Water hyacinth is able to sequester large amounts of carbon dioxide (CO₂) in wetlands. At the same time, the high production of organic matter combined with the plant’s capacity to limit the diffusion of oxygen from the atmosphere into the water creates favorable conditions for the production of methane (CH₄). The combination of these mechanisms challenges the prediction of water hyacinth’s net effects on greenhouse gas (GHG) emissions. To unravel the impact of water hyacinth on GHG fluxes, we performed an extensive fieldwork study encompassing 22 sites dominated by water hyacinth in the Pantanal and Amazon during two different seasons. The highest CH₄ emissions from water hyacinth beds occurred in shallow systems where sediment rooting enabled plant-mediated CH₄ transport (307 ± 407 mg CH₄ m⁻² day⁻¹ in waters shallower than 1 m, as opposed to 6.1 ± 10.6 mg CH₄ m⁻² day⁻¹ in deeper waters). When CO₂ uptake rates are added to the GHG budget (in terms of global warming potential), the water bodies were usually a GHG sink (− 5.2 ± 10 gCO₂ eq m⁻² day⁻¹). The strength of the sink is highest in deeper systems where even a low water hyacinth coverage may already offset open water emissions. This dual effect of strong CO₂ uptake—and at least temporal carbon storage in biomass—in combination with a high CO₂–to-biomass-to-CH₄ (and possibly back to CO₂) conversion highlights the necessity to include vegetation characteristics in relation to depth when estimating GHG fluxes for tropical wetlands.

水葫芦能够隔离湿地中的大量二氧化碳（CO ₂）。同时，有机物的高产量与工厂限制氧气从大气中扩散到水中的能力相结合，为甲烷（CH ₄）的生产创造了有利条件。这些机制的结合挑战了水葫芦对温室气体（GHG）排放的净影响的预测。为了揭示水葫芦对温室气体通量的影响，我们在潘塔纳尔和亚马逊地区两个不同季节进行了一项广泛的野外研究，涉及22个以水葫芦为主的地点。最高CH ₄从水葫芦床排放发生在浅系统，其中沉积物的生根植物启用介导的CH ₄输送（307±407毫克CH ₄ 米^-2 天^-1在水域浅于1μm时，相对于6.1±10.6毫克CH ₄米^-在较深的水域中为期²天^-1）。当将CO ₂吸收率添加到GHG预算中（就全球变暖潜能而言）时，水体通常是GHG汇（− 5.2±10 gCO ₂  eq m ^-2 天^-1）。在较深的系统中，水槽的强度最高，即使是较低的水葫芦覆盖率也可能已经抵消了开放水的排放量。强烈的CO ₂吸收（至少在生物质中暂时储存碳）与高的CO ₂转化为生物质到CH ₄（并可能返回CO ₂）的双重作用突出表明了必须包括植被特征估算热带湿地温室气体通量时与深度的关系。