The process of chemosynthesis can represent an important source of organic matter and energy across the benthic zone. However, its detailed vertical distribution and importance in relation to other microbial processes are still poorly investigated in inland aquatic ecosystems. Here, we determined the rates of dark inorganic carbon fixation (DCF) compared to heterotrophic bacterial production (BP) and oxygen consumption (SOC) across a depth profile of oxic to anoxic sediments in the littoral zone of nine tropical lakes located in one of the most important coastal conservation areas, the Jurubatiba Sandbank National Park (Rio de Janeiro, Brazil). Rates of DCF were highly variable (means of 0.1–1.2 mmol C m⁻² d⁻¹) among the studied lakes, with mostly production occurring below 10 mm of sediment in the anoxic zone. Although presenting a relatively low contribution in relation to BP and SOC, our study showed extensive microbial metabolism in the anaerobic sediment below the top centimeter, highlighting the importance of studying microbial processes across depth at fine scales. To our knowledge, it is the first study to show detailed vertical DCF rates in coastal tropical lake sediments, thus contributing to a better comprehension of the microbial role in the biogeochemical cycles of aquatic systems.

化学合成过程可以代表整个底栖地带有机物和能量的重要来源。然而，在内陆水生生态系统中，其详细的垂直分布及其相对于其他微生物过程的重要性仍未得到很好的研究。在这里，我们确定了位于其中一个热带湖泊中的9个热带湖沿岸带从含氧到含氧沉积物深度剖面上的深色无机碳固定率（DCF）与异养细菌产量（BP）和耗氧量（SOC）的比率。最重要的沿海保护区是Jurubatiba Sandbank国家公园（巴西里约热内卢）。DCF的速率变化很大（平均值为0.1–1.2 mmol C m ^-2 d ^-1）在所研究的湖泊中，大部分产量都发生在缺氧区10 mm以下的沉积物中。尽管相对于BP和SOC而言贡献相对较低，但我们的研究显示了顶部厘米以下的厌氧沉积物中微生物的广泛代谢，突出了研究精细范围内整个深度的微生物过程的重要性。据我们所知，这是第一项显示沿海热带湖沉积物中垂直DCF率的详细研究，从而有助于更好地理解微生物在水生系统生物地球化学循环中的作用。