• Korean Journal of Ecology and Environment
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• v.44 no.4
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• pp.337-346
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• 2011

We investigated nutrient loading and trophic states in a coastal estuarine system in the Asan estuary by assessing phytoplankton biomass and using the trophic index (TRIX). The monthly and yearly nutrient loading (TN, TP) from freshwater discharge from the Asan and Sapgyo reservoirs into the estuary were estimated and analyzed with related factors. Monitoring data (physio-chemical and biological variables) collected at five estuary stations were used to assess trophic states. Descriptive statistics of total phytoplankton cells, chl a concentrations and primary productivity were also used to assess seasonal trophic status. N loading from freshwater ranged $1.0{\sim}1.3{\times}10^4$ ton yearly. The yearly P loading ranged between 350 and 400 ton during 2004~2006, increasing to 570 ton in 2007. Regression results suggest that DIN and DSi were correlated with freshwater discharge at the upper region. Based on phytoplankton biomass and total cell abundance, the trophic state of the estuary was found to be eutrophic during spring due to phytoplankton bloom. Primary productivity level was remarkably high, especially in summer coinciding with high nutrient loading. Pheopigments increased during warm seasons, i.e. summer and fall. Trophic index results indicate that the trophic state varied between mesotrophic and eutrophic in the estuary water body, especially in the upper region. The results suggest that phytoplankton production was regulated by nutrient loading from freshwater whereas biomass was affected by other properties than nutrient loading in the Asan Estuary ecosystem.

• ALGAE
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• v.17 no.4
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• pp.275-281
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• 2002

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.382-392
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• 2005

Data were collected in Lake Daecheong from March 1997 to October 2002 and used to understand an annual change of water environmental factors and trophic states. The surface water temperature was ranged from $3.2^{\circ}C$ to $33.1^{\circ}C$ In the middle of February, water temperature was the lowest. Turbidity was ranged from 0.1 to 203.5 NTU, but the values of above 30 NTU were only measured at site 1. The total mean values of COD and Chl a were $3.6{\pm}1.4\;mg\;O_2\;L^{-1}$, $9.3{\pm}12.8\;{\mu}g\;L^{-1}$respectively. The concentrations of TP and TN were ranged from 0.14 to 5.09 mg N $L^{-1}$, 1 to $247\;{\mu}g\;P\;L^{-1}$ respectively. The total mean value of TN/TP ratio was $98.7{\pm}56.2$. The trophic states were ranged from mesotrophic to eutrophic in Lake Daecheong.

• ALGAE
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• v.21 no.2
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• pp.217-228
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• 2006

Seasonal compositions, standing crops and trophic status of phytoplankton were investigated at 13 sites of Suwon-si, Gyeonggi-do from June, 2004 to March, 2005. Total of 304 taxa were found, and classified as 4 phylums 4 classes 13 orders 36 families 93 genera 246 species 47 varieties 8 forms and 3 unidentified species by Engler’s classification system. Judged by standing crops of phytoplakton, algal blooming was observed at every sampling sites except Pajang reservoir, Hagwanggyo reservoir, Suwon-cheon and Woncheon-cheon throughtout the whole study periods. While Hagwanggyo reservoir appeared to be in mesotrophic or oligomesotrophic status, most of the remaining sampling sites in Suwon-si were in eutrophic status according to trophic status index. In this study, the most abundant taxa revealed in eutrophic status were Anabaena circinalis, Pandorina morum, Scenedesmus acuminatus, and S. quadricauda as previously reported as the most abundant taxa in eutrophic status. But Navicula cryptocephala and Cyclotella stelligera, reported as the abundant taxa of mesotrophic and oligomesotrophic status, respectively, occurred in eutrophic status in this study.

• ALGAE
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• v.19 no.3
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• pp.227-234
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• 2004

A study on the dynamics of phytoplankton community and the physico-chemical environmental factors was performed biweekly from April 1998 to March 1999 in Youngchun Dam. A total 72 phytoplankton taxa was identified and dominant taxa were blue-green algae and diatoms. The highest value of phytoplankton standing crop (24,826cells·ml$^{-1}$) was observed in September 7, 1998, the blooming period of blue-green algae Phormidium sp., while the lowest (318cells·ml$^{-1}$) was measured in June 18, 1999. The phytoplankton communities were dominated by blue-green algae of Anabaena planktonica, Microcystis aeruginosa and Phormidium sp. during the summer and autumn periods and were dominated by diatoms of Synedra acus and Aulacoseira spp. during the spring and winter periods. Secchi disc transparency, chlorophyll-a, total nitrogen, total phosphorus and silicate concentration were varied in the ranges of 0.4-2.5 m, 2.4-32.2mg·m$^{-1}$, 0.845-2.352mg·l$^{-1}$, 0.005-0.093mg·l$^{-1}$, 0.2-15.7mg·l$^{-1}$, respectively. The trophic status of Youngchun Dam were estimated eutrophic according to Lake Trophic States Index (LTSI).

• Korean Journal of Ecology and Environment
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• v.43 no.4
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• pp.492-502
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• 2010

The study objects were to analyze long-term and seasonal variations of nutrients (N, P), suspended solids, N:P ratios, algal chlorophyll, and trophic state along with general water quality parameters in four sampling sites including two intake tower sites supplying drinking water in Daechung Reservoir. For the analysis, we used water quality long-term data sampled during 1998~2007 by the Ministry of Environment, Korea. Interannual and seasonal trends in inflow and discharge near the intake tower facilities over the ten years were directly influenced by rainfall pattern. The distinct difference between wet year (2003) and dry year (2001) produced marked differences in water temperature, pH, dissolved oxygen, organic matter contents, nutrients, and these variables influenced algal biomass and trophic state. Values of TP varied depending on the year and locations sampled, but monthly mean TP always peaked during July~August when river inflow and precipitation were maxima. In contrast, TN varied little compared to TP, indicating lower influence by seasonal flow compared to phosphorus. The number of E. coli were highest in Site 2 (Chudong intake tower) and varied largely, whereas at other sites, the numbers were low and low variations. Contents of chlorophyll-${\alpha}$ (CHL), as an estimation of primary productivity, varied largely depending on the year and season. The maximum of CHL occurred at Muneu intake tower (S4) during 2006 when the precipitation and inflow were lowest. In contrast, another CHL peak was observed in Site 2 (Chudong intake tower) in 2006 when one of the largest typoons (Ewinia) occurred and river runoff were maximum. So the CHL maxima were associated with both wet year (high flow, high nutrient supply) and dry year (low flow, nutrient supply by littoral zone). Such conditions influenced trophic states, based on Trophic State Index of nutrients and CHL. Based on all analyses, we can provide some clues for management and protection strategies of two intake tower sites.

• ALGAE
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• v.22 no.2
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• pp.69-85
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• 2007

From six reservoirs in Gyeonggi-do, we have collected the distribution and standing crop of phytoplankton since Nov. 2005 through Sep. 2006. As a result, the phytoplankton appeared totally 340 taxa belong to 7 classes, 15 orders, 5 suborders, 32 families, 4 subfamilies, 84 genera, 283 species, 43 varieties, 9 forms and 5 unidentified species. The standing crop was shown as minimum was 0.3 × 106 cells and maximum was 5,950 × 106. The relation of standing crop with TN, TP and Chl-a showed as positive. Total 12 taxa including 2 taxa of blue-green algae occurred to every seasons at six lakes, and it was thought that they distributed in mesotrophic state. Also, Achnanthes minutissima, Aulacoseira granulata, Eudorina elegans, Gloeocystis ampla, Pandorina morum, Pediastrum simplex var. duodenarium, Scenedesmus ecornis were regarded as the indicators of eutrophic state. From the estimation of LTSI and TSI, it was shown that the rest of lakes except for Idong reservoir of winter were eutrophic states.

• Korean Journal of Ecology and Environment
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• v.43 no.3
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• pp.418-427
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• 2010

In the four swamps of Jjokjibeol, Mokpo, Upo and Sajipo in the Upo wetland, the nitrogen nutrients, phosphorus nutrients and chl-$\alpha$ had been observed during the period from April 2005 to December 2009 on monthly basis. Based on the results, the fluctuations of trophic state in the Upo wetland were estimated. Measurements of the nitrogen nutrients such as $NO_3$-N, $NH_3$-N and T-N showed to be generally decreased in comparison with those in the precent studies. Yet the T-N was still considerably higher than the general concentration level of eutrophication and algal blooming. $PO_4$-P and T-P showed to have reduced considerably in comparison to precedent studies. However, T-P also turned out to be dissolved over the nutrient standard. Nitrogen nutrients and phosphorus nutrients were the lowest in Jjokjibeol in the Upo wetland. The chl-$\alpha$ concentrations were the highest at summer periods in Jjokjibeol and Mokpo. However, the highest at non-summer periods in Upo and Sajipo. Among the four swamps, Upo had the highest density on average of chl-$\alpha$, and Mokpo the lowest. Through TRIX (Trophic Index) analysis evaluating trophic state of the Upo wetland, all four swamps were estimated of poor water quality (eutrophication).

• Korean Journal of Ecology and Environment
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• v.56 no.1
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• pp.83-93
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• 2023

This study compares the abundance and community structure of zooplankton organisms from pelagic regions, and considers particularly the trophic levels vs. zooplankton abundances and biomass. Zooplankton samples were collected three times from May to November 2022, at 30 temperate lakes and reservoirs, which belong to four different river basins. The total zooplankton abundance, biomass and species index were showed considerable spatial variation. The spatial pattern of rotifer abundance was similar to that of total zooplankton abundance, while there were not showed similar patterns of zooplankton biomass (㎍ L^-1) in lentic ecosystems. The rotifer strongly dominated the zooplankton assemblage in smaller lentic system than that of larger. A total of 130 species of zooplankton were identified (83 rotifers, 34 cladocerans and 13 copepods). The total average of zooplankton abundance and biomass were 213.7±342.3 Ind. L^-1 (n=129) and 1382.8±1850.4 ㎍ L^-1, respectively. Total and average of zooplankton abundance were usually dominated by the rotifers (>56.9%), while those of zooplankton biomass were dominated by the cladocerans and copepods (>73.6%) in lentic ecosystems. Considering the Trophic State Index (TSI), the factors of zooplankton abundance and biomass were included in between meso- and eutrophic states(27 lakes, 90% of all). The mean abundance and biomass of zooplankton in eutrophic systems were higher than that of meso- and hypertrophic systems. From this result, we suggest that management strategy for the lentic ecosystem water environment has to be focused more on small-sized lakes and reservoirs, in terms of zooplankton assemblages.

• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.11-20
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• 2008

In this study, we applied a Particle Swarm Optimization (PSO) algorithm to predict the changes of chlorophyll-${\alpha}$ related to environmental factors in agricultural reservoirs in Korean national scale. Data were obtained from water quality monitoring networks of reservoirs operated by the Ministry of Agriculture and Forestry and the Ministry of Environment of Korea. From the database of the monitoring networks, 290 reservoirs were chosen with variables such as chlorophyll-${\alpha}$ and 13 environmental factors (COD, TN, TP, Altitude, Bank height, etc.) measured in 2002. Based on Carlson's trophic status index, reservoirs were divided into five groups, and most agricultural reservoirs $(TSI_{CHL}\;64.1%,\;TSI_{TP}\;75.5%)$ were in the eutrophic states. The groups were discriminated with environmental variables, showing that COD, DO, and TP were important factors to determine the trophic states. MLP-PSO (Multilayer perceptron (MLP) with PSO for the optimization) was applied for the prediction of chlorophyll-${\alpha}$ with environment factors, and showed high predictability (r=0.83, p<0.001). Additionally, the sensitivity analysis of the MLP-PSO model showed that COD had the strongest positive effects on the concentration of chlorophyll-${\alpha}$, and followed by TP, TN, DO, whereas altitude and bank height had negative effects on the concentration of chlorophyll-${\alpha}$.