Spatial variation in carbon storage within managed and unmanaged saltmarsh systems: A case study in the Rogerstown Estuary, Ireland

Saltmarshes provide many vital benefits (ecosystem services), including carbon sequestration, flood protection and nutrient exchange. As “carbon sinks”, these ecosystems sequester carbon up to twice the rate of terrestrial forests. Recent national and international carbon emissions targets highlight the importance to both protect and increase the area of coastal saltmarshes. In addition, these intertidal wetlands are influenced by complex interacting bio-sedimentary and hydrological processes, thus restoration projects need to consider the various processes impacting such ecosystems. To address carbon emissions targets, upscaled estimates of carbon accumulation are required, for which modelling and time-consuming field surveys are employed. An understanding of within-marsh controls on soil organic carbon content (SOC) and the resulting feedbacks (sedimentary, hydrological, geomorphological, ecological) can improve field survey efficiency and provide training data for models.  Such data aids in constraining uncertainties around scaled-up carbon accumulation estimates per unit area saltmarsh for regional, national and international inventories. Quantitative data on the variation in SOC and the facilitating processes remains relatively scarce.

This research investigates SOC distribution, alongside potential explanatory factors within unmanaged and managed saltmarshes. Through the collection of sediment samples (near-surface, core), alongside location-specific data on elevation, inundation, biomass and accretion rates in Turvey Nature Reserve (Co. Dublin), this project aims to quantify the impact of several key factors (e.g. drainage, topography, biomass and accretion) on carbon accumulation. SOC will be determined through Loss-on-Ignition laboratory analysis. An existing carbon accumulation model will then be improved upon, and the updated model will be utilised to inform an investigation of future carbon storage potential under various climate scenarios.

Initial results from an on-going project are presented to provide quantitative field- and laboratory-derived data, enhancing knowledge of within- and between-marsh variation of SOC in saltmarshes.