Decomposition in coastal wetlands and what may be beyond carbon preservation

In coastal wetland ecosystems, decomposition of plant material is a key process in belowground carbon storage dynamics – the organic matter (OM) that does not break down has the potential to be preserved and contribute to soil/sediment carbon stocks. As such, factors that impact decomposition may also impact the capacity of wetlands to act as natural carbon sinks, particularly in a changing climate. OM decomposition is also an important process for the regeneration of nutrients and the support of ecosystem food webs. However, the paradigm of decomposition as an ecosystem service in its own right is less common in the literature for coastal wetland ecosystems than terrestrial or freshwater aquatic ecosystems.

In this presentation, we will explore the current state of blue carbon cycling in the context of decomposition. Studies on both natural litter and standardise tea litter, i.e. TeaComposition H₂O, are showing how elevated temperatures enhance decay and reduce carbon preservation, but that other ecosystem-dependent characteristics like inundation and OM quality also influence the magnitude of this temperature effect. Increasing temperatures can also increase plant productivity, leading to scenarios where carbon decay could be mitigated by plant carbon production. Rising sea levels may also impact belowground OM production and decomposition that could affect soil/sediment strength and structure. Lastly, we will also explore this other side decomposition including if we can define a ‘good amount’ of decomposition that supports soil/sediment and ecosystem functions, while also promoting carbon preservation, particularly in management and restoration scenarios. The hope is to stimulate conversation and research ideas for understanding decomposition ecology for blue carbon and beyond.