[Coral-List] Some observations on Biorock as a means of coral reef restoration.

[Les Kaufman]

This is in response to querries about Biorock as a means of coral reef
restoration.

   Here are a couple of papers on engineering aspects of Biorock, by
Wolf:

   Hilbertz, W. 1992: Solar-generated building material from seawater as
a
   sink for carbon. Ambio 21(2): 126-129

   Hilbertz, W.H., D. Fletcher and C. Krausse. 1977.  Mineral accretion
technology:
   applications for architecture and aquaculture. Industrial Forum 8:
75-4.

   As already mentioned, the Global Coral Reef Alliance web site hosts
..pdf files of some literature to support the presence of specific
biological effects
   attributable to the electric current (such as changes in
zooxanthellae) or mineral accretion (which can stabilize coral
fragments, an important process in reducing transplant mortality), as
well as a
   number of well-illustrated magazine articles about existing Biorock
installations.

   Last August, in preparation to writing a book chapter on coral reef
restoration, I visited the Biorock installations at Permuteran, Seraya,
and Tulamben, along
   the north coast of Bali, and spoke with some of the local supporters
and caretakers of these projects.  I also examined the structures, their
corals, and the
   adjacent reef, to try and at least superficially understand what was
going on.

   Here are my observations in Bali, limited by time but greatly
facilitated by the gracious hospitality of the Balinese and expats
involved in these projects:

   a) The Balinese Biorock projects are marvelously effective in
focussing a community's environmental concern and stewardship on the
sea.

   b) The more established structure gardens, at Permuteran and
Tulamben, are popular sites for diving and snorkelling in places that
have suffered degradation
   and reduced area of natural reef.   The removal of corals for the
structures did not seem likely to have had much impact on the natural
reef and many of the
   source colonies were chosen because they were broken off or
threatened, but if corals where to be removed from natural reef in very
large numbers this
   could obviously be a problem.  It would be worth knowing, however, if
indeed coral colonies are less vulnerable to bleaching in their new
accomodations.

   c) Mineral accretion on the iron structures is impressive over only a
few months, but the electric current must be maintained and closely
monitored, and that can be challenging where costs and
   resources are limited.

   d) Where I was shown coral colonies of known transplantation dates
and sizes, the colonies were very healthy and robust but did not appear
to have grown at an unusually high rate, except for
   flanges on some corals projecting parallel to and within one or two
centimeters of but not touching the mineral-encrusted surfaces around
the charged reinforcing bars.  Corals high in the water
   column appeared to have done better and grown faster than similar
ones of the same species placed near or next to the sediment-water
interface.  Systematic replicated measurements within and
   among species are essential before conclusions can be drawn about
Biorock effects on coral growth rates.

   The structures are strong and open, and resistant to at least those
storms of average intensity.  I observed corals on the structures being
damaged by divers,
   coral predators (Drupella, Acanthaster) and overgrowth by sessile
invertebrates, in a manner similar to those on nearby natural reef.
Constant vigilance,
   similar to that required for tending any other kind of garden, was
necessary to prevent natural mortality to transplanted corals.

   Some other groups have also been experimenting with this or very
similar methods:

   Schumacher, H.P. and L. Shillak.  1994.  Integrated electrochemical
and and biogenic deposition of hard material- a nature-like colonization
substrate.  Bull.
   Mar. Sci. 55:672-679.

   Schumacher, H., P. van Treeck, M. Eisinger and M. Paster.  2000.
Transplantation of coral fragments from ship groundings on
electrochemically formed
   reef structures.  Proc. 9th Int. Cor. Reef Symp. 2:983-990.

   In sum, the biorock methodology could be very useful in the creation
and maintenance of coral gardens for mass propagation (as part of
restoration programs) or recreational enjoyment.  Biorock
   structures, when composed principally of calcium carbonate (some
proportion of the accreted mineral can be brucite instead), are
wave-resistant (many fishes shelter in their lee) and it is hard to see
   how they wouldn't help to prevent beach erosion if properly placed
and maintained.  In that application they may well be superior to the
dumping of riprap.  As substratum for a coral explant
   nursery, biorock is desirable because the entire structure is very
easily constructed, moved into place, and coated with mineral.  As a
method for large-scale reef restoration, however, at least in the
   Indo-Pacific, which is blessed with a great diversity of rapidly
growing corals (mostly acroporids), it needs to be demonstrated that
Biorock structures are more biologically or cost effective than
   more conventional methods employing coral nursery-grown transplants,
or simply piles of carefully-placed boulders studied by Helen Fox in
Komodo.  Biorock is certainly an aesthetically creative
   approach, with results that can vary from hauntingly beautiful to
kitsch piles according to the sensibilities of both artist and viewer.

   Les