Regulation mechanism of nitrogen cycle by trace metals in the subsurface ocean

2017 Fiscal Year Final Research Report

• Project/Area Number: 16K12586
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Environmental dynamic analysis
• Research Institution: Nagasaki University
• Principal Investigator: TAKEDA Shigenobu 長崎大学, 水産・環境科学総合研究科(水産), 教授 (20334328)
• Co-Investigator(Renkei-kenkyūsha): WADA Minoru 長崎大学, 水産・環境科学総合研究科, 教授 (70292860)
• Project Period (FY): 2016-04-01 – 2018-03-31
• Keywords: 海洋生態 / 物質循環 / 微量金属 / 窒素 / 植物プランクトン

Outline of Final Research Achievements

We tested a hypothesis that iron limitation stimulates nitrite release from phytoplankton cells to the surrounding water near the subsurface chlorophyll maximum (SCM) due to inhibition of nitrite metabolic pathway. The incubation experiments confirmed that the phytoplankton assemblage in the SCM were under iron-limitation. At a station where the primary nitrite maximum (PNM) was observed near the SCM, the iron enrichment resulted in an increase in nitrate consumption and a decrease in nitrite accumulation in the incubation bottles. The bottles incubated under a stronger light intensity also showed similar trend in the nutrient dynamics. These results suggest that the excretion of nitrite by phytoplankton under both iron and light limitation is playing a role for PNM formation. At a station where the SCM was shallower than the PNM, the observed nitrite excretion by phytoplankton assemblage in the bottles was not significant probably due to the severe nitrogen limitation at the SCM.

Free Research Field

海洋生物地球化学