• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.3
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• pp.178-185
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• 2007

Myrionecta rubra Jankowski 1976(=Mesodinium rubrum Lohmann 1908), a mixotrophic ciliate, is very common and often causes recurrent red tides in diverse marine environments. Since the report on the first laboratory strain of this species in 2000, papers on its novel ecological role and evolutionary importance have been high lighted. This review paper is prepared to promote the de novo recognition M. rubra as a marine mixotrophic species. M. rubra is a ciliate which is able to photosynthesize using plastids originated from cryptophyte (including Teleaulax sp. and Geminigera sp.) prey cells (i.e. kleptoplastidic ciliate). Recently, novel bacterivory of M. rubra was firstly reported. Thus, the nutritional modes of M. rubra include photosynthesis, bacterivory, and algivory. In turn, M. rubra was reported as the prey species of metazoan predators such as calanoid copepods, mysids, larvae of ctenophore and anchovy, and spats of bivalves. In addition, it was reported that dinoflagellate Dinophysis causing diarrhetic shellfish poisoning is one among the predators of M. rubra. Thus, M. rubra, a marine mixotrophic ciliate, may play a pivotal role as a common linking ciliate for the flow of energy and organic material in pelagic food webs.

• ALGAE
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• v.20 no.3
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• pp.207-216
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• 2005

Myrionecta rubra, a mixotrophic ciliate, is a cosmopolitan red tide species which is commonly found in neritic and estuarine waters. M. rubra had long been listed as an “nculturable protist”until 2 different laboratory strains were finally established in 2 research groups at the beginning of this century, enabling us to perform initiative investigation into various aspect of the live M. rubra strains (Gustafson et al. 2000; Yih et al. 2004b; Johnson and Stoecker 2005). Field sampling was carried out on high tide at 2 fixed stations around Kunsan Inner Harbor (St.1 near the Estuarine Weir and St.2 off Kunsan Ferry Station) every other day for 4 months from mid-February 2004 to understand detailed figure of the recurrent spring blooms of M. rubra following the onset of the water gates operation of the Keum River Estuarine Weir on August 1994. With its maximum abundance of 272 cells mL$^{-1}$ in St.1, fluctuation pattern of the M. rubra population at the 2 stations was strikingly similar. Notable growth of M. rubra population started on late April, to cause M. rubra red tides during one month from mid-May in which “xceptionally low salinity days”without its red tide were intermittently inserted. High abundance of M. rubra over 50 cells mL$^{-1}$ was recorded at samples with their water temperature and salinity higher than 15${^{\circ}C}$ and 4.0 psu, respectively. During pre-bloom period when salinity fluctuation is moderate and the water temperature is cooler than 15°C, Skeletonema costatum, a chain-forming centric diatom, was most dominant. Cyanobacterial species such as Aphanizomenon flos-aquae and Phormidium sp. replaced other dominant phytoplankters on the days with “xceptionally low salinity”even during the main blooming period of M. rubra. To summarize, M. rubra could form spring blooms in Keum River Estuary when the level of salinity fluctuation was more severe than that for the dominant diatom Skeletonema costatum and milder than that for the predominance by freshwater cyanobacteria. Therefore, optimal control of the scale and frequency of freshwater discharges might lead us to partially modify the fluctuation pattern of M. rubra populations as well as the period of spring blooms by M. rubra in Keum River Estuary. Sampling time interval of 2 days for the present study or daily sampling was concluded to be minimally required for the detailed exploration into the spring blooms by M. rubra populations in estuaries with weirs like Keum River Estuary.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.4
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• pp.164-172
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• 2004

Water temperature, salinity, the phytoplankton community and population of a marine photosynthetic ciliate, Mesodinium rubrum (=Myrionecta rubra), were monitored every 0.5-2 weeks in Gomso Bay and the Geum River Estuary from September 1999 to December 2000. Patterns of temporal variation of the M. rubrum population and phytoplankton community were compared with each other in relation to the differences in temporal fluctuation patterns of the water temperature and salinity in the two study areas. Higher population densities and more frequent blooms of M. rub rum in the Geum River Estuary than those in Gomso Bay could be due to the relatively higher nutrient input by freshwater influx in the Geum River Estuary. In the Geum River Estuary which experience more abrupt and irregular fluctuations of salinity, M. rubrum with its greater tolerance to salinity change exhibited increased dominance while neritic diatoms such as Skeletonema costatum, Asterionellopsis glacialis, A. kariana, Chaetoceros debilis, Eucampia zodiacus, Paralia sulcata, Thalassiosira pacifica, T. nordenskioeldii showed decreased dominance compared with those in Gomso Bay. Thus, it is possible that M. rubrum replaces the dominant diatom species in coastal waters where artificial modification of coast lines as in the case of Saemankeum Reclamation Project should increase the frequency as well as the absolute scale of freshwater discharges.

• Ocean and Polar Research
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• v.30 no.4
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• pp.419-426
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• 2008

Ciliate plankton samples were collected biweekly from July 2006 to June 2008 in Jangmok Bay of Geoje Island. Species composition and abundances were analyzed by quantitative protargol stain and environmental parameters were also examined. A total of 88 ciliate species occurred during the study period, consisting of 22 tintinnids, 51 oligotrichs, and 15 other species. Higher ciliate abundances appeared from June to October during the warm season ($<20^{\circ}C$) and the maximum ($4.0{\times}10^4\;cells\;L^1$) in August, while the lower abundances were found during the cold season. The minimun ciliate abundance was found in November when water temperature rapidly decreased. The temporal succession of dominant species was very clear and opportunistic. Pelagostrombidium sp., Tontonia simplicidens, Helicostomella subulata, and Myrionecta rubra were co-dominant in summer while Rimostrombidium orientale occurred abundantly in winter. Strombidium tressum and S. compressum, eurythermal species, were observed during all seasons. Based on the species-specific ecology of ciliate plankton, it is suggested that the indicative ciliate species can be applied as a biological tool to detect environmental change in the southern coastal waters of korea.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.55-68
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• 2010

The seasonal variation of microbial community, based on the bacteria, heterotrophic nanoflagellates (HNF), phytoplankton and ciliates, was investigated at three sites in the eutrophic brackish water of Lake Shihwa and its adjacent areas from May 2007 through May 2008. At the upstream-region site St. 1, compared to the other two sites, significantly lower salinities and higher concentrations of nutrients and chlorophyll $\alpha$ (Chl. $\alpha$) were recorded. The annual average abundances of bacteria at St. 1, St. 2 and St. 3 were $6.8{\times}10^6$, $7.4{\times}10^6$ and $4.6{\times}10^6\;cells\;mL^{-1}$, respectively. As for the annual average concentrations of HNF, $19{\times}10^2$, $6.7{\times}10^2$ and $5.9{\times}10^2\;cells\;mL^{-1}$, were recorded in St. 1, St. 2 and St. 3 respectively. The highest ciliate abundance appeared at St. 1 on 29 April, 2008 and in which, 99% were autotrophic ciliate Mesodinium rubrum (Myrionecta rubra). Significant linear correlations between the biomass of bacteria and Chl. $\alpha$ were found, however, no significant relationships between ciliates abudance/biomass and their prey organisms were detected in all three sites, implying relatively low energy transfer efficiencies between them. These results indicated that the trophic relationship between ciliates and their prey organisms in the microbial community might be influenced by indirect route since higher trophic level organisms did not directly correlate to those of lower trophic level, although high primary productions were detected in the eutrophic brackish water of Lake Shihwa and its adjacent areas.