[Coral-List] re: rebar & algae, compiled responses

Michele & Karl michka at fellenius.net
Mon Dec 5 09:55:09 EST 2005

Thanks for all the informative comments on my rebar & algae question. Below
is the compilation of responses. There was consensus on that rebar could be
the source of the cyano increase due to the limiting nature of iron in
seawater. But there were some additional ideas on other contributing sources
as well.

One avenue we are also trying now is to coat the rebar in copper sulphate
paint, otherwise known as an anti-fouling paint. Although such paints are
less toxic than they used to be, I still have concerns about introducing
such chemicals. It is an interim measure as we have decided partially based
on your responses to bring in coated rebar at a later date. The anti-fouling
paint might also be used to coat the galvanized mesh as when mesh is re-used
after being down a few months it is less than entirely galvanized. Also, one
respondent suggested that zinc on the galvanized surface could be less than
ideal due to its toxicity. Painting galvanized rebar and mesh might seem a
bit over doing it, but it might slow any galvanized toxicity issues and also
might take care of weaknesses in the coating brought on by bending the

So the question now is if one uses coated rebar, can one get away with
non-galvanized? And is is anti-fouling paint idea a bit whacky or worth
pursuing in the interim? Any point to painting galvanized mesh and non-bent
portions of galvanized rebar?

I will be checking e-mail but may not be able to compile or respond
regularly over the next while as I am on a trip. But I will follow up with
the listserve and send you an update on the coral status and any
implementation of your ideas in January.

Thanks again. Glad to see all the interest in helping a lil' company get
their nubs growin'


Karl Fellenius
Reef Solutions Vanuatu

> The initial guess here is that iron is probably entering the water from
> oxidation of the rebar. The actually rusting process is just oxidizing, but if
> flakes of reef-bar are coming off, some of this is probably being dissolved
> and providing a nutrient source to the algae. You might want to look up some
> background info on iron and plant growth. Anyway, I will see what I can dig up
> on this end.
> Cheers,
> Mark Chiappone
> Center for Marine Science
> University of North Carolina-Wilmington
> 515 Caribbean Drive, Key Largo, FL 33037
> Email: chiapponem at uncw.edu
> Yes, iron rebar will cause this problem.  You can use fiberglass rebar.  An
> even better method involves planting on Reef Balls and the Reef Ball Coral
> Farming method (contact john at reefball.com for more information on that).
> Thanks,
> Todd Barber
> Chairman Reef Ball Foundation, Inc.
> 3305 Edwards Court
> Greenville, NC 27858
> reefball at reefball.com
>Could be the effect of iron enrichment. As was the case in the Southern Iron
>Enrichment Experiment.....see attached article. Sounds interesitng!
>Maia Mukherjee
> I generally try to use no metal what so ever when I deploy apparati under
> water.  PVC piping is a common favorite among reef scientists, as is
> Plexiglass.  Also, cement works well for providing weight (e.g., cinder
> blocks, or you can pour portland cement into molds of size and shapes of
> your choice).  I also use nylon and fiberglass nuts and bolts for attaching
> things together, instead of stainless steel.  Here is a website that you
> can order from online.  They have quite a selection of materials.
> http://www.mcmaster.com/
> And yes, many cyanobacteria are thought to be limited by the supply of
> bioavailable iron.  Many researchers have reported enhance growth of cyanos
> on rusting ship wrecks and other junk metal.  Galvanized mesh is not
> immune, either, it just dissolves away slower.
> Good luck!  I would love to visit your facility someday, if I ever get to
> go to Vanuatu.
> Best, Ilsa
> Ilsa B. Kuffner, Ph.D.
> US Geological Survey
> Center for Coastal and Watershed Studies
> 600 4th Street South
> St. Petersburg, FL 33701
> From: Andrew Williams <A.J.G.Williams at newcastle.ac.uk>
> Date: Fri, 2 Dec 2005 22:00:22 -0000
> To: Michele & Karl <michka at fellenius.net>
> Subject: RE: [Coral-List] Rebar & algae
> Michele & Karl,
> I am no expert in this field, but something has occurred to me that you may
> not have considered, the nutrients may not be deriving directly from the
> rust...
> Perhaps there is some kind of electrolysis affect at work - have you
> considered the possibility that minute electrical currents may be either
> attracting the algae or perhaps the electrical currents are causing nutrients
> within the surrounding water that are normally 'locked' chemically to H+ or
> OH- (or another anion) to become liberated as a cation (e.g. Na+, K+) thus
> becoming available to algal growth. If the mesh is attached using metal wire
> ties then there may be even greater electrolysis potential.
> My apologies if this sounds absurd!
> Best of luck
> From: William Allison <beliamall at dhivehinet.net.mv>
> Date: Sat, 03 Dec 2005 04:45:50 +0500
> To: Michele & Karl <michka at fellenius.net>
> Subject: Re: [Coral-List] Rebar & algae
> Hi Michele and Karl,
> A possible limiting factor for cyanobactrial growth and some phytoplankton
> is iron so one could infer that the iron source is the cause.
> Seems to me that galvanized can have heavy metal toxin problems.
> If you could manage to supply live photos along with the dried I think it
> would be even more useful and interesting. I have lots of field photos but
> nothing less than say half a cm diam and most considerably larger.
> Cheers,
> Bill
> That iron enrichment increases productivity in the ocean has been
> proven in large scale experiments in the tropical Pacific (pretty wild
> experiments actually - large scale release of iron solution and then
> monitoring the response using remote sensing!), and also there are
> reports of increased benthic macroalgae around historic iron ship wrecks in
> the Pacific. There are references for all this, but I just can't put
> my hands on them at the moment - let me know if your mail server can
> take say 1MB and I will dig them out if I can find the PDFs. So I would
> say that your rebar is probably triggering the algal growth.
> But I don't think that going deeper is going to have the effect you
> are looking for. Algae will photoadapt as well or better than the
> coral and you'll probably end up with the same problem. Using
> galvanised rebar might work, but you might want to consider plastic
> coated rebar or even using sacrificial anodes. The anodes corrode
> first (Zn), leaving the iron intact. I guess its a question of cost
> and what is available locally.
> Good luck with it all, and hope you find a solution
> Simon
> Simon Wilson
> Five Oceans LLC
> PO Box 660, CPO 131, Oman
> Tel/Fax: + 968 24696918 and 24696912
> GSM: + 968 99358053
> and
> PO Box 470, Noordhoek 7979
> Western Cape, South Africa
> Tel/Fax: + 27 21 785 1075
> Cell:  + 27 84 612 6673
> From: andrew ross <andyroo_of72 at yahoo.com>
> Date: Sat, 3 Dec 2005 06:49:06 -0800 (PST)
> To: Michele & Karl <michka at fellenius.net>
> Subject: Re: [Coral-List] Rebar & algae
> Michelle and Carl,
>   I'm working in propagation of Acroporids in Jamaica. I've found that algal
> fouling has a lot to do with temperature, and also a lot to do with abundance
> of grazing fish. Out of curiosity, are you getting a lot of fish living about
> your structures?
> Are your structures out in the sand on their own, or close to a reef/bommie
> structure?
>   You may find that your growth forms/morphologies change as you go deeper.
> Check out the idea of morphological plasitcity on "reefbase.org". You may be
> able to expand your product line by something so simple.
>   What are your rates of deterioration of the steel? Will 1.5mm rebar last for
> 18 months or so (or longer)? I ask as i'm looking into using rebar for my own
> structures in Montego Bay. There are also plastic coated rebars availible, or
> just attaching martyr anodes (which may be easier for you so far afield).
>   Please keep in touch. I like the idea of your project. I'll look up your
> website.
>   Andrew Ross
> I read with interest your message regarding algal growth on rusty rebar.
> I worked for years in Kiribati in their Agroforestry Division doing among
> other things nutritional trials on coconut.  What does that have to do
> with your question ......... well, iron oxide (rust) is not a form of iron
> thought to be available for plant uptake however we experimented with
> local practices in Kiribati of placing several rusty tin cans in coconut
> seedling planting holes and not only did the coconuts grow better but leaf
> trace nutrient analysis showed significantly higher iron concentrations
> than control plants.  We surmised that a combination of organic matter
> plus rusty iron possibly changed the form of iron to one which plants
> could utilise.
> Perhaps the same thing is happening with your rusty rebar.  Pristine
> oceanic waters are known to be iron limited so when you place a source of
> iron in the water column I guess the algae may be taking advantage of this
> free source of trace metal and if this is the case, I would expect that as
> more organic matter builds up on these bars all the more iron may become
> available.
> Otherwise, it could be as simple as you have provided an excellent
> physical substrate for the algae to attach to - please let me know how
> your gal. rebars go as this should test this theory - it would also be
> nice to try a more inert substance such as plastic.
> Regards,
> Arthur
> ____________________________________________________________________________
> Dr. Arthur Webb
> SOPAC EDF Coastal Processes Adviser.
> arthur at sopac.org
> You need to cultivate grazers on your structures such as small urchins but
> better would be small trochus snails. Your structures should also be
> suspended off the bottom too. You need to hire some local kids with
> toothbrushes and have them scrub the trays each week. ;-)
> Aloha!
> J. Charles Delbeek M.Sc.
> Aquarium Biologist III
> Waikiki Aquarium
> 2777 Kalakaua Ave.
> Honolulu, HI, USA 96815
> www.waquarium.org
> 808-923-9741
> 808-923-1771 FAX
> In many areas of the open ocean, algal growth is limited by iron
> availability rather than the "usual" nutrients such as nitrogen or
> phosphorus.  Perhaps your rebar is fertilizing the water.  I would be
> careful about using galvanized rebar because the zinc can be poisonous.
> Perhaps a plastic would work.
> Ray Clarke
> Sarah Lawrence College
> * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
> Dr. Raymond Clarke
> Dept. of Biology
> Sarah Lawrence College                          email:   rclarke at mail.slc.edu
> 1 Mead Way                                      phone:  914-395-2343
> Bronxville, NY 10708                            fax:  914-395-2662

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