Monitoring of brevetoxins in the Karenia brevis bloom-exposed Eastern oyster (Crassostrea virginica)
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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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.Toxicon 01/2015; 96. DOI:10.1016/j.toxicon.2015.01.014 · 2.58 Impact Factor
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ABSTRACT: Harmful algal blooms can cause mass mortalities of top predators such as fish, marine mammals and seabirds but the food web transfer from toxic phytoplankton to these organisms has not been fully elucidated. Macrobenthic invertebrates in coastal waters, including bivalve suspension- and deposit-feeders, carnivorous gastropods, deposit-feeding amphipods and polychaetes, are a major food source for a wide variety of predators and can thus play a critical role in the trophic transfer of algal toxins to higher trophic levels. The objective of this study was to investigate toxin accumulation in transplanted juvenile hard clams, Mercenaria mercenaria, a species naturally occurring in the region, and in various macrobenthic functional groups from Florida coastal waters during a natural bloom of the dinoflagellate, Karenia brevis, a producer of brevetoxins. Bloom concentrations in the water column ranged from 100 to 1200 cells ml−1 over the course of the experiment. This study revealed that these lipophilic toxins can be rapidly accumulated by both suspension- and deposit-feeding benthos, especially bivalve molluscs [1.9–2.8 μg PbTx-3 eq (g wet weight)−1]. Transplanted M. mercenaria rapidly accumulated toxins from the water column attaining ∼0.5 μg PbTx-3 eq (g wet tissue)−1 after only 4 h-exposure to the K. brevis bloom and a maximum value of 1.5 ± 0.2 μg PbTx-3 eq (g wet tissue)−1 after 72 h. Relatively high brevetoxin concentrations were also measured in co-occurring benthic carnivorous gastropods [1–2.6 μg PbTx-3 eq (g wet weight, WW)−1]. Mean toxin concentrations in polychaetes and crustaceans varied in the range ∼0.04–0.2 μg PbTx-3 eq (g WW)−1 over the study period, and thus were typically lower than in molluscs. This study demonstrated in situ toxin accumulation by benthic primary and secondary consumers during a natural Florida red tide. Accumulation by primary consumers may be highly variable in space and time (as shown in bivalves from the natural benthic community) and among taxonomic groups. Toxin transfer further up the food web will thus depend on the toxin level accumulated in prey, the number of pathways from which the predator may accumulate toxins and on possible biological magnification of lipophilic toxins. Overall, this study revealed qualitatively and quantitatively that benthic consumers of a number of taxa can serve as vectors for transporting brevetoxins within the food web.Harmful Algae 04/2012; 16:27–34. DOI:10.1016/j.hal.2012.01.001 · 3.34 Impact Factor
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ABSTRACT: The harmful alga, Karenia brevis, produces a suite of polyether neurotoxins, brevetoxins or PbTx, that cause marine animal mortality and neurotoxic shellfish poisoning (NSP). A characteristic of K. brevis blooms is associated airborne toxins that result in severe respiratory problems. This study was undertaken to determine the composition of aerosolized brevetoxins and oxidative derivatives to which beachgoers are exposed during a K. brevis bloom. The suite of brevetoxins and derivatives in seawater is comprised of intra-cellular (IC) and extra-cellular (EC) compounds. We hypothesized that aerosolized compounds are generated primarily from EC, hydrophobic compounds in seawater by bubble-mediated transport. Thus the composition of aerosolized brevetoxins and derivatives, to which beachgoers are exposed, would reflect the EC composition of the source matrix (the local surf zone). Brevetoxins were extracted from water collected along the shore and from marine aerosols along Siesta Beach and Lido Beach in Sarasota, FL, USA, during K. brevis blooms. Water samples were further processed into IC and EC components. The primary brevetoxins observed in water and air included PbTx-1, -2, -3, -PbTx-2-carboxylic acid, and brevenal. Oxidation and/or hydrolysis products of PbTx-1, -2, -3 and -7 were also found in EC water and in aerosol, but not IC.Journal of Plankton Research 02/2011; 33(2):343-348. DOI:10.1093/plankt/fbq115 · 2.26 Impact Factor