The study of the allelopathic agent, Nannochloris sp., interaction with the Florida red tide Karenia brevis

The scientifically complex problem relevant to the coastal areas of Florida harmful algal blooms (HABs). HABs are a proliferation of a harmful or nuisance algae (microalgae or phytoplankton like species) that generally cause a negative impact to our natural resources and/or humans. One of the HABs, referred to as red tide, a worldwide phenomenon, characterized by the sudden discoloration of surface seawater. In Florida, the red tide is an unarmored dinoflagellate called Karenia brevis.; This research project is one aspect of the efforts investigating the management of Florida's red tide, Karenia brevis, through alellopathy. Alellopathy is the control of one organism or species by another. The alellopathic agent used for this study was a yellow green alga; Nannochloris sp. Previous studies indicated that Karenia brevis growth could be managed by Nannochloris sp. and its allelochemicals APONIN-2 and Ψ-APONIN. This study examined the inhibition of the red tide by Nannochloris sp. and demonstrated that in the first 72 hours of exposure Nannochloris sp. could inhibit Karenia brevis growth by as much as 80%.; Toxicity was also examined and it was demonstrated that the Karenia brevis as previously stated, releases the toxin, brevetoxin, only when under stress (agitation). Nannochloris sp. was found to be able to inhibit the release of this toxin and the toxic effects if the toxin was released. Binding assays were done and a proposed mechanism of action of how the Nannochloris sp. managed the red tide came about. Cell integrity was also studied and it was demonstrated that the Karenia brevis goes into what appears to be a “resting state”. The Karenia brevis cells that did not enter a “resting state” were absorbed by the Nannochloris sp.; Also examined was the true alellopathic nature of Nannochloris sp. Studies were conducted on Microcystis aeroginosa, Lyngya sp., Cyclotella menegheniana, and Scenedesmus dimorphis and the Nannochloris sp. was seen to control their toxicity, concluding that Nannochloris sp. is not only an effective management tool for Karenia brevis but also a potentially useful alellopathic agent towards other HAB species.; The research demonstrated that there is a potentially effective, safe, and inexpensive way to manage a controlled outbreak of Karenia brevis . This management is significant because managing the outbreak will have considerable benefits to tourism, the economy, and human health. Knowing the mechanism of action helps to further understand how the interaction works on both a cellular and molecular level. The research also demonstrated that Nannochloris sp. has potential usefulness in managing other harmful algal species.