Chemical Ecology of Cyanobacterial Blooms on the Tropical Reefs of Guam

EPA Grant Number: R826220
Title: Chemical Ecology of Cyanobacterial Blooms on the Tropical Reefs of Guam
Investigators: Paul, Valerie J.
Institution: University of Guam
EPA Project Officer: Hiscock, Michael
Project Period: December 15, 1997 through December 14, 2000 (Extended to December 14, 2001)
Project Amount: $325,000
RFA: Harmful Algal Blooms (1997) RFA Text |  Recipients Lists
Research Category: Aquatic Ecosystems , Water Quality , Water , Ecosystems


Harmful algal blooms (HABs) of many types have increased in abundance and severity in the United States and worldwide in recent years. Of particular concern in coral reef habitats are the frequent and persistent seaweed blooms. These blooms can have many negative impacts including overgrowing corals, negatively affecting seagrass communities, and washing up on beaches in areas where tourism is economically essential. An additional concern for cyanobacterial blooms are the toxins they produce and their impacts on other reef organisms and humans. The production of deterrent and toxic secondary metabolites by benthic cyanobacteria probably facilitates their bloom formation on coral reefs because most generalist grazers avoid this potential food source. Almost nothing is known about the temporal and spatial patterns of bloom formation in reef habitats or about environmental factors affecting bloom formation and persistence. Additionally, secondary metabolite types and concentrations can vary considerably among different collections of cyanobacteria, but environmental factors influencing this chemical variation are not understood. Objectives are: 1) to document the temporal and spatial patterns of cyanobacterial bloom formation in reef and seagrass habitats around the island of Guam; 2) to characterize and quantify the natural products chemistry of these cyanobacterial blooms; 3) to determine the effects of the natural products isolated from cyanobacterial blooms on potential consumers, including herbivorous reef fishes and specialist mesograzers such as sea hares; 4) to examine the types and amounts of compounds released by cyanobacteria and their effects on consumers, competitors, and other microorganisms; and 5) to manipulate light and nutrients (nitrogen, phosphorus, and iron) in field and laboratory experiments to determine their effects on secondary metabolite production by cyanobacteria under natural conditions.


To determine the temporal and spatial patterns of cyanobacterial blooms on Guam, eight reef sites will be monitored biweekly and cyanobacterial populations will be measured. Secondary metabolites associated with these blooms will be isolated by chromatographic methods and characterized by spectroscopic methods including 2D NMR techniques. Effects of these compounds on feeding by herbivores such as fishes and invertebrates will be examined in laboratory and field bioassays. Compounds released by the cyanobacteria into seawater will be characterized and examined for their effects on competitors and other microorganisms in laboratory and field bioassays. Effects of grazing, light, and nutrients (nitrogen, phosphorus, iron) on secondary metabolite production will be examined in a combination of field and laboratory experiments.

Expected Results:

The research will yield information on the timing and persistence of cyanobacterial blooms in tropical reef environments. Secondary metabolites that function as toxins and deterrents will be isolated and chemically characterized. Environmental factors that influence the production of these compounds will be determined. Natural functions of these compounds against herbivores, competitors, and microorganisms present in the habitats will be discovered.

Publications and Presentations:

Publications have been submitted on this project: View all 30 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 6 journal articles for this project

Supplemental Keywords:

marine cyanobacteria, coral reefs, ecological effects, natural toxins, RFA, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecosystem/Assessment/Indicators, Ecosystem Protection, Ecological Effects - Environmental Exposure & Risk, algal blooms, Ecological Indicators, ecological exposure, chemical ecology, ecological effects, spectroscopic methods, bloom dynamics, marine biotoxins, coral reefs, harmful algal blooms, cyanobacterial blooms, tropical reefs, bioassay, benthic algae, natural toxins, cyanobacteria

Progress and Final Reports:

  • 1998
  • 1999 Progress Report
  • 2000 Progress Report
  • Final Report