Article

Monitoring of brevetoxins in the Karenia brevis bloom-exposed Eastern oyster (Crassostrea virginica)

Gulf Coast Seafood Laboratory, U.S. Food and Drug Administration, 1 Iberville Drive, Dauphin Island, AL 36528, USA.
Toxicon (Impact Factor: 2.49). 05/2008; 52(1):32-8. DOI: 10.1016/j.toxicon.2008.04.174
Source: PubMed

ABSTRACT

Brevetoxin uptake and elimination were examined in Eastern oyster (Crassostrea virginica) exposed to recurring blooms of the marine alga Karenia brevis in Sarasota Bay, FL, over a three-year period. Brevetoxins were monitored by in vitro assays (ELISA, cytotoxicity assay, and receptor binding assay) and LC-MS, with in vivo toxicity of shellfish extracts assessed by the traditional mouse bioassay. Measurements by all methods reflected well the progression and magnitude of the blooms. Highest levels recorded by mouse bioassay at bloom peak were 157 MU/100g. Oysters were toxic by mouse bioassay at levels >or=20 MU/100g for up to two weeks after bloom dissipation, whereas brevetoxins were measurable by in vitro assays and LC-MS for several months afterwards. For the structure-based methods, summed values for the principal brevetoxin metabolites of PbTx-2 (cysteine and cysteine sulfoxide conjugates), as determined by LC-MS, were highly correlated (r(2)=0.90) with composite toxin measurements by ELISA. ELISA and LC-MS values also correlated well (r(2)=0.74 and 0.73, respectively) with those of mouse bioassay. Pharmacology-based cytotoxicity and receptor binding assays did not correlate as well (r(2)=0.65), and were weakly correlated with mouse bioassay (r(2)=0.48 and 0.50, respectively). ELISA and LC-MS methods offer rapid screening and confirmation, respectively, of brevetoxin contamination in the oyster, and are excellent alternatives to mouse bioassay for assessing oyster toxicity following K. brevis blooms.

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    • "Red tide blooms formed by the toxic dinoflagellate Karenia brevis are a regular occurrence in the Gulf of Mexico, especially along the coast of Florida, resulting in high fish mortality rates (Ray & Wilson 1957; Naar et al. 2007) and marine mammal, sea turtle, and seabird casualties (Flewelling et al. 2005, Landsberg et al. 2009). Conversely, local bivalves have been documented to have high survival rates during red tide blooms (Pierce et al. 2004; Plakas et al. 2008); however, sublethal effects during short term laboratory studies have demonstrated reduced clearance rates (Leverone et al. 2007), loss of muscle control (Roberts et al. 1979), increased susceptibility to disease and infection (Landsberg 2002), and subcellular effects including lysosomal disruption and alterations in lipid peroxidation (Keppler et al. 2006). Sessile organisms, such as marine bivalves, may be exposed to sublethal concentrations that persist for months, potentially amplifying adverse effects observed in laboratory studies and presenting greater consequences to overall health, growth, and survival of the organism due to chronic effects of prolonged exposure (Griffith et al. 2013; McFarland et al. 2015). "
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    ABSTRACT: Red tide blooms formed by Karenia brevis are frequent along the Gulf coast of Florida and it is unclear what tolerance the green mussel Perna viridis, a recently introduced species to coastal waters, has toward these events. Established populations of P. viridis were monitored along the coastal waters of Estero Bay, Florida before, during and following two consecutive red tide blooms to assess the potential effects on growth, survival and juvenile recruitment. Upon onset of the bloom, growth rates fell from 6 – 10 mm month-1 (March 2011 – November 2011) to less than 3 mm month-1. In the succeeding years, K. brevis blooms were present, and average growth of individually tagged mussels remained below 3 mm month-1. During growth monitoring the use of calcein as an internal marker was tested with positive staining results and no observed effect on growth or survival. In March 2012, following the first red tide bloom, a population-wide mortality event was observed. Following this event, increased mortality rates were observed with peaks during onset of the bloom in the fall of 2012 and 2013. Juvenile recruitment was also limited during years in which blooms persisted into the spring spawning period suggesting gamete and / or larval sensitivity to K. brevis. Although it cannot be conclusively determined that the cause of reduced growth and survival is due to red tide events, the parallels observed suggest that K. brevis is a factor in the observed changes in population structure.
    Full-text · Article · Dec 2015 · Toxicon
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    • "Shellfish beds are monitored regularly for both K. brevis cell counts and tissue toxin concentration, particularly during and following bloom events. Closure of shellfish harvesting is required if K. brevis cell counts exceed 5,000 cells L -1 or shellfish tissue concentrations exceed 800 ng g -1 PbTx-3 equivalent brevetoxin (Plakas et al., 2008). "
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    ABSTRACT: Perna viridis is a recently introduced species to US coastal waters and have vigorously spread throughout the southeastern seaboard since their invasion. Little information regarding their response to local environmental factors has been reported including responses to the local HAB species, Karenia brevis. This study monitored the tissue toxin concentration of brevetoxins in P. viridis from existing populations throughout two consecutive natural K. brevis blooms. The results showed P. viridis to rapidly accumulate PbTx upon exposure to the bloom, far exceeding the peak tissue concentrations of oysters, Crassostrea virginica, sampled during the same period, 57,653 ± 15,937 and 33,462 ± 10,391 ng g−1 PbTx-3 equivalent respectively. Further, P. viridis retained high PbTx concentrations in their tissues post bloom remaining above the regulatory limit for human consumption for 4–5 months, significantly longer than the depuration time of 2–8 weeks for native oyster and clam species. In the second year, the bloom persisted at high cell concentrations resulting in prolonged exposure and higher PbTx tissue concentrations indicating increased bioaccumulation in green mussels. While this species is not currently harvested for human consumption, the threat for post bloom trophic transfer could pose negative impacts on other important fisheries and higher food web implications.
    Full-text · Article · Feb 2015 · Toxicon
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    • ") of 0.5 and 0.6 (Fig. 7), respectively; in the Eastern oyster, correlation coefficient values of 0.7 were reported (Plakas et al., 2008). The mild conditions used for LC-MS and ELISA extract preparation is expected to preserve the structural integrity of brevetoxins as present in clams and the results reflective of the major metabolites. "
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    ABSTRACT: Brevetoxins in clams (Mercenaria sp.) exposed to recurring blooms of Karenia brevis in Sarasota Bay, FL, were studied over a three-year period. Brevetoxin profiles in toxic clams were generated by ELISA and LC-MS. Several brevetoxin metabolites, as identified by LC-MS, were major contributors to the composite brevetoxin response of ELISA. These were S-desoxyBTX-B2 (m/z 1018), BTX-B2 (m/z 1034), BTX-B5 (m/z 911), open A-ring BTX-B5 (m/z 929), and BTX-B1 (m/z 1018). Summed values of these metabolites were highly correlated (R2 = 0.9) with composite B-type brevetoxin measurements by ELISA. S-desoxyBTX-B2, BTX-B2, and BTX-B1 were the most persistent and detectable in shellfish for several months after dissipation of blooms. These metabolites were selected as LC-MS biomarkers of brevetoxin exposure and reflective of composite B-type brevetoxins in hard clam. ELISA and LC-MS values were moderately correlated with toxicity of the shellfish by mouse bioassay. ELISA and LC-MS methods offer rapid screening and confirmatory determination of brevetoxins, respectively, as well as toxicity assessment in clams exposed to K. brevis blooms.
    Full-text · Article · Jan 2015 · Toxicon
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