Agricultural fingerprints in salt-marsh sediments and adaptation to sea-level rise in the eastern Cantabrian coast (N. Spain)

•Criteria to identify records of agricultural activities in salt-marsh sediments are shown.•Benthic foraminifera and sand content are appropriate proxies to recognise human disturbance.•Recently regenerated saltmarshes present difficulties to reconcile 210Pb dating.•Regional sediment availability is fundamental for the environmental regeneration.•Saltmarshes in N. Spain are expected to adapt to ongoing sea-level rise.

A multi-proxy approach based on benthic foraminifera, sand content, short-lived radioisotope activities, heavy metal concentrations and aerial photography was developed to characterise the process of human disturbance on the intensely impacted eastern Cantabrian coast (N. Spain) over the last two centuries. Analysis of two 50 cm long sediment cores from different saltmarshes in the Santoña estuary and their comparison with previous results in nearby coastal areas defines criteria to identify records of agricultural activities in salt-marsh sediments. Agricultural occupation of saltmarshes and the later regeneration was recognised based on foraminifera and sand content. Saltmarshes in the eastern Cantabrian coast are expected to adapt to ongoing sea-level rise based on the high sedimentation rates (14–18 mm yr−1) observed during the regeneration process of previously reclaimed areas. These findings can potentially be useful in other temperate saltmarshes with abundant sediment input, as a cost-effective adaptation measure to counteract the effects of sea-level rise.