October 18 2008

Thomas J. Goreau, PhD
President, Global Coral Reef Alliance

The Biorock® method, invented, developed, and patented by the late Prof. Wolf HIlbertz and Dr. Thomas J. Goreau, uses low voltage direct currents (above 1.2 Volts) to grow solid limestone minerals on conductive substrates. The minerals grown are naturally present in large amounts in seawater, but do not crystallize by themselves. These currents are safe to humans and all marine organisms, all of which are seen to be attracted, and none repelled. The low current also completely prevents rusting of steel substrates, indeed it reverses any rusting that had previously occurred. The strength of Biorock materials is an inverse function of growth rate, but is typically around 3 times the compressive strength of ordinary Portland cement concrete if grown at less than 1-2 centimeters per year. Biorock construction materials are the only known marine construction materials that are growing, get constantly stronger with age (while all others deteriorate), and are unique in being self-repairing, since any physically damaged areas grow back preferentially. There is no limit in principle to the size or shape of Biorock structures, they could be grown hundreds of miles long if funding allowed.

Hard and soft corals, sponges, tunicates, and bivalves are observed to grow on Biorock materials at extraordinary rates. Hard corals typically grow 2-6 times faster than controls (depending on species and conditions), are exceptionally brightly colored and densely branched, heal from physical damage at least 20 times faster, have 16-50 times higher survival from the most severe high temperature bleaching events, and show rates of new coral recruitment hundreds to thousands of times higher per unit area per unit time than recorded in the literature. Fish and lobster population growth in these structures is extraordinary, especially juvenile fishes, and depends on the shape of Biorock structures, which can be made to provide an extraordinary density of hiding places. Biorock reefs have turned severely eroding beaches with erosion scarps into 50 feet of beach growth in a few years by slowing waves so that instead of eroding sand at the shore, they deposit it. They have been found stable in category 4 hurricanes and the Asian Tsunami, because the open frameworks allow large waves to pass through.