# Linking Carbon Fluxes to Flooding Gradients in Sediments of Mediterranean Wetlands

## TL;DR

This study explores how water levels and salinity in Mediterranean wetlands affect greenhouse gas emissions, finding that emissions vary with flooding and season.

## Contribution

The study identifies specific relationships between flooding gradients, salinity, and greenhouse gas fluxes in different wetland types.

## Key findings

- CO2 emissions peak in dry zones and decrease with increasing water depth.
- CH4 emissions are highest in shallowly flooded zones with limited gas exchange.
- Seasonal variation in GHG emissions is most pronounced in saline wetlands due to drought.

## Abstract

This study examines the seasonal variability of greenhouse
gas
(GHG) emissions from wetland sediments in the Iberian Peninsula in
relation to water levels. It included coastal marshes, inland freshwater,
and inland saline wetlands, three typical regional types. GHG fluxes
peaked in coastal wetlands and were lowest in saline ones. Flux variations
were driven by water depth, salinity, and sediment aeration. CO2 emissions peaked in dry zones and declined with water depth,
while CH4 fluxes were more variable in waterlogged transition
zones, particularly in coastal wetlands during spring and summer.
CH4 emissions were lower in well-aerated, less-flooded
areas and highest in shallowly flooded zones, where even a thin water
layer restricts gas exchange, limiting oxygen and maintaining anaerobic
conditions for methanogenesis. However, the lack of a deep-water column
prevented methane oxidation, allowing diffusion into the atmosphere.
Seasonal variation was higher in saline wetlands due to drought, while
patterns in freshwater and coastal wetlands remained spatially more
stable. Understanding these gradients is crucial for accurately modeling
gas exchanges and assessing their role in climate change mitigation
and adaptation. As interest in wetland carbon dynamics increases,
integrating this modeling into management is vital to support restoration
and long-term wetland sustainability.