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The marine sand-dwelling dinoflagellate Polykrikos lebourae possesses obvious gold-brown pigmented plastids as well as taeniocyst-nematocyst complex structures. Despite of the presence of the visible plastids, previous attempts to establish this species in culture all failed and thus the unavailability of cultures of this species has posed a major obstacle to further detailed exploration of ecophysiology of the dinoflagellate. Here, we isolated P. lebourae from sandy sediment of an intertidal flat on Korean western coast, successfully established it in culture, and have been maintaining the stock cul ture over the past 3 years. Using this stock culture, we explored phagotrophy and potential prey resources of P. lebourae, growth and grazing responses of P. lebourae to different prey organisms, the effect of prey concentration on growth and grazing rates and gross growth efficiency (GGE) of P. lebourae when fed three different prey organisms, and the growth kinetics of P. lebourae under different light regimes. P. lebourae captured prey cells using a tow filament and then phagocy tized them through the posterior end. The dinoflagellate was capable of ingesting a broad range of prey species varying in size, but not all prey species tested in this study supported its sustained growth. GGE of P. lebourae was extremely high at low prey concentration and moderate or low at high prey concentrations, indicating that P. lebourae grows heterotrophically at high prey concentrations but its growth seems to be more dependent on a certain growth factor or photosynthesis of plastids derived from the prey. In the presence of prey in excess, P. lebourae grew well at moderate light intensity of 40 µmol photons m -2 s -1 , but did not grow at dim and high (10 or 120 µmol photons m -2 s -1 ) light intensities. Our results suggest that the benthic dinoflagellate P. lebourae is an obligate mixotroph, requiring both prey and light for sustained growth and survival.

Copyright © 2015 The Korean Society of Phycology 121 http://e-algae.kr pISSN: 1226-2617 eISSN: 2093-0860 Evaluation of carbon flux in vegetative bay based on ecosystem production and CO2 exchange driven by coastal autotrophs Ju-Hyoung Kim, Eun Ju Kang, Keunyong Kim, Hae Jin Jeong, Kitack Lee, Matthew S. Edwards, Myung Gil Park, Byeong-Gweon Lee and Kwang Young Kim* Faculty of Marine Applied Biosciences, Kunsan National University, Kunsan 573-701, Korea Department of Oceanography, College of Natural Sciences Chonnam National University, Gwangju 500-757, Korea School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 151-747, Korea School of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea Department of Biology, San Diego State University, San Diego, CA 92182, USA