• ALGAE
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• v.26 no.1
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• pp.41-50
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• 2011

Yellow Sea surface sediment samples collected on October 15-31, 2003 were analyzed using the palynological process to investigate the spatial distribution of dinoflagellate resting cysts. The sampling areas comprised four latitudinal transects, the northernmost of which was located off the Shandong Peninsula, China and the southernmost off Jeju Island, Korea. Each transect line was composed of six to nine stations, spanning the distance between the Chinese and Korean coasts. Twenty-five different types of dinoflagellate cysts were identified. Gonyaulax scrippsae, Alexandrium spp. (ellipsoidal type), and G. spinifera were the most dominant at all stations surveyed. Dinoflagellate cysts belonging to the Gonyaulacales comprised over 50% of all cysts collected. The latitudinal distribution trend showed that cyst concentrations along the two middle transects were much higher than those along the two northern and southern transects. Cyst concentrations in the offshore central areas reached their highest values within each transect and gradually decreased toward the Chinese and Korean coasts. Overall, cyst concentrations were markedly elevated in the offshore central Yellow Sea areas and gradually decreased outward in all four directions. This concentric cyst distribution pattern was consistent with the hydrographic features of the Yellow Sea, such as circular current systems, sedimentary properties, and water depth.

• Korean Journal of Environmental Biology
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• v.36 no.1
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• pp.82-89
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• 2018

To investigate the occurrences of resting cysts of Diplopsalis and Protoperidinium species, sediment trap samples were collected from Gamak Bay, Korea. Based on the germination experiments, nine species of order Peridiniales were identified; cyst of Diplopsalis lebourae, cyst of Protoperidinium excentricum, cyst of Protoperidinium sp. cf. nudum, cyst of Protoperidinium obtusum, cyst of Protoperidinium ventricum, cyst of Protoperidinium sp.1, cyst of Protoperidinium sp.2, Protoperidinium sinuosum (Brigantedinium majusculum) and unidentified Peridiniales.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.1
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• pp.68-72
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• 2009

To gain a greater understanding of the potential for future harmful algal bloom (HAB) outbreaks and to trace the dispersal paths of dinoflagellates, sediment samples were collected from 13 stations in the southeastern Yellow Sea. 23 different types of dinoflagellate resting cysts were identified from the samples. Protoceratium reticulatum (1-391 cells/g dry weight), Gonyaulax scrippsae (0-254 cells/g dry weight), G. spinifera (0-301 cells/g dry weight) and Alexandrium spp. (ellipsoidal type) (0-76 cells/g dry weight) were the dominant species at all surveyed stations. The overall distribution pattern demonstrated that the resting cyst densities were highest in the offshore area and decreased gradually toward the Korean coast. On the other hand, the composition rate of resting cysts of the heterotrophic dinoflagellate species to the total dinoflagellates was higher in the Korean coast region than in the offshore area. We supposed that this distribution pattern of dinoflagellate resting cysts appeared to be influenced by the hydrographic features and environmental conditions of the Yellow Sea.

• Fisheries and Aquatic Sciences
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• v.15 no.1
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• pp.57-62
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• 2012

Interspecific relationship between a euryhaline rotifer Brachionus rotundiformis and a cyclopoid copepod Apocyclops borneoensis was investigated in the laboratory culture. In a mixed culture of B. rotundiformis and A. borneoensis, population growth of B. rotundiformis was suppressed from day 10, while growth in a monoculture population continuously increased throughout the experimental period. However, the population growth of A. borneoensis in the mixed culture did not markedly differ from that in a monoculture population. Suppression of B. rotundiformis growth coincided with a decrease in the numbers of both non-egg-bearing and egg-bearing females, and increasing resting egg formation. Growth of A. borneoensis was not affected by the presence of the rotifer. However, relative growth index of ovisac bearing females in the mixed culture was 1.62 times higher than that in the monoculture. Presence of the copepod did not greatly reduce the food available to the rotifer population. The rotifer B. rotundiformis responded in a unique way, to stresses such as physical damage (filtering by A. borneoensis) with the production of many resting eggs to increase its chances of survival.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.3
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• pp.202-208
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• 2004

The spatio-temporal distribution of dinoflagellate resting cysts was investigated by palynological processing to understand the harmful algal bloom (HAB) potential in the sediment of the Saemangeun area in 2003. In total, thirty-two dinoflagellate species were identified, and their concentrations were in the range of $6-1,618\;cysts{\cdot}g^{-1}$ (dry weight). The concentrations of resting cysts were higher in the spring (26 species, $64-1,101\;cysts{\cdot}g^{-1})$ and summer (30 species, $81-1,618\;cysts{\cdot}g^{-1})$ than in the autumn (32 species, $6-1,150\;cysts{\cdot}g^{-1})$ and winter (24 species, $25-728\;cysts{\cdot}g^{-1}).$ The composition rate of the heterotrophic dinoflagellate species to the total, which is closely related to the eutrophication process, to ranged from 6 to $29\%$ in the study area. The most dominant species was toxic Alexandrium tamarense/catenella $(25\%)$ followed by Gonyaulax scrippsea $(9\%)$ and toxic Protoceratium reticulatum $(5\%).$ Given the high abundance of the toxigenic dinoflagellate species, the Saemangeun area is considered to have the great potential for HABs in the future.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.6
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• pp.837-842
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• 1996

The resting cyst of Gymnodinium catenatum was found in the surface sediments collected from Chinhae Bay in October, 1991. This is the first record of the species in the Korean waters. The relative abundance was low with the maximum of $1.7\%$. The colonial motile form consisting of four cells was observed in 1992 from the excystment of the cyst collected from the Wonmun Bay in Chinhae Bay. No blooms caused by G. catenatum has been observed in Chinhae Bay during the survey.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.6
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• pp.322-330
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• 2003

The unicellular green alga Haematococcus pluvialis has recently attracted great inter-est due to its large amounts of ketocarotenoid astaxanthin, 3,3'-dihydroxy-${\beta}$,${\beta}$-carotene-4,4'-dione, widely used commercially as a source of pigment for aquaculture. In the life cycle of H. pluvialis, astaxanthin biosynthesis is associated with a remarkable morphological change from green motile vegetative cells into red immotile cyst cells as the resting stage. In recent years we have studied this morphological process from two aspects: defining conditions governing astaxanthin biosynthesis and questioning the possible function of astaxanthin in protecting algal cells against environmental stress. Astaxanthin accumulation in cysts was induced by a variety of environmental conditions of oxidative stress caused by reactive oxygen species, intense light, drought, high salinity, and high temperature. In the adaptation to stress, abscisic acid induced by reactive oxygen species, would function as a hormone in algal morphogenesis from veget ative to cyst cells. Furthermore, measurements of both in vitro and in vivo antioxidative activities of astaxanthin clearly demonstrated that tolerance to excessive reactive oxygen species is greater in astaxanthin-rich cysts than in astaxanthin-poor cysts or astaxanthin-less vegetative cells. Therefore, reactive oxygen species are involved in the regulation of both algal morph O-genesis and carotenogenesis, and the accumulated astaxanthin in cysts can function as a protective agent against oxidative stress damage. In this study, the physiological roles of astaxanthin in stress response and cell protection are reviewed.

• Journal of Life Science
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• v.13 no.2
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• pp.163-167
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• 2003

Identification of species within the toxin-producing genus Alexandrium is vital for biotoxin monitoring and mitigation decisions regarding shellfish industry. In particular, the discrimination of resting cysts of only A. tamarense from that of Alexandrium spp. is considerable important to fundamentally monitor and predict this species before vegetative cells occur in the nature. Fluorescent cTAM-F1 DNA probe was responsible to not only binding the activity of the vegetative cells in A. tamarense, but also to the resting cysts, which was treated with methanol after fixation and stained by primuline on the surface The location of fluorescence in cultured vegetative cells and resting cysts was almost at tile bottom of the nucleus. The optimal incubation temperature and time using in situ hybridization were 50-$54^{\circ}C$ and 40-60 min, respectively, to penetrate the DNA probe into cell.

• Korean Journal of Environmental Biology
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• v.37 no.3
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• pp.268-277
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• 2019

Severe damages will result in human society, when several different critical natural phenomena coincide. One example relates to the resting cysts of Alexandrium species (dinoflagellates that cause paralytic shellfish poisoning), which are preserved in surface sediments throughout Osaka Bay, Japan. These cysts have been found to accumulate particularly densely in shallow areas in the inner parts of Osaka Bay, where a tsunami caused by an earthquake could occur any time. Damage by a tsunami could cause a change of the coastal ecosystems at Osaka Bay including the resuspension of surface sediments containing resting Alexandrium tamarense cysts and the subsequent redistribution of the cysts in newly deposited sediment. Under certain environmental conditions, these cysts could germinate and form dense blooms, leading to paralytic shellfish poisoning. Such a scenario could also affect other coastal areas, including the southern coast of the Korean Peninsula.

• Journal of Aquaculture
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• v.7 no.4
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• pp.251-264
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• 1994

To study the causes of occurring toxic dinoflagellate Alexandriwn species, an experiment was undertaken in Jinhae Bay shellfish harvesting areas. The water and sediment samples were collected to record the abundance of Alexandriwn species, and to study the distribution and the germinability of those benthic cysts from September 1993 to July 1994. Alexandrium species were began to appear at all the sample stations after January, and reached maximum concentration (530 cells/l) at Taekok station (Chilcheon-do) in March 1994. Alexandrium cysts were also found at every station surveyed, of which several sites showed the higher concentration of 700-800 $cysts/cm^3$ at the upper sediment profile (0-4cm), but the concentrations were wide range of 100-800 $cysts/cm^3$. The results of each sampling season showed a great difference in the cyst germination experiments, were potentially high in cold season; $72.5\%$ (Jan.), $68\%$ (Apr.),$44\%$(Jul.), and $9\%$ (Oct.). These results suggested that germination of Alexandrium resting cysts in 15 m depth of coastal waters in Jinhae Bay would be controlled by a seasonal endogenous clock instead of the general environmental factors like temperature. Therefore, it is possible that Alexandrium species could be abundant by the germination of resting cysts in cold season, and contribute to the regional paralytic shellfish poisoning (PSP) toxification.