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General Session 2: Marine & estuarine biogeochemistry |
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Neurotoxins and the environment. understanding the production, cycling and fate of domoic acid along the California Coast.
Wednesday 11th @ 0920-0945
Conference Hall
Claudia R. Benitez-Nelson* , University of South Carolina, Columbia, SC 29208, USA
Blaire Umhau, University of South Carolina, Columbia, SC 29208, USA
Clarissa R. Anderson, University of California at Santa Cruz, Santa Cruz, CA 95064
Robert C. Thunell, University of South Carolina, Columbia, SC 29208, USA
Alexandra Burns, University of Miami, Miami, FL 33149, USA
Kelly McCabe, University of South Carolina, Columbia, SC 29208, USA
Christopher Burrell, University of South Carolina, Columbia, SC 29208, USA
Presenter Email: cbnelson@geol.sc.edu
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| Toxic Pseudo-nitzschia blooms are ubiquitous worldwide and are hypothesized to have increased over the past several decades in response to a myriad of factors ranging from natural climate variability to coastal eutrophication. Deciphering the underlying mechanisms associated with domoic acid (DA) production by Pseudo-nitzschia has proven difficult, mainly due to a lack of long time-series measurements coupled with limited geographical and vertical water column sampling. Water column distributions of dissolved and particulate DA and Pseudo-nitzschia spp. abundance was examined in the Santa Barbara Basin (SBB), California and distributions compared to fluxes measured in two moored sediment traps located at 150 and 500 m. Pseudo-nitzschia spp. were present throughout the year with a spatially heterogeneous distribution (< 500 cells/L to > 3 x 10^6 cells/L) that was significantly different from that measured in nearshore pier based collection sites. Highest Pseudo-nitzschia abundances tended to occur in conjunction with upwelling events, yet both led and lagged peaks in upwelling. Water column DA concentrations ranged from < 0.01 ng/mL to > 50 ng/mL and were further equally proportioned into dissolved and particulate phases that were well correlated with one another (R2 > 0.90). However, water column DA concentrations showed little to no correlation with Pseudo-nitzschia abundance, suggesting other factors, such as nutrient stress and variations in Pseudo-nitzschia species diversity. Average sediment trap concentrations of Pseudo-nitzschia were significantly higher in the 150 m versus the 500 m sediment trap (1.2 x 10^7 versus 2 x 10^6 frustules/gram sediment, p < 0.005) suggesting significant frustule remineralization as particles sank through the water column. In contrast, average DA concentrations were similar at the two traps depths (8.5 - 8.9 μg tDA/gram sediment). We argue that the minimal loss in sinking particulate DA occurs due to more efficient transport of DA via Pseudo-nitzschia aggregates, which tend to form when cells are stressed. Combined, these results highlight the complexity of linking DA production with Pseudo-nitzschia abundance, the importance of measuring dissolved DA phases, and the episodic and rapid downward transport of DA laden particles to the seafloor. |
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