Toxic blooms of a variety of algal species (harmful algal blooms -- HABs) have been documented throughout the world?s coastal oceans, ultimately impacting shellfish, finfish, marine mammals and birds over large areas. Several species within the genus of Pseudo-nitzschia, a group of marine diatoms that produce the neurotoxin domoic acid (DA), have been identified as common members of algal assemblages along the coast of California. Key questions in HAB research include not only what causes toxic Pseudo-nitzschia spp. to bloom, but what happens to that bloom after its demise. Causative factors ranging from coastal eutrophication to increased upwelling to resuspension of seed populations from sediments have all been hypothesized, but remain enigmatic, mainly due to a paucity of integrative data. The fate of DA producing Pseudo-nitzschia blooms remains even more elusive, and yet there is increasing evidence of substantial DA concentrations in benthopelagic feeders and benthic organisms both along the coast and offshore.
In this project, a research team at the University of South Carolina at Columbia will build upon intriguing and exciting preliminary data that suggests that sinking particles are a major vertical transport mechanism of DA from surface waters to sediments, with DA fluxes exceeding 50,000 ng DA/m2/d at depths in excess of 500 m. They hypothesize that DA is rapidly transported to sediments and likely persists on greater than seasonal timescales, well after the demise of a Pseudo-nitzschia bloom. Their goal is to create a regional observation and modeling program focused on the Santa Barbara Basin (SBB) that specifically: 1) Examines the temporal relationship between Pseudo-nitzschia blooms, DA toxicity, and the vertical transport efficiency of Pseudo-nitzschia and DA to the benthos, 2) Investigates the incorporation of DA into the sediments, and 3) establishes a historical record of DA toxicity spanning the past decade, and potentially, the last century.
To achieve this goal, they will use a combination of monthly survey cruises of water column biogeochemistry, two continuously moored sediment traps (150 and 550 m), regional surface and down core sediments records, satellite imagery and develop a numerical model that examines the surface timing of toxic Pseudo-nitzschia blooms and the vertical export of DA to the seafloor. They expect that this research will fundamentally change current views on the persistence of DA toxicity in marine systems and that it will provide the groundwork for similar measurements of other harmful toxins. The proposed research leverages sampling opportunities with a number of ongoing programs off coastal California, such as Plumes and Blooms and the Santa Barbara Coastal LTER Project (water column), the Marine Sediments Laboratory at USC (archived and future sediment trap collections), and the Southern California Coastal Water Research Project Bight 2008 campaign (surface and down core sediment collections).
The project is expected to have a number of broader impacts. Beside its obvious relevance to HAB research and marine environmental toxicology, the project will directly support a postdoctoral fellow and one Native American graduate student. Undergraduate students will also participate in the proposed research, supported by internal funds contributed by the University of South Carolina. All students in the principal investigator?s laboratory participate in Science Quest, an after school informal science and technology program geared towards at-risk elementary and middle school students (ages 8 -14).
