• Ecology and Resilient Infrastructure
• /
• v.4 no.3
• /
• pp.130-141
• /
• 2017

We evaluated the field application feasibility that biologically derived substances (Naphthoquinone derivate: NQ 2-0) can be used for the eco-friendly mitigation of natural harmful cyanobacterial blooms in freshwater. We conducted a 30 ton scale mesocosm experiment to investigate the effects of NQ 2-0 on biotic and abiotic factors in water collected from Gi-heung reservoir. In the mesocosm experiments, the abundance of Microcystis sp. was continuously increased in the control. However, the Microcystis sp. cell density was sharply decreased on the $10^{th}$ day. In the treatment, NQ 2-0 showed the strong and selective algicidal activity toward the target cyanobacteria (Microcystis sp.). Accordingly, the algicidal activity of NQ 2-0 compound increased gradually until $10^{th}$, $15^{th}$ days and algal biomass was decreased to 99.4 and 100 %, respectively. NQ 2-0 compound was not only selective algicidal activity but also the growth of other phytoplankton and increased the Shannon-Wiener diversity index of phytoplankton. In the mesocosm experiments, the dynamics of biotic (bacteria, heterotrophic nanoflagellate, ciliates, zooplankton) and abiotic (water temperature, dissolved oxygen, pH, conductivity, nutrients) factors remained unaffected. These results suggest that NQ 2-0 could be a selective and ecologically safe algicide to mitigate harmful cyanobacterial blooms. In addition, it is believed that NQ 2-0 will play a major role in forming a healthy aquatic ecosystem by facilitating habitat and food supply of aquatic organisms.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.23 no.5
• /
• pp.358-368
• /
• 2011

Responses of plankton populations to nutrient enrichment in mesocosm experiments in Shihwa lake were simulated using FVCOM. Dissoloved oxygen module was added to the FVCOM to simulate impacts of its decreased levels. The ecological model included the major components of the pelagic ecosystem including nutrients, phytoplankton (pico-, nano-, micro-), zooplankton (two groups of protozoa, mesozooplankton), particulate organic matter, dissolved organic matter and bacteria, and was calibrated using trophodynamic data collected from Gyeonggi Bay and Shihwa Lake. The model was able to reproduce major responses of plankton populations to nutrient enrichment, including phytoplankton of different size groups, change of dominance of protozoa from < 20 ${\mu}m$ oligotrichs to scuticociliates, and reponses to bacteria and low levels of dissolved oxygen in water column of the mesocosms.

• Korean Journal of Ecology and Environment
• /
• v.44 no.4
• /
• pp.347-357
• /
• 2011

We examined two reservoirs (Inkyung res. and Joongang res.) and two streams (Kyungan str. and Jecheon str.), all of which were eutrophic, during the 2010 warm season, to evaluate the water quality improvement activity (WQIA) of plant-mineral composite (PMC), which was previously developed to control suspended solids, including cyanobacterial bloom (Kim et al., 2010). We simultaneously measured both solid (S-MCLR) and dissolved microcystin-LR (D-MCLR), before and after PMC treatment, in the Joongang reservoir. Taking water body size and volume into account, we conducted the whole-scale experiment in the Inkyung reservoir, and mesocosm-scale experiments in the other three systems. The WQIAs of PMC were found to be comparatively high in SS (70~81%), TP (75~91%), BOD (65~91%), Chl-a (88~98%), phytoplankton (84~92%) and zooplankton (68~88%), except for the Kyungan stream, which was below 45% in all parameters. After PMC treatment, the concentrations of both SMCLR (47%) and D-MCLR (96%) decreased within two days, suggesting a mitigation possibility of hazardous chemicals such as agrochemicals and endocrine disrupters in the aquatic ecosystem. Our results collectively indicate that PMC is a useful agent to control suspended solids, including nuisance cyanobacterial bloom and their exudates, in an undisturbed water system with a long residence time.

• Korean Journal of Ecology and Environment
• /
• v.50 no.4
• /
• pp.422-431
• /
• 2017

The biogeochemical information of riverine organic matter gives a detailed and integrated recording of natural and anthropogenic activity within a watershed. To investigate the changes in quality and quantity of organic carbon transporting from mountain to ocean via river channels, we estimated the concentrations of dissolved (DOC) and particulate organic carbon (POC), and then traced the source origin of POC using stable carbon isotopes ratio before and after summer rainfalls in the Tamjin River and Ganjin Bay, Korea. Along the small watershed, a total of 13 sites including headwaters, dam reservoir, river and estuary were established for the study. We found some interesting findings in the aspect of distribution of DOC/POC concentration changing their origin sources dynamically flowing downstream. In particular, the river channel transport downstream mainly DOC to river mouth, although upper dam reservoir increased POC concentration by phytoplankton production in summer. Whereas, in the river mouth and estuary, POC was dominated not only by local supply from nearby reed saltmarsh, but also by marine phytoplankton production, respectively. The findings can contribute to increasing the understanding of riverine organic carbon transport in upper large dam and lower open estuary system.

• Korean Journal of Environmental Biology
• /
• v.34 no.3
• /
• pp.151-160
• /
• 2016

To understand size fractioned chlorophyll a and material cycles of coastal ecosystem in Uljin marine ranching area (JMRA) of East Sea, 4 times of survey were conducted from April to November 2008. Picoplankton, nanoplankton and netplankton in the surface of UMRA fluctuated with an annual mean of $0.26{\mu}g\;L^{-1}$ between the lowest value of $0.03{\mu}g\;L^{-1}$ and the highest value of $0.87{\mu}g\;L^{-1}$, annual mean $1.32{\mu}g\;L^{-1}$ between $0.11{\mu}g\;L^{-1}$ and $5.60{\mu}g\;L^{-1}$, annual mean $0.45{\mu}g\;L^{-1}$ between no detected (nd) and $4.68{\mu}g\;L^{-1}$, respectively. And the relative ratio of picoplankton, nanoplankton and netplanktons on the phytoplankton biomass was on annual average 12.9%, 65.0% and 22.1%, respectively. The 10 m layer was similar to the surface. The relative ratio of pico- and nano-plankton was higher throughout the year. That is, the material cycle of UMRA consists of a microbial food web rather than traditional food chain at a lower trophic levels. Primary production is deemed to have a higher possibility of being adjusted by top-down dynamics, such as micro-zooplankton grazing pressure rather than nutrients supply.

• Korean Journal of Environmental Biology
• /
• v.26 no.2
• /
• pp.76-86
• /
• 2008

The seasonal variations of primary production were investigated by phyto-PAM chlorophyll fluorometry as well as classical methods (standing crops of phytoplanktons and chlorophyll ${\alpha}$) in the Beopsu Marsh, Haman-gun, Gyeongsangnam-do. The amounts of turbidity, SS, T-N, T-P, BOD, COD, Ca$^{2+}$ and Cl$^-$ were the highest at the station 3, where located in flowout site of wastewater treated by the filtration plants. The water quality was the third level by the standard of BOD and COD. The amount of chlorophyll a (268.8 mg L$^{-1}$) was the highest at the station 2 in April because the cell density (2,677 cells mL$^{-1}$) of Micractinium pusillum increased suddenly from February (180 cells mL$^{-1}$). The patterns of primary production of phytoplankton by phyto-PAM chlorophyll fluorometry were fallen in with those of standing crops and chlorophyll a of phyto-planktons. The primary production was varied according to stations and seasons. The water environments of the Beopsu Marsh as a natural mounument should be under the control of a regular examination in order to preserve the ecosystem.

• Korean Journal of Ecology and Environment
• /
• v.52 no.3
• /
• pp.192-201
• /
• 2019

While a fairly large amount of organic matter is produced daily via phytoplankton photosynthesis in Lake Paldang, South Korea, knowledge of the role of algal-derived organic matter (OM) as a refractory OM source is not adequate. To understand the contribution of algal-derived OM to the refractory pool, biodegradation experiment and $KMnO_4$ oxidation experiment were conducted for 60 days using $^{13}C$ and $^{15}N$ labeled natural phytoplankton assemblage. The assemblage was collected from Lake Paldang on May 20, 2010. The photosynthetically produced total organic carbon ($TO^{13}C$), particulate organic carbon ($PO^{13}C$), and particulate nitrogen ($P^{15}N$) remained at 26%, 20%, and 17% of the initial concentrations, respectively, in the form of non-biodegradable organic matter. In addition, 12% and 38% of $PO^{13}C$ remained after $KMnO_4$ treatment on Day 0 and 60, respectively. These results indicate that photosynthetic products could be an important source of refractory organic matter after microbial degradation. Moreover, the microbially transformed algal-derived OM could contribute to the oxidation rate of the chemical oxygen demand.

• Korean Journal of Environmental Biology
• /
• v.41 no.3
• /
• pp.179-192
• /
• 2023

In this study, changes in the microbial ecosystem of the Yeongheungdo island coastal waters were investigated for five years to collect basic data. To evaluate the influence of distance from the coast on the microbial ecosystem, four sites, coastal Site (S1) and 0.75, 1.5, and 3 km away from the coast, were set up and the changes in physicochemical and biological factors were monitored. The results showed seasonal changes in water temperature, dissolved oxygen, salinity, and pH but with no significant differences between sites. For nutrients, the concentration of dissolved inorganic nitrogen increased from 6.4 μM in April-June to 16.4 μM in July-November, while that of phosphorus and silicon phosphate increased from 0.4 μM and 2.5 μM in April-June to 1.1 μM and 12.0 μM in July-November, respectively. Notably, phosphorus phosphate concentrations were lower in 2014-2015 (up to 0.2 μM) compared to 2016-2018 (up to 2.2 μM), indicating phosphorus limitation during this period. However, there were no differences in nutrients with distance from the coast, indicating that there was no effect of distance on nutrients. Phytoplankton (average 511 cells mL^-1) showed relatively high biomass (up to 3,370 cells mL^-1) in 2014-2015 when phosphorus phosphate was limited. Notably, at that time, the concentration of dissolved organic carbon was not high, with concentrations ranging from 1.1-2.3 mg L^-1. However, no significant differences in biological factors were observed between the sites. Although this study revealed that there was no disturbance of the ecosystem, further research and more basic data on the microecosystem are necessary to understand the ecosystem of the Incheon.

• Korean Journal of Environmental Biology
• /
• v.28 no.4
• /
• pp.202-211
• /
• 2010

The variations of physico-chemical factors and the species compositions of phytoplanktons were investigated to analyze the marine ecosystem at the depths during summer in the coast of Dokdo (stations DOK 1-3). The mean values of conductivity (48.9 mS $cm^{-1}$), salinity (32.9 psu) and total suspended solids (57.9 mg $L^{-1}$) were the highest in DOK 1. The biomass (Chl-a) of phytoplanktons was the highest in the surface of DOK 1 (2.61 ${\mu}gL^{-1}$). By the means of physicochemical factors (salinity, turbidity, Chl-a, TN, TP and Si), the water estimated in the coast of Dokdo was more eutrophicated than that in 2008. The phytoplanktons were a total of 42 species in Dokdo, which were composed of 33 species (78.6%) for Bacillariophyceae and 9 species (21.4%) for Dinophyceae. The standing crops of phytoplanktons were the highest ($18{\times}10^3$ cells $L^{-1}$) in the surface of DOK 2 and in the surface of DOK 3, while they were the lowest ($2{\times}10^3$ cells $L^{-1}$) at depth of 40 m of DOK1 and at depth of 30 m of DOK 3. The dominant species of phytoplanktons were Chaetoceros castracanei ($6{\times}10^3$ cells $L^{-1}$) in the surface, Rhizosolenia alata f. gracillima ($3{\times}10^3$ cells $L^{-1}$) at depth of 20 m and Protocentrum compressum ($4{\times}10^3$ cells $L^{-1}$) at the depth of 30 m of DOK 1. At the surface of DOK 2, the dominant species was Bacillaria paxillifer ($6{\times}10^3$ cells $L^{-1}$), while it was Hemiaulus indicus ($12{\times}10^3$ cells $L^{-1}$) at the surface of DOK 3. The DOK 1, which is affected by upwelling, whirlpool and circulation due to the East Korean Warm Current, was the most eutrophicated water body among three stations. The monitoring of marine ecosystem in the coast of Dokdo should be continued to propose the alternatives for water quality and species conservation and to purify the eutrophicated water body due to artificial pollutants as well as natural effectors by the global warming, the climatic change, etc.

• Korean Journal of Ecology and Environment
• /
• v.36 no.1 s.102
• /
• pp.48-56
• /
• 2003

This study was evaluated about the seasonal variations of ecosystem in Nammae Reservoir based on the interrelation of physico-chemical characteristics, nutrients, chlorophyll a, b, c and standing crops of phytoplanktons. The amounts of chlorophyll a, b, c were respectively maximum (295 mg/, 9.5mg/l and 48mg/l) at station 1 in June and the standing crop of phytoplanktons was the highest ($1.7{\time}10^5$ cells/1) at stations 3 in July. The range of temperature was $7{\sim}37.4^{\circ}C$. The maxium of pH was $9.9{\sim}10.1$ at all stations in August, the minimum was 7 in September. SS was maximum (308 mg/1) at station 1 in June, while it was minimum (4 mg/l) at the same station in November. The maximal COD and DOC were 33 mg/1 and 16 mg/1 respectively at station 1 in June. As for phytoplanktons, Microcystis aeruginosa, blue-green alga in July${\sim}$August, Scenedesmus acutus, green alga in March${\sim}$May and November${\sim}$January and Cyclotella orientalis, Diatoms in October were dominant species. The amounts of P and Si were generally high in summer, they were low in autumn and winter. Nammae Reservoir assessed by trophic state index was eutrophicated and overtrophicated. These results indicated that Nammae Reservoir was faced with heavy water pollution. As preceding management for the basin of the Reservoir, it will have to be continually studied for an ecosystem reservation.