Skeletonema costatum, Chaetoceros didymus, Alexandrium tamarense 그리고 Heterosigma akashiwo의 인 제한에 따른 용존태 유기인(dissolved organic phosphorus; DOP)의 이용성과 alkaline phosphatase(APase)의 활성을 살펴보기 위해 실내실험을 실시하였다. S. costatum, C. didymus, A. tamarense 그리고 H. akashiwo는 인 공급원으로써 용존태 무기인 (dissolved inorganic phosphorus; DIP) 이외에 phosphomonoester와 nucleotide 화합물을 이용하여 성장을 유지할 수 있었다. S. costatum, C. didymus, A. tamarense 그리고 H. a/wshiwo의 APase 활성은 배양액내의 DIP가 각각 $0.30;{mu}M$, $0.33;{mu}M$, $2.04;{mu}M$과 $0.63;{mu}M$에서 최초로 활성을 보였으며, 최대활성은 각각 $0.01;pmol;cell^{-1};hr^{-1}$, $0.11;pmol;cell^{-1};hr^{-1}$, $1.63;pmol;cell^{-1};hr^{-1}$와 $0.19;pmol;cell^{-1};hr^{-1}$였다. APase 활성은 종에 따라 다르게 나타났지만, 최대 활성은 DIP의 흡수속도보다도 높아 인이 제한된 환경에서 효과적으로 DOP를 가수분해하여 성장을 유지 할 수 있을 것으로 보인다. 따라서 DOP의 이용능력은 적조 플링크튼의 성장뿐만 아니라 종간경쟁에도 기여할 것으로 생각된다.
Utilization of dissolved organic phosphorus (DOP) and alkaline phosphatase (APase) activity by Skeletonema costatum, Chaetoceros didymus, Alexandrium tamarense and Heterosigma akashiwo under the phosphorus deficient condition were examined in the laboratory. S. costatum, C. didymus, A. tamarense and H. akashiwo could make use of phosphomonoester and nucleotide compounds for the growth of them as a phosphorus source. APase activity of S. costatum, C. didymus, A. tamarense and H. akashiwo began to be activated at dissolved inorganic phosphorus (DIP) concentrations less than $0.30;{mu}M$, $0.33;{mu}M$, $2.04;{mu}M$ and $0.63;{mu}M$ respectively, and their maximum APase activity were $0.01;pmol;cell^{-1};hr^{-1}$, $0.11;pmol;cell^{-1};hr^{-1}$, $1.63;pmol;cell^{-1};hr^{-1}$ and $0.19;pmol;cell^{-1};hr^{-1}$, respectively. Although each phytoplankton species displayed different APase activity for DOP utilization, their maximum APase activities were higher than maximum phosphorus uptake rates, inferring that these species might be able to keep growing under DIP-limited conditions thought utilizing effectively the hydrolized product of DOP. This result also implies that utilization of DOP might contribute to not only the growth of red tide forming phytoplankton but also the interspecific competition among phytoplankton species in coastal environments.
