9:00 AM - 9:15 AM
[ACG45-01] Seasonal basin-scale variability of diatoms in surface waters of the North Pacific with their controlling environmental factors
Keywords:Phytoplankton, Diatoms, North Pacific Ocean, Ocean warming
Diatoms, considered one of the most ecologically and biogeochemically important phytoplankton, contribute around 20% of global primary productivity through photosynthesis and play a significant role in the exchange of carbon between the ocean and the atmosphere. However, the sizeable spatiotemporal variability of diatoms and their controlling environmental factors are still poorly understood. Here we show the seasonal basin-scale distribution patterns of diatoms in surface waters of the North Pacific between Japan and North America, as estimated from quantitative PCR (qPCR) assays targetting diatom-specific 18S rRNA gene fragments. These surface DNA samples have been collected by ship-of-opportunity observations using the M/V New Century 2 since September 2014. Diatom-specific 18S rRNA gene copies from spring to summer were significantly higher than those in fall or winter, indicating the occurrence of spring-summer diatom blooms. Meridional changes in the surface diatoms were somewhat unclear, as estimated with the 18S rRNA gene copies. Increases in seawater temperature and macronutrient concentrations (nitrate plus nitrite, phosphate, and silicate) in the subarctic region affected the diatom-specific 18S rRNA gene copies negatively and positively, respectively. Additionally, the sea surface height (SSH) anomaly estimated from satellite remote sensing was negatively correlated with the gene abundance in subarctic waters, indicating the influence of mesoscale eddies, which are frequently observed in the study area, on the diatom distribution. Our results suggest that surface diatoms in the subarctic region could be particularly vulnerable to ocean warming.