 6 May 2014. Web. 25 Apr. 2015.

Smeltst. “USS Kittiwake – 8 Months on the Reef.” www.scubadiving.com. N.p., 12 Dec. 2011. Web. 25 Apr. 2015.

“What Are Artificial Reefs and Where Are They Located in the Mid-Atlantic? | Mid-Atlantic Coastal Environment.” EPA. Environmental Protection Agency, 24 Jan. 2013. Web. 25 Apr. 2015.

Wong, Curtis M. “USS Kittiwake, U.S. Navy Ship, Sunk In Cayman Islands To Create Coral Reef (VIDEO).” The Huffington Post. TheHuffingtonPost.com, 7 Jan. 2011. Web. 24 Apr. 2015.

Photo Credit: “Aggressor Fleet and Dancer Fleet – Luxury LiveAboard Diving.” Aggressor Fleet and Dancer Fleet – Luxury LiveAboard Diving. N.p., n.d. Web. 24 Apr. 2015.

For more on this story go to: http://coralreefs.blogs.rice.edu/2015/04/25/uss-kittiwake-a-savior-to-grand-cayman-reef-restoration/