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- SourceAvailable from: Mª.Teresa Moita[Show abstract] [Hide abstract]
ABSTRACT: Gymnodinium catenatum, a dinoflagellate species with a global distribution, is known to produce paralytic shellfish poisoning (PSP) toxins. The profile of toxins of G. catenatum is commonly dominated by sulfocarbamoyl analogs including the C3 + 4 and GTX6, which to date has no commercial certified reference materials necessary for their quantification via chemical methods, such as liquid chromatography. The aim of this study was to assess the presence of C3 + 4 and GTX6 and their contribution to shellfish toxicity. C3 + 4 and GTX6 were indirectly quantified via pre-column oxidation liquid chromatography with fluorescence detection after hydrolysis conversion into their carbamate analogs. Analyses were carried out in mussel samples collected over a bloom of G. catenatum (>63 × 103 cells l−1) in Aveiro lagoon, NW Portuguese coast. Concentration levels of sulfocarbamoyl toxin analogs were two orders of magnitude higher than decarbamoyl toxins, which were in turn one order of magnitude higher than carbamoyl toxins. Among the sulfocarbamoyl toxins, C1 + 2 were clearly the dominant compounds, followed by C3 + 4 and GTX6. The least abundant sulfocarbamoyl toxin was GTX5. The most important compounds in terms of contribution for sample toxicity were C1 + 2, which justified 26% of the PSP toxicity. The lesser abundant dcSTX constitutes the second most important compound with similar % of toxicity to C1 + 2, C3 + 4 and GTX6 were responsible for approximately 11% and 13%, respectively. The median of the sum of C3 + 4 and GTX6 was 27%. These levels reached a maximum of 60% as was determined for the sample collected closest to the G. catenatum bloom. This study highlights the importance of these low potency PSP toxin analogs to shellfish toxicity. Hydrolysis conversion of C3 + 4 and GTX6 is recommended for determination of PSP toxicity when LC detection methods are used for PSP testing in samples exposed to G. catenatum.
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ABSTRACT: This work reports changes of Cr, Cu, Zn, Cd, Hg and Pb concentrations in the dissolved fraction, suspended particulate matter and immobilised Phaeodactylum tricornutum Bohlin (Bacillariophyceae), as well as of microalgae specific growth rates, during a 5-month period dredging operation in a contaminated area of the Tagus estuary, Portugal. Trace element concentrations showed broad variations in the dissolved fraction and suspended particulate matter, presumably reflecting rapid exchanges of redox-sensitive elements between water and particles, in conjunction with the dilution effect caused by the tidal excursion. Immobilised cells exposed to dredging environmental conditions showed significantly higher concentrations of Cr, Cu, Zn, Cd, Hg and Pb than under no dredging conditions. Concomitantly, specific cell growth was significantly lower, suggesting that elements released with dredging affect the microalgae physiology. The results obtained in this in situ work imply that the dissolved fraction and the suspended particulate matter are relatively ineffective indicators of the trace element enhancement during dredging and pointed out immobilised P. tricornutum as a reliable and efficient biomonitoring tool for the assessment of trace element remobilisation.
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ABSTRACT: Marine phycotoxins derived from harmful algal blooms are known to be associated with mass mortalities in the higher trophic levels of marine food webs. Bivalve mollusks and planktivorous fish are the most studied vectors of marine phycotoxins. However, field surveys recently showed that cephalopod mollusks also constitute potential vectors of toxins. Thus, here we determine, for the first time, the time course of accumulation and depuration of paralytic shellfish toxins (PSTs) in the common octopus (Octopus vulgaris). Concomitantly, the underlying kinetics of toxin transfer between tissue compartments was also calculated. Naturally contaminated clams were used to orally expose the octopus to PSTs during 6 days. Afterwards, octopus specimens were fed with non-contaminated shellfish during 10 days of depuration period. Toxins reached the highest concentrations in the digestive gland surpassing the levels in the kidney by three orders of magnitude. PSTs were not detected in any other tissue analyzed. Net accumulation efficiencies of 42% for GTX5, 36% for dcSTX and 23% for C1+2 were calculated for the digestive gland. These compounds were the most abundant toxins in both digestive gland and the contaminated shellfish diet. The small differences in relative abundance of each toxin observed between the prey and the cephalopod predator indicates low conversion rates of these toxins. The depuration period was better described using an exponential decay model comprising a single compartment - the entire viscera. It is worth noting that since octopuses' excretion and depuration rates are low, the digestive gland is able to accumulate very high toxin concentrations for long periods of time. Therefore, the present study clearly shows that O. vulgaris is a high-potential vector of PSTs during and even after the occurrence of these toxic algal blooms.
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