A study on the kinetic parameters, Vmax and Km of algal alkaline phosphate

Article信州大学理学部附属諏訪臨湖実験所報告 9: 161-168(1995)departmental bulletin pape

Eutrophication and the primary productivity of phytoplankton in Lake Soyang, Korea.

Article信州大学理学部附属諏訪臨湖実験所報告 9: 155-159(1995)departmental bulletin pape

The change from phosphorus-limitation to nitrogen-limitation by eutrophication of Lake Soyang.

Article信州大学理学部附属諏訪臨湖実験所報告 9: 111-120(1995)departmental bulletin pape

The distribution of cyanobacterial toxins in Korean lakes

Cyanobacterial blooms in eutrophic lakes often produce algal toxins causing death of livestock, wild animals, and fish. In this work, phytoplankton communities were examined for the appearance of toxic species. The occurrence of toxic bloom was examined with mouse bioassay. Phytoplankton were collected in late summer at the surface of 6 middlestream reservoirs(Soyang, Chungju, Daechong, Jangsung, Hapchon, Jinyang, Okjung), an estuarine reservoir(Yongsan), and a coastal lagoon(Yonglang). Algal cells were freeze-dried for the use in mouse bioassay and chemical analysis. The occurrence of toxic bloom was examined with mouse bioassay and the content of two cyanobacterial hepatotoxins, microcystin-RR and -LR, that are known to be most common in freshwater algae were analyzed with HPLC. In all the study lakes cyanobacteria were dominant phytoplankton. The dominant species implied the possibility of toxin production(Microcystis, Anabaena etc.). In L. Soyang and Chungju, dominant species were Anabaena and Oscillatoria, respectively. In L. Jangsung and Daechong, Anabaena and Microcystis appeared together. Test of toxicity by mouse bioassay showed lethal effect for L. Yonglang, L. Hapchon, L. Yongsan, L. Jangsung. L. Yonglang showed strong lethal effect. Microcystin-LR and -RR both were detected in L. Hapchon, L. Jangsung and L. Yonglang, and microcystin-LR was detected in L. Yongsan, -RR was detected in L. Daechong, L. Chungju, and L. Soyang.Article信州大学理学部附属諏訪臨湖実験所報告 9: 169-174(1995)departmental bulletin pape

Long-term variations of water quality and phosphorus loading in Lake Andong, Korea

Tropic state parameters were measured in a reservoir (Lake Andong, Korea) from 1993 to 2000. Phosphorus loading from the watershed was estimated by measuring total phosphorus concentration in the main inflowing stream (the Nakdong River). Phosphrus discharge of the pen-type fish farms was estimated from the amount of fish feed supplied annually and the rate of phosphrus excretion per feed weight. Minimum transparency in summer was only about 2.0m in 1993 and 1994, but it decreased to about 1.2m in 1997 and 1998, and recovered to about 2.3m in 1999 and 2000. TP increased from 11～30 mgP/m³ in 1993 to 18～42 mgP/m³ in 1998, but recovered to 8～13mgP/m³ in 2000, whereas TN decreased slightly from1.81～2.96mgN/L in 1993 to 1.17～1.80mgN/L in 2000. TN/TP ratio decreased from 82～281 in 1993 to 21～143 in 1998, but again increased to 101～209 in 2000 due to the decrease of TP. The average chlorophyll a concentration in growing season was in the range of 4.8-16.2mg/m³ from 1993 to 1997, but it decreased to 3.7-5.2 mg/m³ after 1998. The major cause of the trophic state recovery is thought to be the removal of fish farms in April 1998.Article信州大学山地水環境教育研究センター研究報告 2: 131-134(2004)departmental bulletin pape

Eutrophication and succession of phytoplankton in reservoir of Korea - monthly variations of plankton community in Lake Soyang

The community of plankton and the environmental factors were investigated in Lake Soyang from January to July 1994. The relationship between transparency and biovolume of phytoplankton was negatively correlated. Phytoplankton dominants in Lake Soyang were Anabaena spp., Microcystis aeruginosa, Asterionella formosa, Asterionella gracillima Melosira distans, Synedra acus, and Asterococcus limneticus, Zooplankton dominants were Polyarthra spp., Keratella spp., Asplanchna placentula, Bosmina coregoni, and Daphnia longispona. Phytoplankton and zooplankton were clearly related each other with respect to biovolume, not to numbers. Microcystis aeruginosa rapidly increased and Daphnia longirostris disappeared in July, because Microcystis aeruginosa secret toxic substances to Daphnia longirostris. Transparency decreased from January to June, but increased in July. The highest number of phytoplankton was obserbed in April, and one month later, the zooplankton reached a maximal level in population density, implicating that spring bloom of phytoplankton was good feeding condition for zooplankton.Article信州大学理学部附属諏訪臨湖実験所報告 9: 175-186(1995)departmental bulletin pape

The limnological survey of a coastal lagoon in Korea: Lake Hwajinpo

Physicochemical parameters, plankton biomass, and sediment were surveyed from 1998 to 2000 on two months interval in a eutrophic costal lagoon (Lake Hwajinpo, Korea) segregated from the sea by a sand dune. Littoral zone is well developed and floating-leaved aquatic plants also thrive, A shallow sill divides the lake into two basins. It has permeation of seawater and chemoclines formed by salinity were observed at 1m demth all the year around. DO was often very low(＜1mgO₂/L) at hypolimnion. Temperature inversions were observed in November. Transparency was 0.2～1.7m. Nitrate and ammonium concentrations were very low (＜0.1mgN/L), even though TN was usually 2.0～3.5mgN/L. TN/TP was generally lower than the Redfield ratio. TSI was 63～74, COD, TP, and TN of sediment were 3.1～40.3mgO₂/g, 0.9～1.39mg/m³. Two basins showed different phytoplankton communities with Oscillatoria sp., Trachelomonas sp., Schiaochlarnys gekatinosa, and Anabaena spiroides dominant in South basin, and with Trachelomonas sp., Schroederia sp., Schizochlamys felatinosa, and Trachelomonas sp. dominant in the North basin. The seasonal succession of phytoplankton was very fast, possibly due to sudden changes in physical characteristics such as wind, turbidity, salinity and light, etc.Article信州大学山地水環境教育研究センター研究報告 2: 127-130(2004)departmental bulletin pape

Determining the probability of cyanobacterial blooms: the application of Bayesian networks in multiple lake systems

A Bayesian network model was developed to assess the combined influence of nutrient conditions and climate on the occurrence of cyanobacterial blooms within lakes of diverse hydrology and nutrient supply. Physicochemical, biological, and meteorological observations were collated from 20 lakes located at different latitudes and characterized by a range of sizes and trophic states. Using these data, we built a Bayesian network to (1) analyze the sensitivity of cyanobacterial bloom development to different environmental factors and (2) determine the probability that cyanobacterial blooms would occur. Blooms were classified in three categories of hazard (low, moderate, and high) based on cell abundances. The most important factors determining cyanobacterial bloom occurrence were water temperature, nutrient availability, and the ratio of mixing depth to euphotic depth. The probability of cyanobacterial blooms was evaluated under different combinations of total phosphorus and water temperature. The Bayesian network was then applied to quantify the probability of blooms under a future climate warming scenario. The probability of the "high hazardous" category of cyanobacterial blooms increased 5% in response to either an increase in water temperature of 0.8°C (initial water temperature above 24°C) or an increase in total phosphorus from 0.01 mg/L to 0.02 mg/L. Mesotrophic lakes were particularly vulnerable to warming. Reducing nutrient concentrations counteracts the increased cyanobacterial risk associated with higher temperatures

Impacts of Land Use Change and Summer Monsoon on Nutrients and Sediment Exports from an Agricultural Catchment

Agricultural non-point source (NPS) pollution is a major concern for water quality management in the Soyang watershed in South Korea. Nutrients (phosphorus and nitrogen), organic matter, and sediment exports in streams were estimated in an agricultural catchment (Haean catchment) for two years. The stream water samples were taken in dry and rainy seasons to evaluate the effect of monsoonal rainfall on pollutants exports. The influence of land use changes on NPS pollution was assessed by conducting a land use census and comparing the NPS characteristic exports. Total phosphorus (TP), suspended solids (SS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) increased dramatically in rainy seasons. Land uses were changed during the study period. Dry fields and rice paddies have decreased distinctively while orchard (apple, grape, and peach) and ginseng crops showed an increase within the catchment. The TP and SS loading decreased in the streams in 2010 compared to the loading in 2009 while the BOD and NO3− did not show distinct significant change. In this study, monsoonal driven rainfalls increased exports of agricultural NPS pollutants into streams. Land use change (mostly crop and paddy fields to orchards and ginseng fields) remarkably mitigated TP and SS exports into the streams