Long-term biodiversity responses to anthropogenic change are spatially and taxonomically heterogeneous across coastal wetlands

In eight Iberian coastal wetlands, the link between an Anthropogenic Enrichment Index and eukaryotic sedaDNA richness depends on both sediment record and marker, with only the Ebro Delta COI positive association remaining significant after calendar-time adjustment.

• Why it matters: Monitoring often covers only recent decades, leaving long-term biodiversity trajectories under centuries of human modification unclear, especially across different environmental contexts and timescales.
• What they did: The study used COI and 18S sedaDNA metabarcoding on dated sediments (210Pb and radiocarbon) from eight wetlands, relating amplicon sequence variant richness and community composition to an AEI built from ten human-associated elements.
• The result: After accounting for calendar time, several initial richness–enrichment relationships weakened, while rolling correlations suggested association direction shifts across historical periods within records; community composition varied strongly among sediment records and differed by marker and wetland.

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