Sea ice, which forms in polar and nonpolar areas, transmits light to ice-associated (sympagic) algal communities. To noninvasively study the distribution of sea-ice algae, empirical relations to estimate its biomass from under-ice hyperspectral irradiance have been developed in the Arctic and Antarctica but lack for nonpolar regions. This study examines relationships between normalised difference indices (NDI) calculated from hyperspectral transmittance and sympagic algal biomass in the nonpolar Saroma-ko Lagoon. We analysed physico-biogeochemical properties of snow and land-fast sea ice supporting 27 paired bio-optical measurements along three transects covering an area of over 250 m × 250 m in February 2019. Snow depth (0.08 ± 0.01 m) and ice-bottom brine volume fraction (0.21 ± 0.02) showed low (0.06) and high (0.58) correlations with sea-ice core bottom section chlorophyll a (Chl. a), respectively. Spatial analyses unveiled the patch size of sea-ice Chl. a to be ~65 m, which is in the same range reported from previous studies. A selected NDI (669, 596 nm) explained 63% of algal biomass variability. This reflects the bio-optical properties and environmental conditions of the lagoon that favour the wavelength pair in the orange/red part of the spectrum and suggests the necessity of a specific bio-optical relationship for Saroma-ko Lagoon.

中文翻译：

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使用冰下高光谱透射率测定日本北海道 Saroma-ko 泻湖的陆地快速海冰藻生物量

在极地和非极地地区形成的海冰将光传输到与冰相关的（同域）藻类群落。为了非侵入性地研究海冰藻类的分布，北极和南极洲已经建立了从冰下高光谱辐照度估计其生物量的经验关系，但缺乏非极地地区。本研究检查了根据高光谱透射率计算的归一化差异指数 (NDI) 与非极地 Saroma-ko 泻湖中的同域藻类生物量之间的关系。我们分析了雪和陆上快速海冰的物理-生物地球化学特性，支持 2019 年 2 月沿面积超过 250 m × 250 m 的三个横断面进行 27 对生物光学测量。雪深 (0.08 ± 0.01 m) 和冰底盐水体积分数 (0.21 ± 0.02) 显示低 (0.06) 和高 (0.一种（氯。一种）， 分别。空间分析揭示了海冰 Chl 的斑块大小。一种为~65 m，与先前研究报告的范围相同。选定的 NDI（669、596 nm）解释了 63% 的藻类生物量变异性。这反映了泻湖的生物光学特性和环境条件，这些条件有利于光谱中橙色/红色部分的波长对，并表明 Saroma-ko 泻湖需要特定的生物光学关系。