ELEMENTAL STOICHIOMETRY, AND NUTRIENT AND MINERAL FLUXES IN THE SANTA BARBARA BASIN OVER THE PAST TWO DECADES

Nutrient composition plays an important role in plankton speciation and therefore marine biological production. In regions dominated by upwelling, the composition and magnitude of nutrients upwelled into surface waters not only influences surface food web dynamics, but also the composition and magnitude of particles that reach deep waters, are remineralized, and even sequestered in deep sediments. The Santa Barbara Basin off the coast of Southern California is an area that encounters seasonal upwelling due to strong northwesterly winds that occur along the west coast of the United States. Several studies suggest that plankton community structure has undergone a large scale shift in the year 2000 due to changes in upwelling intensity or upwelling water concentrations. To determine long term and annual shifts in particulate mineral and nutrient fluxes in this location, total mass, particulate carbon, nitrogen, and phosphorus, as well as carbonate and opal were measured in sediment trap continuously deployed at 500 m since 1993. Fluxes will be analyzed with respect to season, long term trends, and elemental stoichiometry. Preliminary results suggest significant increases in opal and particulate nutrient fluxes over the past decade, coincident with large scale increases in harmful algal blooms in Santa Barbara Basin surface waters.