• Korean Journal of Environmental Biology
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• v.36 no.1
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• pp.11-20
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• 2018

In planktonic ecosystems, the microplastics are considered as a potential food source for the zooplankton. To study a relationship between the zooplankton and the neustonic microplastics, a research experiment was carried out during May in the surface layers of the Yeosu coastal areas including Yeoja Bay, Gamak Bay, Yeosuhae Bay, and Botdol Sea. A neustonic zooplankton net (mesh size $300{\mu}m$; mouth area $30cm{\times}18cm$) was towed from the side of the ship in the event that it would not be affected by waves crashing by the ship at a speed of ca. 2.5 knots. All of the microplastic particles were separated from the zooplankton. The zooplankton and microplastics were appearing in a range of 61 to $763indiv.m^{-3}$ and 0.0047 to $0.3471particle\;m^{-2}$, respectively. It was noted that the Acartia omorii, Paracalanus parvus s. l., Labidocera euchaeta, A. hongi, decapod larvae, and cirriped larvae were predominantly seen in the experiment. For verifying relationships between zooplankton and environmental factors in addition to microplastics, a model redundancy analysis (RDA) was performed. The zooplankton were divided into two groups on the basis of feeding types (i.e. particle feeders, and carnivores), and the associated zooplankton larvae were also separately considered. A review of the additional environmental factors such as water temperature, salinity, turbidity, chlorophyll-${\alpha}$ concentration, diatom density, and dinoflagellate density were also contained in the analysis. The results showed that a noted zooplankton abundance had no close relation with the occurring number of microplastic particles, but rather was significantly related with other noted environmental factors such as temperature, salinity, turbidity, and chlorophyll-${\alpha}$ concentration. This fact implies that most zooplankton can feed themselves as a unit, by selecting the most likely available nutritious foods, rather than microplastics under the circumstance of food-richness areas, such what food resources are available as in the location of coastal waters.

• Korean Journal of Ecology and Environment
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• v.40 no.1
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• pp.61-71
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• 2007

The photosynthetic characteristics and primary production by phytoplankton in open waters of two wetlands (the Banwol and the Donghwa wetland) of Sihwa Constructed Wetland with different water chemistry were investigated to provide the information for the wetland management considering the water treatment efficiency. During the study period (from March to October, 2005) the primary productivity in open waters ranged from 481 to 11,275 mgC $m^{-2}$ $day^{-1}$, which is very high compared with the eutrophic level of 600mgC $m^{-2}$ $day^{-1}$. From the analysis of the photosynthesis-irradiance (P-I) model parameters, the photosynthetic characteristics may be affected by different concentration and ratio of nutrient (N and P) between two wetlands. Assimilation number (AN) was higher in the Donghwa wetland (average AN: 8.5gC $gChl^{-1}$ $hr^{-1}$) with high P and low N/P ratio than the Banwol wetland (average AN: 5.8gC $gChl^{-1}$ $hr^{-1}$) with high N and high N/P ratio. This result indicates that AN may be concerned with phosphorus than nitrogen and low NIP ratio. Positive correlation (R=0.81) was observed between the initial slope and AN, implying that AN was high in case of phytoplankton having more active photosynthesis ability under low light. On the other hand, maximum photosynthesis (Pmax) was related positively with chlorophyll a concentration showing correlation coefficient of 0.47. In this study, considering the high primary production through phytoplankton photosynthesis in open waters of Sihwa Constructed Wetland, the produced organic matter by phytoplankton may affect the water quality within wetland and its efficiency of water treatment. Also, the photosynthetic characteristics may be affected by different nutrient enrichment (especially phosphorus) of wetlands. This study suggests that the production by phytoplankton and its characteristics in open water of constructed wetland for water treatment should be considered to improve the removal efficiency of organic matter.

• Korean Journal of Ecology and Environment
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• v.41 no.2
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• pp.174-187
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• 2008

In an effort to identify structure and function of microbial loop in Paldang reservoir, we monitored environmental and biological factors at Kyungan stream (station K), Paldang dam (station P) and the confluence of North and South Han River (station M) from March to December, 2005. DOC concentration was higher in March to May and November than the others. Nutrient concentration in station K detected relatively higher than that of two stations. Both of phosphate and silicate gradually increased at all stations until September, after then decreased. The highest Chl-$\alpha$ concentration was observed at all stations in April, and November. The carbon biomass of bacteria and HNF were relatively higher in March, May and August than the others, whereas that of the ciliate showed no significant difference in monthly fluctuation. Nevertheless, the significant relationships revealed between ciliate (P<0.001) and HNF (P<0.05) and bacterial density. Tintinnopsis cratera, Didinium sp., Vorticella sp., Paramecium sp. and Strombidium sp. were dominant species in ciliate community. The dominant species of phytoplankton were Stephanodiscus hantzschii and Cyclotella meneghiniana at almost stations in Spring, Summer and Autumn. However, Aulacoseira granulata accounted for >95% of phytoplankton biomass at station P and M in Autumn. The carbon biomass of zooplankton was highest at station P and M in June, and relatively higher biomass observed at all stations in August, October and November. Diaphanosoma brachyurum and Bosmina longirostris were dominant in stations P and M of June and in all stations of October and November, respectively. The maximum growth (A. granulata: $0.17\;d^{-1}$, S. hantzschii: $0.14\;d^{-1}$) and grazing rate (A. granulata: 1.93 preys $d^{-1}$, S. hantzschii: 1.63 preys $d^{-1}$) of Bosmina longirostris revealed in algal preys as Aulacoseira granulata and Stephanodiscus hantzschii. In conclusion, these results suggest that bacteria and phytoplankton can play the most crucial source as prey within microbial food chain in Spring and Summer and grazing food chain in Autumn, respectively.

• Korean Journal of Ecology and Environment
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• v.42 no.2
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• pp.242-252
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• 2009

The purpose of this study was to develop a Multi-metric Water Quality Assessment (MWQA) model and apply it to dataset sampled from Paldang and Daechung reservoir in 2008. The various water dataset used to this study included 5 year data sets (2003${\sim}$2007) in Korean reservoirs which were obtained from the Ministry of Environment, Korea. In this study, suggested MWQA model has 4 metrics that were composed of 4 parameters such as chemical, physical, biological, and hydrological variables. And, each of the variables attributed total phosphorus (TP) concentration in water, secchi depth (SD) measure in water, chlorophyll-${\alpha}$(Chl-${\alpha}$) concentration in water and the ratio of inflow of water into lakes and efflux of water from lakes, input/output (I/O). First, we established the criteria for trophic boundaries. The boundary between oligotrophic and mesotrophic categories was defined by the lower third of the cumulative distribution of the values. The mesotrophic-eutrophic boundary was defined by the upper third of the distribution. Second, each metric was given by a point-oligo=1, meso=3, eu=5. And then, obtained total score from each metric was divided 5 grade-Excellent, Good, Fair, Poor, and Very poor. As the results of applying the proposed MWQA model, the Paldang reservoir obtained "Fair" or "Poor" grade and Daechung reservoir obtained "Excellent" or "Good" grade. The suggested MWQA model through these procedures will enable to manage efficiently the reservoir. And, more studies such as metric numbers and attributes should be done for the accurate application of the new model.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.1
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• pp.1-11
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• 2010

In order to understand the biological environmental characteristics with temporal variations of the physico-chemical factors in 2012 Yeosu Expo site of Korea, we investigated at one station, once per week, from April 2006 to December 2007. The surface water temperature ranged from 6.8 to $27.8^{\circ}C$ and the bottom water temperature ranged from 6.3 to 25.9 $25.9^{\circ}C$. The salinity varied from 12.8 to 33.0 psu in the surface water and from 25.2 to 33.6 psu in the bottom water. A strong halocline was observed between the surface and bottom layers in the summer when a rapid decrease of salinity coincided with heavy rainfall. The DIN concentration ranged from 1.36 to $82.7{\mu}M$ in the surface water and from 0.82 to $25.2{\mu}M$ in the bottom water. Phosphate concentration varied from 0.06 to $2.13{\mu}M$ in the surface water and from 0.07 to $1.38{\mu}M$ in the bottom water. Silicate was $1.68-52.0{\mu}M$ in the surface water and $1.37-30.7{\mu}M$ in the bottom water. The nutrient concentrations were generally high during heavy rainfalls and low water temperature periods, and considerably decreased in spring and autumn. The N/P ratio ranged from 4.43 to 325 in the surface water and from 3.8 to 321 in the bottom water. It increased rapidly during the heavy rainfall season and remained at a value of approximately 16 in other periods. The chlorophyll a concentration ranged from 0.46 to $65.0{\mu}g$ $L^{-1}$ in the surface water and from 0.71 to $15.0{\mu}g$ $L^{-1}$ in the bottom water. $Chl-{\alpha}$ concentration remained low in periods of low water temperature, however rapidly increased in periods of high water temperature. From the results of principal component analysis (PCA) and multiple regression analysis (MRA), we conclude that temporal variations of physico-chemical and biological factors were greatly affected by the influx of fresh water, and that nutrients were well controlled by their uptake and assimilation by phytoplankton. Also, during the low water temperature periods, environmental structure in this study site was affected by recycled nutrients through nutrient cycling and mineralization.

• Korean Journal of Environmental Biology
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• v.17 no.4
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• pp.529-541
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• 1999

In order to elucidate characteristics of water quality, investigation of monthly dynamics of environmental factors and algal populations at major four stations of the mid and lower part in Taechong Reservoir was performed from June 1998 to June 1999. Water temperature, DO and pH were ranged 5.3~27.7$^{\circ}C$, 6.2~13.8 mgO$_2$/1 and 6.4~9.5, respectively. Those were varying as the season changes. Among inorganic nitrogen nutrients, NH$_4$was ranged from 5.5% to 7.2% of NO$_3$and NO$_3$was almost same through the seasons except summer in which it was low. SRP and SRSi were increased in summer when the blue-green algae became dominant. Those were decreased as the cell density of diatom increased when the water temperature dropped. Therefore SRSi was considered to be another important nutrient factor contributing to the increment of biomass of freshwater algae as well as SRP. Average chi-$\alpha$ concentration ranged from s to 12 $\mu$g/1 and in the lower part or the reservoir, the lowest was found. Moreover, there were remarkable increment in summer when TN/TP ratio were decreasing from relationships between TN/TP ratio and chi-$\alpha$ concentration. Annual mean ratio of TN/TP ratio was relatively high as the value was 110, which was relatively high, and it showed that P is the dominant factor in the algal growth. The dynamics of phytoplankton were simply dominated by a few species seasonally. In summer, blue -green algae such as Anabaena, Microcystis and Oscillatoria were dominant and algal bloom of blue -green began from early summer, sustained to late autumn. The average standing crops of A. spiroides v. crassa, M. aeruginosa and O. limosa were ranged 0.3~2.0$\times$10$^4$cells/ml, 6.4$\times$10$^2$~1.0$\times$10$^4$cells/ml and 4.6$\times$10$^3$~1.6$\times$10$^4$cells/ml, respectively. In winter, diatom Stephanodiscus was considered to be an important species whose average standing crops of Stephunodiscus was 4.9$\times$10$^2$cells/ml from November to April of the next year and the highest was 1.3$\times$10$^3$cells/ml in January.

• Korean Journal of Ecology and Environment
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• v.44 no.1
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• pp.75-84
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• 2011

We examined the effect of the turbid water on the periphytic diatom community in an artificial stream system. The artificial stream was constructed with transparent acryl and composed of four channels. Each channel ($20\;cm{\times}200\;cm{\times}40\;cm$) was supplied continuously with eutrophic lake water. In order to the freely colonize and grow diatoms, artificial substrate was installed with commercial slide glass soaked in 1% agar. Prior to introducing turbid water, the artificial stream was operated with lake water for 6 days to permit the propagation of diatom community on the substrates. The turbid water prepared with sediment sieved with ${\varphi}$ $64\;{\mu}m$ at $2\;g\;L^{-1}$ (final concentration, 300 NTU) was provided daily for 50 minute duration. The experiment was conducted for 7 days with manipulated experimental condition of light ($50{\sim}80\;{\mu}mol\;m^{-2}s^{-1}$, light:dark=24:0), temperature ($10{\pm}1^{\circ}C$), and flow rate ($0.31\;cm\;s^{-1}$). Sampling and analysis were conducted daily for water quality and diatom. Turbidity of the water varied 162.2~173.2 NTU during the experiment. After introduction of turbid water, DO, pH and TN were decreased, while SS and TP increased significantly. A total of 14 genera and 47 species of diatoms was observed on the artificial substrates during the experimental period. Of these, Navicula appeared to be a most dominant genus with 10 species, followed by Cymbella (6 species), Fragilaria (6 species) and Gomphonema (5 species). Achnanthes minutissima was the most dominant species (>70% of total frequency) in both control and treatment experiments. Increase in diatom abundance lasted for three days since turbid water introduction, after that they gradually decreased by the termination of the experiment. These results suggest that frequent supply of highly-concentrated turbid water significantly decreases the periphytic diatom community, and retard the recovery of the stable food-web within the stream.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.3
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• pp.151-164
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• 2010

Field observations on the seasonal variations of environmental factors and phytoplankton community were carried out four times at 30 stations in the narrow strait between Yeosu and Dolsan Island of the Korean South Sea from September 2005 to May 2006. The ranges of water temperature, salinity and extinction coefficient in the surface waters were 5.6~26.3, 25.36~33.92 psu and 0.13~2.13, respectively. The water temperature measured higher at Gamak Bay in summer and spring. It measured higher at Yeosuhae Bay in autumn and winter. Salinity showed uniformity of distributions in almost all areas, except for an area near a sewage disposal outlet. Extinction coefficient indicated that the turbidity of Gamak Bay and the area near the sewage disposal outlet were higher than that of the Yeosuhae Bay. In the phytoplankton community were identified a total of 99 species belonging to 51 genera. The species composition showed itself to be various in summer and autumn, but poor in winter and spring with a high ratio of centric diatoms all the year round. Seasonal succession of dominant species were Skeletonema costatum and Chaetoceros curvisetus in summer, Eucampia zodiacus in autumn and winter, and Chaetoceros affinis and Thalassionema nitzschioides inspring. Standing crops of phytoplankton and Chlorophyll $\alpha$ concentration were greatly higher at Gamak Bay in summer with ranges of $0.2{\times}10^4\;cells\;L^{-1}$ to $296{\times}10^4\;L^{-1}$, and $1.94\;L^{-1}$ to $22.12\;L^{-1}$, respectively. From the results of principal component analysis (PCA), the northern part of Dolsan Island was divided into two or three regions from the characteristics of marine environment and phytoplankton community.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.1-10
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• 2010

We used stable isotope analysis to investigate the hypothesis that zooplankton were not able to utilize Microcystis as a food source. We also studied seasonal variation of the zooplankton community in a eutrophic Wangsong reservoir. The dominant copepod species changed from Cyclops vicinus to Thermocyclops taihokuensis. Density of zooplankton was suppressed by high density of Microcystis in June and the density of phytoplankton and chlorophyll a concentration was lowest in July. The difference in $\delta^{13}C$ and $\delta^{15}N$ between cladocerans (Daphnia galeata and Bosmina longirostris) and copepods showed the maximum difference of $12^{\circ}/_{\circ\circ}$ and $4^{\circ}/_{\circ\circ}$, respectively, indicating different energy sources and trophic positions between two taxonomic groups. The difference in $\delta^{13}C$ between Microcystis and zooplankton ranged from $3{\sim}7^{\circ}/_{\circ\circ}$, supporting the hypothesis that Microcystis could not be used as food source of zooplankton.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.350-363
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• 2009

Inter- and intra-specific differences in removal activities, filtering rates (FR) and production of feces-and pseudo-feces (PF) between a native freshwater bivalve in Korea, Anodonta woodiana Lea and Unio douglasiae Griffith et Pidgeon, were compared using a continuous removal of organic matters (CROM) system. The CROM system comprised five steps; input of polluted water, control of water flow, mussel treatment, analysis of water quality and discharge of clean water. The study was designed to compare the removal activity of organic matters between A. woodiana and U. douglasiae, and the intra-specific differences between density and length in A. woordiana. Results clearly indicate that two kinds of mussels had obvious removal activities of seston in the eutrophic reservoir. First, if both are similar in shell length, there were no significant inter-specific differences in removal activity between A. woordiana and U. douglasiae (P>0.5), but FRs of U. douglasiae was relatively high due to low ash-fee dry weight. Second, if both are same in animal density, the smaller mussels (1$\sim$2 years old) showed a higher filtering rate and production of feces- and pseudo-feces and less release of ammonium than the larger mussels. Third, if both are same in biomass, FRs and PF of mussels were higher in the low-density tank than the high-density tank, While the Concentration of $NH_4$-N and $PO_4$-P released WRS similar to each other (P>0.5). Therefore, these results suggest that CROM system using a young bivalve A. woordiana can be applied to control the nuisance seston in eutrophic lake system, if a relevant species and density were selected. Additional pilot tests to optimize the age and density of domestic bivalves were needed for the generalization of CROM operation.