Identifying drivers of the molecular composition of dissolved organic matter (DOM) is essential to understand the global carbon cycle, but an unambiguous interpretation of observed patterns is challenging due to the presence of confounding factors that affect the DOM composition. Here, we show, by combining ultrahigh-resolution mass spectrometry and nuclear magnetic resonance spectroscopy, that the DOM molecular composition varies considerably among 43 lakes in East Antarctica that are isolated from terrestrial inputs and human influence. The DOM composition in these lakes is primarily driven by differences in the degree of photodegradation, sulfurization, and pH. Remarkable molecular beta-diversity of DOM was found that rivals the dissimilarity between DOM of rivers and the deep ocean, which was driven by environmental dissimilarity rather than the spatial distance. Our results emphasize that the extensive molecular diversity of DOM can arise even in one of the most pristine and organic matter source-limited environments on Earth, but at the same time the DOM composition is predictable by environmental variables and the lakes’ ecological history.

中文翻译：

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南极湖泊微生物衍生溶解有机物多样性的决定因素

确定溶解有机物 (DOM) 分子组成的驱动因素对于了解全球碳循环至关重要，但由于存在影响 DOM 组成的混杂因素，对观察到的模式进行明确解释具有挑战性。在这里，我们通过结合超高分辨率质谱法和核磁共振波谱法表明，南极洲东部 43 个湖泊的 DOM 分子组成差异很大，这些湖泊不受陆地输入和人类影响。这些湖泊中的 DOM 组成主要由光降解、硫化和 pH 值的差异驱动。发现 DOM 显着的分子 β 多样性可与河流和深海 DOM 之间的差异相媲美，这是由环境差异而不是空间距离驱动的。我们的结果强调，即使在地球上最原始和有机物质来源有限的环境之一中，DOM 的广泛分子多样性也会出现，但与此同时，DOM 的组成可以通过环境变量和湖泊的生态历史来预测。