Brevetoxicosis: Red tides and marine mammal mortalities

University of North Carolina at Wilmington, Wilmington, North Carolina, United States
Nature (Impact Factor: 41.46). 07/2005; 435(7043):755-6. DOI: 10.1038/nature435755a
Source: PubMed


Potent marine neurotoxins known as brevetoxins are produced by the 'red tide' dinoflagellate Karenia brevis. They kill large numbers of fish and cause illness in humans who ingest toxic filter-feeding shellfish or inhale toxic aerosols. The toxins are also suspected of having been involved in events in which many manatees and dolphins died, but this has usually not been verified owing to limited confirmation of toxin exposure, unexplained intoxication mechanisms and complicating pathologies. Here we show that fish and seagrass can accumulate high concentrations of brevetoxins and that these have acted as toxin vectors during recent deaths of dolphins and manatees, respectively. Our results challenge claims that the deleterious effects of a brevetoxin on fish (ichthyotoxicity) preclude its accumulation in live fish, and they reveal a new vector mechanism for brevetoxin spread through food webs that poses a threat to upper trophic levels.

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    • "If PbTx remains sequestered in tissues after bloom dissipation this poses a threat to predators including commercially important crab and fish, subsequently transferring toxins through the trophic web even long after a red tide event has subsided. Stomach content analyses in post bloom fish and dolphin mortalities have revealed fish with high levels of PbTx (Flewelling et al., 2005) and seabirds with toxic clams in the gut (Forrester et al., 1977) indicating a lethal dose through trophic transfer (Landsberg et al., 2009). Likewise, dead burrfish (Chilomycterus schoepfi) collected during a red tide bloom had the remains of toxic bivalves in their stomachs (Naar et al., 2007). "
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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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    • "Kirkpatrick et al. (2010) found ED visits for digestive illnesses at the Sarasota Memorial Hospital increased by 40% during an FRT bloom event in 2001 (0.07 ± 0.01 per 100,000 cases) relative to 2002 (0.05 ± 0.01 per 100,000 cases) when there was no FRT bloom. Although shellfish harvest areas (SHAs) typically were closed during FRT blooms to mitigate the risks of NSP from the consumption of molluscan bivalves, these authors argued that humans could be contracting digestive illnesses through other pathways, including the consumption of illegally harvested shellfish, whole finfish (especially the entrails, where brevetoxins may be concentrated), the breathing of aerosols contaminated with brevetoxins, or the inadvertent swallowing of contaminated seawater (Flewelling et al., 2005). "
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    ABSTRACT: Human respiratory and digestive illnesses can be caused by exposures to brevetoxins from blooms of the marine alga Karenia brevis, also known as Florida red tide (FRT). K. brevis requires macro-nutrients to grow; although the sources of these nutrients have not been resolved completely, they are thought to originate both naturally and anthropogenically. The latter sources comprise atmospheric depositions, industrial effluents, land runoffs, or submerged groundwater discharges. To date, there has been only limited research on the extent of human health risks and economic impacts due to FRT. We hypothesized that FRT blooms were associated with increases in the numbers of emergency room visits and hospital inpatient admissions for both respiratory and digestive illnesses. We sought to estimate these relationships and to calculate the costs of associated adverse health impacts. We developed environmental exposure-response models to test the effects of FRT blooms on human health, using data from diverse sources. We estimated the FRT bloom-associated illness costs, using extant data and parameters from the literature. When controlling for resident population, a proxy for tourism, and seasonal and annual effects, we found that increases in respiratory and digestive illnesses can be explained by FRT blooms. Specifically, FRT blooms were associated with human health and economic effects in older cohorts (≥55years of age) in six southwest Florida counties. Annual costs of illness ranged from $60,000 to $700,000 annually, but these costs could exceed $1.0million per year for severe, long-lasting FRT blooms, such as the one that occurred during 2005. Assuming that the average annual illness costs of FRT blooms persist into the future, using a discount rate of 3%, the capitalized costs of future illnesses would range between $2 and 24million.
    Full-text · Article · Apr 2014 · Environment international
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    • "natans) may reflect incidental, attritional input or actual HAB-mediated mortality based on extant HAB toxin transfers (i.e. inhalation) for modern herbivorous marine mammals [40]. Collectively, the taphonomy of Cerro Ballena indicates that repeated marine mammal mortalities were relatively rapid (hours to weeks in duration), geographically widespread and allochthonous (i.e. at sea). "
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    ABSTRACT: Marine mammal mass strandings have occurred for millions of years, but their origins defy singular explanations. Beyond human causes, mass strandings have been attributed to herding behaviour, large-scale oceanographic fronts and harmful algal blooms (HABs). Because algal toxins cause organ failure in marine mammals, HABs are the most common mass stranding agent with broad geographical and widespread taxonomic impact. Toxin-mediated mortalities in marine food webs have the potential to occur over geological timescales, but direct evidence for their antiquity has been lacking. Here, we describe an unusually dense accumulation of fossil marine vertebrates from Cerro Ballena, a Late Miocene locality in Atacama Region of Chile, preserving over 40 skeletons of rorqual whales, sperm whales, seals, aquatic sloths, walrus-whales and predatory bony fish. Marine mammal skeletons are distributed in four discrete horizons at the site, representing a recurring accumulation mechanism. Taphonomic analysis points to strong spatial focusing with a rapid death mechanism at sea, before being buried on a barrier-protected supratidal flat. In modern settings, HABs are the only known natural cause for such repeated, multispecies accumulations. This proposed agent suggests that upwelling zones elsewhere in the world should preserve fossil marine vertebrate accumulations in similar modes and densities.
    Full-text · Article · Feb 2014 · Proceedings of the Royal Society B: Biological Sciences
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