Influences of regime shifts on microbial nitrogen removal and retention in hypereutrophic intertidal ecosystems

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K12224
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 63010:Environmental dynamic analysis-related
• Research Institution: Toho University
• Principal Investigator: Senga Yukiko 東邦大学, 理学部, 准教授 (30434210)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 硝化 / ヒドロキシルアミン / 富栄養化 / 干潟

Outline of Final Research Achievements

In this study, to explore the site of active nitrification and elucidate the factors controlling nitrification, hydroxylamine concentrations in the seawater and porewater of the hypereutrophic Yatsu tidal flat, eastern Japan, were measured. The concentrations from 2021 to 2022 indicated that nitrification was more active in the surface sediment than in seawater. In addition, multiple linear regression analysis indicated that nitrification in the surface sediment increases with higher temperature and NH4+ supply from seawater and porewater, as well as under oxic conditions. Sediment denitrification by which N is removed is controlled by the occurrence of nitrification. Therefore, nitrification in the sub-aerobic surface sediment is crucial for N removal. Especially in the hypereutrophic tidal flat, the sub-aerobic surface sediment needs to be protected so as not to inhibit nitrification when seawater is stagnant.

Free Research Field

生物地球化学

Academic Significance and Societal Importance of the Research Achievements

本研究の当初の目的は，15Nトレーサー法を用いて微生物的窒素除去過程(硝化-脱窒，硝化-アナモックス)と貯留過程(硝化-DNRA)を追跡する予定であったが，コロナ感染対策により同位体測定装置を使用する予定であった研究機関への出入りが禁止され，計画通りに研究を遂行することができなかった．しかしながら，本研究で用いたヒドロキシルアミンの測定によって，硝化過程の進行を十分に明らかにすることができることがわかった．ヒドロキシルアミン測定法は，15Nトレーサー法よりも短時間かつ低コストで行うことができる．またこの方法は測定操作も簡便であるため，今後様々な環境下で硝化を評価する際に応用できると考えられた．