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• Four key phenological transition dates in central and northern Japan were evaluated. • AHI phenological transition dates were evaluated against those from MODIS and PEN. • The uncertainty in AHI phenological transition dates differ between Spring and Fall. The Advanced Himawari Imager (AHI) onboard the recently launched next generation geostationary satellite, Himawari-8, provides an opportunity to improve Land Surface Phenology (LSP) detections over the Asia-Pacific region. In this paper, we detected four phenological transition dates (PTDs) using the three-day Two-band Enhanced Vegetation Index (EVI2) time series from AHI based on the Hybrid Piecewise Logistic Model-Land Surface Phenology Detection (HPLM-LSPD) algorithm. The four PTDs are Start of Spring (SOS), End of Spring (EOS), Start of Fall (SOF) and End of Fall (SOF). We evaluated the four AHI-derived PTDs against those detected using eight-day EVI2 time series from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the polar-orbiting satellite Terra, and three-day Green Chromatic Coordinate (GCC) time series from the Phenological Eyes Network (PEN) at six sites in central and northern Japan. The evaluation was performed by conducting regression analyses, and calculating root mean square difference (RMSD) and bias between satellite- and PEN-derived PTDs. First, the difference in the spatial variations of SOS and EOF timing between naturally vegetated areas, and urban areas and croplands indicates the anthropogenic footprints on LSP. Second, the RMSD of either AHI PTDs or MODIS PTDs against PEN PTDs were higher in the fall (i.e., SOF and EOF) than those in spring (i.e., SOS and EOS). Third, the later EOS and earlier SOF derived from satellite EVI2 relative to those derived from PEN GCC might be caused by the difference in the sensitivity of GCC and EVI2 to the increases in leaf area index (LAI) over high-LAI canopies. Fourth, the higher temporal resolution of AHI EVI2 only helped reduce the RMSD during spring compared to the RMSD for MODIS. In contrast, the RMSD for AHI PTDs and MODIS PTDs were comparable in fall. Finally, the between-sensor correlation in the spatiotemporal variability of the four PTDs was higher for SOS and EOF than those for EOS and SOF. [ABSTRACT FROM AUTHOR]

During ice melt in spring, ice algae are released from the ice and could be exposed to variable temperatures and irradiances in surface water. Saroma Lagoon is an embayment with two inlets leading to the Sea of Okhotsk. With seasonal development of sea ice, its water temperature changes dramatically throughout the year. To investigate the living and photoprotective strategies of ice algae in such a coastal water system, we grew Nitzschia cf. neglecta, an ice diatom isolated from the sea ice of this lagoon, under irradiance levels of 30 and 100 μmol photons · m -2  · s -1 , and temperatures of 2°C and 10°C. Then the acclimated cells were exposed to high light in order to investigate the plasticity of their photosynthetic apparatus. At 10°C, cells grew faster and showed decreased susceptibility to high light. At 2°C, an immediate decrease in all pigment content upon exposure, as well as a higher cellular content of diatoxanthin was used to compensate for the more severe excitation stress. Highly efficient photoprotection was achieved through the diadinoxanthin-diatoxanthin cycle-dependent nonphotochemical quenching. While regulation through psbA and rbcL at the transcription level played a minor role in the response to high light stress at both temperatures. The wide tolerance to both temperature and light changes suggest that the thinning of sea ice and higher temperatures in a warmer world will lead to more intense blooms in Saroma Lagoon., (© 2019 Phycological Society of America.)