Modelling the accumulation of PSP toxins in Thau Lagoon oysters (Crassostrea gigas) from trials using mixed cultures ofAlexandrium catenellaandThalassiosira weissflogii

Abstract

In October and November 2003 a bloom of the toxic dinoflagellate Alexandrium catenella was observed in the Northeast zone of Thau lagoon (French Mediterranean coast). Sea water samples were collected every hours to evaluate time-related variations of phytoplankton concentrations and to compare the relative ratio of A. catenella versus other phytoplankton species during the outbreak. From these observations, trials using recirculated sea water systems were performed to: i) evaluate the physiological effects on oyster of increasing proportions of A. catenella within a mixed microalgal diet where the non-toxic diatom Thalassiosira weissflogii was present at concentration: 1500 cells ml −1 , ii) compare the effect of two temperatures (12 • C and 18 • C) on paralytic toxin accumulation rates in oyster flesh by ion-pairing high performance liquid chromatography (IP-HPLC) detection, iii) analyse toxin biotransformation during the contamination process, iv) evaluate the role of the different types of oyster tissue on the bioaccumulation mechanism. The results showed: i) a significant effect of temperature increase on clearance rate and toxin uptake, ii) no detectable time-related effects of toxic algal food on pre-ingestion sorting or on toxin profiles in oyster flesh, iii) either negative or positive effects of A. catenella concentrations on toxin uptake ("threshold" effect), iv) high amounts of toxins in the digestive gland, accounting for more than 80% of overall shellfish toxicity. The daily amount of toxins (Q tox) taken up by each oyster was evaluated by means of a global one-compartment model. However a two-compartment model finally gave the best match with real contamination kinetics, since it integrated both toxins sequestered in oyster tissues and toxins moving in through the digestive tract.

β-N-methylamino-l-alanine (BMAA) and isomers: Distribution in different food web compartments of Thau lagoon, French Mediterranean Sea

“…The distribution of BMAA and DAB within mussel tissues was unusual in comparison to other cyanotoxins and phycotoxins Toxins accumulating in filter-feeding bivalves as a function of consumption of microalgae were mainly found in digestive glands or viscera, independently of the polarity of the toxins, with proportions ranging from 70 to 95% in the digestive gland for both freshwater and marine mollusks (Blanco et al, 2007;Bricelj et al, 1990;Jauffrais et al, 2012;Lassus et al, 2007;Mafra et al, 2010;Medhioub et al, 2010;Negri and Jones, 1995;Strogyloudi et al, 2006;Vasconcelos, 1995). As far as we know, few data concerning the distribution of BMAA in mollusks are available in the bibliography.…”

Warm temperature acclimation impacts metabolism of paralytic shellfish toxins from Alexandrium minutum in commercial oysters

“…the current and predicted rates of ocean temperature increases. Based on experimental feeding studies, variation between bivalve species in the rate of uptake of PSTs, and the total uptake and depuration of PSTs, has been found (Bricelj et al, 1990;Sekiguchi et al, 2001;Chen & Chou, 2002;Blanco et al, 2003;Lassus et al, 2005;Li et al, 2005;Kwong et al, 2006;Asakawa et al, 2006;H egaret et al, 2007;Lassus et al, 2007;Galimany et al, 2008;Murray et al, 2009;Haberkorn et al, 2011;Contreras et al, 2012;Fern andez-Reiriz et al, 2013;Bricelj et al, 2014;Haberkorn et al, 2014). This was hypothesised to be due to differences in the feeding level on Alexandrium among bivalve species (H egaret et al, 2007;Contreras et al, 2012).…”

Exposure to toxic Alexandrium minutum activates the detoxifying and antioxidant systems in gills of the oyster Crassostrea gigas

“…The paralytic shellfish toxins (PST) produced by dinoflagellates are the most widespread and among the most potent of shellfishcontaminating biotoxins (Huss, 2002). In France, PST toxic events have been reported since the 1980's, first in Brittany caused by Alexandrium minutum and later in the Thau Lagoon with Alexandrium catenella (Lassus et al, 2004;Lassus et al, 2007). The last major PST-producing bloom occurred in July 2012 in the Bay of Brest (Brittany) where A. minutum cell counts reached 41,740 cells mL À1 , a record for the French coast.…”