• 한국환경과학회지
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• 제13권11호
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• pp.1001-1007
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• 2004

The rapid industrialization and urbanization in Osaka Bay have produced many serious water pollution problems since the 1960s. A symbolic phenomenon is algae bloom (red tide), which occurred 53 times in 1976. The special law was enacted in 1973 and a number of administrative steps were taken, such as cutting COD loading, reductions in phosphorus (P) and restriction of land reclamation. As a result, the pollution of Osaka Bay has gradually been reduced, and the environment has been improved to some extent. In this study, to analyze the relations between water qualities as well as a social, economic activity by the coastal zone, the water quality data in Osaka Bay of 70 years past since 1921 were collected. Data such as population, livestock, fertilizer, industrial product etc. were also collected for estimating nutrients flowing into bay from land. It was found that the water quality was changed of a similar trend of estimated nutrients load, with delay of about four or five years.

• 한국환경농학회:학술대회논문집
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• 한국환경농학회 2011년도 30주년 정기총회 및 국제심포지엄
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• pp.292-292
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• 2011

• 환경생물
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• 제33권1호
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• pp.1-6
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• 2015

전세계적으로 2000년대 이후로 남조류에 의한 녹조의 발생이 증가하고 있으며, 이와 관련된 환경 문제가 공중건강을 위협하고 인간 활동을 제한하고 있다. 1970년대 캐나다의 호수를 중심으로 수행된 다년간의 현장 연구를 통하여, 녹조발생의 핵심적인 영양 제한인자로 인이 제시되었고, 인 저감에 대한 수계 관리가 진행되었다. 그러나 2000년대 이후, 대형 담수수계에서 특히 Microcystis에 의한 녹조 현상에서는 인뿐만 아니라 질소가 남조류 녹조 발생에 미치는 영향이 부각되고 있다. 한국의 담수 수계에서도 이와 비슷한 남조류에 의한 위해성 녹조 번성 특징을 갖고 있으므로, 이러한 패러다임의 변화는 국내 담수수계의 영양염류 관리에서 중요한 의미를 갖는다. 최근 국제적인 관련 연구를 통하여, 위해성 남조류 번성을 막기 위해 제안된 방법은 다음과 같다. 1) 질소와 인을 함께 관리하는 전략, 2) 폐수의 수집 및 처리, 3) 호소 유입수의 사전처리, 4) 저니의 준설, 5) 체류시간의 단축, 6) 조류의 효율적 회수법, 7) 조류의 침강 및 응집 등이 제시되고 있다. 추가적으로 남조류의 생태학적 특성에 기반한 지속가능하고 통합적인 담수수계의 녹조 관리기법이 수립되어야 한다. 녹조를 유발하는 남조류는 척결되어야 할 생물체가 아니라, 담수 수계에 필수적인 미생물 구성원이기 때문이다.

• ALGAE
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• 제22권4호
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• pp.287-295
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• 2007

Infection of free-living dinoflagellates by endoparasitic dinoflagellates of the genus Amoebophrya are thought to have significant impacts on host population dynamics and have long been proposed to be a potential biological agent for controlling harmful algal bloom (HAB). To understand the impact of Amoebophrya on particular host species, however, it is necessary to quantify aspects the parasites life cycle. Here we used cultures of Amoebophryahost systems from Jinhae Bay, Korea to determine, parasite generation time, and dinospore survival and infectivity. The proportion of host cells infected by Amoebophrya sp. changed sharply from 5% to 87% with increasing dinospore:host inoculation ratios. In the absence of H. triquetra, most free-living dinospores died within 72 hours and their ability to infect host cells decreased remarkably in a day. The relatively short free-living phase of Amoebophrya suggests that the spread of infections is most likely to occur during seasons of high host abundance, as that is when dinospores have the greatest chance of encountering host cells. Infection of host cells inoculated with dinospores during the day was higher than when inoculated during the night, suggesting that infection rates might be related to environmental light conditions and/or diurnal biological rhythm of host species. Total generation times of parasite strains from a thecate dinoflagellate Heterocapsa triquetra were nearly the same regardless of dinospore:host inoculation ratios, representing 54 ± 0.5 h in a 1:1 ratio and 55 ± 1.2 h in a 20:1 ratio. Dinospore production of Amoebophrya sp. infecting Heterocapsa triquetra was estimated to be 125 dinospores per a strain of Amoebophrya sp. There is a growing need to maintain a variety of host-parasite systems in culture and to examine their autecology under various environmental conditions. Such studies would be very helpful in understanding ecological role of these parasites, their overlooked importance in the flow of material and energy in marine ecosystem, and their practical use as biological control agents applied directly to areas affected by HAB.

• 환경생물
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• 제31권2호
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• pp.113-120
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• 2013

본 연구는 초음파의 주파수별 노출 시간이 녹조현상을 일으키는 Microcystis sp.의 군체에 미치는 영향을 알아보고자 하였다. 각 조사 지점 내의 녹조 생물은 남조강(Cyanophyceae)인 Microcystis sp.가 전체 조류의 약 99.5%를 차지하였다. 초음파의 노출에 따른 녹조류의 chlorophyll-a 농도를 분석해보면 노출시간이 길어짐에 따라 점차적으로 감소하였으며, 특히 70 kHz의 주파수 영역에서 녹조 생물이 세포분열을 통한 생물량의 증가를 억제하는 데 효과적인 것으로 조사되었다. 초음파에 노출되기 전 Microcystis sp.는 단세포가 점액성 물질에 조밀하게 쌓여 있는 군체의 형태로 관찰되었으나 70 kHz 초음파에 노출된 후 Microcystis sp.의 군체의 결속이 약화되고 세포가 군체에서 떨어져 나가는 것으로 나타났다. 또한 초음파는 동 식물성 플랑크톤의 형태적 변화와 운동성에 영향을 미치지 않아 다른 수중 미생물에는 부정적인 영향을 주지 않는 것으로 확인되었다. 따라서 초음파는 Microcystis sp.의 군체와 형태적 변화를 유발하고 세포를 파괴시켜 녹조현상을 일으키는 조류의 생물량을 감소시키는 데 효과적으로 작용할 것으로 사료된다.

• 한국해양학회지:바다
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• 제6권2호
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• pp.93-102
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• 2001

1999년 3월, 7월, 9월 및 11월에 섬진강 하구역에서 염분경사에 따른 식물플랑크톤과 동물플랑크톤의 현존량과종 조성의 변화를 조사하였다. 조사 정점은 지리적 위치보다는 각 조사시마다 표층 염분을 현장에서 측정하여 결정하였다. 식물플랑크톤은 총 96종이 동정되었으며, 그 중 돌말류가 60종으로 전 조사해역에서 출현하였다. 저염분역에서는 녹조류의 종수가 비교적 높았으며 고염분역으로 갈수록 와편모조류의 종수가 증가하였다. 월별 식물플랑크톤 현존량의 평균 값은 $183{\sim}833$cells/m의 범위로 11월에는 5${\sim}$15 psu 염분역에서 Skeletonema costatum의 bloom이 발생하였으며 초저염분역에서 현존량의 급격한 감소는 3월에 관찰되었다. 염분이 8.1 psu 이하의 분포를 보였던 강우기인 7월에 대부분의 조사해역에서 녹조류가 우점하였다. Chroomonas spp.는 3월과 9월에 높게 우점하였으며 고염분역으로 갈수록 현존량이 증가하였다. 동물플랑크톤은 3회의 조사에서 총 83개의 분류군이 검색되었고, 이중해산 분류군은 총 72개로 요각류가 34개 분류군을 차지하고 있었으며 담수 분류군은 총 11개로 수서 곤충류가 대부분을 차지하였다. 동물플랑크톤 종 조성은 해수의 유입에 의해 크게 의존하는 것으로 나타났으며 담수종이 출현하는 염분 한계는 시기적으로 달랐는데, 7월에는 8.1 psu 이하에서 , 9월에는 4.7 psu 이하에서 , 11월에는 0.2 psu 이하에서만 출현하였다. 하구역 염분 변화에 따른 동물플랑크톤 출현 양상의 특징은 풍수기에서 갈수기로 진행되면서다소 변화하는 양상을 보이지만 대체로 중간 정도의 염분 구역에서 출현 종과 개체수가 감소하는 경향을 보였다.

• ALGAE
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• 제20권3호
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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.

• ALGAE
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• 제34권3호
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• pp.237-251
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• 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.

• ALGAE
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• 제38권1호
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• pp.57-70
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• 2023

The mortality rate of red-tide dinoflagellates owing to predation is a major parameter that affects their population dynamics. The dinoflagellates Ansanella granifera and Ansanella sp. occasionally cause red tides. To understand the interactions between common heterotrophic protists and A. granifera, we explored the feeding occurrence of nine heterotrophic protists on A. granifera and the growth and ingestion rates of the heterotrophic dinoflagellate Gyrodinium dominans on A. granifera as a function of prey concentration and those of Oxyrrhis marina at a single high prey concentration. The heterotrophic dinoflagellates Aduncodinium glandula, G. dominans, Gyrodinium moestrupii, Luciella masanensis, Oblea rotunda, O. marina, Polykrikos kofoidii, and Pfiesteria piscicida and the naked ciliate Strombidium sp. were able to feed on A. granifera. With increasing mean prey concentrations, the growth and ingestion rates of G. dominans feeding on A. granifera rapidly increased and became saturated or slowly increased. The maximum growth and ingestion rates of G. dominans on A. granifera were 0.305 d^-1 and 0.42 ng C predator^-1 d^-1 (3.8 cells predator^-1 d^-1), respectively. Furthermore, the growth and ingestion rates of O. marina on A. granifera at 1,700 ng C mL^-1 (15,454 cells mL^-1) were 0.037 d^-1 and 0.19 ng C predator^-1 d^-1 (1.7 cells predator^-1 d^-1), respectively. The growth and ingestion rates of G. dominans and O. marina feeding on A. granifera were almost the lowest among those on the dinoflagellate prey species. Therefore, G. dominans and O. marina may prefer A. granifera less than other dinoflagellate prey species. The low mortality rate of A. granifera may positively affect its bloom formation.

• 한국물환경학회지
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• 제21권4호
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• pp.360-367
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• 2005

We have performed to analyze the trophic state resulting of Lake Yongdam as a result of water quality and nutrient concentration. Lake Yongdam is artifitial multi-purpose Dam resulting from the floods of 2001. The water quality of Lake Yongdam may affect the status of the Geum river basin including the Daecheong reservoir. It is necessary to understand the trophic state to assess water quality until stability after flooding. Water quality was surveyed using depth and hydraulic condition analysis. Further density flow was estimated for stratification and trophic state of Lake Yongdam by chlorophyll ${\alpha}$ concentration (2001~2004). And Environmental factors on chlorophyll ${\alpha}$ concentration were analyzed statistically. Trophic state was evaluated as the oligotrophic state at the main stream of the reservoir and eutrophic state at the upper stream in 2001, but evaluated as eutrophic state in 2002 and 2003 by TSI of Aizaki. From the results of multiple regression analysis using stepwise method, chlorophyll ${\alpha}$ concentration was shown to be very significant when nutrient concentration is high upon initial filling of the Dam. Chlorophyll ${\alpha}$ concentration varied according to sample site, season and year. Concentration were high in the upper stream of Lake Yongdam 4, algae bloom in these watershed were affected by location and high nutrient levels in the summer season which have in turn increased phytoplankton bloom into the reservoir.