Survey of Shell-boring Microorganisms Across a Depth Gradient at Point Caution, on San Juan Island, WA

Abstract

Although they are integral to many marine ecosystems, relatively little is known about euendolithic (shell-boring) organisms outside the tropics. Here, I present a short survey of euendoliths inhabiting a site on the Pacific coast of North America. Shells were collected from sites in the intertidal and subtidal zone off Point Caution, on San Juan Island, WA. Casts of boreholes were photographed with a scanning electron microscope, and their morphology and diameter was matched to previously isolated cultures. Several types of green algae, as well as cyanobacteria and fungi, were found in the intertidal shells. The 11 meter deep subtidal site was dominated by the green alga Ostreobium, and the 23 meter site by the cyanobacteria Leptolyngbya. Only heavily eroded tracings were found at the 30 meter deep site.