Authors: Charles L Tilney Kaytee L Pokrzywinski Kathryn J Coyne Mark E Warner
Publish Date: 2014/02/12
Volume: 26, Issue: 5, Pages: 2117-2127
Abstract
Naturally occurring allelopathic compounds specific to some phytoplankton may be a good source of biocontrol agents against microalgae responsible for harmful algal blooms HABs Global expansion of HABs has invigorated research into different approaches to control these algae including the search for naturally derived algicidal compounds Here we investigated the effects of a filtrate from the algicidal marine bacterium Shewanella sp IRI160 on photochemical function of four cultured dinoflagellates Karlodinium veneficum Gyrodinium instriatum Prorocentrum minimum and Alexandrium tamarense The filtrate designated IRI160AA contains bioactive compounds which were recently shown to inhibit growth of several dinoflagellate species Results of this study show that all dinoflagellates but P minimum exhibited photosystem II PSII inhibition loss of photosynthetic electron transport and varying degrees of cellular mortality Exposure assays over 24 h showed that PSII inhibition and loss of cell membrane integrity occurred simultaneously in G instriatum but not in K veneficum where PSII activity declined prior to losing outermembrane integrity In addition PSII inhibition and population growth inhibition were dosedependent in K veneficum with an average EC50 of 79 v/v IRI160AA Application of IRI160AA induced significantly higher PSII inhibition and cell mortality in K veneficum subjected to continuous darkness as compared to cells maintained with 1212 h light/dark cycles while no such dark effect was noted for G instriatum The marked differences in the rate and impact of this algicide suggest that multiple cellular targets and different cascades of cellular dysfunction occur across these dinoflagellates
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