• 한국해양학회지
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• v.28 no.2
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• pp.107-113
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• 1993

Interrelationship between bacterial and phytoplankton variables and associations of this relationship with phytoplankton community structure were studied from July, 1990 to October, 1991 in the estuarine system of Mankyung and dongjin Rivers where estuarine mixing is very active. During the study period only bacterial production and chlorophyll were always significantly correlated (r$^2$>0.36, p<0.02), suggesting that phytoplankton-biomass related process seemed to be related to bacterial production in the estuarine waters. However, bacterial production comprised only a small fraction (on average<2.6) of primary production throughout the study period, suggesting that those parameters were uncoupled. this might be partly due that phytoplankton, food particles for zooplankton, food particles for zooplankton, were mostly composed of large and/or chain-forming diatoms.

• Ocean and Polar Research
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• v.41 no.3
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• pp.135-145
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• 2019

We investigated the mass occurrence of the salp Salpa fusiformis during spring in the southern waters of Korea and the northern East China Sea. Abundance of S. fusiformis and dominant taxonomic groups including copepods, ostracods, euphausiids, and appendicularian was examined along with environmental factors (e.g., temperature, salinity, and chlorophyll-a concentration). The abundance of S. fusiformis at 27 stations ranged from 0 to $183\;inds\;m^{-3}$. Both aggregate and solitary forms of S. fusiformis occurred with a mean abundance of $62\;inds\;m^{-3}$ and $4\;inds\;m^{-3}$, and mean body length of 6.5 mm and 15.4 mm, respectively. Redundancy analysis showed that the abundance of S. fusiformis was negatively correlated with chlorophyll-a concentration, indicating the intensive grazing impact of S. fusiformis on phytoplankton. While the abundance of S. fusiformis increased, the species diversity of zooplankton community decreased. The abundances of total copepods and the dominant copepod species (e.g., adults and/or copepodites of Paracalansus parvus s.l., Calanus sinicus, Oithona similis, and Corycaeus affinis) also decreased with the increase of S. fusiformis abundance. However, the abundance of ostracods, euphausiids, and appendicularians was not affected by the mass occurrence of the salps. These results suggest that the mass occurrence of S. fusiformis in spring could negatively affect ecosystem conditions by changing trophodynamics in the zooplankton community.

• Korean Journal of Ecology and Environment
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• v.41 no.4
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• pp.519-529
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• 2008

Recent studies reveal one of the representative endocrine disrupters of nonylphenol affects on the composition of a planktonic community. Since nonylphenol is sometimes discharged into eutrophic waters, we monitored planktonic community composition of a eutrophic pond after receiving nonylphenol when cyanobacterium Microcystis aeruginosa mainly dominated. The experiment was carried out two times using small-scale microcosms in a laboratory. In both two experiments, ciliate abundances significantly decreased when nonylphenol was added. On the seventh day, the ciliate abundances in $10{\mu}g\;L^{-1}$ added treatments decreased by 36.9% in the first experiment and 33.6% in the second, when compared to the control. The response of other planktonic groups was less obvious to nonylphenol addition. In particular, in the first experiment, Chl. b/Chl. $\alpha$ and Chl. c/Chl. $\alpha$ significantly increased with the addition of nonylphenol, while total Chl. $\alpha$ concentration did not change. Indeed, bacillariophyceae and chlorophyceae abundances tended to increase with nonylphenol dosing. From these results, we tentatively hypothesized that nonylphenolloading positively affects on abundances of edible phytoplankton such as Scenedesmus spp. and diatoms by releasing from grazing pressure due to decrease in ciliate abundances. The present study emphasizes that the indirect effect of endocrine disrupters should be paid more attention when freshwater resources are polluted by them.

• The Korean Journal of Ecology
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• v.22 no.6
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• pp.337-342
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• 1999

Rotifer grazing rates in both species and community levels on bacteria and phytoplankton were determined by using representative models (fluorescent beads: 0.75$\mu m$ for bacteria and 10 $\mu m$ for phytoplankton) at biweekly intervals. One-year study at the lower part of the Nakdong River (Mulgum) indicated that the seasonal pattern of rotifer biomass was similar to that of total zooplankton biomass. Total mean biomass of rotifers was significantly higher than that of other groups (rotifers, 148$\pm $327 $\mu g$C/l; cladoceran. 25$\pm 69$$\mu g$C/l; copepodids. 58$\pm 159$$\mu g$C/l). For laboratory grazing experiments. mean specific filtering rate (SFR: $ml\cdot \; l^{-1}\cdot \; day^{-1}$) for rotifers varied from 0.001 to 0.726, and > 90% individuals of rotifer species took up fluorescent microspheres. The high SFRs were achieved by Brachionus angularis, B. calyciflorus, and Filinia longiseta. Community filtering rates (CFRs, $ml\cdot \; l^{-1}\cdot \; day^{-1}$) varied in the range from 2 ~ 1,670. Rotifer filtering rates on phytoplankton were much higher than bacterial filtering rates, especially in the late growing season (May. June, and November). Rotifers appear to be important in transferring both bacterial and phytoplankton carbon to higher trophic levels at the lower Nakdong River.

• Korean Journal of Environmental Biology
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• v.22 no.1
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• pp.1-11
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• 2004

Ecological methods were reviewed through reports such as environmental impact assessment and damage effect of fishery in the Korean watershed. Survey items in marine ecological field were included: phytoplankton, zooplankton, benthic animal, algae, adult fish, egg and juvenile of fish. A standardization of survey method in the field of community ecology was suggested to consider the convenience, Sequency in Use of device, accuracy of data collected from that. It is necessary that spatial data should be sufficiently acquired toy statistical analysis of biodiversity and spatial comparison. Quantitative sampling method must be inevitably adopted based nature of biota and geographical type of the survey area. The same sampling method can make the data compared spatially but can't be applicable in all area. Standardizing survey method should be by no means under certain restriction of study and would become different according to survey environments. The first thing is minutely understanding about ecological character of biota inhabiting in certain area, and then determining survey method.

• Korean Journal of Environmental Biology
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• v.33 no.1
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• pp.19-26
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• 2015

Pre-monsoon dynamics of zooplankton community were investigated in the estuary of the Tamjin River flowing into the Doam Bay of the southern coast of Korea. Monthly sampling was carried out to collect zooplankters at five sites in the estuary and the river during the period between March and June 2014. Dissolved oxygen contents were low between $5.0{\sim}7.0mgL^{-1}$ in the estuary and high, 7.0~11.0, in the river. Water temperature increased gradually from 12.0 to $28.0^{\circ}C$ and pH fluctuated between the range 7.4~8.8, respectively. A total of 85 taxa consisted of 25 species of rotifer, 30 kinds of copepod, 8 species of cladoceran, six kinds of aquatic insect larvae, four kinds of decapod and two kinds of Cirripedia larvae and Polychaeta larvae and one kind of Amphipoda, Ispopoda, Appenidicularia, Nematoda and Cnidaria, and Nocticluca scintillans was occurred. Brackish copepods distributed at almost all studied sites with freshwater zooplankters being restricted to upper waters of the river. Monthly succession of Acartia spp. was observed in the estuary with the occurrence of A. hudsonica in March and April then A. omori in May and June. Zooplankton abundance showed to vary from 450 to $87,818ind\;m^{-3}$ due to the explosion of copepodite and copepod nauplius in the estuary. Species diversity indices varied between 0.6~2.3 and generally low in the estuary and high in the river. Sea water input into the river seems to affect the river biota for more than some kilometers of the upper waters of the Tamjin River.

• Ocean and Polar Research
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• v.30 no.3
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• pp.303-312
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• 2008

Despite the impacts of the climate changes on the pelagic ecosystem, few studies have examined the pelagic-benthic coupling in the adjacent East China Sea and Korea Strait. Therefore, the species composition and abundance of the macrobenthic community, as well as the potential food sources of benthic fauna were investigated in the present study using stable isotope analysis (${\delta}^{13}C\;and\;{\delta}^{15}N$) for suspended particulate organic matter (SPOM), sedimentary organic matter (SOM), phytoplankton, and zooplankton. A total of 157 macrobenthic fauna were collected, and the density of the macrobenthic fauna ranged from 4 to 434 ind./0.25 $m^2$, with an average density of 149 ind./0.25 $m^2$. The density of the benthic fauna increased moving from offshore shelf sites to coastal sites adjacent to the Korea Strait. Cluster analysis showed that the macrobenthic communities consisted of three distinct groups: group A in the Korea Strait, group B in the East China Sea, and group C near Ieodo. The dominant species in group A were the amphipods Photis japonica and Ampelisca miharaensis, followed by the polychaete Scolotoma longifolia. Environmental variables, such as the temperature of the seawater and sediment, and oxygen, and chlorophyll a levels, appeared to affect the structure of the community, suggesting the importance of coupling with the pelagic system. The ${\delta}^{13}C$ values of SPOM and zooplankton ranged from -22.97 to -23.5% and -19.92 to -21.86%, respectively, showing a relatively narrow range(<1%) between the two components. The difference between the ${\delta}^{13}C$ values of SOM and pelagic organic matter was also within 1%, suggesting that the SOM originated from the pelagic system, which is an important factor controlling the macrobenthic community.

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.319-331
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• 2004

This study was conducted to evaluate the ecological impact of freshwater bivalve (Corbiculidae) on plankton communities in experimental enclosure systems (2 m ${\times}$ 2 m ${\times}$ 2 m). During the acclamation period of one month, cyanobacteria, including Microcystis viridis and Microcystis aeruginosa, dominated in both control and treatment enclosures with no noticeable density difference. After the addition of 100 mussels, dominant species of phytoplankton shifted from Microcystis to Scenedesmus in concert with slight decrease in the cell density and the increase of N/P ratio. However, cell density in the control quickly increased, accompanied with changes of dominant species to Oscillatoria spp. With the introduction of additional 500 musseles in the treatment enclosure, dominant phytoplankton species in both enclosures were replaced with Selenastrum spp. and Cryptomonas sp. In the initial stage, the total zooplankton abundance in the control was higher than that of treatment, but it was reversed after the addition 100 mussels. After mussel density increased up to 600 indivisuals, zooplankton density in the treatment decreased with dominance of small taxa, such as rotifers and nauplius. However, abundance and carbon biomass of large zooplankton, such as Bosmina longirostris and Diacyclops thomasi were maintained in a high level compared with those of control. During the study period, Chl. a concentration in mussel treatment and control increased with DIP and $NH_3-N$, respectively. Due to the increase of $NH_3-N$, especially after the introduction of additional 500 mussels, nitrogen limitation did not occur in the treatment enclosure in contrast with strong nutrient limitation occurred in the control. These results indicate that filter-feeding Corbicula could exert important impact on nutrient recycling and plankton community structure in a freshwater ecosystem, through direct feeding and competition for the same food resource as zooplankton on one hand, and through alteration of nutrient availability on the other.

• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.366-373
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• 2000

Toxin production and low digestibility of cyanobacteria are known to cause low exploitability of cyanobacteria by zooplankton. In this study, we compared relative tolerance and compatibility of zooplankton taxa in eight eutrophic lakes, exposed to frequent cyanobacterial blooms, uring the summer season of 1999. Microcystis, Anabaena, Oscillatoria and Phormidium were common cyanobacteria in all lakes. with relatively lower $NO_3-N$ concentration (<0.2 mgN/l) and TN/TP ratio (<20), compared with other lakes where colonial cyanobacteria dominated. Rotifers were dominant zooplankton in most lakes, and among them, Keratella, Polyarthra and Hexathra were common. The laboratory feeding experiment showed that relative copepods that greatly decreased (90%) after 4 day when cyanobacteria were used as the food source of zooplankton, while rotifers gradually increased with the change of dominant taxa from Keratella through Pompholyx to Monostyla. These results suggest that rotifers may be capable of coexisting with cyanobacteria by exploiting them for the food source.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.5
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• pp.424-437
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• 1993

About three fourths of total variability of zooplankton in Asan Bay was associated with season and the difference between inner bay and outer bay was relatively small. However, the differences in percent compositions of major taxa at inner bay and outer bay increased gradually with time, suggesting the change of ecosystem in this bay due to the human exploitation such as reclamation. Seasons of maximum abundances were different among the taxa but consistent for each taxon throughout the three survey years. Calanus sinicus and Acartia bifilosa showed maximum abundance in spring. Sagitta crassa, Paracalanus parvus, A. pacifica, Tortanus spinicaudatus, Corycaeus affinis and Decapoda larva were most abundant in summer. Labidocera euchaeta and Bivalve larva appeared most abundantly in fall. But in winter no taxon showed maximum. In general, low abundance with many species in fall, low abundance and few taxa in winter, increase in both number of taxa and abundance in spring, and high abundance and many taxa in summer were observed. A hypothesis for the observed patterns was suggested although more evidences were needed to support this.