The tradition of red color of the underwater hull –time to change because barnacles prefer red color
Singapore – November 14, 2024
Jonathan R. Matias, Chief Science Officer of Poseidon Sciences Group, presented a paper at the 12th Annual World Congress of Ocean-2024 (WCO-2024) held at Aloft Novena, Singapore. The paper describes the historical basis of the red color of the underwater hull as it relates to our modern understanding of barnacle behavior.
Historically, the ancient Chinese had used copper plates, while the ancient Greeks used lead plates to protect the hull from barnacles and other fouling organisms. In 1761, the British Royal Navy pioneered the deployment of copper plating to prevent the ships from being destroyed by shipworms (Teredo navalis) and barnacles. By the 1840s, coating with high concentrations of cuprous oxide was invented and became the mainstay of the marine coatings industry by the 1860s.
Thus, the tradition of the red-colored hull was born and continues today, 164 years later. Just watch the fleet of bulk carriers and tankers in the Port of Singapore to see how strong this tradition has been.
But, it is time to reconsider this tradition. Why? Because barnacles actually see and prefer red color.
The barnacle, Balanus amphitrite Darwin, is the most ubiquitous fouler in almost all marine habitats worldwide and is the main cause of billions of dollars’ worth of extra fuel due to the drag experienced by ships as they course through the world’s oceans. It has been our experience that once the cuprous oxide has been depleted from the paint, barnacles readily colonize the underwater surface in a massive way in just a matter of weeks. For over 30 years, Poseidon Sciences Group has been conducting research and evaluating coatings for all of the world’s coatings companies. With today’s new technologies using other biocides besides cuprous oxide, the final choice of color for the underwater hull should be taken with more serious consideration than simply because it is a “tradition.”
Here’s why. The landmark paper by Matsumura and Qian in 2014 demonstrated that the cyprid (the larvae of the barnacle that selects the surfaces to settle) actually prefers and is attracted to red color. Even surprisingly, the adult barnacles already growing on the underwater surface emit red fluorescence that therefore attracts new settlements near the older colonies. Hence the piling up of barnacles together to form colonies to create more havoc on the previously polished surface of the coating. Even before this 2014 paper, we have already noticed preferences of barnacle settlement to darker colors of longer wavelengths (such as black, green, and cyan) than lighter colors, such as white, light blue, and Caribbean blue. See the figure below.
More recently, we are extending this research program first to revalidate this notion and second, also develop the perfect alternative color. The figure below again reinforces the color preference of barnacles to red.
The data are compelling enough to begin reconsidering that the RED COLOR as a tradition may no longer be appropriate in extending the performance life of coatings in the marine environment. The potential cost savings for shipowners and lowering the carbon footprint of shipping in general are long-term considerations for a future shift from the traditional red color.
The question is, which color? And, we think it ought to be WHITE. Perhaps, it is time to begin a new tradition in light of what we know now about barnacles.
About Poseidon Sciences Group
Poseidon Sciences is a research and development company with biological research stations worldwide. Its main marine research station, located in the port city of Tuticorin in India, celebrates its 30th year of collaboration with SHMRC India. Poseidon Sciences evaluates marine coating’s performance in the natural environment through its floating immersion platforms for static and dynamic tests in the India Ocean. To learn more about Poseidon and SHMRC: www.poseidonsciences.com
