Abstract Biological soil crusts (biocrusts) are terrestrial micro-habitats distributed in drylands and also in temperate coastal dunes. Biocrusts harbor phototrophic and heterotrophic microorganisms in the upper soil layer, which fulfil important ecological functions such as primary production and energy channelling via the microbial loop. Heterotrophic protists, although being an essential component of the microbial food web of biocrusts, have rarely been investigated. Therefore, in the present study, we used the liquid aliquot method (LAM) to assess the abundance and diversity of protists in biocrusts from coastal dunes at the Baltic Sea for the first time. The total abundance of protists ranged between 10 × 103 and 128 × 103 individuals g−1 dry weight. The community was dominated by naked amoebae (54 %) and flagellates (44 %). The most common taxa were Spumella-like flagellates (Stramenopiles), Paracercomonas-like amoeboflagellates, and Sandonidae-like glissomonads (both from the phylum Cercozoa) as well as heteroloboseans. Despite significant differences in the beta diversity of protist morphotypes, the measured environmental drivers, such as pH, total organic carbon, nitrogen, and phosphorus did not explain these differences. Also, the geographical distance could not predict the community dissimilarity, suggesting that the diversity of protists in biocrusts is controlled by biotic or other physicochemical parameters.

中文翻译：

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无论土壤因素如何，原生藻菌和尾蚴在生物土壤结皮的异养原生生物群落中占主导地位

摘要 生物土壤结皮（biocrusts）是分布在旱地和温带沿海沙丘中的陆地微生境。生物结皮在上层土壤中含有光养和异养微生物，它们通过微生物回路实现重要的生态功能，例如初级生产和能量通道。异养原生生物虽然是生物结壳微生物食物网的重要组成部分，但很少被研究。因此，在本研究中，我们首次使用液体等分法 (LAM) 来评估波罗的海沿海沙丘生物地壳中原生生物的丰度和多样性。原生生物的总丰度介于 10 × 103 和 128 × 103 个体 g−1 干重之间。群落以裸变形虫（54%）和鞭毛虫（44%）为主。最常见的分类群是 Spumella 样鞭毛虫 (Stramenopiles)、Paracercomonas 样变形虫和 Sandonidae 样 glissomonads（均来自 Cercozoa 门）以及异叶藻。尽管原生生物形态类型的 β 多样性存在显着差异，但测量的环境驱动因素（如 pH 值、总有机碳、氮和磷）并不能解释这些差异。此外，地理距离无法预测群落差异，表明生物地壳中原生生物的多样性受生物或其他理化参数控制。尽管原生生物形态类型的 β 多样性存在显着差异，但测量的环境驱动因素（如 pH 值、总有机碳、氮和磷）并不能解释这些差异。此外，地理距离无法预测群落差异，表明生物地壳中原生生物的多样性受生物或其他理化参数控制。尽管原生生物形态类型的 β 多样性存在显着差异，但测量的环境驱动因素（如 pH 值、总有机碳、氮和磷）并不能解释这些差异。此外，地理距离无法预测群落差异，表明生物地壳中原生生物的多样性受生物或其他理化参数控制。