Unravelling some physiological and molecular processes involved in the allelopathic interactions between toxic and non-toxic phytoplankton

Abstract

The physiological and molecular processes defining interspecific interactions of various phytoplankton species are still not presently understood in quantitative terms. Most co-culture experiments have been very restricted methodologically and in most cases limited to cell counts, biovolume and growth rate determinations, which are not sufficient to explain phytoplankton successional processes. Based on our previous studies with anatoxin-a (ATX) and microcystins (MC), the proposed study aims to investigate interspecific interactions involving toxic (Microcystis aeruginosa) and non-toxic (Anabaena flos-aque, Microcystis wesenbergii, Scenedesmus acuminatus) phytoplankton species. In the first experiment, the phytoplankton species will be co-cultured using culture chambers with and without membrane separation partitions to allow for direct and indirect contact between the organisms, while simultaneously sharing the same culture medium resources. The next experiment will determine the physiological effect of MC and ATX mixture (25 µg/L of each toxin) on the phytoplankton species. In all experiments, cell counts, growth rates, pigment and photosynthetic rates fluorescence measurements, antioxidant enzyme activities and genes (MC-mcyE, photosynthetic-psaA and psaB, and housekeeping-18S rRNA and 16S rRNA) expression will be determined. The results from this study will contribute to unravelling some physiological and molecular processes involved in phytoplankton interspecific interactions in aquatic ecosystems. (AU)