• 한국패류학회지
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• 제28권4호
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• pp.349-359
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• 2012

The purpose of this study is to compare the clearance rate (CR) and intake rate (IR) of juvenile purple clam, Saxidomus purpuratus when feeding on different unialgal diet of red tide dinoflagellates (RTDs), and to know what is the most important cell characteristic of RTDs to cause the differences in feeding parameters. Experiments were performed to measure the CR and IR of juvenile S. purpuratus as a function of algal concentration when food was either the standard food, Isochrysis galbana or one of 9 RTDs. Patterns of CR with increasing algal concentration were similar among different RTDs. The highest $C_{max}$ was observed when S. purpuratus was feeding on A. affine, while the lowest on C. polykrikoides. The patterns of IR with increasing algal concentration were also similar among different RTDs. However, there were great differences in the maximum value of IR ($I_{max}$) among different RTDs. The highest $I_{max}$ was observed when S. purpuratus was feeding on A. carterae, while the lowest on G. catenatum. Some RTDs similar in size showed different $C_{max}$. Other RTDs different in size showed similar $I_{max}$. Life form of each RTD affected significantly the $I_{max}$, which was higher for single-celled RTDs than chain-forming RTDs. There were no significant differences in feeding parameters between toxic and nontoxic RTDs. Moreover, a toxic dinoflagellate, A. carterae recorded the highest $I_{max}$ among RTDs. The most important characteristic of RTD as a factor affecting the feeding rate of S. purpuratus was life form, not size or toxicity of RTD species.

• ALGAE
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• 제18권1호
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• pp.49-58
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• 2003

The short-term dynamics of the summer phytoplankton community structure were investigated in coastal waters around Namhae Island, the Southern Sea of Korea. The study was based on a comprehensive survey constituting 39 collections from 13 stations on July 18-22, August 1-2, 14-16 and 27-30, respectively. The community structure was analysed using cluster analysis and important environmental correlates of the assemblage structure were identified with canonical correspondence analysis (CCA). Water temperature, salinity, NO₂, NO₃, NH₄, PO₄, chlorophyll a and transparency were measured as physico-chemical environmental factors which may be associated with the phytoplankton community structure. Variations of salinity and concentrations of NO₃ and chlorophyll a were not significant. In addition to warmer water temperature, concentrations of NO₂, NO₄and PO₄ decreased at the beginning of August. And transparency was deeper and water column became very unstable after the middle of August. A wide taxonomic diversity was encountered during the survey, including a total of 121 taxa which was composed of 72 diatoms, 48 dinoflagellates and 1 euglenoid species. Cluster analysis showed that the Phytoplankton community could be divided into 4 distinct groups, indicating rapid changes of the community in the short course of this survey. These phytoplankton groups also showed distinctive dispersion patterns in 2-dimensional canonical space, indicating distinct groupings for stations at each survey. Dominant taxa of diatoms (Chaetoceros curvisetus, Chaetoceros spp., Leptocylindrus danicus, Leptocylindrus mediteraneus, Skeletonema costanum, and Pseudo-nitzschia pungen) clustered in region of CCA space corresponding to stations surveyed at the middle of July. Dominant taxa of dinoflagellates were tightly associated with stations surveyed at the middle (Karenia breve) and end (Cochlodinium polykrikoides and Polykrikos schwartzii) of August. The CCA also showed that the phytoplankton community compositions were highly associated with water temperature, transparency, NO₂, NH₄ and PO₄, suggesting that gradients in physical and nutrient conditions affect short-term changes in phytoplankton composition.

• Journal of Microbiology and Biotechnology
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• 제28권7호
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• pp.1185-1198
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• 2018

The nucleosomal organization of chromatin using histone proteins is a fundamental and ubiquitous feature of eukaryotic nuclei, with the major exception of dinoflagellates. Although a number of recent genomic and transcriptomic analyses have detected numerous histone genes in dinoflagellates, little is known about their expression. Here in, we aimed to investigate the expression pattern of histone genes under nutritional stress, and an attempt was made to detect histone expression at the protein level in Alexandrium pacificum. The presence of histones at the mRNA level was confirmed in this study by the amplification, cloning, and sequencing of 10 different genes. Relative expression profiling of these genes under different growth conditions was determined with real-time PCR and revealed considerable levels of histone transcription in nutritionally stressed cells. We were unable to detect the expression of histones at the protein level even after immunodetection and analysis using mass spectrometry, although a histone-like protein was detected as a major nuclear component. A. pacificum expresses multiple variants of histone, and protein sequences revealed both conservation and divergence with respect to other eukaryotes. We concluded that A. pacificum maintained an active transcription of histone genes within the cell, and enhanced expression of histone genes in nutritional stress strongly suggest that histones have functional significance in dinoflagellates, although expression at the protein level was below our current detection limits, which suggests a limited role of histones in DNA packaging. Finally, the plausible regulation of histone expression at the gene and protein levels in A. pacificum is discussed.

• 한국해양학회지
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• 제4권1호
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• pp.1-8
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• 1969

1967년 5월에 교통부 수로국 조사선 제1수로호(240톤)는 C.S.K.조사의 일환으로서 주로 해역의 단기간동안의 각종 해양요인의 변동상황을 관찰하는 목적으로 한국해협과 동해가 연속되는 207, 208정선을 동일코스로 이차에 걸쳐 횡단관측을 하였으며, 이때에 얻은 표층의 식물성 플랭크톤을 조사하는 기회를 갖었었다. 제1차 관측은 5월초순에, 제2차 관측은 5월하순에 실시되었으며, 두 관측의 시일차는 19일간이었다. 그러나 이러한 단기간의 시일간에도 나타난 식물성 플랭크톤의 종류상과 분포상에 적지않은 변화가 있었으며, 이것은 이 해역의 해양사항의 특수성을 나타내는 하나의 자료로서 흥미가 있었기에 여기에 그 결과를 보고한다.

• Ocean Science Journal
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• 제42권2호
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• pp.117-127
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• 2007

The dynamics of phytoplankton abundance with seasonal variation in physicochemical conditions were investigated monthly at 10 stations around the Chagwi-do off the west coast of Jeju Island, Korea, including inshore, middle shore, and offshore in the marine ranching are a from September 2004 to November 2005. Water temperature varied from 12.1 to $28.9^{\circ}C$ (average $18.8^{\circ}C$), and salinity from 28.9 to 34.9 psu (average 33.7 psu). The chlorophyll a concentration was $0.02-2.05\;{\mu}g\;L^{-1}$ (average $0.70\;{\mu}g\;L^{-1}$), and the maximum concentration occurred in the bottom layer in April. A total of 294 phytoplankton species belonging to 10 families was identified: 182 Bacillariophyceae, 52 Dinophyceae, 9 Chlorophyceae, 12 Cryptophyceae, 6 Chrysophyceae, 4 Dictyophyceae, 13 Euglenophyceae, 6 Prymnesiophyceae, 5 Prasinophyceae, and 5 Raphidophyceae. The standing crop was $2.21-48.69\times10^4\;cells\;L^{-1}$ (average $9.23\times10^4\;cells\;L^{-1}$), and the maximum occurred in the bottom layer in April. Diatoms were most abundant throughout the year, followed by dinoflagellates and phytoflagellates. A phytoplankton bloom occurred twice: once in spring, peaking in April, and once in autumn, peaking in November. The spring bloom was represented by four Chaetoceros species and Skeletonema costatum; each contributed 10-20% of the total phytoplankton abundance. The autumn bloom comprised dinoflagellates, diatoms, and phytoflagellates, of which dinoflagellates were predominant. Gymnodinium conicum, Prorocentrum micans, and P. triestinum each contributed over 10% of the total phytoplankton abundance.

• Ocean and Polar Research
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• 제43권3호
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• pp.99-111
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• 2021

Occurrence of epiphytic dinoflagellates (EPDs) in coastal waters off Jeju was first reported in 2011 based on 45 substrate samples from 24 macroalgal species. When re-analyzing, the extreme heterogeneous distribution of whole and genus-specific EPDs was reconfirmed across the sampling stations and substrate macroalgal species, as well as even across substrate samples of the same species. Abundance maximum of an EPD genus (cells g-wwt^-1) at a fixed surface-to-volume ratio (SA/V ratio) of the macroalgal species increased as the SA/V ratio increased up to 500 (cm² cm^-3). However, the abundance maximum of Ostreopsis further increased even in the MG2 (morphological group 2) macroalgae with the SA/V ratios over 500. The number of substrate macroalgal species on the plane of the MG and sampling station was more or less evenly scattered than the average EPD abundance, which was primarily driven by Gambierdiscus and Ostreopsis. Of the total EPD abundance of the five stations, 90.6% were represented by the two most common and abundant genera, Gambierdiscus and Ostreopsis, each accounting for 41.6% and 49.0%. Spatially, 95.9% of the total EPD abundance was found in St. 4 and St. 5, of which St. 4 with higher water temperature had more Ostreopsis spp. (31.8%), and St. 5 with higher salinity had more Gambierdiscus spp. (27.3%). Thus, the environmental transition to favorable T-S condition to MG2, the thin filamentous macroalgal group with very high SA/V ratios, is thus likely to support further success in EPD genera led by Ostreopsis in the coastal waters of Jeju.

• 한국해양학회지:바다
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• 제25권4호
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• pp.160-172
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• 2020

2014년 춘계에 독도 주변해역에서 전례없이 높은 개체수를 나타낸 야광충의 섭식특성을 이해하고자 야광충 식포 내 먹이생물의 조성과 출현량을 분석하였다. 출현 야광충 개체수는 4,328~17,791 inds.m^-3이었고, 야광충 식포 내 먹이생물 출현율은 평균 32%(24~50%)이었다. 관찰된 먹이생물의 조성은 분변립, 원생생물, 꽃가루, 규조류, 와편모조류, 요각류, 어란, 그리고 치자어로서 매우 다양하였고, 분변립의 출현율이 가장 높았다(43%). 원생생물(19%)과 꽃가루가 18%를 차지한 반면, 규조류와 와편모조류가 각각 7%와 4%를 나타냈다. 식포 내의 출현율을 근거로 분변립, 원생생물과 꽃가루가 어란, 규조류, 와편모조류 그리고 치자어에 비해 더 선호된 것으로 여겨졌다. 본 연구결과는 연구기간에 독도 주변해역에서 출현한 높은 개체수의 야광충이 기존에 알려진 먹이생물 규조류보다 다른 먹이생물과 관련이 높음을 의미하였다.

• ALGAE
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• 제38권4호
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• pp.265-281
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• 2023

Hypoxia can indeed impact the survival of protists, which play a crucial role in marine ecosystems. To better understand the protistan community structure and species that can thrive in hypoxic waters, we collected samples from both the surface and bottom waters during the hypoxic period in Jinhae and Masan Bays and the non-hypoxic period in Jinhae Bay. Subsequently, we utilized metabarcoding techniques to identify the protistan species. During hypoxia, with dissolved oxygen concentrations of 0.8 mg L^-1 in Jinhae Bay and 1.8 mg L^-1 in Masan Bay within the bottom waters, the phylum Dinoflagellata exhibited the highest amplicon sequence variants richness among the identified protist phyla. Following the Dinoflagellata, Ochrophyta and Ciliophora also displayed notable presence. In hypoxic waters of Jinhae and Masan Bays, we identified a total of 36 dinoflagellate species that exhibited various trophic modes. These included one autotrophic species, 14 mixotrophic species, 9 phototrophic species with undetermined trophic modes (either autotrophic or mixotrophic), 2 kleptoplastidic species, and 10 heterotrophic species. Furthermore, the hypoxic bottom water exhibited a greater number of heterotrophic dinoflagellate species compared to the non-hypoxic surface water within the same water column or the non-hypoxic bottom water. Therefore, feeding by mixotrophic and heterotrophic dinoflagellates may be partially responsible for their dominance in terms of the number of species surviving in hypoxic waters. This study not only introduces the initial documentation of 26 dinoflagellate species surviving in hypoxic conditions but also establishes a foundation for a more comprehensive understanding of the ecophysiology of dinoflagellates in hypoxic marine environments.

• ALGAE
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• 제39권1호
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• pp.1-16
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• 2024

Many dinoflagellates produce bioluminescence. To estimate the intensity of bioluminescence produced by populations of the heterotrophic dinoflagellates Noctiluca scintillans and Polykrikos kofoidii and autotrophic dinoflagellate Alexandrium mediterraneum in Korean waters, we measured cellular bioluminescence intensity as a function of water temperature and calculated population bioluminescence intensity with cell abundances and water temperature. The mean 200-second-integrated bioluminescence intensity per cell (BL_cell) of N. scintillans satiated with the chlorophyte Dunaliella salina decreased continuously with increasing water temperature from 5 to 25℃. However, the BL_cell of P. kofoidii satiated with the mixotrophic dinoflagellate Alexandrium minutum continuously increased from 5 to 15℃ but decreased at temperatures exceeding this (to 30℃). Similarly, the BL_cell of A. mediterraneum continuously increased from 10 to 20℃ but decreased between 20 and 30℃. The difference between highest and lowest BL_cell of N. scintillans, P. kofoidii, and A. mediterraneum at the tested water temperatures was 3.5, 11.8, and 21.0 times, respectively, indicating that water temperature clearly affected BL_cell. The highest estimated population bioluminescence intensity (BL_popul) of N. scintillans in Korean waters in 1998-2022 was 4.22 × 10¹³ relative light unit per liter (RLU L^-1), which was 1,850 and 554,000 times greater than that of P. kofoidii and A. mediterraneum, respectively. This indicates that N. scintillans populations produced much brighter bioluminescence in Korean waters than the populations of P. kofoidii or A. mediterraneum.

• 수산해양기술연구
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• 제41권2호
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• pp.129-139
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• 2005

We investigated the characteristics of the thermohaline structure and phytoplankton community from the southwestern areas of Jeju to the nothern areas of Taiwan in the Ease China Sea, in June 2004. According to the analysis of a T-S diagram, three characteristic of water masses were identified. We classified them into the mixed water mass by the Chiness continental coastal waters and Yellow Sea cold water (Region A), Chinese continental coastal waters (Region B) and Taiwan warm current (Region C). Region A was characterized by low temperature, low salinity, high density and high Chl-a concentration. Region B was characterized by high temperature, low salinity, low density and high Chl-a and Region C was characterized high temperature, high salinity, low density and low Chl-a concentration. The phytoplankton community identified a total of 56 species belonging to 31 genera. The dominant species was mainly dinoflagellates, Gymnodinium breve, Scrippsiella trochoidea, Ceratium fusus, Prororcentrum triestinum, centric diatoms, Chaetoceros lorenzianus, Leptocylindrus danicus, Proboscia alata, Skeletonema costatum and pennate diatoms, Pseudonitzschia pungens, Cylidrotheca closterium. Standing crops of phytoplakton fluctuated between $0.1{\times}10^2$ cells/L and $5.7{\times}10^4$ cells/L by dominance of dinoflagellates. In the phytoplankton community, the Region A was characterized by the various species composition in 39 species, the dominint species with di-atomes, Pn. pungen, Ch. lorenzianus and standing crops from 6.9 cells/$m\ell$ to 56.6 cells/$m\ell$, Region B by the various species composition in 37 species, the dominant species with dinoflagellates, G.breve, S. trochoidea and standing crops from 4.6 cells/$m\ell$ to 26.7 cells/$m\ell$, and the Region C by low species number with 28 species, the dominant species with one dinoflagellate, S.trochoidea and one diatom, L.danicus and very low standing crops from 0.1 cells/$m\ell$ to 5.7 cells/$m\ell$. Phytoplankton productivity in the East China Sea was controlled by Chinese continental coastal waters which include a high concentrations of nutrients.