• 한국해양학회지
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• v.14 no.1
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• pp.15-25
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• 1979

A study on field bioassay test using four species of commercially important shellfish was carried out to assess the effect of pollutants and determine the extent of marine environmental pollution of the Masan Bay from 9 to 15 August 1978. Water quality analysis and planktological examination of sea water were made during the experiment and the examination gave the following results. The water temperature was so high at 31.7$^{\circ}C$ in maximum and rather subject to change on weather condition of the land than on the effect of the water mass from outer bay. The range of DO,COD and SS at the stations were 0.3-7.08cc/l, 0.07-3.31ppm and 5.5-117ppm, respectively with the high values of COD and SS at the stations 7 and 1. The concentrations of the dissolved inorganic nitrogen in sea water, NH$\sub$4/-N, NO$\sub$2/-N, NO$\sub$3/-N, and PO$\sub$4/-P were 18.90-99.80, 2.48- 19.60, 13.00-39.00 and 1.04-14.0$\mu\textrm{g}$ at/l, respectively with decrease of their values in the outer part of the Bay. The high values mentioned above were caused by the sewage and industrial activities. The effects of organic waste are increased oxygen demand, nutrient concentration, turbidity and a higher input of pathogens, leading to structural changes in the marine ecosystems and to a considerable hazard to public health. The percentage composition of phytoplankton standing crop between diatom and dinoflagellate was characterized by making a difference between the two groups in respect of location: a decrease of diatom and a increase of dinoflagellate in numerical abundance toward inner part from outer part of the bay. Namely phytoplankton organisms were composed of 80% of diatom and 20% of dinoflagellate in outer bay, on the contrary, only 4% of diatom and 96% of dinoflagellate occupied by 94% of prorocentrum micans known as tolerant species to polluted reaas in the inner bay. On the occurrence and composition of zooplankton, there are two significant communities in the bay:one is characterized by the predominance of Oithona nana and the other by Favella sp They were composed of a range from 84% to 90% of the total organisms and monotonously constituted of themselves only at most inner station 3 even small numbers. From the results mentioned above, Oithona nana, Favella and prorocentrum micans recommed themselves as valuable indicators for judging the extent of the marine pollution.During the period of the biossays Mytilus edulis showed the highest mortality and Tapes japonica the lowest one between the four test species. The highest death rate by stations was found at most inner stations 3'and 4near Masan Free Export Zone with the most sensitive response and the lowest one occured at outer station 13 where no death specimen of oyster and arkshell was found during the whole test period.As for mussel,85 percent death rate appeared after 72 hours and 100percent rate after 120hours at station 4. It was found that the significant high mortality of the test shellfish mentioned above was caused by severe pollution with mainly organic pollutants from domestic sewage and industrial wastes from the results of too much higher concentrations of dissolved inorganic nitrogen especially ammonia-N,COD,SS and lack of dissolved oxygen,and furthermore occurrence and abundance composition of Prorcentrum,Favella and Oithona nana by stations, valuable indicator species of coastal pollution by orgnic and boilogical pollutants.

• Korean Journal of Ichthyology
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• v.34 no.3
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• pp.186-200
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• 2022

In order to understand the species composition and distribution characteristics of larval assemblages in the East Sea, Korea, larvae were collected at 13 stations every other month from February to December 2018. Fish larvae were identified through DNA barcoding along with morphological methods, and as the result, a total of 104 taxonomic groups appeared during the survey. Among these, Engraulis japonicus, which accounted for 76.2% of the total population, was the most dominant species, followed by Maurolicus japonicus, which accounted for 15.0%. In addition, Ammodytes personatus, Champsodon snyderi, Scomber japonicus and Echelus uropterus appeared more frequently than other taxa. The above six species accounted for 93.2% of the total catch. The number of taxa and the amount of larvae collected in the survey area were higher during the high water temperature periods (June to October) than during the low water temperature periods (February, April and December). Analysis of similarity (ANOSIM) showed a statistically significant difference in monthly larval assemblages. The results of the canonical correspondence analysis (CCA) show that the distributions of larval community were mainly affected by sea surface temperature during low water temperature periods, and various environmental factors such as salinity, dry weight of zooplankton, and the concentrations of nutrients during high water temperature periods.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.10 no.4
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• pp.243-258
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• 1977

1 The coastal area between Youngdo and Jodo was a common coastal water not much different from other coastal waters before the construction of the breakwater between them. 2. The breakwater between the two islands shuts off the tidal currents and divides the area . into the two small isolated bays to create quite different environments. 3. To understand the differences between then, present study examined some environmental factors such as water temperature, salinity, dissolved oxygen, transparency, and major nutrients, phosphates, sillicates and nitrites and the phytoand zooplankton. The samplings were carried out monthly from March 1976 to February 1977 at 4 stations: 2 stations in each bay. 4. Some differences were observed in the environmental factors such as water temperature, salinity, dissolved oxygen and transparency between the two bays. 5. The distribution and occurence of nutrient salts of the two bays were distinctly different each other. Northern Bay had $138\%$ of nutrients in comparison with Southern Bay. 6. Phytoplankton in Northern Bay was about $200\%$ plentier than in Southern Bay. 7. Zooplankton in Southern Bay was about $180\%$ richer than in Northern Bay. 8. One of the pollution indicator species, Synedra ulna, was observed in Northern Bay and the occurence of Euglena sp. and ciliates were much higher in Northern Bay than in Southern Bay, but, in contrast, Sagitta sp. was more abundant in Southern Bay than in the other. 9. The areas of the two bays seem to be in its way to eutrophication especially in Northern Bay. 10. The two bays have been differentiated enough to identify each other.

• Ocean and Polar Research
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• v.32 no.3
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• pp.269-289
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• 2010

In Summer 2008, a multidisciplinary survey was conducted onboard R/V Haeyang 2000 to understand plankton response to the three distinct physico-chemical settings that developed in the Ulleung Basin of the East Sea. Baseline settings of hydrographic conditions included the presence of the thin (<20 m) Tsushima Surface Water (TSW) on top of the Tsushima Middle Water (TMW). It extends from the Korea Strait to $37^{\circ}N$ along the $130^{\circ}E$ and then turns offshore and encompasses the relatively saline (T>$26^{\circ}C$, S>33.7) Ulleung Warm Eddy surface water centered at $36.5^{\circ}N$ and $131^{\circ}E$. A relatively colder and saline water mass appeared off the southeastern coast of Korea. It was accompanied by higher nutrient and chlorophyll-a concentrations, suggesting a coastal upwelling. Most of the offshore surface waters support low phytoplankton biomass (0.3 mg chl-a $m^{-3}$). A much denser phytoplankton biomass (1-2.3 mg $m^{-3}$) accumulated at the subsurface layer between 20-50 m depth. The subsurface chlorophyll-a maximum (SCM) layer was closely related to the nutricline, suggesting an active growth of phytoplankton at depth. The SCM developed at shallow depth (20-30 m) near the coast and deepened offshore (50-60 m). A fucoxanthin/zeaxanthin ratio was high in coastal waters while it was low in offshore waters, which indicated that diatoms dominate coastal waters while cyanobacteria dominate offshore waters. The community structure and biomass of phytoplanktonare closely related to nitrogen availability. Zooplankton biomass was higher in the coastal region than in the offshore region while species richness showed an opposite trend. Zooplankton community structure retained a coastal/offshore contrast. These suggest that summer hydrography is a stable structure, lasting long enough to allow a hydrography-specific plankton community to evolve.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.4
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• pp.527-536
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• 1996

The patterns of diel horizontal migration (DHM) of 7 copepod species are compared as part of a general investigation of the zooplankton adaptations to the surf zone habitats. In a sandy shore surf zone of Yongil Bay, 3 sites such as the bottom and surface of 1 m water depth and water's edge are sampled with a sledge net(n=108). The surf zone copepod assemblage is dominated by 7 species; Acartia hudsonica, Fseudodiaptomus marinus, Paracalanus indicus, Calanus sinicus, Oithona similis, Sinocalanus tenellus and Labidocera bipinnata. Threefold variations in copepod abundance are observed within a diel cycle. Abundances of 7 dominant species and total copepods captured in the surface exhibit significant diel differences, but those taken in the bottom are not significantly affected by diel period. It is shown that about $90\%$ of the surf zone copepods performed DHM. The nocturnal high densities of copepods occurred for a neap tide when the offshore winds prevailed, suggesting the animals' ability for horizontal orientation and an active locomotion without invoking passive transportation by currents. Photoreactive behavior of copepods triggered by relative changes in light intensity may be a primary factor inducing DHM by aggregating in the surf zone during the night and spreading out at day; then copepods may reduce encounters with visual predators. In A. hudsonica, ontogenetic variations in timings of DHM are evident. Such variations are likely to minimize intraspecific competition for diets. Data on shoreward migration of copepods indicate that A. hudsonica, P. indicus, O. similis and S. tenellus can maintain swimming velocities of about $20m\;h^{-1}$ for durations of more than an hour. Our observations of strong diel difference in abundances point out the need for both day and night samplings in surf zone habitats, if the importance of these habitats to planktonic copepods are to be fully understood.

• Journal of Environmental Impact Assessment
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• v.26 no.6
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• pp.404-417
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• 2017

In this study, we analyzed response patterns of rotifer community to eutrophic state, and estimated the applicability of rotifer community as an environmental indicator for highly eutrophicated reservoirs. In order to evaluate the relationships among spatial and temporal distributions and the water quality of rotifer community, we selected the Jundae Reservoir and Chodae Reservoir in Chungcheongnam-do, Korea, which are geographically adjacent but have different water quality, particularly in their eutrophic states. For the analyses on their correlations, monthly survey of water quality and rotifer community, was conducted from April to November 2013 in both reservoirs. The rotifer community was divided into different compositions of functional groups as well as species. Functional groups were classified according to the structure and shape of trophi which can represent feeding behavior of rotifer genus. To reflect ecological characteristics of species, body size and habitat preferences were also considered. Species-based composition did not show a consistent tendency with water quality parameters related with eutrophication. On the contrary, functional group composition showed relatively clear group-specific patterns, increasing or decreasing according to the parameters. The results suggest the possible application of rotifer functional group composition as an indicatorforthe lentic systems, especially hyper-eutrophicated reservoirs. The present study can suggest the applicability based on the field observations from the limited time scale and sites, and further studies on feeding behavior of the rotifer functional group and its interactions with environmental variables are necessary for the further application.

• Ecology and Resilient Infrastructure
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• v.7 no.1
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• pp.72-81
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• 2020

Blooms of the small centric diatom Stephanodiscus is quite occasional in winter season in temperate freshwater ecosystems. Often, it leads to degradation of water quality and affects quality of supplied drinking water. In previous studies, naphthoquinone (NQ) compounds have been shown to be effective and selective for controlling winter bloom species Stephanodiscus hantzschii. We conducted a 5 ton scale mesocosm experiment to investigate the effects of NQ on native Stephanodiscus sp. collected from Nakdonggang River in water. After treatment with NQ 4-6 compound (0.2 μM), the cell density of Stephanodiscus sp. was rapidly reduced from 5 × 10³ cells mL^-1 to 0.2 × 10³ cells mL^-1 for 10 days. Additionally, NQ 4-6 compound did not affect physicochemical factors (water temperature, dissolved oxygen, pH, conductivity, nutrients) and biological factors (bacteria, heterotrophic nanoflagellates, zooplankton). Therefore, these findings suggest that the NQ 4-6 compound has potential as an alternative algicidal substances to effectively mitigate natural Stephanodiscus sp. blooms, and the application of NQ 4-6 compound will restore the healthy aquatic ecosystems.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.1
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• pp.9-15
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• 2012

Worldwide development of harmful algal blooms causes serious problem for public health and fisheries industries. To evaluate the algicidal impact on the harmful algae bloom species in aquatic ecosystems of coast, a new algicide thiazolidinedione derivative (TD49) were tentatively examined in the growth stages (i.e., lag, logarithmic and stationary phase) of rapidophyceae $Heterosigma$ $akashiwo$, $Chattonella$ $marina$ and $Chattonella$ sp..Three strains could easily destroy in the lag phase due to relatively weak cell walls than those of the logarithmic and stationary phase. It is thought that inoculation of TD49 substances into initial or developmental natural blooms with a threshold concentration ($2{\mu}M$) can maximize the algicidal activity. Also, bio-chemical assays revealed that the algicidal substances from all culture strains were likely to be extracellular substances because those cells have easily destroyed in cell walls. On the other hand, natural zooplankton communities were influenced within the exposure experiments of $2{\mu}M$, which is showed the maximum algcidal activity of tested organisms. These results indicate that although the TD49 substance is potential agents for the control of $H.$ $akashiwo$, $C.$ $marina$ and $Chattonella$ sp. in the enclosed eutrophic bay and coastal water, more detailed research of acute toxicity effect on high trophic organism in marine ecosystems need to be conducted.

• Journal of Wetlands Research
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• v.6 no.1
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• pp.149-166
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• 2004

Water quality and ecological environment in the Han River estuary was analyzed using the longterm water quality monitoring data from National Fisheries Research and Development Institute (NFRDI) and the existing data collected in this area. Based on the salinity distribution and changes of current direction in the lower Han River and its estuary, boundaries of the estuary were identified and also, distribution patterns of the phyto- and zooplankton, benthos, ichthyoplankton and fish were discussed related with the salinity changes in the macrotidal subestuary of Han River. Seasonal and spatial distribution of salinity suggested that the direct impact of freshwater be limited to the Incheon North Harbour all the year round and even extended to the southern area of Gyunggi Bay near Palmi island during limited time, usually in summer. Upper limit of salt water intrusion through the Han River is likely to be Singok underwater dam located Gimpo, Gyunggi Province, and normally limited to much lower part of the river, Jeonryuri, Gimpo. Biological boundaries of the Han River estuary exceeded the physical boundaries based on the salinity distribution. Many estuarine species in plankton and fish were found at the totally freshwater or saltwater depending on the seasons and tidal cycles. Some estuarine ichthyoplanktons showed extremely limited distributions in the estuary whereas adult fish revealed wide ranges of salinity adaptation. Critical environmental issues in the Han River estuary and its drainage basin are likely to be 1) pressure on development-promoted district for new town in the drainage area of the estuary, 2) reduction of tidal flat by reclamation, 3) pollutant input through river from municipal sewages and industrial wastes, and 4) ecological barrier between river and terrestrial systems by the military wire fence and riverside road.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.6
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• pp.459-471
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• 1991

The community structure and micro-scale distribution of plankton in relation to hydrography were investigated in Masan Bay, Korea in October 1989. Warmer and less saline waters with stratification was located in the inner part of the Pudo Strait, and chlorophyll-a and nutrients were higher. Both phytoplankton biomass and nutrients was changed dramatically around the Strait. Offshore/oceanic species in phytoplankton i.e., Chaetoceres decipiens, Rhizosolenia stolterforthii, Rhizosolenia styliformis and Ceratium trichoceros and zooplankton i.e., Sagitta enflata, Oncaea uenusta and Oikopluera longicaudata occurred mainly in well mixed waters of the outer part. This suggests that discontinuous layer seems to play an important role as an approximate border for the plankton population. This layer was located between Station 3 and Station 4 near the Pudo Strait, since the layer consisted of a series of micro-scale discontinuties of salinity and dissolved inorganic nutrients gradient. Phytoplankton patchs of more than 801e1 were found only in the inner part of the bay. Depletion of silicate caused by a rapid assimilation of phytoplankton in the inner part of the bay seemed to be responsible for the decline of blooms.