Cooperative Fish and Wildlife Research Units Program: Texas
Education, Research and Technical Assistance for Managing Our Natural Resources

Golden alga (Prymnesium parvum) is a euryhaline haptophyte that produces compounds highly toxic to fishes and other gill-breathing aquatic organisms. In the USA, harmful blooms of golden alga were first reported in 1985 in the Pecos River and they have now spread through most of Texas and the sunbelt states. The ecological impacts of toxic blooms have been severe; unfortunately, effective field control methods are presently unavailable. The goal of this research is to develop effective and environmentally friendly methods to control harmful blooms of golden alga.

Giant reed (Arundo donax) is a harmful invasive plant in the USA. A previous study showed that extracts from giant reed and two of its known constituents, gramine and skatole, inhibit growth of golden alga and suggested this plant is a potential source of natural products for controlling blooms. Extract are relatively difficult to prepare, however, and may not be a viable option for field application. Also, the two allelochemicals previously tested were less potent than extracts thus indicating the existence of additional, more potent allelochemicals. The objectives of this research are to determine if giant reed chips or their aqueous leachate can effectively inhibit golden alga growth and to screen other known giant reed constituents for their growth effects.

Preliminary observations showed vigorous bacterial growth in cultures of golden alga in the presence of giant reed. This finding suggests the presence of algicidal bacteria in the cultures. Therefore, another objective of this study is to determine the growth effects of bacterial strains isolated from the cultures and their mechanisms. This information may inform the development of probiotic treatments to prevent or control harmful booms.