Chemically-mediated competition in the marine plankton

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

Competition is a major force structuring communities, including the marine plankton. The release of compounds that inhibit competitors, a process known as allelopathy, is hypothesized to be important among phytoplankton, especially for species that compete poorly for resources yet successfully form dense blooms. Ecological interactions involving the toxic red tide dinoflagellate Karenia brevis present an ideal system for understanding chemically-mediated competitive and food web interactions. K. brevis blooms occur frequently in accessible coastal areas of the Gulf of Mexico, causing massive fish kills and contaminating shellfish. The dramatic consequences of these blooms provide a basis for asking: How do harmful algae out-compete co-occurring species? What roles do toxin dynamics and other chemical cues play? How are other members of the plankton community affected and how do they respond? In previous work, the investigators found that K. brevis was allelopathic to 6 out of 12 naturally co-occurring phytoplankton species tested, but that K. brevis compounds other than the known neurotoxic brevetoxins produced by K. brevis were generally responsible. They also found that natural, field blooms of K. brevis were strongly allelopathic to the competing diatom Skeletonema costatum, but that S. costatum retaliates against K. brevis, reducing its allelopathic effects. In addition, waterborne brevetoxins were degraded in the presence of competitors. Thus, environmental context may be critical for predicting what ecologically-important chemical mediators are released into marine systems and the consequences of these compounds on plankton communities, which vary spatially and temporally. In this project, the investigators will use field and lab experiments to: 1) Explore variability in Karenia brevis allelopathy, including whether interactions with S. costatum undermine the allelopathic effects of natural K. brevis blooms on multiple competitors. 2) Characterize mechanisms of allelopathy, including identifying allelopathic compounds exuded by K. brevis blooms that suppress Gulf of Mexico competitors, and determining mechanisms of action of allelopathic compounds. 3) Assess community impacts of allelopathy, by testing how allelopathic effects vary as a result of phytoplankton species diversity and trophic interactions in natural plankton communities. Broader impacts: Phytoplankton blooms can be devastating to local economies and pose human health risks. The discovery of new chemically-mediated interactions in the marine plankton could eventually lead to prediction and mitigation strategies to alleviate the harmful consequences of these blooms. This project will build on past success using chemistry to teach us about ecological processes and applying ecological insights to discover unique natural products with important biological functions. This project will provide training for a Latina postdoc, a PhD student, and several undergraduates. The PhD student will expand on our previous public education training activities, participating in an NSF GK-12 program that places Georgia Tech students in Atlanta-area public high schools with high proportions of minority students. These African-American students will learn about the question-asking nature of scientific research and issues surrounding red tides in the U.S. with connections to human impacts on marine environments, exciting the students about science by connecting it with daily life.