Abstract The freshwater microalgal species, Gonyostomum semen, has increased in abundance and distribution in boreal lakes during the past few decades, concerning ecologists and water managers. Due to its rapid spread, G. semen has often been referred to as an invasive species, although it was first described in the 1800s. We hypothesized that G. semen is not an invasive species in Norwegian lakes, and that the increasing success is due to beneficial changes in environmental conditions for this species during the past century. We tested these hypotheses by performing a paleolimnological study of a Norwegian Lake, Skjeklesjoen, with known mass occurrence of G. semen. A specific G. semen pigment biomarker, heteroxanthin, was used to detect this species in layers of a sediment core with known age determinations. Environmental factors in both lake and catchment were further investigated and the relationships with the amounts of G. semen was tested. Our results suggested that G. semen was in fact not an invasive species in this lake the past decades. Several factors were identified as plausible drivers for G. semen in this boreal lake. Between 1874-2016, the increasing levels of G. semen in Lake Skjeklesjoen was most closely correlated with Carbon (C), lake color (measured as absorbance of sediment extracts), Nitrogen (N) and spring temperature. Our results suggest that the rapid increase in G. semen population in this boreal lake over the past 70 years was probably due to a combination of climate change and local anthropogenic activities in the catchment, causing increased browning and increased inputs of organic matter and nutrients.

中文翻译：

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Gonyostomum semen（Raphidophyceae）在北方湖泊中的成功是由于环境变化而不是最近的入侵

摘要 在过去的几十年中，淡水微藻物种 Gonyostomum semen 在北方湖泊中的丰度和分布有所增加，这引起了生态学家和水资源管理者的关注。由于其迅速传播，G. semen 经常被称为入侵物种，尽管它在 1800 年代首次被描述。我们假设 G. semen 不是挪威湖泊中的入侵物种，并且越来越多的成功是由于过去一个世纪该物种的环境条件发生了有益的变化。我们通过对挪威的 Skjeklesjoen 湖进行古湖泊学研究来检验这些假设，该湖已知大量存在 G. semen。一种特定的 G. 精液色素生物标志物异黄质用于在已知年龄测定的沉积物核心层中检测该物种。进一步调查了湖泊和集水区的环境因素，并测试了与 G. 精液量的关系。我们的结果表明，在过去的几十年里，G. semen 实际上不是这个湖中的入侵物种。有几个因素被确定为这个北方湖中 G. 精液的合理驱动因素。1874 年至 2016 年间，Skjeklesjoen 湖中 G. semen 水平的增加与碳 (C)、湖色（以沉积物提取物的吸光度测量）、氮 (N) 和春季温度最密切相关。我们的研究结果表明，过去 70 年来这个北方湖泊中 G. semen 种群的快速增加可能是由于气候变化和流域当地人为活动的共同作用，导致褐变增加以及有机物质和营养物质的输入增加。