Home > News
View of Pilgrim Monument in Provincetown from the research site at the National Seashore. (Zoe Cardon)
Suzanne Thomas and Claire Lunch examine "living crusts," sand glued together by microscopic, photosynthetic organisms. (Zoe Cardon)

Why are the Cape Cod sand dunes crusty?

Over the course of the last century, the inland parabolic, or U-shaped, sand dunes at Cape Cod National Seashore have marched from the northwest to the southeast, pushed by winter winds. Aerial photographs show that the dune fronts have moved 130 to 230 meters since 1938, some fronts even intersecting with Route 6.

Distinct plant communities have developed as the dunes envelop trees and create moist troughs. The surface of the dunes is, in some places, surprisingly dark-colored and tough, and the darkened crust turns green with spring rains -- sand in the crust is glued together by microscopic, photosynthetic organisms. Steve Smith, of the National Park Service, has identified major members of the microbial community in the crusts as green algae.

Close-up of sand crust (Zoe Cardon)

Claire Lunch, postdoc in the Ecosystems Center, is particularly intrigued by the similarity between green algae in these crusts and green algae from the desert microbiotic crusts of the Southwestern U.S. As part of a NASA-funded project headed by Zoe Cardon, Claire is examining the physiology of green algae isolated from desert crusts, and the Cape Cod dunes provide an excellent local field site for exploring how crusts respond to water and temperature, how they influence dune erosion and thus perhaps movement, and how they may affect seed germination and thus plant community structure on the landscape.