• Korean Journal of Ecology and Environment
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• v.49 no.4
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• pp.320-333
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• 2016

This study was carried out to elucidate the development of unprecedented water-bloom caused by a single species of colonial green algae Eudorina elegans in the upstream area of the Seungchon weir located in the Yeongsan River from late April to May 2013. The Yeongsan River is typically regulated system and the waterbody is seriously enriched by both external and internal sources of nutrients. Seasonal algal outbreaks were highly probable due to various potential factors, such as the excessive nutrients contained in treated wastewater, slow current, high irradiation and temperature, in diatom (winter), green algae (spring) and bluegreen algae (summer). Spring green-tide was attributed to E. elegans with level up to $1,000mg\;m^{-3}$(>$50{\times}10^4cells\;mL^{-1}$). The bloom was exploded in the initial period of the algal development and after then gradually diminished with transporting to the downstream by the intermittent rainfall, resulting in rapid expansion of the distribution range. Although the pulsed-flows by the weir manipulation was applied to control algal bloom, they were not the countermeasures to solve the underlying problem, but rather there still was a remaining problem related to the impact of pulsed-flows on the downstream. The green-tide of E. elegans in this particular region of the Yeongsan River revealed the blooming characteristics of a colonial motile microalga, and fate of vanishing away by the succeeding episodic events of mesoscale rainfall. We believe that the results of the present study contribute to limno-ecological understanding of the green-tide caused by blue-green algae in the four major rivers, Korea.

• Journal of Korean Society on Water Environment
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• v.31 no.2
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• pp.110-119
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• 2015

The construction of the eight large weirs in the Nakdong River, the second largest river in Korea, caused big changes in the physical environment of the water system. Algal communities and their correlations with environmental factors, mainly nutrients were studied at five weir areas in the Nakdong River from 2010 to 2013. Water quality, hydrodynamics and algal composition were investigated. Results showed that flow velocities were reduced compared with that before weir construction near the areas where are located in the mid and upstreams of the Nakdong River. A seasonal algal community succession was observed and it was mainly correlated with temperature and phosphorus. Diatoms were dominated from winter to spring months and massive diatomic blooms of Stephanodiscus sp. occurred early in March during survey period. Cyanobacterial blooms of Microcystis sp. occurred from July to September 2013 and was preceded by the lower total phosphorus concentration of $0.05mg\;L^{-1}$. The correlations between total phosphorus concentrations and algal abundances were not significant during the survey periods. However, significant correlation with cyanobacteria was found in the period of weir construction after only at the GG survey site and blooms periods of 7 times in the survey sites, and its correlation coefficients were 0.53 (p<0.001) and 0.42 (p<0.01) respectively. When algal bloom was observed, partially low nutrient concentration was observed in the Nakdong River. In conclusion, partially low nutrient concentration which may result from algal bloom was observed, and we presume it caused the reduction of algal abundunces.

• 수도
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• v.26 no.1 s.89
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• pp.48-54
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• 2000

• ALGAE
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• v.18 no.4
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• pp.281-288
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• 2003

To study the environmental features causing a bloom of the novel dinoflagellate Heterocapsa circularisquama (Dinophyceae), hydrographic and chemical aspects were measured in the Uranouchi Bay, Kochi Prefecture, Japan, from January to December, 1997. The cell density of H. circularisquama increased rapidly in early October, and dropped sharply in mid-October. Growth rate of H, circularisquama during bloom period appeared 1.50 division day$^{-1}$ under high water temperature (25$^{\circ}C$) and salinity (32 psu) conditions. Althought the result from hydrographic aspect indicated good condition for their growth, dissolved inorganic phosphorus (DIP) concentration in surface layer before bloom formation was less than 0.70uM, which is lower than their half saturation constant(Ks). Dissolved inorganic nitrogen(DIN): DIP ratio was > 30, indicating potential P-limitation. However, before bloom formation period of H. circularisquama, DIP concentrations were high in bottom layer (> 4.0 uM). Some studies reported that H. circularisquama had the ability to migrate vertically and to utilize dissolved organic phosphorus (DOP). Thus, DIP in bottom layer might have been utilized by H. circularisquama for their growth.DOP might have weakly affected their growth because of low reactive DOP concentrations owing to low DOP concentration (ca. 0.39 uM). Thus, if nutrient condition of bottom layer in Uranuchi Bay is not improved, the outbreaks of H. circularisquama red tides may became an annual feature.

• Journal of Microbiology and Biotechnology
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• v.14 no.2
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• pp.290-296
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• 2004

The effects of potassium, sodium, calcium, magnesium, and iron on cyanobacterial bloom potentials were investigated in Daechung Reservoir, Korea. Potassium showed the highest correlation with the cyanobacterial cell number (r=0.487, P<0.05) and phycocyanin concentration (r=0.499, P<0.05). However, it was not likely that the potassium had directly affected the bloom formation, because the variations of its concentration were not significantly large. In contrast, the Fe concentration fluctuated drastically and exhibited a negative correlation with the cyanobacterial cell number (r=- 0.388, P<0.1) and phycocyanin concentration (r=-0.446, P<0.05). Accordingly, the K:Fe atomic ratio would appear to reflect the extent of cyanobacterial bloom more precisely than K or Fe alone. The K:Fe ratio specifically correlated with cyanobacterial percentage, the cyanobacterial cell number and phycocyanin concentration (r=0.840, P<0.001; r=0.416, P<0.05; r=0.522, P<0.01, respectively). With the K:Fe atomic ratio of over 200, the chlorophyll-a concentration, cyanobacterial cell number, and phycocyanin concentration exceeded $10\mu$g $1^{-1}$20,000 cells $ml^{-1}$, and 20 pM, respectively, the general criteria of eutrophic water.

• Korean Journal of Environmental Biology
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• v.37 no.3
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• pp.433-445
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• 2019

This study was designed to develop simple tools to easily and efficiently predict the occurrence of algal bloom in agricultural lakes. Physicochemical water quality parameters were examined to reflect the phytoplankton productivity in 182 samples collected from 15 agricultural lakes from April to October 2018. Total phytoplankton abundance was significantly correlated with chlorophyll-a (Chl-a) (r=0.666) and Secchi depth (SD) (r= -0.351). The abundances of cyanobacteria and harmful cyanobacteria were also correlated with Chl-a (r=0.664, r=0.353) and SD (r= -0.340, r= -0.338), respectively, but not with total nitrogen (TN) and total phosphorus (TP). The Chl-a concentration was correlated with SD (r= -0.434), showing a higher similarity than phytoplankton abundance. Therefore, Chl-a and SD were selected as diagnostic factors for algal bloom prediction, instead of analyzing the standing crop of harmful cyanobacteria used in algae alarm systems. Specifically, accurate diagnoses were made using realtime SD measurements. The algal bloom diagnostic tool is an inverse cone-shaped container with an algal bloom diagnosis chart that modified SD and turbidity measurement methods. Lake water was collected to observe the number of rings visible in the container or the number indicated in each ring, depending on the degree of algal bloom,and to determine the final stage of algal blooming by comparison to the colorimetric level on the diagnosis chart. For an accurate diagnosis, we presented 4-step diagnostic criteria based on the concentration of Chl-a and the number of rings and a fan-shaped algal bloom diagnosis chart with Hexa code names. This tool eliminated the variables and errors of previous methods and the results were easily interpreted. This study is expected to facilitate the diagnosis of algal bloom in agricultural lakes and the establishment of an efficient algal bloom management plan.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.5
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• pp.515-521
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• 2003

To understand interrelations between water quality and community structure of phytoplankton around the season of red tide outbreak, field surveys were conducted 10 times off the coast of Tongyeong from July to September in 2002. Because of heavy rain for 10 days, environmental conditions were changed and differed from the previous year, sustaining high nutrients and low salinity. During the surveyed period 48 species of 29 genera of phytoplankton were identified, and diatom and dinoflagellate was $51.8\%\;and\;38.0\%,$ respectively, At the time of bloom, cell counts of C. polykrikoides were outstanding but the number of species remarkably decreased. There were striking differences in dominant species among research stations before the bloom. Diatoms were the most dominant group in the whole study area in that period. Diversity and evenness index were highest just before outbreak of the red tides (2 Aug, 2002). During the bloom (4 Aug.), it decreased to the lowest value and then began to increase slowly. The result of PCA on water quality vs phytoplankton biomass showed that the land loads of nutrient may be the main cause of summer rally of phytoplankton biomass.

• Korean Journal of Ecology and Environment
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• v.35 no.3 s.99
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• pp.187-197
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• 2002

To analyze the structure of phytoplankton community of the Asan Reservoir in Korea, samples were collected 6 times from March to November in 1997. A total of 204 phytoplanklon species were identified from the samples of 19 stations. Green algae dominated the phytoplankton community, accounting for 51% of species number, followed by diatoms (29%), cyanobacteria (12%), dinoflagellates (2%) ,euglenoids (3%) and other flagellates (3%). Standing stocks of phytoplankton were very high in the range of 741-613,066 cells/ml, with the highest standing stock in July. Water Booms seemed to occur in the Asan Reservoir regardless of seasons, with water bloom-causing species being Micractium pusillum, Stephanodiscus, hantzschii, Dictyospharium pulchellum, cryptomonad(> 20 ${\mu}$m), Microcystis aeruginosa, Oscillatoria tenuis, Oscillatoria sp., Aphanocapsa sp. Euglena sp., Volvox aureus. In the summer, cyanobacteria dominated algal bloom. Species diversity of phytoplankton community in the reservoir was in the range of 0.13 ${\sim}$ 3.20, and showed much difference temporally and spatially. The cluster analysis identified two different regions of upstream area and downstream area for the Asan Reservoir.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.217-224
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• 2005

This study was aimed to analyze the long-term fluctuation of water quality and phytoplankton dynamics of Paldang reservoir in Korea and to assess the relationship between algal bloom patterns and hydrological, limnological data. Diatoms in Paldang reservoir occurred continuously through the year. Blue- green algae occurred during the summer season (from June to Sept.), and the highest count was observed in July. Occurrence pattern of green algae was similar to that of blue-green algae. The rest of algae contained a lot of Cryptomonas spp. whose concentration was high from May to Aug. Dominant algal genera (>>7,000 cells $mL^{-1}$) in Paldang reservoir were Aulacoseira, Cyclotella, Microcystis, and Cryptomonas spp. Microcystis and Anabaena occurred during the summer season. Many different green algal genera were found in Paldang reservoir but their abundances were very low. There were some significant correlations (r>0.3, p<0.05) between algal taxa and water quality; diatoms and water temperature, TP:blue-green algae and water temperature, pH, DO saturation, COD, TP; green algae and water temperature, pH, DO saturation, COD, SS, TP. Furthermore, algal genera and water quality was significantly correlated (r>0.3, p<0.05) ; Aulacoseira and TN, TP; Anabaena and water temperature, DO saturation, COD, TP : Microcystisand water temperature, pH, DO saturation, TP; Coelastrum and COD, SS; Scenedesmus and water temperature, COD, TN, TP; Cryptomonas and DO saturation, TN. In Paldang reservoir, the water temperature had relatively big effect on blue-green algal bloom that was also dependant upon its hydrologic condition.

• Korean Journal of Remote Sensing
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• v.33 no.2
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• pp.111-123
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• 2017

The phycocyanin pigment (PC) is a marker for cyanobacterial presence in eutrophic inland water. Accurate estimation of low PC concentration in turbid inland water is challenging due to the optical complexity and criticalforissuing an early warning of potentialrisks of cyanobacterial bloom to the public. To monitor cyanobacterial bloom in eutrophic inland waters, an approach is proposed to partition non-water absorption coefficient from measured reflectance and to retrieve absorption coefficient of PC with the aim of improving the accuracy in remotely estimated PC, in particular for low concentrations. The proposed inversion model retrieves absorption spectra of PC ($a_{pc}({\lambda})$) with $R^2{\geq}0.8$ for $a_{pc}(620)$. The algorithm achieved more accurate Chl-a and PC estimation with $0.71{\leq}R^2{\leq}0.85$, relative root mean square error (rRMSE) ${\leq}39.4%$ and mean relative error(RE) ${\leq}78.0%$ than the widely used semi-empirical algorithm for the same dataset. In particular, low PC ($PC{\leq}50mg/m^3$) and low PC: Chl-a ratio values of for all datasets used in this study were well predicted by the proposed algorithm.