[Coral-List] Rebar, algae, paint, alternatives; compiled responses 3

Michele & Karl michka at fellenius.net
Fri Dec 9 21:31:05 EST 2005

Coral listers,

Very informative responses on alternative materials. I am recommending:

-we do not use metal-based anti-fouling paints
-we try to obtain silicon-based anti-fouling paints
-we look into getting plastic coated rebar and possibly, stainless steel
-we look into getting plastic mesh
-and in the interim, just use the galvanized rebar & mesh as is until these
other alternative materials have been obtained. All attachment points to be
cable-tied, rather than using wire. Since I had no algae for several months
using regular rebar, we buy some time and maintain productivity while
materials can be obtained.

Thanks again for all your opinions and references for more info. This last
week. Really helpful. Below are the last series of responses compiled for
your info.

I meant to contact you as well.  Yes, proximity to metallic antifoulants
alone would be enough to at least retard the coral growth.  What may be
beneficial would be to consider the use of new-generation, silicon
antifoulants (expensive) that are non-toxic and work by slowly sloughing
off their super-slippery surface.

A short-term alternative would be to have your frames epoxy powder
coated and then baked, leaving a hard paint-like surface.  Refrigerator
baskets and shelves are treated in this way.  The coating does chip,

A last suggestion would be to try the electro-galvanic process
recommended for accelerated accretion on artificial reefs.
Controversial and also expensive but worth trying.  We did so for other
reasons in coral propagation experiments and decided it was not
effective, especially in the matter of algal control when compared with
algivorous surgeonfish in the grow-out tanks.

Michael Schleyer

Prof. M.H. Schleyer
Deputy Director
Oceanographic Research Institute
P.O. Box 10712
Marine Parade
4056 South Africa
Post-script to previous message: Electrolytic treatment did reduce algal
fouling - I have just checked the student thesis - but my previous
argument stands.

Michael Schleyer
I was forwarded your email post to the coral listserv.  For the last few
years my colleagues and I have been working in American Samoa on a remote
atoll that was impacted by a ship grounding and subsequent breakup.  We
installed rebar stakes in the reef top in order to mark our survey

We found that rebar and the ship's metal fostered intense growth by
cyanobacteria (blue-green algae).  We hypothesized that this was due to the
fact that in much of the Pacific and certain other oceanic areas, there is
essentially no dissolved iron (Fe) in the water.  It is therefore the
limiting nutrient, and when it is supplied, algae can bloom.  Cyanobacteria
have a special advantage in some nitrogen-limited areas because they can
fix nitrogen.  We have documented a very tight correlation between Fe
concentrations in the water and disrupted algal community structure.  This
is being prepared for publication.

In an effort to stop this process, our agency has spent a lot of money and
time removing as much iron from the reef as possible, including most of the
shipwreck and all of our rebar stakes.  We replaced our stakes with
stainless steel threaded barstock, and the areas around each stake that
were affected are recovering well.

Rust itself is not the problem, because oxidized (rusty) iron is
essentially non-soluble.  But once a crust of rust forms, the iron
underneath can begin to dissolve into a very soluble ferrous (reduced)
form.  In protected sites (such as under sediment or around where a bar
touches a rock) the rebar will dissolve pretty quickly.

So I would work very hard to replace your rebar.  I haven't tried
galvanized, but I suspect that small defects in the zinc coating would
allow seawater access to the rebar, and then the galvanized coat would act
just like a rust crust, keeping out oxygen and allowing the iron to
dissolve and diffuse into the water, fueling the algae.  This might take a
while to occur, just as you saw with the rebar.

We now use only stainless steel and epoxy putty to embed them in the reef.

Hope this is helpful,

Jeff Burgett, Ph.D.   Invasive Species Specialist
US Fish and Wildlife Service, Pacific Islands Office
300 Ala Moana Blvd
Box 50088 (Rm 3-122)   Ph:  (808) 792-9400   Fax: (808) 792-9581
Honolulu HI 96850   E-mail: jeff_burgett at fws.gov
Has anyone from Goreau's camp suggested
the biorock low DC electrical/galvano method?
Evidently any conducting material exposed to DC
current will get coated in CaCO3 precipitate, and Tom
claims that coral growth is stimulated while algae are
inhibited.  I imagine the amount of electricity
required is small, and affordable, but I am not sure.
You can contact him at goreau at bestweb.net

If copper was not so toxic to coral, it would be ideal
for cyanos.  (Copper is also super toxic to
dinoflagellates, which may be why coral are so
The cyanos are certainly flourishing on the coral
tables you made at the Resort; other cyanos are much
more common, such as Lyngbia (spelling?) which is now
covering the sand, 50%, at Enemonet.  I wonder if all
the COTs coral mortality (from Woja to Ajeltake to
Irooj Island) is causing nutrients to build up.
Cyanos, including red Phormidium and other algae,
carpet freshly-killed coral.

Dean Jacobson,
CMI, Marshall Islands
I work with developing new antifouling paints and testing new products that
come onto the market. There is something in what you say regarding proximity
and not just contact. This was a real problem with TBT based paints that
lead to the virtual destruction of the oyster fisheries in North-West
France. This is because TBT has a very long half life (about 3 months) and
so can be very persistent in the wider marine environment around where it is
being used. TBT is now banned so this problem has been dealt with.

The previous responses you have had are correct. Irgarol does work as a PSII
inhibitor and there is a evidence that it can harm corals  - there was a
significant impact found in the corals off Bermuda. Some of the newer
biocides (e.g. Sea Nine) have a half life of less than an hour and are
supposed to be environmentally ³safe². As for the Cu issue, there are some
that would have you believe that around 95% of labile, bioavailable Cu is
bound to particulate material and immobilised in the sediment very quickly
thus becoming harmless to marine life. I am not so convinced of this and
there are studies showing the toxicity of Cu in natural systems.

In short I would not be using biocidal antifouling coatings near coral I was
trying to grow. There are new foul release coatings based on silicon that
are being tested in fish farms at the moment and seem to be showing some
positive results. Applied correctly with an anticorrosive these would
protect your rebars and mesh and would need simple pressure jet cleaning
occasionally or light scrubbing underwater ­ the foul release systems are
designed to have very low free energy and a very smooth surface so fouling
literally cannot get a hold of it, or if it can, it is knocked off very
easily indeed. These coatings are normally used for high speed ships (the
high speed ensures all fouling is released) but if you¹re going to use an
epoxy anti-corrosive with no antifouling, you may as well us a foul-release
coating as it will do the same thing and biota cannot easily grow on it.

Hope this is of help


Dickon Howell

PhD Student
School of Marine Science and Technology
Ridley Building
Newcastle University
Newcastle Upon Tyne

0191 222 5345

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