[Coral-List] Artificial reef - cement or metallic /w electrical stimulation?

[Dennis Hubbard]

Philippe:

While this is an area outside of my expertise, I do have some unique
history on this topic. First, all the photos I have seen of reef balls show
localized fish aggregations but little or no coral actually atop them. I'm
sure that someone can come up with a photo of a reef ball or pile of cinder
blocks with anomalously high coral cover, but none of these have created
any real new structure, vis a vis recent discussions of coral growth vs
reef building and spatial complexity vs diversity. The bottom line here
seems to be that if you drop anything on a flat bottom with little or no
complexity/protection, fish will be attracted to them. Awhile back a friend
who worked with early ALVIN projects described myriad fish hugging close to
leaking toxic waste drums (including nuclear material) in Hudson Canyon
(wish he'd sent a photo).

On the other matter (electrical stimulation of CaCO3 precipitation), I
believe this started out on St. Croix when a researcher named Wolf Hilbertz
(the spelling is only an approximation) set up a series of electrified
chicken-wire structures on Tague Reef just NW of then West Indies Lab where
I was the newest marine geologist. I believe the project was funded by the
Endowment for the Arts and was creating underwater sculptures. Somewhere
along the line, the idea of creating engineering structures rose to the
surface and I remember a number of tongue-in-cheek discussions about
creating a chicken-wire English Channel Tunnel (pre-Chunnel) and turning on
the power until it could be pumped out and paved. Since then, a number of
folks have broadened the scope of the idea to include artificial reef (aka
"biorock") structures. Ive seen a lot of nie photos with corals on the
structures, but still have not seen anything that I would call a true "reef
structure".

By way of history, the early experiments were powered by a small
wind-generator, but the Virgin Islands government made them abandon that
power source after a couple of Pelicans got injured. This was replaced by
solar panels and the pelican community got even by fouling them.

Reminiscence aside, samples of the carbonate were sent to Lynton Land, then
at UT-Austin, for analysis. It turned out that the carbonate was Brucite, a
polymorph of CaCO3 that is not stable in sea wateras soon as the current is
turned off. After awhile, WIL asked the PI to not return, so he abandoned
the St. Croix experiments, which still littered the forereef last time I
checked (wires, rotting chicken wire and no carbonate). If you want details
on the chemistry, you might contact Lynton directly; he's retired and an
environmental activist in the Chesapeake Bay area last time I heard - but
still one of the best geochemists I've ever known. I believe the
experiments subsequently appeared somewhere else and somehow Walter
Cronkite was involved, but don't have any details.

The bottom line is that this is probably why the method isn't "more well
known". You should take my comments as parenthetical information and
personal opinion only, but to my knowledge everything in this missive is
accurate. This experience may have something to do with my general lack of
excitement over artificial "reefs" as something that in any real functional
way substitute for the real thing. If your main interest is attracting
fish, them my comments may be less pertinent. However, it seems like
something that dissolves in sea water once the power supply is lost as not
a formula for success. Perhaps this problem has been resolved; it's been
awhile since I checked and perhaps the structures are more robust than all
the photos I've found on the web..

Best,

Dennis

On Thu, Jul 6, 2017 at 7:24 AM, Philippe Sanchez <pipobs at gmail.com> wrote:

> Hi all,
>
> I've been looking at some artificial reef projects, specifically in the
> UAE. Reef balls seem to be quite popular. A friend recently told me about
> increasing growth and survival rate by applying a small electrical current
> (I'd never heard of this before). I read the paper (Goreau, T.J. 2014) and
> it seems very promising. I wondered why this wasn't more well known??
> Perhaps it's too expensive for people to set up?
>
> Does anyone here have any experience working with such a project or can
> give some insight on the pros and cons of this innovative method?
>
> Thanks!
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-- 
Dennis Hubbard
Chair, Dept of Geology-Oberlin College Oberlin OH 44074
(440) 775-8346

* "When you get on the wrong train.... every stop is the wrong stop"*
 Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"