Monitoring phytoplankton and marine biotoxins in production waters of the Netherlands: results after one decade.

Shellfish products may be contaminated with marine biotoxins which, after consumption, may lead to human illness. The Netherlands has a regular monitoring programme for marine biotoxins and the possible toxic phytoplankton in shellfish production waters. The aim of the current study was to evaluate the presence of potential toxic phytoplankton species and marine biotoxins in Dutch production waters over the last decade, and to analyse the relationship between toxin levels and abundance of possible causative phytoplankton species. The results of the monitoring programme of the period 1999-2009 were used. The presence of Alexandrium spp. were negligible, but Pseudo-nitzschia spp. and phytoplankton causing diarrhetic shellfish poisoning (DSP toxin-producing phytoplankton) were present in nearly all three main production areas and years. The main DSP toxin-producing species was Dinophysis acuminata followed by D. rotundata and Prorocentrum lima. Toxins causing paralytic shellfish poisoning (PSP) and amnesic shellfish poisoning (ASP) were present in only a few individual shellfish samples, all at low levels. At the end of 2002, an episode of DSP toxicity was recorded, based on the rat bioassay results. Of the samples that were chemically analysed for DSP toxins in 2007 and 2008, about half of the samples in 2007 contained these toxins, although levels were low and no positive results were obtained using the rat bioassay. There was a slight positive correlation between concentrations of DSP toxin-producing phytoplankton and levels of DSP toxins in 2007. Increased DSP toxin levels were found up to 5 weeks after the peak in DSP toxin-producing phytoplankton. This positive, but weak, relationship needs to be confirmed in future research using more samples and chemical methods to quantify the presence of DSP toxins. If this relationship is further substantiated and quantified, it could be used within the current monitoring programme in the Netherlands to predict the risk areas regarding DSP toxicity in shellfish.

Quantitative determination of marine lipophilic toxins in mussels, oysters and cockles using liquid chromatography-mass spectrometry: inter-laboratory validation study.

Thirteen laboratories participated in an inter-laboratory study to evaluate the method performance characteristics of a liquid chromatography-tandem mass spectrometric method (LC-MS/MS) for marine lipophilic shellfish toxins. Method performance characteristics were evaluated for mussel (Mytilus edulis), oyster (Crassostrea gigas) and cockle (Cerastoderma edule) matrices. The specific toxin analogues tested included okadaic acid (OA), dinophysistoxins-1 and -2 (DTX1, -2), azaspiracids-1, -2 and -3 (AZA1, -2, -3), pectenotoxin-2 (PTX2), yessotoxin (YTX), and 45-OH-yessotoxin (45-OH-YTX). The instrumental technique was developed as an alternative to the still widely applied biological methods (mouse or rat bioassay). Validation was conducted according to the AOAC-harmonised protocol for the design, conduct and interpretation of method-performance studies. Eight different test materials were sent as blind duplicates to the participating laboratories. Twelve laboratories returned results that were accepted to be included in the statistical evaluation. The method precision was expressed as HORRATs. For the individual toxins (except for 45-OH-YTX) HORRATs were found to be ≤1.8 (median HORRAT=0.8) in all tested materials. The recoveries of OA-, AZA- and YTX-group toxins were within the range of 80-108% and PTX2 was within the range of 62-93%. Based on the acceptable values for precision and recovery, it was concluded that the method is suitable for official control purposes to quantitatively determine OA/DTXs, AZAs, YTXs and PTX2 in shellfish.