A scoping and consensus building model of a toxic blue-green algae bloom

Nuisance blooms of Lyngbya majuscula have been occurring with increasing frequency in tropical coastal waters around the world. Outbreaks of this cyanobacterium (blue-green algae) threaten water quality, coastal ecosystems, and can be harmful in instances of human contact. While scientific and popular theories abound regarding Lyngbya bloom initiation and growth, a clear research agenda has not emerged. This article offers a scoping and consensus building model for the development of research directions. The model is based on the hypothesis that Lyngbya is iron limited and that blooms are initiated and perpetuated in response to increased bioavailable iron concentrations. Interacting model sectors for Lyngbya, bioavailable iron, dissolved oxygen, and seagrass have been developed. Simulations show that the occurrence of Lyngbya bloom is sensitive to a number of uncertain parameters and model structures, including inflows and decay times of organically complexed iron, Lyngbya maximum growth rate and half-saturation constant for bioavailable iron, and bioturbation. Development of the first stage scoping model is reported here, as are simulation results that are instrumental in setting priorities for empirical investigations and future simulation-based research. It is expected that this model, after additional empirical work is completed, will lead to research and management models that will help set policy for community response to Lyngbya blooms. Copyright (C) 2004 John Wiley Sons, Ltd.