Abstract. Seagrass meadows are among the most valuable ecosystems on Earth. However, in tropical countries, there is a substantial knowledge gap in “seagrass science”. To address this gap, seagrass soils from three Brazilian coastal regions were investigated (the northeastern, southeastern, and southern coasts). Soil profiles from different geological and bioclimatic settings were sampled, described, and analyzed. Thus, detailed macromorphological descriptions, soil classification, physicochemical analysis (soil particle size, soil pH, pHoxidation, Eh, total organic carbon: TOC), Fe partitioning, and X-ray diffractometry were performed. Additionally, water samples were analyzed for pH, salinity, and ion concentrations. Different environmental settings in the coastal compartments produced contrasting geochemical conditions, which caused different intensities of pedogenetic processes. On the northeastern coast, the denser plant coverage favored higher TOC contents (2.5 ± 0.1 %) and an anaerobic environment (Eh = +134 ± 142 mV) prone to an intense sulfidization (i.e., pyrite formation: Py-Fe). Py-Fe contents in northeastern soils were 6- and 2-fold higher than in southeastern and southern coastal soils, respectively. Conversely, lower TOC contents (0.35 ± 0.15 %) and a suboxic environment (Eh + 203 ± 55 mV) in the southeastern soils, along with the Fe-rich geological surroundings, decreased the intensity of gleization. The contrasting intensities in the soil processes, related to the (seemingly subtle) differences in the geochemistry of each environment, ultimately caused relevant pedodiversity among the studied sites. Our findings contribute to a better understanding of the general functioning of tropical seagrass meadows but also have significant environmental implications for studies focused on carbon sequestration in these ecosystems.

中文翻译：

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热带海草草甸的掩蔽多样性和对比土壤过程：环境设置的控制

摘要。海草草甸是地球上最有价值的生态系统之一。然而，在热带国家，“海草科学”方面的知识差距很大。为了解决这一差距，研究人员调查了巴西三个沿海地区（东北部、东南部和南部海岸）的海草土壤。对来自不同地质和生物气候环境的土壤剖面进行了采样、描述和分析。因此，进行了详细的宏观形态描述、土壤分类、物理化学分析（土壤粒径、土壤 pH 值、pH 氧化作用、Eh、总有机碳：TOC）、Fe 分配和 X 射线衍射。此外，还分析了水样的 pH 值、盐度和离子浓度。沿海隔间的不同环境设置产生了截然不同的地球化学条件，这导致了不同强度的成土过程。在东北海岸，更密集的植物覆盖有利于更高的 TOC 含量 (2.5 ± 0.1 %) 和易于强烈硫化的厌氧环境 (Eh = +134 ± 142 mV)（即黄铁矿形成：Py-Fe）。东北部土壤中的 Py-Fe 含量分别比东南部和南部沿海土壤高 6 倍和 2 倍。相反，东南部土壤中较低的 TOC 含量 (0.35 ± 0.15 %) 和低氧环境 (Eh + 203 ± 55 mV)，以及富含铁的地质环境，降低了 gleization 的强度。土壤过程中的对比强度与每个环境的地球化学（看似微妙的）差异有关，最终导致研究地点之间的相关土壤多样性。