A 1-D Simulation Analysis of the Development and Maintenance of the 2001 Red Tide of the Ichthyotoxic Dinoflagellate Karenia brevis on the West Florida Shelf
NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
Pagination or Media Count:
A one-dimensional 1-D ecological model, HABSIM, examined the initiation and maintenance of the 2001 red tide on the West Florida shelf WFS. Phytoplankton competition among toxic dinoflagellates Karenia brevis, nitrogen fixing cyanophytes Trichodesmium erythraeum, large siliceous phytoplankton diatoms, and small non-siliceous phytoplankton microflagellates explored the sequence of events required to support the observed red tide from August to December 2001. The ecological model contained 24 state variables within five submodels circulation, atmospheric iron deposition, bio-optics, pelagic phytoplankton, nutrients, bacteria, zooplankton, and fish, and benthic nutrient regeneration. The 2001 model results reaffirmed that diazotrophs are the basis for initiation of red tides of K. brevis on the WFS. A combination of selective grazing pressure, iron fertilization, low molar nitrogen to phosphorus ratios, and eventual silica limitation of fast-growing diatoms set the stage for dominance of nitrogen fixers. New nitrogen was made available for subsequent blooms of K. brevis through the release of ammonium and urea during nitrogen fixation, as well as during cell lysis, by the Trichodesmium population. Once K. brevis biomass reached ichthyotoxic levels, rapid decay of subsequent fish kills supplied additional organic nutrients for utilization by these opportunistic toxic algae. Both nutrient vectors represented organic non-siliceous sources of nitrogen and phosphorus, further exacerbating silica limitation of the diatom population. The model reproduced this spring transition from a simple estuarine-driven, diatom-based food chain to a complex summer -fall system of Trichodesmium and toxic dinoflagellates. While the model was able to replicate the initiation and maintenance of the 2001 red tide, bloom termination was not captured by this 1-D form on the WFS.
- Physical and Dynamic Oceanography