• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.5
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• pp.493-505
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• 2020

Food web structures in the lower trophic levels of the seas around the Korean peninsula were investigated in August 2019 using stable isotopes. There were variable ratios of the carbon (-26.18 ~ -20.61 ‰) and nitrogen stable (5.36 ~ 15.20 ‰) isotopes in the particulate organic matter (POM). Most of the organisms ingested micro-POM as a major food source, but this varied spatially. The chaetognaths (3.40 ± 0.61) occupied the highest trophic level. The isotope mixing model showed that the proportions (13 ~ 51 %) of some organisms (i.e., copepods and euphausiids) reflected the relative contributions as major food sources for chaetognaths at each site.

• 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.

• Korean Journal of Ecology and Environment
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• v.45 no.1
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• pp.82-92
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• 2012

In this study, we identified spatial and temporal patterns of reservoir trophic state within Keum-river watershed and analyzed correlations between chlorophyll-$a$ (Chl-$a$) and water quality parameters including conductivity and total phosphorus (TP). The reservoirs were separated into three trophic categories by the criteria of TP: 2 oligotrophic (9.3~9.4 ${\mu}g\;L^{-1}$), 15 mesotrophic (10.3~19.2 ${\mu}g\;L^{-1}$), and 14 eutrophic reservoirs (38.9~117.1 ${\mu}g\;L^{-1}$). Water quality parameters such as conductivity, TP, and Chl-$a$ reflected rainfall patterns, and the patters of annual mean TP were similar to the variation of annual mean Chl-$a$. Empirical models of Chl-$a$ against TP in reservoirs showed that statistical significance ($p$ <0.05) occurred in only some seasons and the trophic relations were modified by a washing-out effect or high non-algal light attenuation.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.4
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• pp.263-267
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• 2013

Long-term (from 1995 to 2012) data of phytoplankton biomass (chlorophyll-a, Chl-a) and water quality were analyzed to investigate trends of eutrophication in downstream of Nakdong River (Mulgum). Long-term annual average concentration of water quality parameters and phytoplankton biomass at Mulgum showed an decreasing trends for 18 years. Phytoplankton biomass was high from annually December to March. Trophic state was evaluated as the eutrophic state annually from 1995 to 2012 by TSI (trophic state index) by Aizaki. From the results of simple regression analysis, correlation coefficient between Chl-a concentration and BOD concentration was high ($r^2$ = 0.82).

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.3
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• pp.3-15
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• 2001

The in situ observations and the seawater analyses were conducted for 3 years from August 1996 to August 1999 in order to elucidate and evaluate seasonal variations of marine water quality and trophic state in Mokpo harbour of Korea. Compared the seasonal seawater qualities of Mokpo harbour with the OECD standards of trophic classification in parameters such as Secchi depth, dissolved inorganic nitrogen, phosphate phosphorus and chlorophyll-a, the trophic level of seawater in Mokpo harbour was evaluated to be in mesotrophic or eutrophic state through all 4 seasons and to be in eutrophic state, particularly In summer. The estimation of pollution index by eutrophication showed the seawater quality of Mokpo harbour to deteriorate and fall under the regular grades through all 4 seasons, although the seawater quality of Mokpo harbour was evaluated to be equivalent to the second or third class of the Korean seawater quality standards in view of COD values. The results of eutrophication index estimation showed the high potentiality of red tide occurrence In Mokpo harbour, particularly in summer or fall. In the light of the average atomic ratio of N/P in seawater, the limiting nutrient factor against the growth of phytoplankton was concluded to be phosphorus rather than nitrogen in Mokpo Harbour.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.330-337
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• 2018

The Korean Eutrophication Index($TSI_{ko}$) was estimated using water quality monitoring data of eight main sites in the SoOoak River watershed. The environmental characteristics of rivers were classified and evaluated using the $TSI_{ko}$ for each factor calculated by COD, T-P, and Chl-a. There is a good condition for the algae to grow due to shallow water depth, inflow of non-point source pollution during rainfall, influx of sewage treatment effluent and increase of residence time. It shows trophic state more than mesotrophication year round. Especially, in case of Chuso point, which is the inflow point of Daecheong Lake, the water quality deteriorated due to hydraulic characteristics and showed the eutrophic state. Therefore, it is necessary to establish the measures to improve the water quality through the precise monitoring of SoOak River.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.4
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• pp.180-195
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• 2011

A balanced trophic model for Sinjido marine ecosystem was constructed using ECOPATH model and data obtained 1994 in the region. The model integrates available information on biomass and food spectrum, and analyses ecosystem properties, dynamics of the main species populations and the key trophic pathways of the system, and then compares these results with those of other marine environments. The model comprises 17 groups of benthic algae, phytoplankton, zooplankton, gastropoda, polychaeta, bivalvia, echinodermata, crustacean, cephalopoda, goby, flatfish, rays and skates, croaker, blenny, conger, flatheads, and detritus. The model shows trophic levels of 1.0~4.0 from primary producers and detritus to top predator as flathead group. The model estimates total biomass(B) of 0.1 $kgWW/m^2$, total net primary production(PP) of 1.6 $kgWW/m^2/yr$, total system throughput(TST) of 3.4 $kgWW/m^2/yr$ and TST's components of consumption 7%, exports 43%, respiratory flows 4% and flows into detritus 46%. The model also calculates PP/TR of 0.012, PP/B of 0.015, omnivory index(OI) of 0.12, Fin's cycling index(FCI) of 0.7%, Fin's mean path length(MPL) of2.11, ascendancy(A) of 4.1 $kgWW/m^2/yr$ bits, development capacity(C) of 8.2 $kgWW/m^2/yr$ bits and A/C of 51%. In particular this study focuses the analysis of mixed trophic impacts and describes the indirect impact of a groupb upon another through mediating one based on 4 types. A large proportion of total export in TST means higher exchange rate in the study region than in semi enclosed basins, which seems by strong tidal currents along the channels between islands, called Sinjido, Choyakdo and Saengildo. Among ecosystem theory and cycling indices, B, TST, PP/TR, FCI, MPL and OI are shown low, indicating the system is not fully mature according to Odum's theory. Additionally, high A/C reveals the maximum capacity of the region is small. To sum up, the study region has high exports of trophic flow and low capacity to develop, and reaches a development stage in the moment. This is a pilot research applied to the Sinjido in terms of trophic flow and food web system such that it may be helpful for comparison and management of the ecosystem in the future.

• Korean Journal of Ecology and Environment
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• v.45 no.2
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• pp.174-189
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• 2012

The objective of this study was to determine the weight-length relations and condition factor (K) of Zacco platypus, along the trophic gradients from oligotrophic to eutrophic state in six reservoir ecosystems ($B_aR$, $Y_yR$, $J_yR$, $G_pR$, $Y_dR$, and $M_sR$), during 2008~2010. The species was selected as a sentinel species for the study, due to its wide distribution and wide trophic gradient. The analysis of trophic state index (TSI), based on total phosphorus (TP) and chlorophyll-a (Chl-a), indicated that reservoirs of $Y_yR$ and $B_aR$ were classified as to be in an oligotrophic state (30~40), the $J_yR$ and $G_pR$ as mesotrophic (40~50), and the $Y_dR$ and $M_sR$ as eutrophic state (50~70). Total 47 species and 26,226 individuals were sampled from 6 reservoirs and sensitive species dominated in the oligotrophic reservoirs ($Y_yR$ and $B_aR$). In the mean time, the tolerant speciesdominated the community in the mesotrophic ($J_yR$ and $G_pR$) and eutrophic ($Y_dR$ and $M_sR$) reservoirs. Regression analysis of body weight, against the total length, indicated that the regression coefficient (b value) was lower in the oligotrophic reservoir (2.77~2.79) than the mesotrophic (3.07~3.17) and eutrophic reservoirs (3.15~ 3.21). This result suggests that the population growth rate Zacco platypus reflected the trophic gradients of the reservoirs. The analysis of condition factor (K) against the total length showed positive slopes (b>3.0) in mesotrophic and eutrophic reservoirs, and a negative slope (b<3.0) in oligotrophic reservoir. The variation of the regression slope of "b" in Z. platypus was accounted for 79.7% [$b=0.012{\times}TSI(TP)+2.395$, p=0.017] by the variation of TSI (TP) and 82.2% [$b=0.013{\times}TSI(Chl-a)+2.36$, p=0.013] by the variation of TSI (Chl-a). The proportion of DELT abnormality increased as the trophic state increases in the reservoirs. The overall data suggest that the growth of the fish populations, based on the length-weight relations and condition factor, reflected the trophic state of nutrient and phytoplankton biomass of the reservoir waters. Thus, in spite of the tolerant characteristics of Z. platypus, hypertrophic states might negatively affect the health of the population.

• 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 Environmental Biology
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• v.30 no.1
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• pp.64-70
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• 2012

This study compares the abundance and community structure of zooplankton organisms from the littoral and pelagic regions, and considers particularly trophic levels vs. zooplankton abundances. Zooplankton samples, collected every 3 months over a year from 2010 to 2011 at 29 temperate lakes and reservoirs, which belong to two different river basins (Youngsan and Seomjin River). The spatial pattern of rotifers was similar to that of total zooplankton abundance. This reflected the fact that rotifers strongly dominated the zooplankton community. There were considerable spatial variations in total zooplankton abundance (ANOVA, p<0.01), while there were no significant differences both in littoral and pelagic regions in abundance of zooplankton (ANOVA, p=0.205). The mean abundance of zooplankton in eutrophic systems was much higher than that of mesotrophic systems, while significant difference in number of species and diversity index were not shown in both trophic systems.