• Korean Journal of Environmental Biology
• /
• v.17 no.3
• /
• pp.271-278
• /
• 1999

In order to clarify water quality, dynamics and structure of phytoplankton communities, and red tides, the present study was carried out monthly from July to September 1998 at 19 stations in Deukryang Bay. Water temperature varied from 24.$0^{\circ}C$ to 28.6$^{\circ}C$, and salinities ranged from 25.0$\textperthousand$ to 28.6$\textperthousand$. During red tides in July, chlorophyll-$\alpha$ contents were rather high in August, it showed that phytoplankton controlled primary production in this bay. Phytoplankton was composed of 89 diatoms, 19 dinoflagellates, and 3 silicoflagellates. Phytoplankton standing crops varied from a minimum of 1.3$\times$10$^4$cells/ι(Sept., St. 17) to a maximum of 3.8$\times$10$^{6}$ cells/ι (July, St. 10). Red tides occurred in July when the standing crops averaged 1.8$\times$10$^{6}$ cells/ι. Leading the causative organisms of red tide were Prorocentrun minimum in the upper bay, Chaetoceros curvisetus in the mouth and middle part of the bay, Ceratium furca and Thazassio- sira sp. around Nokdong Harbour. Concentration of nutrients such as nitrogen was high in the upper bay, during red tides, water temperatures varied from 23.8$^{\circ}C$ to 29.7$^{\circ}C$ and salinity were 23.l$\textperthousand$ to 27.0$\textperthousand$.

• Journal of Environmental Science International
• /
• v.7 no.1
• /
• pp.8-19
• /
• 1998

The dicriminant function was introduced to understand the cause and establish the prediction method of red tides occurring In Jinhae Bay. Korea. Two sea re91ons of Masan and Haengam Bays and Dang- dong and Wonmun Bays had different types of causes and patterns for red tides. In Masan and Haengam Bays, the red tides concentrically occurred during June and September. For example, in .lune the red tides occurred from physical and meteorological factors, which are related to the stratification and the increase in planktons. However in August the red tides occurred from the water quality environment, based on these conditoins. Futhermore, in September the red tides were caused by the balance between the meteorological and water quality environmental factors. In contrast to those, In Dangdong and Won-mun Bays, the red tides mainly occurred during July and October and the frequency of occurrence was not as much as Masan and Haengam Bays. Especially, in August and September most meteorological and physical factors or water quality environmental factors appeared to contribute to the occurrence of red tides. This indicates that red tides do not easily occur as they are controlled by various environmental factors particularly in these regions The discriminant functions were applied to predict red tides which they were actually occurred In Masan and Haengam Bays in June. The results showed that they were successful for the prediction of red tide at Haengam Bay but not at Masan Bay. The reason for their discrepancy in Masan Bay could have come from using a slight higher value of pH or COD in May, instead of its value in June.

• ALGAE
• /
• v.36 no.1
• /
• pp.25-36
• /
• 2021

The mixotrophic dinoflagellate Tripos furca causes red tides in the waters of many countries. To understand its population dynamics, mortality due to predation as well as growth rate should be assessed. Prior to the present study, the heterotrophic dinoflagellates Noctiluca scintillans, Polykrikos kofoidii, Protoperidinium steinii, and mixotrophic dinoflagellate Fragilidium subglobosum were known to ingest T. furca. However, if other common heterotrophic protists are able to feed on T. furca has not been tested. We explored interactions between T. furca and nine heterotrophic dinoflagellates and one naked ciliate. Furthermore, we investigated the abundance of T. furca and common heterotrophic protists in coastal-offshore waters off Yeosu, southern Korea, on Jul 31, 2020, during its red tide. Among the tested heterotrophic protists, the heterotrophic dinoflagellates Aduncodinium glandula, Luciella masanensis, and Pfiesteria piscicida were able to feed on T. furca. However, the heterotrophic dinoflagellates Gyrodiniellum shiwhaense, Gyrodinium dominans, Gyrodinium jinhaense, Gyrodinium moestrupii, Oblea rotunda, Oxyrrhis marina, and the naked ciliate Rimostrombidium sp. were unable to feed on it. However, T. furca did not support the growth of A. glandula, L. masanensis, or P. piscicida. Red tides dominated by T. furca prevailed in the South Sea of Korea from Jun 30 to Sep 5, 2020. The maximum abundance of heterotrophic dinoflagellates in the waters off Yeosu on Jul 31, 2020, was as low as 5.0 cells mL-1, and A. glandula, L. masanensis, and P. piscicida were not detected. Furthermore, the abundances of the known predators F. subglobosum, N. scintillans, P. kofoidii, and Protoperidinium spp. were very low or negligible. Therefore, no or low abundance of effective predators might be partially responsible for the long duration of the T. furca red tides in the South Sea of Korea in 2020.

• Journal of Wetlands Research
• /
• v.3 no.2
• /
• pp.107-118
• /
• 2001

The aim of this paper is to grasp eutrophication aspects in Namhae coastal seas, statistically analyzing existing data for their surface seawater and bottom mud. A pollution level(ignition loess) of bottom mud, on the whole, trended to increase as moving the coastal sea around Mokpo-Wando toward the east(Gyeongnam Namhae coastal seas). Especially, the pollution level(ignition loss=10.5%) of bottom mud for the coastal sea around Tongyeong-Keoje-Gosung was similar to that(10.3%) for the coastal sea around Masan-Jinhae, whose coastal marine pollution was the severest in Namhae coastal seas. It indicates that large amounts of pollutant from aqualculture facilities have been, thus far, accumulated on the coastal sea around Tongyeong-Keoje-Gosung, considering there was no significant inflow of sewage and industrial wastewater into this coastal sea. A COD, T-N, and T-P level of surface seawater, on the whole trended to increase as moving the coastal sea around Mokpo-Wando toward the east(Gyeongnam Namhae coastal seas). A COD level appeared to be the second grade of coastal water quality over the entire year throughout all Namhae coastal seas A T-N level exceeded the third grade of coastal water quality throughout all Namhae coastal seas except the coastal sea around Mokpo-Wando. Especially, a T-N level exceeded as many as three and six times over the third grade of coastal water quality in the coastal sea around Tongyeong-Keoje-Gosung and Masan-Jinhae, respectively. A T-P level appeared to be the second grade of coastal water quality in the coastal sea around Mokpo-Wando and the third grade of coastal water quality in the coastal sea around Yosu-Narnhae and Tongyeong-Keoje-Gosung, while it exceeded as many as two times over the third grade of coastal water quality. A degree of eutrophication of the surface seawater was 1.5 in the coastal sea around Mokpo-Wando and 11.9 In the coastal sea around Tongyeong-Keoje-Gosung, gradually increasing as moving toward the east(Gyeongnam Narnhae coastal seas). It sharply increased to 146.1 in the coastal sea around Masan-Jinhae. Because the degree of eutrophication throughout all Namhae coastal seas exceeded 1, a red tide organism could pose a possibility of proliferation at any place of Namhae coastal seas if other requirements were satisfied. It indicates that a red tide may move to another place once a red tide breaks out at a place of Namhae coastal seas.

• ALGAE
• /
• v.31 no.4
• /
• pp.351-362
• /
• 2016

We investigated a possible reduction in $CO_2$ uptake rate by phototrophic red tide dinoflagellates arising from mixotrophy. We measured the daily ingestion rates of Prorocentrum minimum by Prorocentrum micans over 5 days in 10 L experimental bottles, and the uptake rates of total dissolved inorganic carbon ($C_T$) by a mixture of P. micans and P. minimum(mixotrophic growth), and for the predator P. micans (phototrophic growth; control) and prey P. minimum (phototrophic growth; control) alone. To account for the effect of pH on the phototrophic growth rates of P. micans and P. minimum, measurements of $C_T$ and pH in the predator and prey control bottles were continued until the pH reached the same level (pH 9.5) as that in the experimental bottles on the final day of incubation. The measured total $C_T$ uptake rate by the mixture of P. micans and P. minimum changed from 123 to $161{\mu}mol\;C_T\;kg^{-1}\;d^{-1}$ over the course of the experiment, and was lower than the $C_T$ uptake rates shown by P. micans and P. minimum in the predator and prey control bottles, respectively, which changed from 132 to $17{\mu}mol\;C_T\;kg^{-1}\;d^{-1}$ over the course of the experiment. The reduction in total $C_T$ uptake rate arising from the mixotrophy of P. micans was 7-31% of the daily $C_T$ uptake rate seen during photosynthesis. The results suggest that red tide dinoflagellates take up less $C_T$ during mixotrophy.

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

• ALGAE
• /
• v.34 no.3
• /
• pp.237-251
• /
• 2019

The dinoflagellate genus Alexandrium is known to often form harmful algal blooms causing human illness and large-scale mortality of marine organisms. Therefore, the population dynamics of Alexandrium species are of primary concern to scientists and aquaculture farmers. The growth rate of the Alexandrium species is the most important parameter in prediction models and nutrient conditions are critical parameters affecting the growth of phototrophic species. In Korean coastal waters, Alexandrium affine and Alexandrium fraterculus, of similar sizes, often form red-tide patches together. Thus, to understand bloom dynamics of A. affine and A. fraterculus, growth rates and nitrate uptake of each species as a function of nitrate ($NO_3$) concentration at $100{\mu}mol\;photons\;m^{-2}s^{-1}$ under 14-h light : 10-h dark and continuous light conditions were determined using a nutrient repletion method. With increasing $NO_3$ concentration, growth rates and $NO_3$ uptake of A. affine or A. fraterculus increased, but became saturated. Under light : dark conditions, the maximum growth rates of A. affine and A. fraterculus were 0.45 and $0.42d^{-1}$, respectively. However, under continuous light conditions, the maximum growth rate of A. affine slightly increased to $0.46d^{-1}$, but that of A. fraterculus largely decreased. Furthermore, the maximum nitrate uptake of A. affine and A. fraterculus under light : dark conditions were 12.9 and $30.1pM\;cell^{-1}d^{-1}$, respectively. The maximum nitrate uptake of A. affine under continuous light conditions was $16.4pM\;cell^{-1}d^{-1}$. Thus, A. affine and A. fraterculus have similar maximum growth rates at the given $NO_3$ concentration ranges, but they have different maximum nitrate uptake rates. A. affine may have a higher conversion rate of $NO_3$ to body nitrogen than A. fraterculus. Moreover, a longer exposure time to the light may confer an advantage to A. affine over A. fraterculus.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.7 no.3
• /
• pp.140-147
• /
• 2002

We investigated the temporal variations in the heterotrophic dinoflagellates (hereafter HTD), tintinnid ciliates(TC), and naked ciliates(NC) from August to November 1999 in the coastal waters off the southern Saemankeum areas where a huge red tide dominated by Cochlodinium polykrikoides/Gymnodinium impudicum was first observed in 1998. We took water samples from 2-5 depths of 4 stations in each of the 5 cruises and then measured the species composition and abundances of HTD, TC, and NC The maximum species numbers and densities of HTD, TC, and NC(11, 12, and 10 cells $m\ell$$^{-1}$ , respectively) were observed when the density of diatoms was highest (August 10), while the lowest values (1.0, 0.5, and 2.4 cells $m\ell$$^{-1}$ , respectively) were found when the red tide dominated by C. polykrikoides/G. impudicum took placed (October 18). On August 10 and November 11 when diatoms dominated the abundance of phytoplankton, the correlation coefficients between TC, NC and diatoms were relatively high. However, On September 16 and October 18 when autotrophic+mixotrophic dinoflagellates(ATD+MTD) were abundant, the correlation coefficients between HTD and ATD+MTD were relatively high. The large HTD Noctiluca scintillans was the most dominant heterotrophic protists during the C. polykrikoides/G. impudicum red tide on October 18. N. scintillans has been known to feed on the prey cells when the swimming speeds of C. polykrikikoides/G. impudicum markedly reduced at the decline stage of the red tide. Therefore, N. scintillans could be effective grazers on C. polykrikoides/G. impudicum. The maximum densities of HTD, TC, and NC in the study area were fairly lower than those obtained in the waters off Kohung-Yeosu areas in the summer-fall, 1997. The results of the present study provide the basis of understanding predator-prey relationships between dominant phytoplankton and heterotrophic protists and the roles of the protist grazers in bloom dynamics in the waters off the western Korea.

• Proceedings of the KSRS Conference
• /
• 2004.10a
• /
• pp.494-497
• /
• 2004

To date the KOMPSAT OSMI(Ocean Scanning Multi-spectral Imager) data have been widely used in natural disaster monitoring such as Typhoon, Asian Dust, Red Tide, and Forest Fire. Quantitative analyses related to the marine ecosystem have been delayed because they require good quality of data through Cal/Val activities. To resolve such problem, KARI performed the OSMI crosscalibration study with SeaWiFS team. In this study, we will demonstrate the OSMI ocean color products with updated cross-calibration coefficients and compare them to the previous cross-calibration results.

• Bulletin of the Korean Space Science Society
• /
• 2007.04a
• /
• pp.61-61
• /
• 2007