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Simulating cell death in the termination of Karenia brevis blooms: Implications for predicting aerosol toxicity vectors to humans

Author(s): Lenes, J. M.; J. J. Walsh; B. P. Darrow


Name of Publisher: Inter-Research Science Center

Place of Publication: Lüneburg, Germany

Publication Type: Journal Article

Journal Title: Marine Ecology Progress Series

Date of Publication: 2013

Reference Information: 493

Extent of Work: 71-81

Keywords: harmful algal blooms; brevetoxins; Karenia brevis; lysis; bacteria; asthma

Abstract: To predict both waterborne and aerosolized toxin vectors associated with harmful algal blooms (HABs) of Karenia spp. in European, Asian, and North American waters, loss processes associated with distinct stages of bloom development, maintenance, and termination must be 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 during cell death leads to respiratory difficulties of mammals. Human asthma attacks and chronic obstructive pulmonary disease occurs once HAB toxins are aerosolized and transported to the coast. Here, we test the hypothesis that heterotrophic bacterioplankton are a major source of mortality for Karenia HABs. A non-linear lysis term for simulation of K. brevis HAB termination on the West Florida Shelf is introduced, with the assumption that particle encounters of planktonic microalgae and bacteria can be described as the square of the phytoplankton biomass. This formulation also accounts for nutrient-limitation of K. brevis as a precondition for susceptibility to bacterial and viral attack, and potentially programmed cell death. Two model simulations were run of linear and non-linear lysis cases. Model output was compared against observed weekly maximum K. brevis concentrations, with statistical metrics calculated over three HAB phases during 2001. Introduction of the non-linear lysis term increased the modeling efficiency by 0.68 due to improved reproduction of the bloom termination.

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