[Coral-List] From Les Re: Artificial reef - cement or metallic /w electrical stimulation?
Kaufman, Leslie S
lesk at bu.edu
Sun Jul 9 12:01:44 EDT 2017
Hi all. Biorock as a reef restoration tool is purveyed by Dr. Tom Goreau and his colleagues via the NGO, “Global Coral Reef Alliance”; their website with many beautiful photographs is here: http://www.globalcoral.org. Note that GCRA is very different from the “Coral Reef Alliance” at http://coral.org/.
I was good friends with Tom for decades. I had seen several of the Biorock installations, during many phases of development of the process, and I also knew Wolf Hilbertz a bit. During that time, Tommie asked me to assess the Biorock process objectively to strengthen the credibility of the enterprise. Under this mandate I spent some time studying the process and the existing projects, including a visit to Permuteran, in Bali, which I think may still be the largest of these installations.
Biorock as applied to coral reef restoration actually involves two components: the accumulation of (one hopes) durable limestone on the base framework of iron reinforcing bar, and the growth of corals on the new carbonate. Dennis has provided some good background on the Biorock “electric reef” structures and the problem with brucite forming instead of calcium carbonate. However, it does appear that under the right conditions, limestone is deposited (I’ve seen cross-sections with several centimeters of apparent carbonate overlying the rebar), and it remains long after the current is turned off. I saw this on structures whose solar electrical supply had failed months or years prior to my visit, though I did not run any tests on the material.
As for the corals, that is a bit more complicated. I’d rather sidestep directly confronting GCRA claims about increased coral growth rates on Biorock structures. The limited experimental literature on this topic is generally not supportive, and photographs I’d seen taken over time of individual coral colonies at Permuteran suggested to me that the corals placed on these structures were growing near the maximum nominal rate for their species, but not many times faster than this. They were in very good condition, however, as compared to conspecific colonies on nearby patches of reef. At first I thought that this was just due to the fact that the colonies were elevated in the water column, above the fine mud of Permuteran Bay. That probably was a factor, but in addition, I learned that there was an inspiring level of community engagement, involving scores of people (including many kids) swimming around the structures every day, lovingly removing coral predators and competitors. I reported on this little social miracle in Bill Precht’s “Coral Restoration Handbook” and if anyone is interested there is a longer discussion of this matter there.
In conclusion, there are things that we can learn from Biorock, both encouraging and precautionary, and it is well worth learning from. However, the evidence for Biorock as a magical process that is far superior to other methods of coral reef restoration is, unfortunately, very weak at best. I do suspect that we may have undersold a potential contribution of Hilbertz’s idea to some kind of hybrid bio-engineering approach to shoreline protection. The practicality of this rests partly on the precision with which the mineral composition can be controlled. So lately my sense is that Biorock as a coral reef restoration method is interesting though not miraculous, and perhaps worth approaching, but with great caution. Best is to speak with Tommie about it. Actually, as has already been said here by John Ogden and others, the very best is to push the Paris accord forward and meanwhile do everything we can to stick our fingers in the dike for existing reef habitat. Like other forms of ecological restoration, coral reef restoration can plug some of those holes for a while, over and over again, and as it matures and is ever more deeply informed by science, technology and good governance, it could well prove to be a critical tool. Just not outside the bigger picture of what we are doing to and with this world.
Professor of Biology
Boston University Marine Program
Faculty Fellow, Pardee Center for the Study of the Longer-Range Future
Betty and Gordon Moore Center for Science
lesk at bu.edu<mailto:lesk at bu.edu>
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