Environmental Regulation of Harmful Cyanobacterial Blooms in the St. Johns River System, Florida

Background Information
 
 

Cyanobacterial bloom, L. George

Water quality, ecological condition, recreational, fishing and drinking water use of the St. Johns River system and downstream estuary are impaired by proliferating nuisance blue-green algal (cyanobacterial) blooms.  Intensifying and geographically-expanding blooms of toxic (to a wide range of animals, including humans) cyanobacterial genera, including the nitrogen (N2) fixers Cylindrospermopsis, Anabaena, and the non-N2 fixer Microcystis are of concern. There are needs to identify and characterize harmful taxa (as to their toxicity and ecological impacts), and to understand environmental factors regulating bloom formation.  Nutrient and hydrodynamic factors associated with expanding human use are of special interest, since there are the most likely targets for management actions aimed at controlling this troubling trend.

 

The following objectives provide information needed for developing and supporting management actions:                Cyanobacterial bloom, L. George

• Isolate and culture harmful (toxic, food web disrupting, hypoxia/anoxia-generating) strains of cyanobacterial bloom genera, including: Anabaena, Cylindrospermopsis, Microcystis
• Characterize harmful N₂ fixing cyanobacterial strains using molecular techniques (based on detection and sequencing of the gene for the N₂ fixing enzyme, nifH).  This information will be used to develop DNA probes, capable of “early warning” detection and identification of harmful strains in waters threatened by blooms.
• Characterize non-N₂ fixing strains (and develop detection probes) using 16S rRNA and microscopic techniques
• Identify environmental factors (nutrients, light, hydrodynamics, salinity) controlling phytoplankton community composition, bloom potentials, and toxicity

Link information obtained from above studies with ongoing environmental/water quality monitoring, hydrodynamic, nutrient loading and modeling studies to develop management options for controlling harmful cyanobacterial blooms.

Anabaena sp. Crescent L., FL

Cylindrospermopsis raciborskii Isolated from L. Dora, FL

Microcystis sp.

Research

Cubitainers containing L. George or Shands Pier water amended with various nutrient addition and dilutions, incubated in situ near experimental docks, St. Johns River

To achieve these objectives, we are conducting seasonal bioassays in which nutrient concentrations (N and P) are manipulated to simulate two situations: an increase in nutrient loading to the St. Johns River system (nutrient additions) or a decrease in nutrient loading/ change in N:P loading ratio (nutrient dilutions).  The effects of these nutrient manipulations on the phytoplankton community are measured by a number of techniques.  Changes in the activity of these populations are measured by primary productivity (14CO2 uptake), nitrogen fixation (acetylene reduction), and presence of cyanotoxins.  Changes in community composition are measured by diagnostic photopigments (HPLC, high performance liquid chromatography), and DNA analysis.  The phytoplankton communities in L. George (one of the upstream source lakes for St. Johns River) and Shands Pier (on the St. Johns River, at times has measurable salinity) are currently being investigated.

 
 
 
 
 

In situ incubation of productivity and acetylene reduction assays at Shands Pier

Setting up primary productivity assays for  in situ incubation

Sampling bioassay cubitainers from the R/V Gator Bait

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UNC-Chapel Hill	UNC-Marine Sciences

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