Abstract Identifying the lacustrine haptophyte species that produce long-chain alkenones (LCAs) is essential for using alkenone unsaturation ratios to create lake water temperature reconstructions. We discovered LCAs in the brackish Lake Takahoko in northern Japan. The identity of LCA-producing species was investigated using 18S ribosomal DNA (rDNA) and organic geochemical analysis. Two distinct genetic groups, termed Tak-A and Tak-B, were identified within the Group II haptophyte phylotype. Tak-A was closely related to Hap-A, which was obtained from Lake George, USA; and Tak-B was identified as Isochrysis galbana. Because Hap-A and Isochrysis galbana have similar temperature calibrations, Tak-A and Tak-B were also expected to share similar calibrations. Therefore, the changes of their relative abundances in the lake should not significantly disturb paleotemperature reconstructions. The alkenone temperature recorded in the surface sediment corresponded to the lake temperature in early to late summer. This is likely related to the haptophyte bloom season in Lake Takahoko suggesting that this lake may be a viable location for creating a lacustrine alkenone paleotemperature record.

中文翻译：

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日本高穗湖河口长链烯酮生产者的基因组和地球化学鉴定：对温度重建的影响

摘要 鉴定产生长链烯酮 (LCA) 的湖相触生植物物种对于使用烯酮不饱和度比创建湖水温度重建至关重要。我们在日本北部微咸的高穗湖中发现了 LCA。使用 18S 核糖体 DNA (rDNA) 和有机地球化学分析研究了产生 LCA 的物种的身份。两个不同的遗传组，称为 Tak-A 和 Tak-B，在组 II 触须植物系统发育型中被鉴定。Tak-A 与 Hap-A 密切相关，Hap-A 来自美国乔治湖；Tak-B 被鉴定为 Isochrysis galbana。由于 Hap-A 和 Isochrysis galbana 具有相似的温度校准，因此预计 Tak-A 和 Tak-B 也具有相似的校准。所以，它们在湖中相对丰度的变化不应显着干扰古温度重建。表层沉积物中记录的烯酮温度与夏初至夏末的湖泊温度相对应。这可能与 Takahoko 湖的触手植物盛开季节有关，这表明该湖可能是创建湖泊烯酮古温度记录的可行地点。