Karenia nutrient dynamics in the Eastern Gulf of Mexico

  • Funded by EPA ECOHAB.  September 2006 to August 2011 Bronk, Co-PI.
  • Bronk part $499,823.  Lead PI Cindy Heil (FFWCC)...and many others.

The nutrient sources that support and regulate environmentally and economically destructive blooms of Karenia brevis  in the eastern Gulf of Mexico remain enigmatic. K. brevis blooms in Florida are annually predictable, have severe economic and environmental impacts, and are closely monitored and so are an ideal system to examine the complexity of nutrient interactions with harmful algal blooms (HABs) throughout entire bloom cycles (initiation and development, maintenance, and decline). To examine how nutrients regulate K. brevis blooms, the following two hypotheses will be tested:

  1. multiple nutrient sources and forms support K. brevis blooms, with the relative contribution of each source depending on bloom physiological state, bloom environment (e.g., lagoonal, lower estuarine, coastal, offshore), and location along a latitudinal gradient, and
  2. K. brevis is a mixotroph with a flexible metabolism whose limiting growth factors and metabolic preferences vary with the environment.
We propose a workplan that will combine biological, chemical, and physical measurements with modeling efforts to examine how K. brevis is able to sustain high biomass blooms in oligotrophic environments for extended periods.

This proposal brings together a multidisciplinary team with extensive expertise on nutrients, HABs, K. brevis, and the southwest Florida environment to identify, quantify and model nutrient inputs and cycling over the entire range of K. brevis bloom stages and environments. Efforts will combine a retrospective analysis of the 2001 bloom with targeted laboratory studies, comparative field studies across environments and bloom stages, identification and quantification of multiple nutrient sources, measurement of physical flows, and three-dimensional coupled biophysical modeling of near and offshore K. brevis blooms and environments.