Site menu:

Dawn Sephton


M.Sc.: 2001 - 2005

Co-supervisor: Dr. Katsuji Haya, DFO St. Andrews, New Brunswick, Canada

Present occupation: Technician at DFO Bedford Institute of Oceanography, Darthmouth, Nova Scotia, Canada

Thesis: Uptake, disposition, biotransformation and depuration of marine biotoxins by Mytilus edulis L. in Passamaquoddy Bay, Bay of Fundy, Canada

Dawn Sephton Photograph Dawn Sephton doing some seawater sampling to test for PSP causing algae in the Bay of Fundy, Canada (photo: Thierry Chopin).

Abstract: The potential to culture filter-feeding shellfish in marine ecosystems must consider management and mitigation of accumulated phycotoxins. The presence of Alexandrium fundyense, which produces saxitoxin and its derivatives (STX+) which cause paralytic shellfish poisoning (PSP) in humans, has resulted in annual regulated closures of shellfish harvesting in the Bay of Fundy since the 1940s, while the occurrence of Pseudonitzschia pseudodelicatissima, which produces domoic acid (DA) which causes amnesic shellfish poisoning (ASP), has resulted in closures in 1988 and 1995. As part of an integrated multi-trophic aquaculture project (AquaNet EI17) where kelp, shellfish and salmon are grown together, my research is focused on determining the seasonal dynamics of these two phytoplanktonic species and phycotoxin presence in Mytilus edulis, the filter-feeding component in this aquaculture system.

Concomittant sampling of the phytoplankton and mussel communities is conducted at monthly to twice-weekly intervals throughout 2002 to determine seasonal cycles of (1) algal abundance, (2) water column toxin content, and (3) patterns of phycotoxin accumulation and depuration by mussels. HPLC analysis of mussel tissues for STX+ and DA content are conducted to determine toxin uptake, tissue storage, disposition and depuration in the field. The ability of M. edulis to biotransform saxitoxin and its derivatives is also investigated, especially from low to higher potency forms. Toxin uptake and depuration experiments were conducted in the laboratory during the fall and winter of 2002-2003. These data will facilitate the development of a mussel culture and harvest management plan in an integrated multi-trophic aquaculture system.