Hyeong Kyu Kwon

Ecological significance of alkaline phosphatase activity and phosphatase-hydrolyzed phosphorus in the northern part of Gamak Bay, Korea.

We investigated the ecological significance of alkaline phsophatase (APase) and alkaline phosphatase-hydrolyzable phosphorus (APHP) in the northern part of Gamak Bay, Korea. APase activity was detectable throughout the year, and dissolved inorganic phosphorus (DIP) concentration and APase activity are highly correlated and can be regarded as an indicator of DIP-limiting conditions. Also, a strong linear positive correlation between APase activity and Chl a concentration indicated that the major part of APase activity may have been induced by phytoplanktons. The APHP proportion in dissolved organic phosphorus (DOP) was above ca. 30% from winter to spring and below ca. 15% from summer to autumn due to freshwater discharge and uptake by phytoplankton. APHP may play an important role in species competition in coastal area such as northern part of Gamak Bay where DIP is limiting. Thus, APase induction by phytoplanktons may be ecologically significant, allowing dominance by these organisms under DIP-limiting conditions.

Distribution of Water Masses and Distribution Characteristics of Dissolved Inorganic and Organic Nutrients in the Southern Part of the East Sea of Korea: Focus on the Observed Data in September, 2011

2011년 9월에 동해의 수괴 분포와 용존 무기 및 유기 영양염의 분포 특성을 파악하였다. 수온, 염분, 용존산소의 분포를통하여 연구해역의 수괴 기원은 WM(water mass)-I, WM-II, WM-III, WM-IV 등 4개의 대표적인 수괴로 구분되었으며, 그 성격은 각각 대마난류표층수, 대마난류중층수, 북한한류수, 동해고유수와 유사하였다. 용존 영양염의 경우, 용존무기 질소(DIN; dissolved inorganic nitrogen)와 용존 무기 인(DIP; dissolved inorganic phosphorus)은 WM-IV에서 가장 높았으며, WM-III, WM-II, WM-I 순으로 나타났다. 반면에 용존 유기 질소(DON; dissolved organic nitrogen)와 용존 유기 인(DOP; dissolved organic phosphorus)은 무기 영양염과 상반되는 분포를 보였다. 연구해역에서 수괴 전체에대한 DIN : DIP 비는 약 15.8로 Redfield ratio(16)에 근접한 수치를 보이고 있으나, 혼합층의 경우 5.3으로 무기질소가식물플랑크톤 성장의 제한 요인으로 작용할 수 있는 것으로 보였다. 하지만 무기 질소가 제한된 혼합층에서 DON은 용존 총 질소(DTN; dissolved total nitrogen) 중 약 70%를 구성하였다. 따라서 풍부한 DON은 동해에서 식물플랑크톤의성장을 위한 중요한 영양염 공급원으로 판단된다.Abstract − Distribution characteristics of water masses, dissolved inorganic and organic nutrients were investi-gated in the southern part of the East Sea of Korea in September, 2011. On the basis of the vertical profiles of tem-perature, salinity and dissolved oxygen, water masses in the study area were divided into 4 major groups, such asWM (water mass)-I, WM-II, WM-III, WM-IV. Their characteristics were similar to Tsushima Surface Water (TSW),Tsushima Middle Water (TMW), North Korea Cold Water (NKCW) and East Sea Proper Water (ESPW), respec-tively. In the vertical profiles of dissolved nutrients, dissolved inorganic nitrogen (DIN) and dissolved inorganicphosphorus (DIP) concentrations were highest in the WM-IV, followed by WM-III, WM-II, WM-I. On the con-trary, distribution of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) were highest inthe WM-I, followed by WM-II, WM-III, WM-IV. Although the DIN : DIP ratio in all of the water masses was sim-ilar to Redfield ratio(16), the DIN : DIP ratio in mixed layer was about 5.3, indicating that inorganic nitrogen is thelimiting factor for the growth of phytoplankton. However, the DON proportion in dissolved total nitrogen (DTN)was about 70% in the mixed layer where inorganic nitrogen is limiting factor. Thus, enriched DON may play animportant source of the nutrient for the growth of phytoplankon in the East Sea.Keywords: East Sea(동해), Water mass(수괴), Dissolved inorganic nitrogen(용존 무기 질소), Dissolved inorganicphosphorus(용존 무기 인), Dissolved organic nitrogen(용존 유기 질소), Dissolved organic phosphorus(용존 유기 인)

Dominance and Survival Strategy of Toxic Dinoflagellate Alexandrium tamarense and Alexandium catenella Under Dissolved Inorganic Nitrogen-limited Conditions

Abstract − Dominance and survival strategy of toxic dinoflagellate Alexandrium tamarense and A. catenellaunder the dissolved inorganic nitrogen (DIN) limited conditions were examined in the laboratory and fieldobservations. In Masan Bay, DIN was limiting factor for growth of phytoplankton during spring to early summerwhen Alexandrium spp. have been observed. They have a disadvantageous position compared with diatomsbecause Ks of nitrate calculated from growth kinetics experiment of A. tamarense and A. catenella was higherthan diatoms. However, A. tamarense and A. catenella were able to grow using dissolved organic nitrogen (DON)compounds such as urea and amino acids as well as DIN. Therefore, DON utilization of A. tamarense, A.catenella might contribute to not only their population growth but also dominance and interspecific competitionin the DIN-limited conditions in Masan Bay.Keywords: Alexandrium tamarense, Alexandrium catenella, dissolved inorganic nitrogen (DIN; 용존무기질소),dissolved organic nitrogen (DON; 용존유기질소 )

Phytoremediation by benthic microalgae (BMA) and light emitting diode (LED) in eutrophic coastal sediments

In this study, we examined whether phytoremediation using benthic microalgae (BMA) and a light emitting diode (LED) can remediate eutrophic sediments caused by promoting the growth of BMA. A field application experiment was conducted from September 9 to December 3, 2011, in Masan Bay, Korea. Two chambers were used: an experimental site, which included a red LED (650 nm) lamp and replanted Nitzschia sp. on the surface sediment, and a control site, which did not contain an LED lamp and replanted Nitzschia sp. on the surface sediment. Chlorophyll a (Chl. a) concentration increased at the experimental site, and was 2 times the concentration at the control site. Acid-volatile sulfide (AVS) concentration decreased at the experimental site, with a removal rate of AVS as high as 28%. In addition, the removal rates of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) were as high as 19% and 24%, respectively. The removal fluxes for DIN and DIP were 2.02 mg N/m2/day and 0.22 mg P/m2/day, respectively, at the experimental site, and 0.88 mg N/m2/day and 0.10 mg P/m2/day, respectively, at the control site. These changes indicate that oxygen produced by the replanted Nitzschia sp. may have enhanced aerobic bacterial activity, and the nutrients may have been taken up by the Nitzschia sp.. Therefore, phytoremediation using BMA and LED shows potential as a novel and eco-friendly method for the remediation of eutrophic coastal sediments.

Effects of Temperature and Salinity on the Growth of Marine Benthic Microalgae for Phytoremediation

Abstract − To improve sediment quality in eutrophic coastal areas using benthic microalgae, we examined theeffects of temperature and salinity on the growth of benthic microalgae Achnanthes sp., Amphora sp., Naviculasp. and Nitzschia sp. isolated from Sujeong Bay, Korea, using batch cultures. The maximum growth rates wereobtained under the combined temperature and salinity conditions of 25 o C and 25 psu for Achnanthes sp. (0.60/day), 15 o C and 25 psu for Amphora sp. (0.56 /day), 20 and 30 psu for Navicula sp. (0.53 /day), 20 o C and25 psu for Nitzschia sp. (0.48 /day). Considering these results of temperature and salinity conditions requiredfor optimum growth (≥ 70% of maximum specific growth rate), Amphora sp. Navicula sp. and Nitzschia sp.were characterized as eurythermal and euryhaline species, while Achnanthes sp., which exhibited extremely lowsurvival at low temperature. In conclusion, Amphora sp., Navicula sp. and Nitzschia sp. may be useful speciesfor phytoremediation, to control eutrophication and hypoxic water and thus improve environmental conditionsof polluted coastal areas.Keywords: Benthic microalgae(저서미세조류), Achnanthes sp., Amphora sp., Navicula sp., Nitzschia sp.,Growth(성장), Temperature(수온), Salinity(염분), Phytoremediation(식물환경복원 )