Diarrhetic shellfish poisoning (DSP) associated with a sub-surface bloom of Dinophysis norvegica in Bedford Basin, eastern Canada

Abstract

The first diarrhetic shellfish poisoning (DSP) red tlde associated w ~t h the dinoflagellate Dlnophysls norveglca recorded tor eastern Canada occurred In Bedford Basin from 20 July to 3 August 1990 The abundance of D norveylca was up to ca 0 5 X 10%ells I ', which IS the highest ever reported It constituted up to 88 % of the total dlatoms and d~noflagellates, and was most abundant at ca 10 m depth in the pycnocllne at almost all the statlons In the Basln The temporal pattern of partlcle size spectra matched closely the abundance of D nonreglca Okadalc acld (OA) content In the vertlcal plankton tows ranged from 0 7 8 to 6 08 ug OA g ' dry plankton The OA In the dlgestlve tract of exposed experimental scallops Placopecten magellan~cus was 320 n g g.' on 27 July and increased to 469 ng g ' on 3 August 1990 The toxin's temporal distnbutlon In scallops was the inverse of that in the plankton samples OA content In scallops Increased In spite of its decrease in plankton, which suggests that the scallops accumulated OA but depurated slowly The potential for a DSP episode exists In Nova Scotlan waters if a similar growth of toxicogenlc D norveglca occurs In aleas of consumable molluscs