Characterization of paralytic shellfish toxins in seawater and sardines (Sardina pilchardus) during blooms of Gymnodinium catenatum

Abstract

The re-emergence of Gymnodinum catenatum blooms after a 10 year hiatus of absence initiated the present investigation. This study aims to evaluate the exposure of small pelagic fishes to paralytic shellfish toxins (PST) during blooms of G. catenatum. Sardines (Sardina pilchardus) were selected as a representative fish species. In order to assess toxin availability to fish, both intracellular PSTs (toxin retained within the algal cells) and extracellular PSTs (toxin found in seawater outside algal cells) were quantified, as well as toxin levels within three fish tissue matrices (viscera, muscle and brain). During the study period, the highest cell densities of G. catenatum reached 2.5 9 10 4 cells l -1 and intracellular PST levels ranged from 3.4 to 398 ng STXeq l -1 as detected via an enzyme linked immunosorbent assay (ELISA). Measurable extracellular PSTs were also detected in seawater (0.2-1.1 lg STXeq l -1 ) for the first time in Atlantic waters. The PST profile in G. catenatum was determined via high performance liquid chromatography with fluorescence detection (HPLC-FLD) and consisted mostly of sulfocarbamoyl (C1?2, B1) and decarbamoyl (dcSTX, dcGTX2?3, dcNEO) toxins. The observed profile was similar to that reported previously in G. catenatum blooms in this region before the 10-year hiatus. Sardines, planktivorous fish that ingest a large number of phytoplankton cells, were found to contain PSTs in the viscera, reaching a maximum of 531 lg STXeq kg -1 . PSTs were not detected in corresponding muscle or brain tissues. The PST profile characterized in sardine samples consisted of the same sulfocarbamoyl and decarbamoyl toxins found in the algal prey with minor differences in relative abundance of each toxin. Overall, the data suggest that significant biotransformation of PSTs does not occur in sardines. Therefore, planktivorous fish may be a good tracer for the occurrence of offshore G. catenatum blooms and the associated PSTs produced by these algae.

Gymnodinium catenatum Graham isolated from the Portuguese coast: Toxin content and genetic characterization

“…The distribution and population dynamics of Gymnodinium catenatum have been studied along the Portuguese coast (e.g. Amorim et al, 2001;Moita et al, 2003;Pitcher et al, 2010), but still little is known about toxin and genotypic variability of G. catenatum strains within regional populations (Costa et al, 2010). The aim of this study was to investigate possible toxin and genetic variability of G. catenatum populations present in Portuguese coastal waters.…”

Paralytic shellfish toxins in the Atlantic horse mackerel (<i>Trachurus trachurus</i>) over a bloom of <i>Gymnodinium catenatum</i>: the prevalence of decarbamoylsaxitoxin in the marine food web

“…While a good correlation was previously reported between cell densities of G. catenatum and sardines (Costa et al 2010), the Atlantic horse mackerel does not feed directly on algae, which means that toxin levels may not correlate well with the toxigenic algae. The relatively weak intensity of the bloom, expressed by the maximum cell density of 5.0 10 3 cells l -1 , may suggest that mackerel must have ingested a high biomass of contaminated prey to accumulate such high PST levels.…”

“…While dcSTX is a minor component of the profile of G. catenatum, usually corresponding to approximately 4% of the toxins (Negri et al 2007, Costa et al 2010, 2012, it accounted for more than 50% of the amount of toxins in Atlantic horse mackerel. B1 was the second most important toxin analogue detected in fish.…”

“…In fact, investigations on the profile of PSTs in sardines (Sardina pilchardus) exposed to blooms of Gymnodinium catenatum have shown minor changes between the fish and algae, suggesting that sardines, which have a filter feeding behavior in the presence of algal blooms, ingesting large amounts of toxic algae, are a good tracer for the occurrence of harmful algal blooms and the associated PSTs (Costa et al 2010). Conversely, fishes at higher trophic levels are expected to reveal an altered profile of PSTs (Landsberg 2002).…”

“…Toxin extraction and cleanup procedures were performed according to Lawrence and Niedzwiadek (2001) and Costa et al (2010). Before HPLC analysis, aliquots of the C18 extracts were derivatized with peroxide and periodate oxidants while aliquots of SPE-COOH fractions were only used for periodate oxidation.…”