[Coral-List] Mineral Accretion/ Biorock (Dennis Hubbard)
dennis.hubbard at oberlin.edu
Mon Jun 24 15:47:18 UTC 2019
Thanks for the update. The extent of my direct knowledge dates back to when
Wulf Hilburtz was a visiting researcher at West Indies Lab; he was
ultimately asked to not return for reasons I won't go into except to say
that, at about the same time, the the local CZM office asked for the
submerged chicken-wire structures and the cables going to them to be
removed (there was never any compliance and the problem was resolved by a
passing storm). Ironically (at least to those of us at WIL), CZM had
required that the small wind generator be replaces with solar panels due to
pelicans being injured by the blades when they tried to land. Eventually,
the birds got even by defecating all over the panels which were never
The Brucite diagnosis was based on analyses done by Lynton Land. I believe
that this was done at Tom Goreau's request, but the results were never made
public to my knowledge (the latter is my recollection and I am open to
someone correcting me - if the Brucite diagnosis and related stability
issues have been published, please give me a citation). On the
timing/current-intensity issue, can someone explain the
geochemical-intensity relationship that results in different mineral
polymorphs. Again from an aging memory of times long gone, I remember the
currents being weak enough that one could grab the bare wires and
structures deployed on St. Croix with no negative result. Some time later,
when we ultimately checked, there was no current going to the submerged
structures on the forereef. This led to some discussion of whether the
eventually significant carbonate coatings on the St. Croix forereef
(likewise, nice and rigid once the wiring was no longer maintained).
Perhaps, the deployment strategies used elsewhere were significantly
different from those on St. Croix. Having seen no publications and not
being able to discern and visible differences between "current" and
"no-current" structures on the web page I viewed awhile back, I just went
on to other things until this tread started. If you have any more specific
information on "Tom & Wolf’s 1980’s structures", could you perhaps pass on
On Mon, Jun 24, 2019 at 9:36 AM Andrew Ross <ross.andrew at mac.com> wrote:
> Hi Dr Baker,
> I’ve been puttering in raw, anodized & electrified steel for a bunch of
> years. We recently set nursery head-started *Acropora* to a cement block
> & electrified steel AR array in Jamaica, in collaboration with Coralive
> I would tend to agree with you, that the rates of growth (in branching
> *Acropora*) seem to be about the same on the electrified steel as they
> are on the nursery line, or any other elevating low-stress structure. We’re
> not measuring specifically on this project and the current control has
> apparently been problematic. There is definitely some chemistry/pH
> excitement in the ~1.5m around & downstream of the anode, but everything
> gets back to normal beyond that halo.
> Dr Hubbard,
> Brucite forms when the current is too high & accretion too rapid. To
> tune-down, you do get a nice durable aragonite- some of Tom & Wolf’s 1980’s
> structures are just off the dock at Discover Bay Marine Lab and still very
> solid (unplugged since ~'92). Once a structure has been plugged-in for a
> few months, the nicely uniform aragonite insulates the steel. The issue
> comes if you chip the aragonite away, such as to plant a coral to the
> electrified metal. All current goes to that bare point and a mushroom of
> foamy brucite forms within a week or two, which smothers any nearby
> flora/fauna incl. coral. Even fully-electrified brucite is mushy so coral
> attachment is poor, to be lost in the first bit of weather. In this, Tom’s
> suggestion that the structures are self-healing becomes a little
> Mike & Alice,
> Buki Rinkevich suggested using electrified chickenwire to stabilize
> chronically reanimated rubble-fields when I was in grad-school. We’ve got
> plenty of shallow sites of fist-size cobble that move & pulverize every
> living thing in any good norther (storm), regardless of how established the
> CCA(etc). Buki's idea was to peg-out the wire over the cobble and then
> scatter a layer of cobble/rubble overtop, and then plug it in to make it
> all into a single rigid sheet/mass (hopefully before the next bit of
> weather). We’ve never tried it, though I do think it’s worth following-up.
> Bigger issues, certainly, but this may be a head-starting fix at high-value
> per-spot scales.
> Andrew M. Ross, Ph.D.
> Seascape Caribbean
> On Jun 21, 2019, at 11:19 AM, dmbaker via Coral-List <
> coral-list at coral.aoml.noaa.gov> wrote:
> To follow on Dennis’ comment: the papers I have seen on bio rock have
> lacked proper controls.
> There was no comparison of corals on bio rock vs. corals on natural
> There was no use of an unnelectrified bio rock framework to refute the
> hypothesis that elevation in the water column was a factor in coral growth
> and health.
> There are many impressive photos of corals on bio rock nurseries but fewer
> rigorous studies of their performance. Some works have reported that
> skeletal density is reduced.
> Moreover, the electrolysis process can form a number of strong acids which
> could have small-scale effects (though likely rapidly diluted in seawater).
> Interesting comment on the rapid dissolution once electricity ceases.
> David M. Baker, Ph.D.
> Associate Professor
> The University of Hong Kong
> The Swire Institute of Marine Science
> School of Biological Sciences
> Kadoorie Biological Sciences Building 6S-14
> Pokfulam Road, Hong Kong, PRC
> dmbaker at hku.hk<mailto:dmbaker at hku.hk <dmbaker at hku.hk>>
> Coral-List mailing list
> Coral-List at coral.aoml.noaa.gov
Chair, Dept of Geology-Oberlin College Oberlin OH 44074
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