북서태평양에서 diazotrophs와 질소고정율 분포연구

Abstract

Diazotrophs로 불리는 질소고정 식물플랑크톤들은 해수 중에서 질소고정을 통해 암모니아를 생성함으로서 해양 유광대의 일차생산력 및 탄소순환에 중요한 역할을 한다. 이러한 생태계에서의 중요한 역할로 인해 열대 대양을 중심으로 전지구적인 질소고정율과 diazotrophs의 다양성 및 분포등에 대한 연구가 활발히 진행되고 있다. 본 연구는 질소고정에 대한 연구가 부족한 북서태평양을 대상으로 해역별 질소고정율과 diazotrophs의 다양성 및 주요 우점종의 분포 특성을 밝히고자 하였다. Pyrosequencing 방법을 이용한 분석결과 총 60,837개의 nifH 유전자 염기서열을 얻을 수 있었다. 얻어진 염기서열은 0.97의 DNA 유사도를 기준으로 총 241개의 OTU로 분류되었다. 이들 염기서열은 cyanobacteria와 다양한 proteobacteria에 속하는 것으로 나타났다. 열대와 아열대 수역에서는 cyanonacteria인 Crocosphaera, UCYN-A, Trichodesmium이 우점하였다. 이들 주요 그룹은 뚜렷한 생물지리적 분포 특성을 나타냈다. Crocosphaeara는 열대의 저위도 해역에서 우점하였으며, 위도가 증가하며 UCYN-A가 우점하였고, Trichodesmium은 쿠로시오수역에서 우점하였다. 이러한 결과는 수온에 따라 분포가 구분되는 기존 연구 결과와 일치하였다. 질소고정율은 정점에 따라 11.6∼1,106.4 μmol N m−2 d−1의 변화를 나타냈다. 동중국해 정점이 평균 15.3μmol N m−2 d−1으로 낮았고, 열대수역이 638.5μmol N m−2 d−1로 높은 값을 보였다. Diazotrophs의 분포를 고려할 때 Crocosphaera가 열대 해역의 높은 질소고정율에 영향을 미친 것으로 사료된다. 이 연구에선 북서태평양의 diazotrophs의 다양성과 주요 우점종 및 질소고정율을 파악하였다. 또한 북서태평양의 열대수역에서 Crocosphaera에 의해 매우 높은 질소고정이 발생함을 밝혔으며, 이 결과는 전 지구적 질소 고정 연구의 진행방향을 결정하는데 중요한 지표가 될 것으로 판단된다.| Nitrogen fixing phytoplankton groups called diazotrophs fix nitrogen in the sea waters and convert to ammonia which is biologically more useful form of nitrogen. This is important part of marine nitrogen cycle and plays essential role in the primary production and carbon cycle in the photic zone of marine environment. Because emerging significance of nitrogen fixation by diazotrophs in the marine ecosystem, very active investigations are being carried to better understand the global nitrogen fixation rates as well as diversity and distribution of diazotrophs mostly centering around the tropical open ocean. The present study examined nitrogen fixation in the northwestern Pacific Ocean which lack information on nitrogen fixation than other regions. The present study attempted to determine nitrogen fixation rates for different types of water in the study areas, diversity of diazotrophs and distributional characteristics of dominant species observed during the study period. Using pyrosequencing method, the analyses obtain total of 60,837 nifH gene reads. The obtained sequences alignment is based on 0.97 DNA similarity and separated into total of 241 OTUs. These sequences seemed to belong to cyanobacteria and diverse proteobacteria groups. Cyanobacteria such as Crocosphaera, UCYN-A, Trichodesmium seemed to be dominant in the tropical and sub-tropical waters. These important groups clearly showed biogeographical distribution. Crocosphaera sp. were dominant in the tropical and low latitude waters. As latitude increases, UCYN-A became the dominant group. The results of this study confirmed that various reported studies that distribution is related to the changes in temperature range. The nitrogen fixation rates were different among sampling stations ranging 11.6∼1,106.4 μmol N m−2 d−1. The lowest nitrogen fixation rates were observed in the East China Sea at average of 15.3μmol N m−2 d−1, and the highest rates were observed at the sampling station of tropical waters at average of 638.5μmol N m−2 d−1. When considering the distribution of diazotrophs, the results indicated that Crocosphaera sp. seemed to contribute a significant rate in high total nitrogen fixation. The present study examined the diversity and dominant species of diazotrophs and their the nitrogen fixation rates in the study area of the northwestern Pacific Ocean. The study also ascertained that the contribution of Crocosphaera sp. in the total nitrogen fixation in the tropical north Pacific Ocean is very high. Thus it is important to continue to study global nitrogen fixation of marine environment and this the current results may help to determine the direction of investigating to global marine nitrogen fixation.; Nitrogen fixing phytoplankton groups called diazotrophs fix nitrogen in the sea waters and convert to ammonia which is biologically more useful form of nitrogen. This is important part of marine nitrogen cycle and plays essential role in the primary production and carbon cycle in the photic zone of marine environment. Because emerging significance of nitrogen fixation by diazotrophs in the marine ecosystem, very active investigations are being carried to better understand the global nitrogen fixation rates as well as diversity and distribution of diazotrophs mostly centering around the tropical open ocean. The present study examined nitrogen fixation in the northwestern Pacific Ocean which lack information on nitrogen fixation than other regions. The present study attempted to determine nitrogen fixation rates for different types of water in the study areas, diversity of diazotrophs and distributional characteristics of dominant species observed during the study period. Using pyrosequencing method, the analyses obtain total of 60,837 nifH gene reads. The obtained sequences alignment is based on 0.97 DNA similarity and separated into total of 241 OTUs. These sequences seemed to belong to cyanobacteria and diverse proteobacteria groups. Cyanobacteria such as Crocosphaera, UCYN-A, Trichodesmium seemed to be dominant in the tropical and sub-tropical waters. These important groups clearly showed biogeographical distribution. Crocosphaera sp. were dominant in the tropical and low latitude waters. As latitude increases, UCYN-A became the dominant group. The results of this study confirmed that various reported studies that distribution is related to the changes in temperature range. The nitrogen fixation rates were different among sampling stations ranging 11.6∼1,106.4 μmol N m−2 d−1. The lowest nitrogen fixation rates were observed in the East China Sea at average of 15.3μmol N m−2 d−1, and the highest rates were observed at the sampling station of tropical waters at average of 638.5μmol N m−2 d−1. When considering the distribution of diazotrophs, the results indicated that Crocosphaera sp. seemed to contribute a significant rate in high total nitrogen fixation. The present study examined the diversity and dominant species of diazotrophs and their the nitrogen fixation rates in the study area of the northwestern Pacific Ocean. The study also ascertained that the contribution of Crocosphaera sp. in the total nitrogen fixation in the tropical north Pacific Ocean is very high. Thus it is important to continue to study global nitrogen fixation of marine environment and this the current results may help to determine the direction of investigating to global marine nitrogen fixation.