b'SURFACE WATERPrincipal EffortEelgrass research is not just interesting to SonTek:Tyburczy and his colleagues have been studyingTyburczy\'s project is funded by the Ocean Protection Council. It involves eelgrass beds and plan to start experimenting withcollaboration among California Sea Grant, Humboldt State University, removing cobble and shell riprap laid in the shallowsOregon State University, the Wiyot Tribe, the California Department of years ago by oyster farmers. For decades, California\'sFish and Wildlife and the Hog Island Oyster Companya wide range of farmed oysters were grown directly on the mudflatsstakeholders illustrating the broad impact of ocean acidification.and eelgrass beds and harvested by dredge. Eelgrass, which grows in soft sediment, was disrupted"Velocity is a key covariate," he explains. "If velocity by the dredging, as well as by the cobble and shellis high and chemical change is high, the eelgrass laid by shellfish producers to prevent the oysters fromis doing a lot. If there\'s not a lot of change in the sinking into the mud and being smothered. Today,chemistry and not a lot of motion in the water, then oysters are farmed on long lines festooned withthe eelgrass is not doing much. Instead of just the groups of the growing bivalves in clusters or cagesmagnitude of the difference in the chemistry, having instead. Though far less damaging than dredging,data on the flow tells you about the flux."these lines can pose other kinds of challenges for eelgrass, like shading eelgrass plants or abradingBecause the Argonaut-ADV uses acoustic signals their leaves.to measure flow at a single, small point just a few centimeters from its transmitter, it is highly effective Though the circular scars from past dredge harvestingin the shallow water that favors eelgrass growth and have largely filled in with eelgrass, many areasextremely accurate at measuring the highly variable covered in shell and cobble remain mostly bare. Byflows that are common in Humboldt Bay, he adds. removing the hard material and restoring the soft sediment, Tyburczy and his colleagues are confidentDr. Xue Fan, an application engineer for SonTek, that eelgrass can be restored to those cleared areas. points out that Tyburczy\'s use of an Argonaut ADV underscores the importance of accurate flow Tyburczy\'s study of the ability of eelgrass to capturemeasurement in a wide range of waterCO 2from the water and reduce acidity could helpchemistry research.illustrate the importance of the coexistence of oyster farms and eelgrass beds. One idea was that if the"The data from the Argonaut can provide the vital carbon-capturing effect were great enough, oystercontext for changes in chemistry that we observe," she hatcheries could site their water intakes near eelgrassnotes. "We are very excited to see Dr. Tyburczy using beds and draw in water after it had sat over thethe Argonaut-ADV to shed light on one of today\'s eelgrass and some of its CO 2had been extractedandmost pressing issues: how underwater communities its pH had increased.are operating as the pH of the oceans continuesto fall." Tyburczy and his team use two key instruments for the research: a Burke-o-lator designed by Oregon StateTyburczy also measures temperature, salinity, University oceanographer Burke Hales to measuredissolved oxygen and pH both inside and outside carbonate chemistry in the water in real time, and athe eelgrass beds, tracking the diurnal and seasonal SonTek Argonaut-ADV (Acoustic Doppler Velocimeter)cycles in water chemistry and comparing water quality to measure the movement of water in the inside and outside the beds under various conditions. shallow beds.Photo: Joe TyburczyTo keep its SonTek Argonaut-ADV from sinking into the soft sediments preferred by eelgrass, Joe Tyburczy\'s team mounts the velocity-measuring instrument on a sturdy, well-anchored PVC structure.42'