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Yoo, YD, Seong KA, Myung G, Kim HS, Jeong HJ, Palenik B, Yih W.  2015.  Ingestion of the unicellular cyanobacterium Synechococcus by the mixotrophic red tide ciliate Mesodinium rubrum. Algae. 30:281-290.   10.4490/algae.2015.30.4.281   AbstractWebsite

We explored phagotrophy of the phototrophic ciliate Mesodinium rubrum on the cyanobacterium Synechococcus. The ingestion and clearance rates of M. rubrum on Synechococcus as a function of prey concentration were measured. In addition, we calculated grazing coefficients by combining the field data on abundance of M. rubrum and co-occurring Synechococcus spp. with laboratory data on ingestion rates. The ingestion rate of M. rubrum on Synechococcus sp. linearly increased with increasing prey concentrations up to approximately 1.9 x 10(6) cells mL(-1), to exhibit sigmoidal saturation at higher concentrations. The maximum ingestion and clearance rates of M. rubrum on Synechococcus were 2.1 cells predator(-1) h(-1) and 4.2 nL predator(-1)h(-1), respectively. The calculated grazing coefficients attributable to M. rubrum on co-occurring Synechococcus spp. reached 0.04 day(-1). M. rubrum could thus sometimes be an effective protistan grazer of Synechococcus in marine planktonic food webs. M. rubrum might also be able to form recurrent and massive blooms in diverse marine environments supported by the unique and complex mixotrophic arrays including phagotrphy on hetrotrophic bacteria and Synecho coccus as well as digestion, kleptoplastidy and karyoklepty after the ingestion of cryptophyte prey.

Yoo, YD, Seong KA, Kim HS, Jeong HJ, Yoon EY, Park J, Kim JI, Shin W, Palenik B.  2018.  Feeding and grazing impact by the bloom-forming euglenophyte Eutreptiella eupharyngea on marine eubacteria and cyanobacteria. Harmful Algae. 73:98-109.   10.1016/j.hal.2018.02.003   AbstractWebsite

The phototrophic euglenophyte Eutreptiella eupharyngea often causes blooms in the coastal waters of many countries, but its mode of nutrition has not been assessed. This species has previously been considered as exclusively auxotrophic. To explore whether E. eupharyngea is a mixotrophic species, the protoplasm of E. eupharyngea cells were examined using light, epifluorescence, and transmission electron microscopy after eubacteria, the cyanobacterium Synechococcus sp., and diverse algal species were provided as potential prey. Furthermore, the ingestion rates of E. eupharyngea KR on eubacteria or Synechococcus sp. as a function of prey concentration were measured. In addition, grazing by natural populations of euglenophytes on natural populations of eubacteria in Masan Bay was investigated. This study is the first to report that E eupharyngea is a mixotrophic species. Among the potential prey organisms offered, E. eupharyngea fed only on eubacteria and Synechococcus sp., and the maximum ingestion rates of these two organisms measured in the laboratory were 5.7 and 0.7 cells predator(-1) h(-1), respectively. During the field experiments, the maximum ingestion rates and grazing impacts of euglenophytes, including E. eupharyngea, on natural populations of eubacteria were 11.8 cells predator(-1) h(-1) and 1.228 d(-1), respectively. Therefore, euglenophytes could potentially have a considerable grazing impact on marine bacterial populations. (C) 2018 Elsevier B.V. All rights reserved.