The role of bioremediation in mitigating urban expansion impacts on coastal lagoons: A comparative study of Araçatiba and Padre Lagoons, Rio de Janeiro

This study examines the impact of urban expansion on organic matter gradients in two coastal lagoons, Araçatiba (AL) and Padre (PL), in Rio de Janeiro, Brazil, using benthic macrofauna as ecological indicators. To mitigate the effects of organic enrichment, a microbial consortium (Lactobacillus casei, Lactobacillus acidophilus, and Saccharomyces cerevisiae) was applied in AL for nine months prior to sampling, while PL remained untreated. Sediment samples were collected from 43 stations and analyzed for Total Organic Carbon (TOC), Total Nitrogen (TN), and Total Phosphorus (TP), alongside water column parameters (e.g., dissolved oxygen, salinity, chlorophyll-a) and benthic macrofaunal composition. Results indicated higher macrofaunal abundance and diversity in AL compared to PL, where organic pollution and eutrophication were more severe. Canonical Correspondence Analysis (CCA) identified salinity and eutrophication as primary drivers of community structure, with taxa such as Capitella spp. and Streblospio sp. tolerating high organic loads and hypoxia. AL's benthic community was dominated by mollusks (Heleobia australis, Mytilopsis leucophaeata), while PL was dominated by annelids (oligochaetes, Alitta succinea), reflecting divergent environmental conditions. The AMBI index classified PL as moderately to severely disturbed and AL as slightly to moderately disturbed, aligning with geochemical data showing higher TOC and nutrient concentrations in PL sediments. Microbial bioremediation in AL correlated with improved water quality (higher WQI, lower BOD) and benthic health, underscoring its potential as a management tool. The study highlights the need for tailored strategies to address anthropogenic pressures and restore ecological balance in coastal lagoons.