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- Title
Phytoplankton blooms in summer and autumn in the northwestern subarctic Pacific detected by the mooring and float systems.
- Authors
Fujiki, Tetsuichi; Hosoda, Shigeki; Harada, Naomi
- Abstract
We conducted in situ observations in the northwestern subarctic Pacific between 2015 and 2020 using a profiling buoy system and a biogeochemical (BGC) Argo float to examine a series of mechanisms for occurrence and termination of phytoplankton blooms in summer and autumn. The summer and autumn blooms with surface chlorophyll (Chl) a concentrations of > 1 mg m–3 were observed roughly in June–July and September–October of each year, respectively. The depth-integrated Chl a in the upper 50 m during the two seasonal blooms reached > 40 mg m–2 and increased more than twice as much as during the non-bloom period of January–April. The summer blooms were induced by increase in water temperature and available light, and were terminated by Fe deficiency in the upper mixed layer due to Fe exhaustion by phytoplankton and decreasing Fe supply from deeper waters. On the other hand, the autumn blooms were probably triggered by Fe resupply from deeper waters due to stratification weakening and turbulent mixing, and were terminated by light limitation due to deepening of vertical mixing and seasonal decrease in solar radiation. Our observations suggest that the summer and autumn blooms are a periodic phenomenon related to changes in environmental factors such as light, temperature, and Fe in this region.
- Subjects
MOORING of ships; ALGAL blooms; TURBULENT mixing; SUMMER; PHYTOPLANKTON; MIXING height (Atmospheric chemistry); SOLAR radiation
- Publication
Journal of Oceanography, 2022, Vol 78, Issue 2, p63
- ISSN
0916-8370
- Publication type
Article
- DOI
10.1007/s10872-021-00628-z