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Oyster Study May Help Ship Coatings

Thursday, August 26, 2010

Lessons learned from declining oyster reefs may hold promise for developing coatings that prevent marine bioadhesion and keep ship hulls clean, researchers say.

Researchers from Purdue University and the University of South Carolina have shown that oysters produce a unique adhesive material for affixing themselves to each other, a cement that differs from the glues used by other marine organisms.  Unlocking the keys to that bond could help advance biofouling research and improve marine coatings, the researchers say.

"By understanding how various marine organisms attach themselves to surfaces, it may be possible to rationally design coatings to inhibit this process without the use of toxic components," said Linda Chrisey, a program officer in the Naval Biosciences and Biocentric Technology program, which helped fund the research. "This is one of the goals of the Office of Naval Research's Biofouling Control Coatings research program."

The research began as a study into the rapidly declining oyster reefs. Because the reefs have a critical role in filtering water, preventing erosion, guarding coasts from storm damage, and providing habitat for other organisms, researchers have been investigating how the reefs form so as to offer guidance on oyster re-introduction projects.

At the same time, researchers have been studying marine animals' various adhesives, uncovering fundamental properties that could yield new innovations, including surface coatings that keep waterborne craft from picking up marine hitchhikers.

The researchers presented their findings Tuesday (Aug. 24) at the 2010 Annual Meeting of the American Chemical Society in Boston, MA, and will publish their results Sept. 15 in the Journal of the American Chemical Society. (The article is available online now.)

"We wanted to learn how oysters attach themselves to surfaces, and each other, when building reef structures," said Purdue University chemist Jonathan Wilker, one of the lead researchers on the study.

The findings could lead to development of new surgical adhesives and other biomedical materials, Wilker say, and “may also help us prevent marine bioadhesion for keeping ship hulls clean, thereby reducing drag, fuel consumption, and carbon emissions."

The researchers studied the common Eastern oyster, Crassostrea virginica, which they collected from the Baruch Marine Field Laboratory on the South Carolina coast.

By comparing the inside and outside of oyster shells with the material connecting oyster to oyster, the researchers were able to determine the chemical composition of the cementing material.

"Our results indicate that there is a chemically distinct adhesive material holding the oysters together," said Wilker. "The cement contains significantly more protein than the shell. We also observed both iron and highly oxidized, cross-linked proteins, which may play a role in curing the material."

Cross-linked proteins are an emerging theme in the study of marine biological materials, central to the glues of mussels, barnacles and, now, oysters.  However, the oysters use far less protein in their adhesive when compared to the analogous materials from mussels and barnacles.

Beyond this relatively minor protein component, the oyster adhesive appears to be unique, composed largely of chalky calcium carbonate. Oysters seem to prefer an adhesive that is more like a hard, inorganic cement versus the softer, organic glues of other organisms.

This research was supported by the National Science Foundation through the Chemistry of Life Processes program and the Office of Naval Research through its Biofouling Control Coatings research program.

"This is exactly the kind of interdisciplinary, cutting-edge research that we strive to support, particularly by looking at research that lies outside the traditional sub-disciplines in the field," said Dan Rabinovich, the program officer in the NSF Division of Chemistry.

The researchers next hope to determine the interplay between the cement's organic and inorganic components, then use that information to create new classes of synthetic materials as well as adhesion-preventing surfaces.