Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $25,000 Total Non-Federal Funds: $50,058
Abstract: Incidence and severity of harmful cyanobacterial algal blooms have been increasing infreshwater systems in recent years. Cereal straws are known for releasing allelopathic (inhibitory)compounds and Arkansas produces over a million acres of rice annually. Mechanisms ofcyanobacterial inhibition include production of reactive oxygen species, especially hydrogenperoxide, but also other phenolic compounds during decomposition of cereal straws. However, aninitial 14-week field study in nine farm ponds in Northwest Arkansas in 2018 resulted ininconsistent algal concentrations, measured as chlorophyll-a, throughout the summer. Concernsabout direct use of cereal straw in water include lag time between initiation of strawdecomposition and inhibition of algal growth and decreased dissolved oxygen in water.Furthermore, toxin production may increase as algal cell numbers decrease. Therefore, objectivesare to evaluate the effectiveness of aqueous extract collected from decomposing rice straw toinhibit harmful cyanobacteria in culture bioassays. Approaches will utilize the effects of rice strawextract and of hydrogen peroxide on cyanobacterial growth and microcystin toxin release, and onthe green alga Selenastrum capricornutum, under controlled culture conditions and in thepresence of natural organic matter of farm pond water. Potential impacts on the bacterialcommunity composition in pond water, which can have implications for ecosystem functionsincluding nutrient cycling, will be assessed. If the extract from rice straw decompositiondemonstrates antagonism to growth and toxin production of a harmful algal species under nonlimitingnutrient concentrations, and temperatures characteristic of the region during summer,then rice straw extract from aerobic decomposition may be a locally sourced, environmentallyfriendly approach to prevent and treat harmful algal blooms. If hydrogen peroxide is moreeffective, then use of a simple chemical compound, to achieve the same goal may result in abetter, low cost, environmentally friendly approach across multiple recreational, aesthetic, andsource water bodies.