Iron is one of the most abundant elements on the planet and a micronutrient for most organisms. In many coastal regions worldwide, mangrove forests affect the dynamics and mobility of different elements to the oceans especially through their soils. The biogeochemistry of mangrove soils responds to numerous factors that vary within different spatial and time scales. In this sense, seasonality can be crucial in determining the role of these ecosystems towards the iron biogeochemical cycle. Thus, the main goal of the present study was to assess the effects of contrasting climatic conditions on iron biogeochemistry in different mangrove forests along the Brazilian coast. We studied the soils (n = 435) of 14 different mangrove forests distributed along two contrasting climate regions: the semi-arid Northeast and the humid Southeast coasts of Brazil. In the SE region, water surplus and lower temperatures in both seasons did not cause significant changes in iron concentrations (wet season: 216 µmol g⁻¹; dry season: 230 µmol g⁻¹) where oxyhydroxides and pyrite immobilize iron in the mangrove soils. In contrast, in the semi-arid mangroves, a marked water deficit during the dry season caused both pyrite oxidation and iron reprecipitation as oxyhydroxides. Contrarily, in the rainy season, the establishment of a suboxic environment (Eh ~ + 100 mV) favored significant iron losses via iron reduction. We conclude that seasonality can affect the maintenance and cycling of iron in mangrove soils, which may function as important sources of this element for adjacent ecosystems.

铁是地球上最丰富的元素之一，也是大多数生物体的微量营养素。在全球许多沿海地区，红树林影响不同元素进入海洋的动态和流动性，尤其是通过土壤。红树林土壤的生物地球化学响应于在不同空间和时间尺度内变化的众多因素。从这个意义上说，季节性对于确定这些生态系统对铁生物地球化学循环的作用至关重要。因此，本研究的主要目标是评估不同气候条件对巴西海岸不同红树林中铁生物地球化学的影响。我们研究了分布在两个截然不同的气候区的 14 种不同红树林的土壤 (n = 435)：巴西半干旱的东北部和潮湿的东南部海岸。^-1 ; 旱季：230 µmol g ^-1 )，其中羟基氧化物和黄铁矿将铁固定在红树林土壤中。相比之下，在半干旱红树林中，旱季显着缺水导致黄铁矿氧化和铁以羟基氧化物形式再沉淀。相反，在雨季，低氧环境（Eh ~ + 100 mV）的建立有利于铁还原导致铁的显着损失。我们得出结论，季节性会影响红树林土壤中铁的维持和循环，这可能是邻近生态系统该元素的重要来源。