title: Particle size fractionation of paralytic shellfish toxins (PSTs): seasonal distribution and bacterial production in the St Lawrence estuary, Canada.
abstract: We determined the seasonal distribution of paralytic shellfish toxins (PSTs) and PST producing bacteria in > 15, 5-15, and 0.22-5 microm size fractions in the St Lawrence. We also measured PSTs in a local population of Mytilus edulis. PST concentrations were determined in each size fraction and in laboratory incubations of sub-samples by high performance liquid chromatography (HPLC), including the rigorous elimination of suspected toxin 'imposter' peaks. Mussel toxin levels were determined by mouse bioassay and HPLC. PSTs were detected in all size fractions during the summer sampling season, with 47% of the water column toxin levels associated with particles smaller than Alexandrium tamarense (< 15 microm). Even in the > 15 microm size fraction, we estimated that as much as 92% of PSTs could be associated with particles other than A. tamarense. Our results stress the importance of taking into account the potential presence of PSTs in size fractions other than that containing the known algal producer when attempting to model shellfish intoxication, especially during years of low cell abundance. Finally, our HPLC results confirmed the presence of bacteria capable of autonomous PST production in the St Lawrence as well as demonstrating their regular presence and apparent diversity in the plankton.
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D001681:Biological Assay; D049872:Bivalvia / Q000737:chemistry* / Q000382:microbiology; D005591:Chemical Fractionation / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D051379:Mice; D010243:Paralysis / Q000139:chemically induced / Q000503:physiopathology; D010316:Particle Size; D011792:Quebec; D012530:Saxitoxin / Q000031:analogs & derivatives / Q000302:isolation & purification*; D012621:Seasons; D012623:Seawater; D012758:Shellfish / Q000382:microbiology; D057096:Shellfish Poisoning
chemical_list: D001427:Bacterial Toxins; D012530:Saxitoxin