b"SURFACE WATEROn pirate maps in movies and kids' books, X has always marked the site of buried treasure. For California Sea Grant Extension ecologist Joe Tyburczy, a four-foot (1.21 meter) X marks the location of his SonTek Argonaut-ADV (Acoustic Doppler Velocimeter). Tyburczy uses the Argonaut to measure water flow in the shallow eelgrass beds of Humboldt Bay in northern California, where he is studying eelgrass' ability to capture carbon and reduce acidity levels in bay water.Eelgrass thrives in soft sedimentso soft that getting to the study sites at low tide is a grueling slog through knee-deep mud or a trudge on snowshoe-like mudders. It's the sort of bottom that can quickly suck in a pole-mounted instrument. Tyburczy deploys his Argonaut-Photo: Joe Tyburczy The Burke-o-lator, designed by Oregon State University oceanographerADV on a cross-shaped PVC rig that Burke Hales, provides real-time measurements of the carbonate status ofis augered deep into the mud at seawater. Carbonate is the main ingredient in crustacean shells.all four cornersa pair of stacked, horizontal Xs held together by two-foot lengths of pipe at the end of each arm and the crossing point at the center. The Argonaut-ADV is strapped to the center pipe, its acoustic transmitter and receivers aimed just above the bed to measure the velocity and direction of water flow using the Doppler effect. It's stable, unsinkable, and cleverand it provides vital context for the water chemistry data Tyburczy is generating nearby. Treasure indeed.43"