Using benthic foraminifera as bioindicators of environmental change in coastal lagoons

Benthic foraminifera (BF) are effective bioindicators of environmental changes in coastal ecosystems due to their ecological specificity, rapid response to stressors, and sedimentary preservation. This study assessed the environmental preferences and bioindicator potential of 12 dominant BF species across five tropical lagoons in Rio de Janeiro, Brazil, using weighted averaging and Generalized Least Squares (GLS) models. Species distributions were primarily driven by salinity, dissolved oxygen (DO), and sulphur levels. Ammonia tepida emerged as a generalist species highly tolerant to salinity and carbohydrate-rich environments, while Bolivina variabilis and Quinqueloculina seminulum were identified as sulfide-sensitive taxa. Cribroelphidium gunteri, Elphidium excavatum, and A. tepida showed strong associations with oxic conditions, reinforcing their value as indicators of well-oxygenated environments. Species like Quinqueloculina miletti and Triloculina oblonga exhibited affinity to alkaline pH and aversion to high protein concentrations, potentially reflecting sensitivity to organic over-enrichment. The novel application of GLS modelling revealed nuanced species-environment relationships and emphasized total sulphur (TS) as a critical but underexplored factor shaping BF distribution. Our findings demonstrate that integrating trait-based metrics and species-specific tolerances enhances the reliability of BF as environmental indicators in tropical coastal lagoons.