Yang Ho Yoon

Reconstruction of historical nutrient levels in Korean and Japanese coastal areas based on dinoflagellate cyst assemblages.

Dinoflagellate cysts acquired from sediment cores were analyzed in order to reconstruct historical nutrient levels in Gamak Bay, Korea and Ariake Bay, Japan. Dinoflagellate cyst assemblages in Gamak Bay were characterized by high proportions of heterotrophic cysts such as Brigantedinium spp., Protoperidinium americanum and Polykrikos cysts, which suggested that nutrients levels may have already been high before 1970s, and then increased further to the hypertrophic conditions of the 1990s. In contrast, dinoflagellate cyst assemblages in Ariake Bay were characterized by high relative abundances of Lingulodinium machaerophorum and Spiniferites spp., which suggested that nutrient levels in Ariake Bay had increased gradually since the mid 1960s, and may have been significantly enhanced by the mid 1980s. Dinoflagellate cyst assemblages reflecting environmental changes in the two bays are contrasting, perhaps due to different nutrient enrichment mechanisms. This suggests that the indicators of nutrient levels encoded in dinoflagellate cyst assemblages may exhibit site-specific information.

Effects of Light Quantity and Quality on the Growth of the HarmfulDinoflagellate, Cochlodinium polykrikoides Margalef (Dinophyceae)

해양의 기초생산자인 식물플랑크톤은 태양에너지를 이용 하여 무기물로부터 유기물을 합성한다. 식물플랑크톤의 광 합성과 성장은 빛의 성질에 따라 크게 영향을 받게 되며, 특 히 빛의 파장과 조성은 광합성 생물 및 비광합성 생물의 신 진대사에까지 영향을 미친다(Sanchez-Saavedra and Voltolina 1994). 특히, 와편모조류를 포함하는 식물성 편모 조류는 미약하지만 운동능력을 보유하고 있어, 광학적으로 성장할 수 있는 심도까지 내려가 저층에 풍부한 영양염을 섭 취하여 성장할 수 있다(Honjo et al. 1989). 따라서 보다 낮은 광 조건에서도 성장할 수 있는 종은 유영심도가 더욱 깊어져 다른 종보다 유리한 생존 전략을 가진다. 또한, 수심에 따라 빛의 파장은 크게 다르기 때문에 여러 파장대 빛을 이용할 수 있는 종이 보다 효율적으로 성장할 수 있다. 한편 1995년 이후 매년 남해안과 동해안에서 대규모로 적 조를 발생시켜 막대한 경제적 손실과 해양생태계의 황폐화 를 초래하고 있는 유해성 와편모조류(NFRDI 1999, 2000), Cochlodinium polykrikoides Margalef는 Caribbean Sea에 위치 하는 Puerto Rico에서 처음으로 명명되었다(Margalef 1961). 더욱이 C. polykrikoides에 의한 적조는 우리나라에만 국한되 지 않고, 2005년에는 일본 Tottori현(동해에 위치한 현)에서 이 종에 따른 적조로 대량의 어패류 폐사가 있었다. 이곳의 Algae Volume 21(3): 311-316, 2006

Modern Dinoflagellate Cysts Distribution off the Eastern Part of Geoje Island, Korea

Distributional characteristics of dinoflagellate cysts in surface sediments were investigated in relation to environmental factors in the eastern part of Geoje Island, Korea. Samples were collected from 10 stations in February of 2004 and water temperature and salinity were measured in February, May, September and November of 2004. Total 30 taxa of dinoflagellate cysts were identified representing 19 genera, 28 species and 2 unidentified species. Among these dinoflagellate cysts,Brigantedinium spp. of which relative proportion in the total dinoflagellate cysts was 23.5%, was the most abundant at all stations except St. 1, and was followed bySpiniferites bulloideus (8.6%),Lingulodinium machaerophorum (8.2%) andDiplopsalis lenticula (6.7%). In addition, ellipsoidal cysts of the genusAlexandrium (Alexandrium catenella - tamarense type) andGymnodinium catenatum, known to be causative organisms for PSP, occurred with high concentrations.Scrippsiella trochoidea was also found; however, its cyst concentration was low. Generally, species composition in the study area was similar to these reported from Jinhae Bay and Busan Harbor and several dinoflagellate cysts reflected the eutrophic condition. Cyst distribution in the eastern part of Geoje Island seems to be influenced by the Tsushima Warm Current flowing from the southwest. The mean water temperature was 12.0°C in February, 14.7°C in May, 20.9°C in September and 17.2°C in November, which was most favorable forAlexandrium spp. growth. The abundances of dinoflagellate cysts ranged from 528 to 2,834 cysts/g dry sediment. Higher concentrations were recognized in sediments of west area of the Jisimdo than at other stations. The cyst composition of this area was closely related to these of Jinhae Bay and Busan Harbor from which currents flow into this area. Higher cyst concentration in the west area of Jisimdo might be due to formation of the gyre.

The First Appearance of Toxic Dinoflagellate Alexandrium tamarense (Gonyaulacales, Dinophyceae) Responsible for the PSP Contaminations in Gamak Bay, Korea

In Gamak Bay, Paralytic Shellfish Poisoning (PSP) was first detected from seafoods in 2003, however the toxin source is unknown yet. In this study, we report potential PSP producers of toxic dinoflagellates, describing morphology and abundance of cysts isolated from surface sediment of Gamak Bay. The most abundant type in these cysts was characterized with ellipsoidal and transparent wall identical to Alexandrium catenella and/or A. tamarense. Germination experiment of the cysts revealed that all motile cells germinated were morphologically identified as A. tamarense. This result suggests that A. tamarense may relate to PSP contaminations in Gamak Bay. Moreover, bottom water temperature in Gamak Bay is favorable for germination of A. tamarense cysts. Further studies are required to carry out the PSP monitoring for preventing the risk of PSP events that may outbreak in future at Gamak Bay.

The First Records of Two Neustonic Calanoid Copepods, Pontella securifer and P. sinica (Calanoida, Pontellidae) in the South Sea, Korea

The neustonic calanoid copepodsPontella securifer Brady, 1883 andP. sinica Chen and Zhang, 1965 are first recorded in Korea. These species occur in high temperatures over 23 °C and in a range of salinity from 26.6 to 31.2 psu. We provide full descriptions of the two species and discuss their zoogeography.

Formation and germination of temporary cysts of Cochlodinium polykrikoides Margalef (Dinophyceae) and their ecological role in dense blooms

While the initiation and development of dense bloom of Cochlodinium polykrikoides have been shown to be related to some environmental factors, little is known about the ecological role of the formation and germination of temporary cysts, nor of their significance for the rapid expansion of dense regional-scale blooms. This study examined the factors affecting the formation and germination of temporary cysts of C. polykrikoides, and provides details about the germination process. In the laboratory experiments, C. polykrikoides produced the chain-forming temporary cysts that are immobile and surrounded by a hyaline membrane. The encystment experiment indicated that darkness induces the formation of chain-forming temporary cysts, consistent with field observation of morphology and fluxes of temporary cysts. Germination occurred twice from a single four-celled temporary cysts within 24h after exposure to light, and the germlings appeared as two-celled chain-forming vegetative cells. The germination behavior of temporary cysts of C. polykrikoides differs from that of other dinoflagellates, and this may be a survival strategy for the maintenance of population size during dense blooms.

Summary on the Dinoflagellate Cyst Assemblages of Modern Sediments from Korean Coastal Waters and Adjoining Sea

To investigate the research state and characteristics of dinoflagellate cyst along the Korean coastal waters, this work analyzed 45 studies conducted in the Korean coasts and basin, the south of Jeju, East China Sea including some part of the Yellow Sea. It was found that the research on dinoflagellate cyst began in the later half of the 1980s in Korea, and that the research areas focused on eutrophied regions where a red tide occurred or on the seas where coastal development occurred. In other words, no research on the East Sea was found. In terms of research contents, there were various studies on analysis of cyst assemblage, tracking of the changes in marine environment like process of eutrophication, roles as a seed population in occurrence of a red tide, creation of cyst by use of sediment trip and tracking of its changes, morphological changes by the change of pH concentration in the hypoxia zone of eutrophied region, germination of a specific species, and other international-level studies. Species composition and cell density also varied in the Korean coastal waters. However, much research on dinoflagellate cyst in Korea is not systematic, and is fragmentary and individual and hencesuffers from great limitations. The research results so far have focused only on specific regions, and sporadic research had been conducted by specific research groups. Dinoflagellate cyst of surface sediments represents the accumulation index of pelagic environment in the sea and is a useful index to understand the marine environment efficiently. In conclusion, Korea requires organized human resources and collaborative research on dinoflagellate cyst which in turn should be considered as a component of marine ecosystem and as an essential aspect of marine biology.

Redescription ofPontella species (Calanoida, Pontellidae) from Korean waters, with notes on their spatio-temporal distribution

To understand physical structures in the Korean waters, we investigated the spatio-temporal distribution ofPontella species known as indicator species of water mass using a David-Hempel neuston net from April 2002 to March 2003. FivePontella species (P. chierchiae Giesbrecht,P. fera Dana,P. latifurca Chen and Zhang,P. securifer Brady andP. sinica Chen and Zhang) were found. Their abundance increased from May to October with increasing the surface water temperature.Pontella chierchiae predominantly appeared in the whole areas whileP. latifurca scarcely occurred in coastal waters. The other three species (P. fera, P. securifer andP. sinica) were rarely found in the South Sea of Korea on August to September. We suggest thatP. securifer andP. fera as oceanic species can play a role in an indicator species of the Tsushima Warm Current whileP. sinica as Chinese coastal species is affected by the diluted waters of the Yantze River. We also provide re-description of the three species (P. chierchiae, P. fera andP. latifurca) insufficiently described and discuss their zoogeography.

Morphological identification of Alexandrium species (Dinophyceae) from Jinhae-Masan Bay, Korea

Outbreaks of paralytic shellfish poisoning (PSP) and dense blooms caused by Alexandrium species in Jinhae-Masan Bay, Korea have been nearly annual events for many years. However, excluding some Alexandrium species responsible for PSP, there are no critical reports on the morphology of Alexandrium species in this bay. To identify the Alexandrium species based on detailed morphological features, vegetative cells collected water samples and established by the incubation of resting cysts isolated from sediment trap samples were analyzed. Four species of Alexandrium were identified: Alexandrium affine, A. fundyense, A. catenella, and A. insuetum. Morphological features of these species were basically consistent with those outlined in previous studies. However, the ventral pore and the connecting pore on the sulcal plate, which have been accepted as diagnostic characteristics for the identification of A. fundyense and A. catenella, need to be reevaluated, indicating that useful morphological features for identifying these two species should be recommended to avoid confusion in the classification of species in genus Alexandrium.

Morphology and phylogeny of Pentapharsodinium jinhaense sp. nov. (Dinophyceae) producing a calcareous resting cyst

Abstract: A new species, Pentapharsodinium jinhaense sp. nov., was established by incubating resting cysts, which were collected from trap samples from Jinhae-Masan Bay, Korea. The resting cysts of P. jinhaense were spherical or ovoidal, with a large reddish pigment body and a thick wall covered by numerous needle-shaped calcareous crystals. The size, shape and plate tabulation of motile cells that germinated from the resting cysts were similar to those of Pentapharsodinium tyrrhenicum and Ensiculifera carinata; however, the motile cells had a spine located in the anterior sulcal plate and many pores and spines on the thecal surface. Molecular phylogenetic analysis using internal transcribed spacer and 5.8s rDNA showed that P. jinhaense was closely related to P. tyrrhenicum. Large subunit ribosomal DNA sequences also revealed that P. jinhaense was nested within Pentapharsodinium and formed a strongly supported clade with Pentapharsodinium dalei and P. tyrrhenicum.