Most organic matter synthesized in surface waters of the sea is returned to inorganic constituents within the upper 500 m, or "regeneration zone." Oceanographers attribute these chemical transformations mostly to living organisms. Yet surprisingly little is known about the biology of remineralization below the euphotic zone: whether the responsible organisms are dominantly metazoan or microbial and whether or not they occur on the larger particles that deliver material to depth. Dr. Pilskaln, together with Dr. Silver will conduct a 2-year study in Monterey Bay, and accessible, comparatively deep water site, to study the role of both microbes and zooplankton in the remineralization of particles >1mm. Using a combination of in situ observations and laboratory measurements, she will study both the abundant marine snow particles and very large aggregates (m size) that can serve as model systems for such studies. She plans to (1) measure the size and abundance of the aggregates, (2) determine their chemical properties and associated living communities, (3) measure regeneration-related activities of the communities on the particles, and (4) compare and particle-related remineralization rates to those measured by sediment traps in the area. For these measurements, she will use field surveys with a Romotely Operated Vehicle (ROV) and a Marine Snow Camera, a variety of sampling devices operated from the ROV, and a series of experiments on natural samples incubated on shipboard and in the laboratory. In year 2, Dr. Pilskaln transects the California Current to learn whether the very large aggregates, which are hypothesized to be regeneration centers to Monterey Bay, occur in significant numbers further offshore. These results will increase the understanding of the biology of midwater remineralization and the role that particles can play in the process.
