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Natural coral reefs grow oh-so-slowly. Artificial ones sometimes grow by leaps and bounds, as scientists from Harte Research Institute for Gulf of Mexico Studies at Texas A&M University-Corpus Christi recently discovered.

The scientists are in the midst of a two-year survey of marine life around artificial structures in the Gulf , which I've been covering since late summer . In October, they spent two weeks on board the R/V Falkor . On that cruise, they created 3-D maps of several artificial reef study sites using multi-beam sonar.

In post-cruise analysis of those maps, it was clear that several of the sites have had new structures placed on them. Jennifer Wetz , a project manager in the Fisheries and Ocean Health Lab at HRI, says that between August and October, one site, MU-828, had two or three additional platform structures reefed there. In the multibeam image, you can clearly see the new structures (the ones on the left), which contrast nicely with those that have been there for quite a while and have become part of the natural landscape. Another platform structure is headed for the MU-828 site, while two other study sites will each get two additional platforms, and another site is scheduled for one addition. Fishermen and divers in the area likely didn't even realize how these artificial reef sites have been growing, Wetz says.

The Texas Parks and Wildlife Department manages the state's rigs-to-reef program. Under this set-up, when a platform is due for removal, its owners can donate it to a state's federally approved program, along with a chunk of cash that is supposed to equal half of what it would have cost the company to take the structure out (and that could be from $1 to $7 million or more). The company saves some money, while the state gets funds to run the program. The owner caps the well under the structure according to federal regulations, the federal Bureau of Safety and Environmental Engineering approves the reefing plan, the Corps of Engineers issues a permit (because this is all happening in navigable waters), and the structure is, usually, dropped on its side or in pieces in a designated reef site.

In all, 133 rigs or oil- and gas-associated parts have been converted to reefs off the coast of Texas , according to Chris Ledford, TPWD artificial reef program specialist. Thirty-four of those were reefed in place. Water depths range from 60 to 305 feet, with most in the 150-280 foot range, he says.

TPWD recently revamped its rigs-to-reefs website to show platforms in negotiations to join the artificial reef program . Besides the platforms on this list already reefed or scheduled to be dropped in HRI study sites, a total of 13 more have agreements in place with another seven still in negotiations. The bad news is that this reflects the still-rapid and controversial pace at which these structures - which provide valuable habitat for marine life, not to mention popular fishing and diving spots - are disappearing from the Gulf. But the good news is that at least they're ending up in the water, where they still have potential to provide habitat, rather than becoming scrap metal.

As of October 2, 2012, the Department of Interior also approved two new reef planning zones off Corpus Christi , which will improve options for reefing in the region, Wetz says.

HRI scientists plan to head back out in the spring for another round of counting fish at the study survey sites. I'll post more about what they learn.

Previously in this series:

Counting Fish: Gulf of Mexico Artificial Reef Survey

Counting Fish: on the artificial reefs

Counting Fish: well, thanks Isaac, no counting fish this week

Counting Fish: Longlines, Lionfish and Liberty Ships

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