Graduation Year


Document Type




Degree Granting Department

Marine Science

Major Professor

Gabriel A. Vargo, Ph.D.

Committee Member

Karen A. Steidinger, Ph.D.

Committee Member

Gary L. Hitchcock, Ph.D.

Committee Member

Kent A. Fanning, Ph.D.

Committee Member

John J. Walsh, Ph.D.


Synechococcus, competition, salinity, light, phosphorus, nitrogen


Areally expansive, persistent and recurring blooms frequently dominated by cyanobacteria have developed primarily in the north-central region of Florida Bay since approximately 1991. This part of the bay has a history of the following: periodic hypersalinity, high sediment-derived turbidity, P limitation, N limitation, light limitation and long water residence time. Clonal isolates of selected dominant bloom species of cyanobacteria (Synechococcus cf. elongatus and Synechocystis sp.) and diatoms (Chaetoceros cf. salsugineus and Thalassiosira cf. oceanica) from Florida Bay were examined in an effort to explain their relative dominance of the phytoplankton community.

The following physiological characteristics and nutrient strategies of the study species were examined: (1) salinity-growth response; (2) light-growth response; (3) phosphorus-dependent growth kinetics; (4) ERC-theory phosphorus competitiveness; (5) cellular quotas and luxury storage capabilities of N and P; (6) optimal N:P ratios; (7) P and N-limited competitiveness under various salinities, N:P ratios, forms of N and P, and rates of nutrient delivery; (8) aerobic nitrogen fixation; (9) production of allelochemic compounds, and (10) response to resuspended sediment.

This study identified salinity and nutrient limitation as the factors having the greatest potential to regulate the development of cyanobacteria and diatom bloom dominance in Florida Bay. The results strongly suggest that the frequent dominance of Synechococcus cf. elongatus, and Synechocystis sp. in the recurring phytoplankton blooms of the north-central region of Florida Bay can be attributed to their superior P-competitiveness and to a lesser degree to their greater salinity tolerance limits.