Simulating Cell Death in the Termination of Karenia brevis Blooms: Implications for Predicting Aerosol Toxicity Vectors to Humans

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Harmful algal blooms, Brevetoxins, Karenia brevis, Lysis, Bacteria, Asthma

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To predict both waterborne and aerosolized toxin vectors associated with harmfulalgal blooms (HABs) of Kareniaspp. in European, Asian, and North American waters, loss pro-cesses associated with distinct stages of bloom development, maintenance, and termination mustbe defined in relation to their toxins. In the case of Karenia brevis, exposure to brevetoxins (PbTx)during maintenance phase is detrimental to marine life. In addition, release of PbTx-2, 3 duringcell death leads to respiratory difficulties in mammals. Human asthma attacks and chronicobstructive pulmonary disease occur once HAB toxins are aerosolized and transported to thecoast. Here, we tested the hypothesis that heterotrophic bacterioplankton are a major source ofmortality for KareniaHABs. A non-linear lysis term for simulation of K. brevisHAB termination onthe West Florida Shelf was introduced, with the assumption that particle encounters of planktonicmicroalgae and bacteria can be described as the square of the phytoplankton biomass. This for-mulation also accounts for nutrient-limitation of K. brevisas a precondition for susceptibility tobacterial and viral attack, and potentially programmed cell death. Two model simulations wererun of linear and non-linear lysis cases. Model output was compared against observed weeklymaximum K. brevisconcentrations, with statistical metrics calculated over 3 HAB phases during2001. Introduction of the non-linear lysis term increased the modeling efficiency by 0.68 due toimproved reproduction of the bloom termination.

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Marine Ecology Progress Series, v. 493, p. 71-81