The sedimentary record of the Junquera salt marsh (Nalón estuary, N Spain): a tale about contemporary fluvial processes, mining pollution and land-use changes

Current climate change is causing profound environmental changes in coastal ecosystems, such as rising temperatures, increased precipitations and extreme weather events, including flooding. The stratigraphic record of the salt marshes of northern Spain constitutes a unique archive for exploring natural and anthropogenic processes and dynamics. While salt marshes located along the northeastern margin of Spain have received considerable attention in the scientific literature, those located in the northwestern sector have not been extensively studied, thus creating a fundamental gap in our knowledge.

This research aims to investigate recent environmental changes recorded in a salt marsh setting from the Nalón estuary (Asturias, N Spain). A comprehensive multidisciplinary approach (benthic foraminifera, pollen content, grain size, TOC, TN, trace metals and magnetic susceptibility), coupled with a robust chronology (²¹⁰Pb, ¹³⁷Cs, ^239+240Pu), has been applied to a short sediment core drilled in the Junquera salt marsh, located in the middle estuary.

This sedimentary record, which spans to the last ~150 years, reveals the dominance of fluvial processes in the Nalón estuary, with the occurrence of a strong flood in the mid-20^th century. This extreme natural event, which disturbed previous environmental dynamics, can be stratigraphically constrained with distinctive micropaleontological and geochemical signatures. Subsequently, trace metals, magnetic susceptibility and pollen content show variable patterns consistent with the extensive mining activities and land-use modifications developed upstream.