A Brief Background on Antifouling Products and Poseidon’s Antifouling Program
Nontoxic antifouling compounds, substances which repel marine life but do not harm the environment, are the focus of Poseidon’s research. Knowing the history of biofouling will help you understand more about the impetus for Poseidon’s quest for the discovery of an effective antifoulant.
In the marine environment, all surfaces are affected by the attachment of fouling organisms, such as bacteria, algae and invertebrates including barnacles and mussels. These fouling organisms contribute to the corrosion of submerged surfaces. The efficiency of ships traveling through the open sea is particularly hampered when biofoulers, such as algae, clams and barnacles, are attached to the bottom. Barnacles need to be sandblasted away from the surface during dry docking of the ship prior to painting the hull. Expensive dry-docking, increased fuel costs and corrosion are important economic factors that mandate the prevention of barnacle attachment to the underwater surface of ships.
The Use of Toxic Chemicals
Biofouling organisms are killed upon contact with such painted surfaces, thereby preventing fouling for periods ranging from 6 months to 5 years depending upon the composition of the paint and the amount of heavy metals present.
The Environmental Consequences
The Future of Antifouling Paints
Poseidon’s Antifouling Program
Fouling organisms are cultured in artificial raceways and painted panels are exposed for various durations of time. Field research stations, such as the one shown here, serve as testing grounds for painted panels exposed to seawater rich in barnacles, oysters, clams and other biofouling organisms. The culture of macro-algae and micro-algae are also maintained here.
An in vitro screening system developed by Dr. Daniel Rittschof at Duke University Marine Laboratory (Beaufort, North Carolina) that utilizes laboratory-reared barnacles was employed to select effective repellents. Larvae or cyprids are collected and natural compounds (such as NB17, a series of naturally occurring compounds with antifouling properties) are tested in an assay that measures the settlement of the barnacle larvae on surfaces. The critical step in barnacle fouling is the period when the cyprid larva is selecting the appropriate surface to attach. Once attached, dislodging the larvae becomes difficult because it secretes one of the strongest adhesive known to man to secure it to the surface. A typical assay result for NB17 is shown on the left.
In December 1995, Poseidon completed the first series of studies at SHMRC, under the direction of Dr. Avelin Mary, demonstrating the efficacy of NB16 and NB17. These compounds prevent the attachment of barnacles when incorporated into marine paints at concentrations as low as 0.1 microgram per gram of paint. On a panel of 40 bacteria normally associated with biofouling, these compounds were found to be highly bacteriostatic.
More importantly, when tested against larval organisms, these compounds prevented attachment but did not cause death to the organism even when exposed for a long duration of time.
In 1998, Poseidon completed field studies to validate the efficacy of NB17 compounds when incorporated into paint formulations . These compounds were found to inhibit the attachment of algae to surfaces coated with NB17 compounds. Most notably, barnacles were prevented from attachment when NB17 was substituted in the place of tributyl tin paint formulations.