Carbon provenance study of Irish saltmarshes using bacteriohopanepolyol biomarkers

Coastal blue carbon ecosystems (BCEs) are one the of largest carbon sinks and play a significant role in the global carbon cycle. Approximately 40 km² of coastline in Ireland are saltmarshes. Despite their importance, globally BCEs are being lost at an alarming rate of 1–2% for tidal marshes and 0.4–2.6% for seagrass beds annually, primarily due to anthropogenic activity, which is exacerbating climate impacts. Understanding the relative contributions of allochthonous and autochthonous carbon sources to saltmarsh carbon sequestration and the origin and sources of organic carbon, termed “carbon provenance”, is essential for accurately assessing the carbon sequestration potential of saltmarshes and developing effective strategies for climate change mitigation. This study aims to develop our understanding of the carbon sequestration mechanisms in saltmarshes in Ireland using organic carbon (OC) concentration and bacteriohopanepolyol biomarkers (BHPs, a group of membrane lipids that can be used to trace major microbial groups). We sampled two estuarine saltmarsh sites, one on the east coast (North Bull Island, county Dublin) and one on the west coast (Derrymore island, county Kerry) of Ireland. Initial OC concentrations ranged from 0.40 to 23.69 wt% in samples from North Bull Island and from 0.40 to 28.53 wt% in Derrymore island. Further, we expect to gain a better understanding of terrestrial versus marine input of OC using an R_soil index using relative distribution of soil specific BHPs and bacteriohopanetetrol (used as a marine signature). These results will guide management and successful saltmarsh restoration schemes aimed at enhancing blue carbon sequestration in Ireland.