An algal assay procedure using an indigenous phytoplankton assemblage was tested to estimate the propagation of red tide phytoplankton species and determine the optimal time interval at which to measure growth yield in eutrophic marine waters where red tides frequently occur. Various red tide phytoplankton species were propagated on a large scale by adding nitrogen or phosphorous. This procedure was useful for estimating the limiting nutrient, elucidating the mechanisms underlying red tides, and determining the levels of increases in organic matter in eutrophic coastal waters. The algal assay using indigenous C. polykrikoides showed that this species did not always propagate, apparently because of very low concentrations of trigger elements that are necessary for its growth, rather than as a result of other environmental characteristics, e.g., water temperature or stress from sampling. In the winter, when water temperatures are lower than in spring, summer, or autumn, maximum propagation and the limiting nutrient could be estimated by measuring phytoplankton biomass at 2–3-day intervals. However, in the other seasons, when water temperatures are higher, phytoplankton biomass should be measured at 2-day intervals. In particular, daily monitoring will be required to determine precise growth yields in warm seasons.

적토로부터 활성화시킨 물질에 대한 적조구제제로서의 가능성에 대하여 연구하였다. 적토는 보오크사이트로부터 알루미나를 생산하기 위해 사용되는 베이어 공정의 부산물로써 적철석, 보에마이트, 방해석, 소달라이트, 석영, 저어콘, 아나타제 및 미지의 광물 등 다양한 광물로 구성되어 있다. 중금속 흡착실험결과, As (92%)를 제외한 모든 중금속이 거의 100%에 가까운 높은 흡착률을 보였다. 이는 중금속에 대한 철산화물의 높은 흡착능력에 기인된 것으로 사료된다. 적토에 대한 pH (pH 1∼13)별 용출률 측정 결과, 산성에서 As, Cu 및 Zn가 높은 값을 보임으로써, 적토를 산처리 할 때, 중금속 제거 효과가 탁월함을 지시하였다. 적토의 산처리 산물인 활성적토는 적철석 및 보에마이트 등으로 구성되어 있으며, 온도가 증가할수록 중금속의 제거 효과가 증가하였다. 활성적토는 입도가 수십 nm로써, 5종의 적조에 대한 적조구제 효율을 측정한 결과, 구제효율은 pH특히, 반응 후 pH에 반비례하였다. 이들 5종의 프랑크톤 중, Prorocentrum minimum 및 Alexandrium tamarense의 경우, 살포 즉시 90% 이상을 그리고 약 30분 후에는 거의 100%에 가까운 구제효율을 보임으로써, 활성적토가 이들 적조에 대한 우수한 구제제로서의 가능성을 지시하고 있다.

해조류의 증식에 가장 큰 영향을 주는 것은 증식에 필요한 영양소와 적절한 수온 등 성장환경을 적절하게 유지시킬 필요가 있으나 해조류의 종류가 매우 다양하여 이들 각각에 개별적으로 대처하는 것이 매우 어렵다. 그러므로 본 연구에서는 실제의 미생물이 서식하고 있는 원수를 이용하여 적절한 온도를 유지시켜 미생물의 증식을 촉진시키고 이러한 미생물의 개체수를 측정하는 센서를 개발하였다. 이 센서를 이용하면 해조류의 양이 갑자기 증가하는 초기상황을 찾아낼 수 있으므로 해조류의 급격한 증식을 미리 예측할 수 있다.

We studied the appearance and proliferation of red tide organisms from March, 1998, to February, 1999, in the Jindong Bay. There were two red tide events during investigation, and we found that the dominant species Ceratium furca in May and Gymnodinium sanguineum in September, 1998. At surface, temperature and salinity showed 18.3∼19.7℃ and 30.6∼30.9 psu in May and 25.6∼27.0℃, 28.0∼28.5 psu in September, respectively. When the red tide occurred, the water mass was stable. Dissolved inorganic nitrogen(DIN) and dissolved inorganic phosphate(DIP) in Jindong Bay showed seasonal variability. In May, the nitrogen was a limited nutrient in which the ratio of DIN versus DIP was less than 16 (Redfield ratio), while in September phosphate. During June to September, 1998, phosphate acted as a limited nutrient due to the increased river run-off from land. In May, chlorophyll-a, dissolved oxygen(DO) and chemical oxygen demand(COD) showed higher than 20㎍/ℓ, l0㎎/ℓ and 5.0㎎/ℓ, respectively. In September, they showed in turns 100㎍/ℓ, 10㎎/ℓ and 10㎎/ℓ, respectively.

The effect of UV on the mortality rate of toxic dinoflagellate Amphidinium carterae causing a red tide in the coastal area of south Korea was investigated in the batch and continuous-scale reactor equipped with ultraviolet irradiation-apparatus. Degussa P25 titanium oxide, a photocatalyst proved to be effective for the mortality of Amphidinium carterae supplied with photocatalyst and UV radiation were greater than 95% in 2 minutes of UV radiation and the rate were higher than that by UV-radiation without titanium dioxide in the batch and continuous-flow scale reactor. The mortality time of Amphidinium carterae increased with the cell density under UV-illumination in the batch scale reactor. The mortality rate in the density of 5.0×104 cells/mL at the same experimental condition was more than 90% in 4 minutes in the continuous flow scale reactor. The percentage of 99.9±0.1% of Amphidinium carterae in the density of 5.0×104 cells/mL was died in 20 minutes when the phytoplankton was illuminated with UV-radiation without photocatalyst.

The relationship between the distribution of sea surface temperature(SST) and dinoflagellate(Cochlodinium polykrikoides) bloom areas were studied. The SST data were derived from the infrared channels of AVHRR(Advanced Very High Resolution Radiometer) sensor on NOAA(National Oceanic and Atmospheric Administration) 12 and 14 satellites during 1995-1998. The initial water temperature at C. polykrikoides bloom was about 21℃ at the coastal areas of the South Sea and along the shore of the East Sea of Korea during the summer season of 1995. The northern limit of red tides was coincident with that of 21℃ isothermal line in the East Sea. The red tides that initially bloomed at the coast of Pohang on September 21, 1995 moved to the coast of Uljin on September 26, 1995. The skipped appearance of the red tides in the areas between Pohang and Uljin was due to the East Korean Warm Current, which was moving offshore from Pohang to approach to Uljin. The cold water which was formed by tidal front in the western coast of the South Sea and by upwelling water from deep layer in the southeastern coast of the Korean peninsula played a role in blocking the spreading of red tides during summer season in 1997 and 1998. In conclusion, the distribution of red tides appeared to be dependent on the initial water temperature at red tides bloom. The SST at the red tides varied from 21℃ to 25℃ ; 21℃, 23℃, 24℃ and 24-25℃ in 1995, 1996, 1997 and 1998, respectively.