Estuarine Biofilm Communities Adapt to Changing Conditions While Retaining Crucial Pollutant‐Combatting Functions

Abstract

Industrialization has increased the influx of toxicants into intertidal and estuarine ecosystems. Intertidal sediments are exposed to heavy metals, polycyclic aromatic hydrocarbons, pesticides, and other xenobiotics through effluents, shipping, spillages, battery disposal, and agricultural run‐off. Pollutants accumulate in sediments, disrupting nutrient cycling and impairing primary productivity, thereby threatening coastal food webs. Sediment‐bound biofilms or microphytobenthos are complex assemblages of microorganisms embedded in extracellular polymeric substances and play vital roles in biogeochemical cycling, sediment stabilization, and pollutant remediation. Their functional responses to contaminant exposure remain poorly understood, particularly in tropical estuaries. Biofilms from contaminated estuarine sediments were analysed using metagenome‐assembled genomes (MAGs) and genome‐scale metabolic models (GEMs) in a paired field‐laboratory approach. Greater metabolic diversity of field biofilms indicated broader functional capacities to sustain pollutant exposure. Conserved genes linked to organic compound degradation and metal transport co‐occurred across MAGs, suggesting integrated detoxification strategies. GEM‐based simulations revealed metabolic cross‐feeding underlying contaminant transformation. Culture conditions shaped microbial succession and ecological roles, yet core pollutant degradation and nutrient processing functions persisted, operated by dominant taxa. Microphytobenthic experimental studies rely on laboratory‐cultured communities derived from field‐collected samples. Contrasting community dynamics and altered metabolism due to ‘bottle effect’ are foundational for correctly interpreting laboratory‐based experimental outcomes.