Theses and Dissertations

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Defense Date

7-2008

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology

Department

Oceanographic Center

First Advisor

Bernhard Riegl

Second Advisor

Valerie Paul

Third Advisor

Kenneth Banks

Abstract

The frequency, magnitude and persistence of cyanobacteria bloom events are increasing worldwide and can be attributed to many factors associated with urban, industrial and agricultural expansion (Pittman and Pittman 2005; Ahern et al. 2006b). In Florida, filamentous cyanobacteria of the genus Lyngbya was first observed in the early 1990s, first documented on the southernmost extent of Broward County reefs in 2002, and have since progressed northward into West Palm Beach County (Paul et al. 2005; Tichenor 2005). Previously, cyanobacteria would appear during the summer months, however they began surviving through the winter in 2003. The two main species of Lyngbya affecting Broward County have been identified through morphological and molecular methods as Lyngbya confervoides and Lyngbya polychroa, neither of which have been established as toxic (Paul et al. 2005).

The purpose of this study is to describe the patterns of Lyngbya spp. presence along the southeast coast of Florida from the period of May 2004 to September 2005. Digital photographs are used to analyze the Lyngbya bloom and describe the geographical variability of Lyngbya spp. presence along a north-south and east-west gradient. Preferential relationships between Lyngbya spp. and affected reef organisms are investigated and correlations based on physical parameters of the study site are examined.

Lyngbya presence is dominant in the south corridor, middle and inner reef tracts, and the crest zone of the sites evaluated in this study. Further investigation is needed to compare possible nutrient sources on the reefs to determine if a connection exists between nutrient loads and blooms. Attachment correlations exist between Lyngbya and the algae substratum as well as Lyngbya and soft corals. Lyngbya prefer to attach to live reef and do not prefer to settle on bare substrate. Areas with high live reef cover were conducive to Lyngbya settlement and proliferation. Lyngbya color variations exist within the bloom. Patterns of color dominance along the ecological gradients of the study sites exist and may provide insight into the length of blooms as well as the stage of the bloom at a given time.

The overgrowth and proliferation of cyanobacteria along the coast of Broward County should raise cause for concern because of the negative effects the blooms cause to soft coral assemblages. Lyngbya is capable of nitrogen fixation which gives it a competitive edge for survival. The secondary metabolites produced by the cyanobacteria make it unpalatable to most herbivores so it can continue to grow unchecked in a reef system unless other factors play a role. The presence and persistence of Lyngbya may continue to worsen with time if the full nature of the blooms is not understood.

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