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Old Tampa Bay Monitoring Program

Locations of Pyrodinium bahamense sampling stations on a map

Figure 1. This map shows the 10 routine stations (purple circles) sampled as part of the OTB Monitoring Program. Circle size reflects frequency of P. bahamense bloom occurrence at these stations between 2011 – 2020.

Since 2011, FWRI has maintained a research-based monitoring program in Tampa Bay primarily focused on understanding blooms of the harmful alga species Pyrodinium bahamense in the Old Tampa Bay (OTB) subbasin of Tampa Bay (Figure 1).  Pyrodinium bahamense is a species of harmful algae characterized by several ecological advantages that may allow it to outcompete other algae and form blooms. For example, it produces a toxin called saxitoxin, which can deter grazers, and as a motile dinoflagellate, it can move vertically in the water column to better access resources it needs to grow, such as light and nutrients. Pyrodinium bahamense also has a dormant stage of its life cycle, called a resting cyst, that settles to the seafloor after blooms and allows the alga to lay dormant in sediments during the cooler months of the year. Each year in the early spring, these resting cysts begin to germinate, forming swimming cells again, and the annual bloom cycle continues.

In Florida, blooms of P. bahamense most commonly occur during the summertime in estuaries like the Indian River Lagoon and Tampa Bay because, as a tropical/sub-tropical species, its growth rates and life cycle transitions are closely tied to temperature. Although P. bahamense cells can occasionally be found in lower parts of Tampa Bay, high biomass blooms occur in the OTB subbasin where water circulation is more restricted (another niche characteristic of this species). These blooms reach high biomass, discolor the water, and can commonly be seen from the major road bridges that span OTB.

FWRI-HAB Staff monitoring Old Tampa Bay

Figure 2. FWRI HAB staff with the CTD, equipped with sensors for measuring conductivity, temperature, depth, dissolved oxygen, chlorophyll a fluorescence, pH, and photosynthetically active radiation (PAR).

P. bahamense Bloom Monitoring

The FWRI OTB Monitoring Program samples 10 stations—nine stations within OTB and one station in middle Tampa Bay (Figure 1). Sampling occurs twice-monthly April through September and monthly during the October through February (non-bloom times). Scientists collect discrete surface and bottom water samples, which are analyzed microscopically for harmful algae, including P. bahamense. Scientists also conduct vertical profiles of physical and water quality parameters in the water column using an instrument called a CTD (Figure 2). In addition to the on-station measurements, a flow-through sampler is used to capture high resolution measurements of salinity and chlorophyll fluorescence (which can be used as a proxy for algal biomass) in surface waters along the boat path.   

This long-term dataset provides a relatively high-resolution characterization of P. bahamense bloom development and decline in OTB, which has improved scientific understanding of bloom dynamics. In addition, we are continuing to add new tools, such as continuous in situ monitoring during blooms, to improve our understanding of harmful algal blooms.

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