• The Korean Journal of Malacology
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• v.27 no.3
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• pp.205-211
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• 2011

This study presents physiological rates of oxygen consumption, ammonia excretion, feeding rates, O/N ratio and assimilation efficiency of the blood cockle, Scapharca subcrenata, determined from specimens collected in Yeoja bay on the south coast of Korea. Physiological parameters were measured monthly under static, laboratory controlled conditions with ambient conditions, and measurements were performed seasonally in order to estimate scope for growth and its probable sources of variation. Oxygen consumption and ammonia excretion rates have been increased as temperature increased with the highest value of August, 2008. Feeding rate was the highest during April whereas the lowest was during August which is a period of gametogenesis with minimum biomass of phytoplankton around sampling area. Assimilation efficiency was not significantly different seasonally and O/N ratio decreased during July to August. The scope for growth was negative during high temperature months(July to August), reflecting the high temperature and low feeding rate, and had its highest positive values during spring and autumn. Data on the physiological parameters and scope for growth of Scapharca subcrenata obtained in this study will be used to assess the carrying capacity for blood cockle cultivation.

• ALGAE
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• v.22 no.3
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• pp.193-199
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• 2007

This study was carried out to investigate the charateristics of environmental factors and the species compositions of phytoplanktons and periphytons in order to analyze the marine ecosystem (DOK1-3) with freshwater (Mul) in the coast of Dokdo. Mean values of conductivity (TSD) (44.3 mS cm–1), total dissolved solids (30.9 mg L–1), salinity (31.8 psu), total suspended solids (39.2 mg L–1), and ash-free dry matter (AFDM) (8.8 mg L–1) were higher in DOK1- 3 than those in Mul (3.2 mS cm–1, 2.3 mg L–1, 1.9 psu, 2.8 mg L–1 and 2.8 mg L–1, espectively), while mean amounts of soluble reactive phosphorus (SRP) (7.5 μg P L–1) and soluble reactive silicon (SRS) (0.1 μg Si L–1) were significantly lower in DOK1-3 than those in Mul (117.3 μg P L–1 and 4,105 μg Si L–1, respectively). The phytoplanktons was a total of 59 species in Dokdo, which were composed of 1 species (1.7%) for Chrysophyceae, 43 species (72.9%) for Bacillariophyceae and 15 species (25.4%) for Dinophyceae. The biomass (Chl-a, phaeopigment and AFDM) of epilithic algae (ELA), epizooic algae (EZA) and epiphytic algae (EPA) were varied with the kinds of substrates (EPA > ELA > EZA) in the whole stations. Water environments was comparatively clean in the coast of Dokdo as comparing with those of the land. However, the monitoring of marine ecosystem in the Dokdo should be continued for species conservation according to the global warming by the climatic change.

• 한국해양학회지
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• v.29 no.3
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• pp.258-268
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• 1994

Nitrogenous new production and regenerated production were measured in the southern part of the Yellow Sea (Hwanghae) using a stable isotope /SUP 15/N nitrate and ammonia between April 25∼30, 1993. Nitrogen production varied between 155 and 688 mg N m/SUP -2/ d/SUP -1/, which belongs to meso to eutrophic area values. This is equivalent to 881∼3909 mg C m/SUP -2/ d/SUP -1/, assuming the Redfield ratio for C:N of 5.7:1 (by weight). the f0ratio which is the fraction of new production from primary production, varied between 0.12 and 0.26, indicating that 74 to 88% of primary production was supported by the regeneration of nutrients within the euphoric zone. This low f0ratio is the characteristics of the oligo- to mesotrophic area. Contrary to the expected, the ambient nutrient concentration was not an important factor for controlling productivity in this area during the study period. The difference in productivity among stations was mainly due to the variations in phytoplankton biomass in different water masses.

• Korean Journal of Ecology and Environment
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• v.46 no.2
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• pp.225-233
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• 2013

We examined the effect of different field temperatures on water quality improvement (WQI) of natural domestic plant-mineral composites (PMCs). This method was previously used by Kim et al. (2011), to monitor the restoration of water quality of a eutrophic lake, Lake Shingal (Korea). Results indicate that PMCs on phytoplankton, BOD and phosphorus showed more than 70% WQI below $20^{\circ}C$, and less than 40% WQI over $25^{\circ}C$, respectively. The WQIs of PMCs on blue-green algae were gradually decreased with the increase of temperature, whilst diatoms exhibited more than 90% higher WQIs, regardless of water temperature. Additionally, the WQIs on bacterial biomass and total nitrogen were low at all temperatures. These results collectively indicate that water quality improvement activity of plant-mineral composites was dependent on the water temperature, and that the field application of above chemical during temperatures over $25^{\circ}C$, would be less effective in treating a cyanobacteria bloom dominated by Microcystis aeruginosa, than by diatoms.

• Journal of Korean Society on Water Environment
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• v.29 no.6
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• pp.746-753
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• 2013

The aim of this study was to evaluate artificial fish shelter, which was known to increase prey survival and expand habitat space to improve species diversity and fish communities in a freshwater ecosystem. The experiment was performed at an outdoor test-bed for three months from 2011 by comparing the responses to adjustments in the volume of the artificial patch (juvenile fish shelter, JFS) in the control and experimental groups. Analysis of the environmental conditions over two periods (Period1 ~ 2) showed minor differences in the physichemical characteristics of water quality, phytoplankton, and zooplankton biomass, thus, allowing comparative analysis of feeding ecology. However, high water temperature conditions in Period1 ($25.6{\pm}2.0^{\circ}C$), affected the predation activity of the piscivorous fishes, Coreoperca herzi (C. herzi, size $89{\pm}4mm$). Survival rates of the prey fishes, Rhynchocypris oxycephalus (R. oxycephalus, size $29{\pm}1mm$), improved as the patch volume increased and were higher than those of the control group by 35.9 ~ 46.7%. Analysis showed that JFS reduced the chances of predator-prey encounter, and thereby minimized prey vulnerability.

• Journal of Korean Society on Water Environment
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• v.27 no.5
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• pp.699-709
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• 2011

The uses of multi-dimensional hydrodynamic and water quality models are increasing to support a sustainable management of large dam reservoirs in Korea. Any modeling study requires selection of a proper spatial dimension of the model based on the characteristics of spatial variability of concerned simulation variables. For example, a laterally averaged two-dimensional (2D) model, which has been widely used in many large dam reservoirs in Korea, assumes that the lateral variations of hydrodynamic and water quality variables are negligible. However, there has been limited studies to give a justification of the assumption. The objectives of this study were to present the characteristics of spatial variations of water quality variables through intensive field monitoring in Daechung Reservoir, and provide information on a proper spatial dimension for different water quality parameters. The monitoring results showed that the lateral variations of water temperature are marginal, but those of DO, pH, and conductivity could be significant depending on the hydrological conditions and local algal biomass. In particular, the phytoplankton (Chl-a) and nutrient concentrations showed a significant lateral variation at R2 (Daejeongri) during low flow periods in 2008 possibly because of slow lateral mixing of tributary inflow from So-oak Stream and wind driven patchiness.

• Ocean and Polar Research
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• v.43 no.1
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• pp.31-43
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• 2021

To understand the temporal variation of prokaryotic communities in a temperate coastal area, prokaryotic abundance, activity, and community composition were investigated every week for over a year at a coastal monitoring station of Yeong-do, Busan. The prokaryotic abundances fluctuated about 10 times, ranging from 2.0 to 20.1 × 10⁵ cells mL^-1 and tended to be high in spring when phytoplankton bloom occurred. The prokaryotic thymidine incorporation rates (TTI) varied in a low range between 0.2 and 11.5 pmol L^-1 h^-1 in winter. However, in summer, TTI were increased up to a range of 8.3 to 17.4 pmol L^-1 h^-1, showing an increasing pattern in summer. During the study period, Alphaproteobacteria was the most dominant class for most of the year, followed by Flavobacteria. While the seasonal variation of prokaryotic composition was not apparent at the class level, many prokaryotic species showed a distinct temporal or seasonal variation for the year. In the coastal site, prokaryotic biomass and activity did not show significant correlations with temperature and chlorophyll-a, which are well known to regulate prokaryotic growth in marine environments, suggesting that the study area may be affected by diverse sources of organic matter for their growth.

• Ocean and Polar Research
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• v.44 no.1
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• pp.13-27
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• 2022

The Yeongsan River estuary was altered by a sea dike built in 1981 and the sluice gates in the dike were extended recently in 2014. The construction has caused changes in water properties and hydrodynamics and also produced disturbances including hypoxia and algal blooms. We analyzed the water quality and chlorophyll-a data (2009-2018) collected seasonally at 3 stations (Sts. 1-3) along the channel of the estuary by the Marine Environmental Monitoring System. Variations in water quality and chlorophyll-a (an index of phytoplankton biomass) were examined and their stressors were also identified by statistics including correlation and multivariate principal component analyses (PCA). The water quality was mainly affected by freshwater discharge from the dike. Salinity, nutrients and chlorophyll-a were especially affected by the discharge and the effect enhanced during summer and at the upper region near the sea dike decreasing downstream. Three factors were extracted for each station in the PCA accounting for 66.07-72.42% of the variations. The first was an external factor associated with freshwater discharge and the second and third were seasonal or biological factors. The results indicate that the water quality is more affected by short-termed and episodic events such as freshwater discharge than seasonal events and the influence of freshwater discharge on water quality is more extensive than that previously reported. This suggests that the boundary of the estuary should be extended to take into account the findings of this study and a management strategy linked to the freshwater zone is required to manage the integrity and water quality of the Yeongsan River estuary.

• Korean Journal of Environmental Biology
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• v.22
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• pp.86-92
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• 2004

The marine viral density in the Gwangyang Bay was abundant about 2.0${\times}$10$^{8}$ particles ml$^{-1}$ . For each season, viral abundances were recorded from 9.0${\times}$10$^{8}$ particles ml$^{-1}$ in summer to 0.7${\times}$10$^{6}$ particles ml$^{-1}$ in winter. The spatial distributions of the viral, bacterial and phytoplankton biomass in the Gwangyang Bay were mostly highey in closed estuarine system (Station 2, 5, 10, 12, 16, 20) than open ocean system (Station 28, 38, 42, 46, 51), And the othey closed estuarine system (Station 22, 26, 32, 34) indicated higher viral abundances, lower bacterial and plankton biomass than open oceanic system. In depths of some stations, the bacterial abundances exceeded a hundred fold than viral abundances. Seasonal abundances of marine viruses and their host systems were dynamically changed, and their seasonal variations were closely correlated. In summer, viral and bacterial abundances were increased, and phytoplankton chlorophyll $\alpha$ concentrations were maintained in average values. In winter, viral and bacterial abundances were dramatically decreased, and chlorophyll a concentrations were decreased, but, immediately increased. The viral abundances were peaked in August 2001, and bacteyial abundance, in August 2001 and June 2002, while chlorophyll a concentrations were peaked in April. 2002. In total host and viral abundances, it was seemed that their pools were maintained to steady-states by viral mortality, and viral abundance maintained steady-states. In our assessments, this report is a unique research about marine viral ecology of the Gwangyang Bay in Korea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.750-763
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• 2018

This study conducted 10 sampling sites survey 4 times to determine the trophic structure and energy flow of marine ecosystems for Uljin marine ranching area, Korean East Sea from March to October 2013. Based on the ecological characteristics of biological species, one used the non-Metric Multidimensional Scaling method based on the similarity of species. A total of 19 classified species groups formed categories including, top predators, seabirds, large pelagic fishes, small pelagic fishes, rockfishes, pleuronectiformes, benthic fishes, semi-benthic fishes, cephalopods, benthic feeders, epifauna, bivalves, abalone, Cnidaria, zooplankton, benthic algae, microalgae, phytoplankton and detritus. The biomass, production/biomass, consumption/biomass, diet composition data of each species groups to input data used in Ecopath mode estimated the trophic structure and energy flow of marine ecosystems in the Uljin marine ranching area. One estimated each species groups on the trophic level from 1 to 5.687. The sum of all consumption was estimated at $229.7t/km^2/yr$ and the sum of all exports was as estimated $3,432.4t/km^2/yr$. Total system throughput was at $6,796.2t/km^2/yr$, and the sum of all production was estimated at $3,613.1t/km^2/yr$. Net system production according to these results was estimated at $3,490.3t/km^2/yr$ and total biomass (excluding detritus) was estimated at $167.3t/km^2/yr$ in the Uljin marine ranching area.