• Korean Journal of Ecology and Environment
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• v.40 no.3
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• pp.449-458
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• 2007

Fish community and its temporal-spacial variation in the Lagoon Hwajinpo, Korea were seasonally investigated with different types of fishing gears from November, 2005 to August, 2006. Total 35.812 fishes caught during the period were belonged to 24 families 37 species. Dominant species was H. nipponensis(60.8%), T, hakonensis (19.8%), and K. punctatus (5.5%) ana these species were peripheral freshwater fish. Among 37 species, primary freshwater and seawater fish were 8 species (21.6%), respectively and peripheral freshwater fish were 21 species (56.8%). Total biomass of collected fish was 279.3kg, and biomass of each species was T. hakonensis 152.9 kg, H. nipponensis 40.0 kg, K. punctatus 31.4 kg and C. haematochelius 25.3 kg, respectively. Hence, productivity of the Lagoon Hwajinpo was much higher than those of inland reservoirs. The aspect of community classified by surveyed period was changed according to the 'Breaking-sandbar', but some of peripheral freshwater fish populations made stable community in their life cycle in the lagoon. In conclusion, the Lagoon Hwajinpo seems to be maintained more natural ecosystem better than other lagoons in Korea. Therefore, the findings provide consideration of the management and restoration for this lagoon and others through the continuous observation and monitoring in future.

• Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.333-337
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• 2011

A new and a unique Brachionus rotifer was found in Hwajinpo coastal lagoon in Gangwon Province, South Korea. This Brachionus certainly originated from the wild rather than from aquaculture stations because Hwajinpo coastal lagoon has been under rigorous control as a military protected area and therefore could not have been contaminated by aquaculture stations. The new strain was identified as Brachionus rotundiformis based upon its morphological characteristics. The parthenogenetic female of this new rotifer strain typically shows characters similar to those of B. rotundiformis, such as the pot shape of the body, rounded dorsal plate compared with flattened ventral plate, elliptical mictic egg, four frontal spines, six pointed occipital spines, non-nodal foot, two toes, trophi typical of the Brachionus genus with five uncus plates resembling comb teeth, one wide symmetrical manubrium and ramus, and no stiffened spine as is seen in freshwater Brachionus rotifers. Moreover, its lorica was rather small in size compared with other common rotifer strains that serve as live-food organisms (Guam, Thai, and Bali strains). This new and unique Korean brackish rotifer, a B. rotundiformis strain, was therefore named the National Fisheries Research and Development Institute (NFRDI) $N^{\circ}1$ rotifer strain.

• Economic and Environmental Geology
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• v.54 no.6
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• pp.699-707
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• 2021

Hwajinpo Lagoon, located on the eastern coast of Korea, is a unique environment where freshwater and saltwater are mixed. Systematic management of the lagoon is required because it is a biodiversity-rich and area of high conservation value. The existing environment of the lagoon was evaluated by identifying the distribution of the groundwater level and groundwater flow characteristics. In addition, hydrogeochemical fluctuations were analyzed to determine the effect of seawater intrusion into the aquifer. The results demonstrate that the freshwater-saltwater interface is distributed throughout the aquifer and rises when water of the lagoon evaporates due to prolonged periods of low rainfall and high temperature, thereby increasing the possibility of seawater inflow through groundwater. As for the ionic delta properties (difference between the measured and theoretical concentration of mixed waters), it was estimated that the cation-exchange and precipitation reactions occurred in the aquifer due to seawater intrusion. The ratio of seawater mixed at each point was calculated, using oxygen isotopes and chloride as tracers, resulting in an average of 0.3 and a maximum of 0.87. The overall seawater mixing ratio appears to be distributed according to the distance from the coast. However, some of the results were deviated from the theoretical expectations and reflected the characteristics of the nearby aquifers. Further research on seasonal changes and simulation of seawater intrusion mechanisms is required for specific analysis.

• Korean Journal of Ecology and Environment
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• v.45 no.3
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• pp.329-339
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• 2012

In the spring (March to June) in 2010, one diatom Skeletonema costatum occurred outbreaks in Lake Hwajinpo, one of the typical lagoons on the east coast of South Korea. We compared the characteristics of the phytoplankton community during the bloom and extinction period of S. costatum, and evaluated the water quality based on nutritional indices. Results indicate that 1) this bloom showed the highest cell density ($>10^5$ cells $mL^{-1}$) among outbreaks of S. costatum occurred Korea, 2) occurred in below or over $20^{\circ}C$ water temperature, and 3) was destroyed in the early summer with higher temperature than the bloom period. Water quality or trophic status of the lake was eutrophic to hypertrophic with high salinity, BOD, COD and phosphate, and low N/P ratios and transparency. Phytoplankton community in the spring bloom had a high dominance and low diversity, but rightly recovered to low dominance and high diversity in the summer season. Therefore, we temporarily conclude that the bloom of S. costatum in Hwajinpo was triggered by the extended spring drought and the reduced influx of river water, and appeal that the bloom can happen repeatedly every year.

• Proceedings of the Korean Quaternary Association Conference
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• 2003.05a
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• pp.39-40
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• 2003

• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.12-25
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• 2004

Physicochemical parameters, plankton biomass, and sediment were surveyed from 1998 to 2000 at two months interval in a eutrophic coastal lagoon(Lake Hwajinpo, Korea). The lake is separated from the sea by a narrow sand dune. Littoral zone is well vegetated with leafing-leaved aquatic plants. The lake basin is divided into two subbasins by a shallow sill. It has intrusion of seawater by permeation and stormy waves. Stable chemoclines are formed by salinity difference at 1m depth all the year round. DO was often very low (< 1 mg$O_2\;L^{-1}$) at hypolimnion. Temperature inversions were observed in November. Nitrate and ammonium concentrations were very low(< (1.1 mgN $L^{-1}$), even though TN was usually 2.0 ${\sim}$ 3.5 mgN $L^{-1}$. TN/TP was generally lower than the Redfield ratio. Transparency was 0.2 ${\sim}$ 1.7 m, and COD, TP, and TN of sediment were 3.1 ${\sim}$ 40.3 mg$O_2\;g^{-1}$, 0.91 ${\sim}$ 1.39 mgP $g^{-1}$, and 0.34 ${\sim}$ 3.07 mgN $g^{-1}$, respectively. Phytoplankton chlorophyll- a concentrations were mostly over 40 mg $m^{-3}$. Two basins showed different phytoplankton communities with Oscillatoria so., Trachelomonas sp., Schizochlamys gelatinosa, and Anabaena spiroides dominant in South basin, and with Trachelomons sp., Schroederia so., schizochlamys gelatinosa, and Trachelomonas sp. dominant in the North basin. The seasonal succession of phytoplankton was very fast, possibly due to sudden changes in physical conditions, such as wind, turbidity, salinity and light.

• Journal of the Korean Geographical Society
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• v.43 no.4
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• pp.449-465
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• 2008

Coastal lagoon has experienced a natural geomorphic development process which has been aggraded after the climax of transgression in Holocene. This study estimates superiority on landscape conservation of lagoons and degree of landscape changes during the 20th century as conservation ratios of area and shore length, and analyzes the causes of the changes and classifies the lagoons based on the data by case study of the major 7 coastal lagoons(Hwajinpo, Songjiho, Gwangpoho, Yeongrangho, Maeho, Hyangho, and Gyeongpoho) in the middle East Coast of the Korean Peninsular. Based on the conservation ratios of area and shore length, the areal change is in order of Songjiho($0.56km^2$, 92%), Hwajinpo($2.06km^2$, 90%), Yeongrangho($0.96km^2$, 86%), Hyangho($0.32km^2$, 76%), Gyeongpoho($0.90km^2$, 52%), Maeho($0.14km^2$, 50%), and Gwangpoho($0.07km^2$, 32%), and the shore length change is in order of Hwajinpo(11.90km, 100%), Hyangho(3.34km, 90%), Yeongnangho(7.21km, 89%), Gyeongpoho(7.11km, 79%), Songjiho(5.56km, 79%), Gwangpoho(1.16km, 62%), and Maeho(2.16km, 58%). Therefore, the characteristics of landscape changes of the lagoons in the study area can be represented in order of Hwajinpo(Al), Hyangho(A2), Yeongrangho(A3), Songjiho(A4), Gyeongpoho(B4), Gwangpoho(B5), Maeho(B6). Serious process for land use and industrial development has changed landscape around lagoons decreasing the area of coastal plains dramatically up to this century. Because small lagoons such as Maeho and Gwangpoho have experienced severe transformation and destruction, and Gyeongpoho was transformed into artificial lake for urbanization and tourism, they show dramatic landscape change.

• Korean Journal of Ecology and Environment
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• v.44 no.1
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• pp.9-21
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• 2011

This study is conducted to know the change in water environment of Lake Hwajinpo from 2000 to 2008 with physico-chemical parameters; salinity, dissolved oxygen, total phosphorus and total nitrogen and others. And zooplanktons and phytoplanktons were studied from 2007 to 2008. From the water quality data of Lake Hwajinpo from 2000 to 200S; water temperature, salinity, transparency, chemical oxygen demand and dissolved oxygen ranges are $2.8{\sim}29.4^{\circ}C$, 0.23~33.2‰, $0.2{\sim}1.8\;m$, $0.2{\sim}20.2\;mg\;L^{-1}$ and $0.1{\sim}17.4\;mg\;L^{-1}$ and the average values are $18.0^{\circ}C$, 15.7‰, 0.7 m, $5.7\;mg\;L^{-1}$ and $8.0\;mg\;L^{-1}$, respectively. Total phosphorus (TP) and total nitrogen (TN) ranges are $0.024{\sim}0.869\;mg\;L^{-1}$ (average 0.091) and $0.240{\sim}5.310\;mg\;L^{-1}$ (average 1.235). Average TN/TP ratio is 16.4. The annual variations in COD, TP, TN and Chl.${\alpha}$ are compared. COD in 2000 is $4.83\;mg\;L^{-1}$ and 2008 is $1.80\;mg\;L^{-1}$ which is reduced by $0.34\;mg\;L^{-1}$ every year. TP in 2000 is $0.07\;mg\;L^{-1}$ and 2008 is $0.05\;mg\;L^{-1}$ reduced gradually. Yearly reduction in TN is $0.09\;mg\;L^{-1}$, in 2000 and 2008 the values are $1.54\;mg\;L^{-1}$ and $0.77\;mg\;L^{-1}$ respectivly. Chl.${\alpha}$ in 2000 is $46.30\;{\mu}g\;L^{-1}$ and $5.78\;{\mu}g\;L^{-1}$ in 2008; yearly reduction is $4.50\;{\mu}g\;L^{-1}$. The tropic state index (TSI) in south and north parts of Lake Hwajinpo in 2000 are 67 and 63 which are reduced to 63 and 59 in 2008 respectively. North and south part of Lake Hwajinpo have 67 species of phytoplankton under 47 families in 2007 and 2008. Dominant species in south part in 2007 are; Asterococcus superbus in May, Lyngbya sp. in September and Trachelomonas spp. in November and in 2008 Anabaena spiroides in August are abundant and varies with time. Zooplankton species in Lake Hwajinpo are 25 of 25 families. Dominant species in south part in May and August 2007 and May and November in 2008 Copepoda larvae and in September 2007 Protozoa spp. of Protozoan and Brachionus plicatilis and Brachionus urceolaris of Cladocera in August 2008. Dominant species in north part Asplanchna sp. of Cladecera in August and November 2007 and rest of the time are larvae of Copepoda. In this way, the water quality of Lake Hwajinpo is changing with slow rate in the long period specially nutrients concentration (TP, TN etc) is decreasing.