• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.10 no.3
• /
• pp.154-163
• /
• 2005

Irregular discharges of freshwater through the water gates of the Keum River Estuarine Weir, Korea, whose construction had been completed in 1998 with its water gates being operated as late as August 1994, drastically modified the estuarine environment. Sharp decrease of salinity along with the altered concentrations of inorganic nutrients are accompanied with the irregular discharges of freshwater into the estuary under the influence of regular semi-diurnal tidal effect. Field sampling was carried out on the time of high tide at 2 fixed stations(St.1 near the Estuarine Weir and St.2 off Kunsan Ferry Station) every other day for 4 months from mid-February 2004 to investigate into the semi-weekly variation of spring phytoplankton community in relation to the freshwater discharges from Keum River Estuarine Weir. CV(coefficient of variation) of salinity measurements was roughly 2 times greater in St.1 than that in St.2, reflecting extreme salinity variation in St.1 Among inorganic nutrients, concentrations of N-nutrients($NO_3^-,\;NO_2^-$ and $NH_4^+$) were clearly higher in St.1, to imply the more drastic changes of the nutrient concentrations in St.1. than St.2 following the freshwater discharges. As a component of phytoplankton community, diatoms were among the top dominants in terms of species richness as well as biomass. Solitary centric diatom, Cyclotella meneghiniana, and chain-forming centric diatom, Skeletonema costatum, dominated over the phytoplankton community in order for S-6 weeks each (Succession Interval I and II), and the latter succeeded to the former from the time of <$10^{\circ}C$ of water temperature. Cyanobacterial species, Aphanizomenon Posaquae and Phormidium sp., which might be transported into the estuary along with the discharged freshwater, occupied high portion of total biomass during Succession Interval III(mid-April to late-May). During this period, freshwater species exclusively dominated over the phytoplankton community except the low concentrations of the co-occurring 2 estuarine diatoms, Cyclotella meneghiniana and Skeletonema costatum. During the 4th Succession Interval when the water temperature was over $18^{\circ}C$, the diatom, Guinardia delicatula, was predominant for a week with the highest dominance of $75\%$ in discrete samples. To summarize, during all the Succession Intervals other than Succession Interval III characterized by the extreme variation of salinity under cooler water temperature than $18^{\circ}C$, the diatoms were the most important dominants for species succession in spring. If the scale and frequency of the freshwater discharge could have been adjusted properly even during the Succession Interval III, the dominant species would quite possibly be replaced by other estuarine diatom species rather than the two freshwater cyanobacteria, Aphanizomenon flosaquae and Phormidium sp.. The scheme of field sampling every other day for the present study was concluded to be the minimal requirement in order to adequately explore the phytoplankton succession in such estuarine environment as in Keum River Estuary: which is stressed by the unpredictable and unavoidable discharges of freshwater under the regular semi-diurnal tide.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.28 no.4
• /
• pp.475-488
• /
• 1995

In order to see the seasonal variation of nutrients and the limiting factors to the primary production in Deukryang Bay, both dissolved inorganic nutrients and salinity were measured in the surface waters during the periods from July 1992 to March 1993. The mean value of salinity was the lowest in ?all and the highest in early spring. Dissolved inorganic nitrogen (DIN) was the highest in winter and the lowest in summer. However, both phosphate and silicate were the highest in summer and the lowest in fall. Salinity was generally higher in the outer region than in the inner region of the bay.DIN content was nearly depleted (less than $2{\mu}M$) in summer. From fall to spring, DIN content was nearly depleted in the inner region and relatively high in the outer region of the Day. Phosphate was the highest in summer showing an opposite distribution pattern to salinity, and it was nearly depleted (less than $0.1{\mu}M$) in fall and winter. In spring, however, phosphate content was slightly high in the outer region. Silicate content showed an opposite distribution pattern to salinity in summer. in other seasons, However, the distribution pattern of silicate was similar to the salinity. DIN seemed to be a limiting factor for the primary production at all area of the bay in summer and at the inner region in other season. However, phosphate seemed to be a limiting factor at all area of the bay in fall and winter and at the inner region in spring. Silicate may limit the production of diatoms at the inner region of the bay in winter and spying. Both phosphate and silicate showed a good inverse relationship with salinity in summer, which indicates inputs of these nutrients from the freshwater runoff. In the other seasons, both nitrate and silicate showed a positive linear relationship with salinity in the outer region of the bay, suggesting that these two nutrients were mainly supplied by the inflow of the offshore costal water which had high nitrate content associated with vertical mixing.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.33 no.4
• /
• pp.668-678
• /
• 2004

The purpose of this study was to estimate seasonal variation of nutritional intake and quality in adults in longevity areas. Dietary survey was given to 469 subjects over age 20 living Bukjeju-gun, Yecheon-gun, and Sunchang-gun of Korea, using 24-hour recall method every 4 seasons over one-year period. The mean daily intakes (%RDA) of 4 seasons were 1313.3 ㎉ (72.0%) for energy, 47.3 g (82.2%) for protein, 20.2 g for fat, 228.0 g for carbohydrate, 12.8 g for dietary fiber. The differences were hardly significant among the seasons. Mean daily intakes of most of the vitamins and minerals were lower than RDA except vitamin C and folate, especially %RDAs of Ca, vitamin D, vitamin B$_2$, vitamin E were less than 60% of RDA. In general, nutrient intake were high in spring compared to other seasons except vitamin C which was high in fall and winter. Mean daily intakes of cholesterol were 151.7 mg and 124.3 mg in males and females, respectively. The differences was significant between the two sexes but not among the seasons. PUFA : MUFA : SFA ratio of the subject was 1.0 : 1.3 : 1.2. Average CPF ratio of energy intake was 72.7 : 14.4 : 12.9, and energy intake ratio from carbohydrate was low in spring, in contrast energy intake ratios from protein was significantly high in spring. Mean adequacy ratio (MAR), an index of overall nutritional quality was 0.64 for female and 0.71 for male. The indices of nutritional quality (INQ) were over 1 for most of nutrients except 0.73 of Ca, 0.87 of vitamin A, 0.69 of vitamin B$_2$, and 0.65 of vitamin E. Both MAR and INQ were significantly different among sex and seasons, values were higher in males than in females and were higher in spring with the exception of vitamin C. In conclusion, subjects in longevity areas did not consume enough nutrients quantitatively as well as qualitatively, especially Ca, vitamin A, vitamin B$_2$, and vitamin E. Also mean daily intakes of most of vitamins and minerals were insufficient in females, and were significantly different among season. Therefore we must consider a counterplan to augment nutrition intake for them. In addition, it seems to be essential to micro nutrients to the food composition database to estimate dietary intakes more accurately.

• Korean Journal of Environmental Biology
• /
• v.26 no.3
• /
• pp.252-263
• /
• 2008

The purpose of this study was to determine trophic state, based on nutrients (TN, TP), transparency (SD), and chlorophyll-${\alpha}$ (Chl) and identify their empirical relations of TN-Chl, TP-Chl and Chl-SD depending on the dataset used along with dynamics of conductivity and suspended solids. Analysis of trophic states showed that more than half of 36 reservoirs were judged as eutrophic-hypertrophic conditions depending on the trophic variables. Seasonal values of TP varied by nearly 500% and showed greater in August than any other months. In contrast, TN varied within less than 90% and all monthly mean values of TN were never fall less than 1.2 mg L$^{-1}$ indicating low seasonal variations and high ambient concentrations (eutrophic-hypertrophic state). Analysis of empirical relations in the trophic variables showed that transparency had greater functional relations with Chl (R$^2$=0.31, p<0.001) than TP (R$^2$=0.15, p<0.001) and TN (R$^2$=0.20, p<0.001). Ratios of TN : TP in the ambient water indicated that most reservoirs showed a potential phosphorous limitation on the algal growth. Thus, algal biomass, based on Chl values, was more regulated by phosphorous than nitrogen. Analysis of linear regression model, based on log-transformed annual mean values, showed that only 30% in the variation of Chl was explained by TP (R$^2$=0.295, p=0.001, n=36) and 15% by TN (R$^2$=0.151, p=0.019, n=36). However, linear regression model, based on individual system, showed that Chl-TP model had strong positive relations (R$^2$=0.62, p=0.002, n=12), whereas the model had no any relations (p=0.892, n=12). Overall, our data suggested that averaging effect in the empirical model developments may influence the significance in the statistical analysis.

• Korean Journal of Ecology and Environment
• /
• v.39 no.1 s.115
• /
• pp.73-84
• /
• 2006

The objective of this study was to analyze long-term temporal trends of water chemistry and spatial heterogeneity for 10 sampling sites of the Yeongsan River watershed using water quality dataset during 1995 to 2004 (obtained from the Ministry of Environment, Korea). The water quality, based on multi-parameters of biological oxygen demand (BOD), chemical oxygen demand (COD), conductivity, dissolved oxygen (Do), total phosphorus (TP), total nitrogen (TN) and total suspended solids (TSS), largely varied depending on the sampling sites, seasons and years. Largest seasonal variabilities in most parameters occurred during the two months of July to August and these were closely associated with large spate of summmer monsoon rain. Conductivity, used as a key indicator for a ionic dilution during rainy season, and nutrients of TN and TP had an inverse function of precipitation (absolute r values> 0.32, P< 0.01, n= 119), whereas BOD and COD had no significant relations(P> 0.05, n= 119) with rainfall. Minimum values in conductivity, TN, and TP were observed during the summer monsoon, indicating an ionic and nutrient dilution of river water by the rainwater. In contrast, major inputs of total suspended solids (TSS) occurred during the period of summer monsoon. BOD values varied with seasons and the values was closely associated (r=0.592: P< 0.01) with COD, while variations of TN were had high correlations (r=0.529 : P< 0.01) with TP. Seasonal fluctuations of DO showed that maximum values were in the cold winter season and minimum values were in the summer seasons, indicating an inverse relation with water temperature. The spatial trend analyses of TP, TN, BOD, COD and TSS, except for conductivity, showed that the values were greater in the mid-river reach than in the headwater and down-river reaches. Conductivity was greater in the down-river sites than any other sites. Overall data of BOD, COD, and nutrients (TN, TP) showed that water quality was worst in the Site 4, compared to those of others sites. This was due to continuous effluents from the wastewater treatment plants within the urban area of Gwangju city. Based on the overall dataset, efficient water quality management is required in the urban area for better water quality.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.15 no.2
• /
• pp.76-88
• /
• 2012

In order to investigate the distribution of water masses and spatio-temporal variation of nutrients in the coastal areas of Gangwon province of the Korean East Sea, a survey of the physico-chemical parameters (temperature and salinity) and nutrients ($NO_2$-N, $NO_3$-N, $NH_4$-N, $PO_4$-P, and $SiO_2$-Si) was carried out at 5 locations (Goseong, Sokcho, Yangyang, Gangneung, and Donghae) in February, May, August, and November 2009. The water masses included in the study area were divided into 4 groups; 1) Tsushima Surface Water (TSW), 2) Tsushima Middle Water (TMW), 3) North Korean Cold Water (NKCW), and 4) East Sea Proper Water (ESPW). The distribution of water masses was affected by the change of season. In February, surface water was derived from the TMW. The TSW was not observed in May, but only observed in August. In November, as the influence of the TSW weakened, that of the NKCW strengthened. Considering the vertical profiles of nutrients, the concentrations in all the seasons were very low within the surface water, but increased rapidly near the thermocline. Most of nutrient concentrations, except for dissolved silicate, remained constant below the depth of 200 m. However, the dissolved silicate concentration increased with depth, suggesting that silicate has a delayed regenerative pattern. The ESPW had the highest nutrient concentration, followed by the NKCW, TMW, and TSW. In February, May, and November, the N/P ratio in most of the water masses was similar to or larger than the Redfield ratio, indicating that nitrogenous nutrients did not act as a limiting factor for phytoplankton growth. However, in August, the N/P ratio in the TSW was less than the Redfield ratio, and the concentration of $NO_2$-N+$NO_3$-N was 0.86 ${\mu}m$, indicating that nitrogenous nutrients did act as a limiting factor for phytoplankton growth in the study area.

• 한국해양학회지
• /
• v.21 no.1
• /
• pp.13-24
• /
• 1986

The daily net primary production by phytoplankton in the southeastern sea of Korea in October 1985 ranged from 0.7 to 2.7 gCm$\^$-2/ d$\^$-1/ and averaged to be 1.3 gCm$\^$-2/ d$\^$-1/. Surface total chlorophyll ranged from 0.97 to 3.59mg chlm$\^$-3/. Primary production by nano-phytoplankton(〈20$\mu\textrm{m}$) ranged from 43 to 97% in the surface layer. Optimum light intensity(Iopt)was around 300 to 700${\mu}$Es$\^$-1/m$\^$-1/. Surface primary production from 9:00 to 15:00 h was evidently inhibited by strong light intensity beyond the Iopt. Phytoplankton near the base of euphotic zone(30-40m) showed extremely low Iopt suggesting adaptation to a low light environment. Since Iopt represents the history of light experience of phytoplankton at a given depth, the extent of variation in I of phytoplankton at different depth seems to be related to the in tensity of turbulence mixing in the surface mixed layer. From the present study, ammonium excretion by macrozooplankton (〉350$\mu\textrm{m}$) contributes from 3 to 19% of daily total nitrogen requirement by phytoplandton in this area. Calculation of upward flux of nitrate to the surface mixed layer from the lower layer, based on the simple diffusion model, approximates 3% of nitrogen requirement by phytoplankton. However, large portion of nitrogen requirement by phytoplankton remains unexplained in this area. In upwelling area near the coast, adjective flux might be the major source for the nitrogen requirement by phytoplankton. This study suggests that the major nitrogen source for the phytoplankton growth might come from the pelagic regeneration by nano-and micro-sized heterotrophic plandkon. Enhancement of primary production during the passage of the warm Tsushima Current is discussed in relation with nutrient dynamics and hydrlgraphic processes in this area.

• Korean Journal of Ecology and Environment
• /
• v.38 no.1 s.110
• /
• pp.54-62
• /
• 2005

The present study was to determine how seasonal rainfall intensity influences nutrient dynamics, ionic contents, oxygen demands, and suspended solids in a lotic ecosystem. Largest seasonal variabilities in most parameters occurred during the two months of July to August and these were closely associated with large spate of rainfall. Dissolved oxygen (DO) had an inverse function of water temperature (r = = = - 0.986, p<0.001). Minimum pH values of<6.5 were observed in the late August when rainfall peaked in the study site, indicating an ionic dilution of stream water by precipitation. Electrical conductivity (EC) was greater during summer than any other seasons, so the overall conductivity values had direct correlation (r = 0.527, p<0.01) with precipitation. Ionic dilution, however, was evident 4 ${\sim}$ 5 days later in short or 1 ${\sim}$ 2 weeks in long after the intense rain, indicating a time-lag phenomenon of conductivity. Daily COD values varied from 0.8 mg $L^{-1}$ to 7.9 mg $L^{-1}$ and their seasonal pattern was similar (r = 0.548, p<0.001) to that of BOD. Total nitrogen (TN) varied little compared to total phosphorus (TP) and was minimum in the base flow of March. In contrast, major input of TP occurred during the period of summer monsoon and this pattern was similar to suspended solids, implying that TP is closely associated (r = 0.890, p<0.01) with suspended inorganic solids. Mass ratios of TN : TP were determined by TP (r= -0.509, p<0.01) rather than TN (r= -0.209, p<0.01). The N : P ratios indicated that phosphorus was a potential primary limiting nutrient for the stream productivity. Overall data suggest that rainfall intensity was considered as a primary key component regulating water chemistry in the stream and maximum variation in water quality was attributed to the largest runoff spate during the summer monsoon.

• Korean Journal of Ecology and Environment
• /
• v.35 no.4 s.100
• /
• pp.273-284
• /
• 2002

During January 1998-October 1999, the impact of free-floating plants (FFP) on limnology of the wetland ecosystem was evaluated through the investigation of physicochemical characteristics of the Woopo Wetland along with in situ manipulation experiments of aquatic plants. Flooding events occurred in the wetland during the summer period (Jun.-Aug.) and water levels rose to 2-3 m due to precipitation from the catchment and inflow from the main channel of the Nakdong River. Physicochemical parameters and plankton dynamics in the wetland during the summer were greatly influenced by floods and growth of free-floating plants. Dissolved oxygen (Jun.-Sept., 4.5${\pm}$2.5 mg/1; Oct.-May, 8,1 ${\pm}$4.0 mg/1) and pH (Jun.-Sept., 6.9${\pm}$0.4; Oct.-May,7.4${\pm}$0.8) levels were significantly lower during the summer than any other seasons. Three types of enclosure experiments (100 L, treatments with floating plants, screened and opened) were conducted under the presence and absence of sediment for 15 days in the 1999 summer. The treatments with sediment had higher levels of nutrient concentrations than those of the others. Among the treatments with sediment, nutrient concentrations in the treatments with free-floating plants were higher than the others. Zooplankton communities in each treatment showed a similar variation, although the scale of zooplankton densities differed. Rotifer community dominated the zooplankton at the initial phase of the experiment, but decreased drastically along with an increase of cladoceran and copepod communities. In conclusion, low levels of dissolved oxygen and pH in the Woopo Wetland during the summer seemed to be caused by a proliferation of free-floating plants and active decomposition process at the bottom of the sediment.

• Proceedings of the Korean Aquaculture Society Conference
• /
• 2003.10a
• /
• pp.141-142
• /
• 2003

본 연구는 전복의 유생사육을 목적으로 먹이생물인 부착미세조류의 파판 배양시 배양기간에 따른 종조성과 영양성분의 변화를 파악하기 위하여 수행되었다. 실험은 완도지역에서 봄철인 2~4월에 8주 동안 실시되었다. 배양을 위한 기초 조사로 배양지역 연안해수의 수온, 염분, pH, 총질소, 총인, Chlorophyll-a를 측정 하였다. 실험에 사용된 파판은 전복 종묘생산에 이용되는 규조배양용 파판과 틀을 이용하여 2주마다 파판을 수거한 뒤 부착된 미세조류를 부드러운 솔로 분리하여 원심분리한 후 지방산과 아미노산을 측정하였다. 각각의 시료는 광학현미경(Nikon)으로 동정한 후 Sedwick-rafter counting chamber를 이용하여 종별로 계수하고 이를 단위면적당 개체수 (cells/$\textrm{cm}^2$)로 환산하여 정량분석을 하였다. 실험 결과 봄철 완도지역의 평균 수온과 염분은 각각 15.4$^{\circ}C$와 33.88$\textperthousand$이었고 pH는 8.21이었다. 총질소와 총인은 각각 0.078mg/$\ell$, 0.018mg/$\ell$였고 chlorophyll-$\alpha$는 1.47$\mu$g/$\ell$ 였다. 부착미세조류의 아미노산 분석 결과는 배양 2주째의 총아미노산 양이 5.63%로 가장 낮았고, 4주는 6.50%, 6주 7.82% 8주 7.87%로, 6주까지 증가하다가 정체하는 경향을 보였다. 필수아미노산의 경우 총아미노산의 경향과 비슷하였고 2, 4, 6, 8주째의 양은 각각 2.75%, 3.16%, 4.01%, 3.96%였다. 필수 아미노산과 비필수아미노산의 비는 2, 4, 6, 8주 각각 0.95, .095, 1.05, 1.01의 결과를 보였다. 지방산의 경우 palmitic acid( $C_{16:0}$)와 palmitoleic acid( $C_{16:1}$)가 43.10~67.66%의 함량을 보였으나 4주째에는 검출되지 않았으며 EPA는 6주에서 10.97%를 보였고 나머지 구간에서는 검출되지 않았다. 부착미세조류의 biomass는 기간별로 2.4$\times$$10^3$ cells/$\textrm{cm}^2$, 7.8$\times$$10^3$ cells/$\textrm{cm}^2$ 25.1$\times$$10^3$ cells/$\textrm{cm}^2$, 44.3$\times$$10^3$ cells/$\textrm{cm}^2$ 이었다. 출현량은 총 64종으로 대부분이 부착규조류였으며 2주, 4주, 6주, 8주 각각 43종, 25종, 19종, 24종의 부착 규조류가 출현하였다. 그리고 우점종은 2주째 Nitzschia petitiana, Fragilia psedonana, 4주 Navicula mollis, Flagilia cylindrus, 6주 Flagilia capucaina, Achnanthes haukiana, 8주 Flagilia islandica, Flagilia cylindrus였다.s였다.