ABSTRACT

Permanent freshwater and brackish marshes are the typical wetland type of the Mediterranean Spanish coast. Historically, alterations to the original morphological and hydrological characteristics of some these ecosystems have increased their trophic status, which could influence the carbon (C) balance, while other ecosystems remain close to their natural condition. In this work, the main processes related to the C cycle were studied in several Mediterranean coastal marshes with different degrees of alteration and in sites restored and managed in different ways. Carbon associated with greenhouse gases (CO₂ and CH₄) was determined using gas exchange methods for plankton, benthos, and sediments, as well as net production estimations for helophytes, to determine the influence of wetland conservation status, restoration, and management practices on C balances. Freshwater and brackish marshes showed capacity for C capture, especially in the restored sites (∼950 g m⁻² yr⁻¹), with a paramount role of helophytes. Differences among the study sites revealed the importance of alterations and restoration for C exchange. Specifically, a highly altered site showed increased rates of aerobic respiration compared to undisturbed sites, with a decrease in C storage capacity to ∼50 g m⁻² yr⁻¹. Management practices resulting in instability of the organic sediments favoured degradative metabolism, with release of stored C and concomitant increases in CH₄ emissions. Our results indicate that the hydromorphological alterations in these sites may convert healthy ecosystems contributing to C sequestration and climate change mitigation into C-emitting ecosystems.

摘要

永久淡水和咸淡的沼泽是地中海西班牙海岸的典型湿地类型。从历史上看，对某些生态系统的原始形态和水文特征的更改增加了其营养状态，这可能会影响碳（C）平衡，而其他生态系统仍保持接近自然状态。在这项工作中，研究了与C循环有关的主要过程，研究了几个地中海海岸沼泽地，它们的变化程度不同，并且以不同的方式进行恢复和管理。与温室气体相关的碳（CO ₂和CH ₄）是通过使用浮游生物，底栖生物和沉积物的气体交换方法以及对藻类植物的净产量估算来确定的，以确定湿地保护状态，恢复和管理措施对碳平衡的影响。淡水和微咸水沼泽显示出对C的捕获能力，特别是在恢复的位置（约950 gm ^-2 yr ^-1），具有最重要的物种多样性。研究地点之间的差异揭示了改变和恢复碳交换的重要性。具体而言，与不受干扰的地点相比，高度变化的地点显示出有氧呼吸速率增加，碳储存量降低至约50 gm ^-2 yr ^-1。导致有机沉积物不稳定的管理措施有利于降解代谢，释放出储存的碳并随之增加CH ₄排放。我们的结果表明，这些地点的水文形态变化可能将有助于固碳和缓解气候变化的健康生态系统转化为排放C的生态系统。