In 1880, Chesapeake Bay was heaven for oyster-lovers, as the native common Eastern oyster Crassostrea virginica was hauled ashore in about a hundred times the quantities now harvested. But over-fishing has so devastated the population that non-native varieties have lately been introduced, albeit with little success.

It's the same story the world over. Along the coasts of Europe and Australia too, oyster populations have been reduced to less than 10 percent of their historical abundance1. This is not just a gastronomic disaster, for oyster reefs — agglomerated mounds of billions of oyster shells — are a vital component of estuarine and coastal marine ecosystems. The reefs harbour other aquatic organisms, filter the sea water, and help protect the coastline from storms. The shift in the ecological balance has also led to eutrophication of estuarine waters.

Last year brought a ray of light to this gloomy picture, when researchers reported that artificial reefs constructed since 2004 in estuarine sanctuaries in Chesapeake Bay from the shells of native C. virginica dumped by the US Army Corps of Engineers have helped to boost oyster populations2 — not to the levels of a century ago, but enough to demonstrate the potential of the method.

This study showed that the higher the artificial reef (the highest were up to 45 cm above the river bottom), the more effectively it stimulated oyster growth. Reefs are not, however, simply piles of old shells: they have a complex architecture in which shells are bonded together by material excreted by the living oysters. The research showed that the long-term stability of a reef depends crucially on whether it acquires enough cohesion from this cement.

That's why a new study of the adhesive used for oyster-reef construction could prove so important. Burkett et al. have analysed the chemical composition of this material in C. virginica reefs offshore from South Carolina3. They find that it is an organic–inorganic composite made up mostly of calcium carbonate deposited within a matrix of phosphorylated protein.

There is less of the mineral in the adhesive (about 20 percent) than in the oyster shells (about 30 percent), and moreover it is a mixture of the polymorphs calcite and aragonite in the ratio 2:1, whereas the shell is mostly calcite. So the inorganic component of the adhesive is clearly tailor-made. And the glue as a whole is very different from that used by mussels and barnacles to stick to surfaces, which is mostly protein. Mussel adhesive proteins in particular have inspired biomimetic efforts to create resilient polymeric adhesives4. Both these and barnacle glues (which are less well understood) are strongly hydrated, whereas the inorganic–organic material of oysters has only a tenth of the water content of barnacle adhesive.

As well as suggesting a new strategy for biologically inspired adhesion — and, on the other hand, for preparing antifouling coatings for marine structures — the new findings might offer critical information for promoting the integrity of artificial reefs, which could become central to restoring this vital component of coastal ecology.