A brief summary of the physiology and ecology of Karenia brevis Davis (G. Hansen and Moestrup comb. nov.) red tides on the West Florida Shelf and of hypotheses posed for their initiation, growth, maintenance, and termination

Abstract

This contribution represents a review of the historical and recent literature describing the environmental factors that relate to the distribution, growth, primary production, nutrient requirements and utilization along with hypotheses that are extant for the initiation, growth, maintenance and termination of Karenia brevis blooms on the West Florida Shelf. Potential nutrient sources that support blooms and relate to recent questions on the duration, frequency, and intensity of WFS blooms are summarized and some thoughts are presented which relate to the question of why K. brevis, a slow growing dinoflagellate, becomes dominant in a nearshore shelf region that is typically dominated by diatoms. There is no single hypothesis that can account for blooms of K. brevis along the west coast of Florida. Of the approximately 24 thoughts and hypotheses described herein (including the 1880s speculation), seven are related to rainfall and/or riverine flux, six invoke the benthos or bottom flux in one form or another, seven involve water column hydrodynamics or are unrelated to the benthos or land sources, and four are primarily chemical/allelopathy based. Nutrient sources for growth and maintenance range from atmospheric deposition, N-fixation, riverine and benthic flux, and zooplankton excretion to decaying fish killed by the toxic dinoflagellate with no one source being conclusively identified as a primary contributor to prolonged bloom maintenance. Insufficient information is available to delimit specific mechanisms that may play a role in the termination of K. brevis blooms. However, general processes such as macro- and microzooplankton grazing, bacterial and viral cell lysis, and dispersal by physical advection and the break down of fronts, that originally may have acted as concentrating mechanisms, are reviewed.