Freshwater wetlands are a key component of the global carbon cycle. Wet–dry tropics wetlands function as wet-season carbon sinks and dry-season carbon sources with low aquatic metabolism controlled by predictably seasonal, yet magnitude-variable flow regimes and inundation patterns. However, these dynamics have not been adequately quantified in Australia’s relatively unmodified wet–dry tropics freshwater wetlands. A baseline understanding is required before analysis of land-use or climate change impacts on these aquatic ecosystems can occur. This study characterises geomorphology and sedimentology within a seasonally connected wet–dry tropics freshwater wetland system at Kings Plains, Queensland, Australia, and quantifies soil carbon stocks and wet- and dry-season aquatic metabolism. Soil carbon stocks derived from loss-on-ignition on samples to 1 m depth were 51.5 ± 7.8 kg C m⁻², higher than other wet–dry tropics wetlands globally, with potential for long-term retention at greater depths. Gross primary productivity of phytoplankton (GPP) and planktonic respiration (PR) measured through biological oxygen demand bottle experiments in the water column of sediment inundated under laboratory conditions show overall low GPP and PR in both wet- and dry-season samples (all wetland samples were heterotrophic with GPP/PR < 1). Despite the short-term dominance of aquatic respiration processes leading to net release of carbon in the water column under these conditions, there is appreciable long-term storage of carbon in sediment in the Kings Plains wetlands. This demonstrates the importance of wet–dry-tropics wetland systems as hotspots of carbon sequestration, locally, regionally and globally, and consideration should be given to their conservation and management in this context.

淡水湿地是全球碳循环的关键组成部分。湿干热带湿地起着湿季碳汇和干季碳源的作用，其水生代谢低，可预测的是季节性的，但其量级可变的流态和淹没模式对其进行控制。但是，在澳大利亚相对未改良的湿-干热带淡水湿地中，尚未对这些动态进行充分量化。在分析土地利用或气候变化对这些水生生态系统的影响之前，需要有基线了解。这项研究描述了澳大利亚昆士兰州金斯普兰斯一个季节性连接的湿-干热带淡水湿地系统中的地貌和沉积学，并定量了土壤碳储量和湿季和枯季的水生代谢。⁻²，高于全球其他干湿热带湿地，具有长期保留在更大深度的潜力。通过生物需氧量瓶实验在实验室条件下淹没的沉积物水柱中测得的浮游植物的总初级生产力（GPP）和浮游呼吸（PR）显示，湿季和干季样品（所有湿地样品）的GPP和PR总体较低是GPP / PR <1的异养型）。尽管在这些条件下水生呼吸过程的短期优势导致了水柱中碳的净释放，但在Kings Plains湿地中沉积物中的碳仍可长期储存。这证明了湿-干-湿地湿地系统作为局部，区域和全球碳固存热点的重要性，