Document Type

Theses, Ph.D

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This item is available under a Creative Commons License for non-commercial use only

Abstract

The consumption of shellfish that accumulate marine biotoxins produced by harmful Algae can result in severe gastrointestinal or neurotoxic illnesses depending on the nature of the toxin. Therefore, it is essential that suitable monitoring programs are implemented in order to protect public health. This PhD study focused on aspects of the characteristics and monitoring of azaspiracids and toxins from Dinophysis spp. Passive samplers were used in this study in parallel with both indigenous and transplanted mussels that did not contain toxins to investigate the accumulation of toxins on the West coast of Ireland during 2005. This approach allowed for a number of observations including the persistence and contamination characteristics of azaspiracids, high levels of okadaic acid toxins in the water which did not induce shellfish contamination and non-suitability of passive sampling for early warning of shellfish contamination when placed in the same location as the shellfish. Furthermore, several sampling materials were compared in mesocosm experiments (culture of Prorocentrum lima) where the adsorption and desorption behaviour of okadaic acid and dinophysistoxin-1 were examined. A rapid and efficient extraction method was developed for a wide range of toxins. The current EU reference method for the determination of lipophilic marine toxins is the mouse bioassay. Efforts toward the replacement of the non-ethical and non specific animal test has been suggested and LC-MS is perceived as an alternative method of choice. However, LC-MS methods suffer from highly variable matrix effects affecting quantitation of the toxins. This study has evaluated three approaches fro the evaluation of matrix effects in the analysis of okadaic acid, azaspiracid-1 and pectenotoxin-2. The influence of shellfish species, heat treatment and amount of dry residue in the shellfish extracts on the degree of matrix effects were evaluated. Additionally, a rapid Ultra-Performance LC-MS method for the analysis of 21 lipophilic marine toxins in 6.5 min was developed and matrix effects were evaluated. A phytoplankton survey was carried out in the Celtic Sea in July 2007. Dinophysis acuta was found at high concentrations. Seawater was sampled from specific depths. The toxin profile of the phytoplankton was established in samples collected over a 14 h cycles. Pectenotoxins, okadaic acid and dinophysistoxin-2 were detected in the phytoplankton and were not found to be produced at a particular time of the day. The toxins accumulated and their concentration ratios in passive samplers were identical to those observed in D. acuta. Passive samplers deployed at 110m depth and a phytoplankton sample from 80 m depth allowed for the establishment of the toxin profiles. In both cases, the toxin profiles and concentration ratios compared well with the samples obtained from other depths suggesting that D. acuta can occur and produce toxins in the absence of light. Recent developments in the field of chromatography have shown that the water octanol partition coefficient (log Pow) of chemicals can be evaluated from the retention time. The method uses a calibration curve from compounds with know logPow. The partition coefficient of toxins was investigated as an important physicochemical parameter governing the accumulation of toxins in passive samplers. Knowledge of the acidity constant (pKa) is essential as log Pow should be established in dissociated molecules.

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