Screening of heavy metals on cyanobacterial mats in tropical benthic marine environments

Cyanobacteria, diverse prokaryotes, are impacted by anthropogenic activities introducing chemical elements into marine environments, affecting benthic organisms. This study investigated benthic filamentous cyanobacteria and heavy metal in their biomass in two reef systems on Bahia coast, Brazil. Taxonomic identification was done using optical and electron microscopy, and heavy metals were analyzed using Energy Dispersive X-Ray Spectroscopy. A total of 108 samples were analyzed: four species were identified in Praia de Tubarão (TB), the more anthropized area (Trichocoleus tenerrimus, Lyngbya confervoides, L. aestuarii and Lyngbya sp.), while ten species were found in Praia Sítio do Conde (SCB), a less anthropized area (Spirulina subsalsa, S. subtilis, S. major, Calothrix scopulorum, Phormidium sp., Oscillatoria margaritifera, O. nigro-viridis, L. confervoides, L. aestuarii, and L. semiplena). Fourteen metals were detected in TB and only four metals in SCB. These findings suggest that variations in species richness and metal diversity in cyanobacterial biomass are related to different levels and types of anthropogenic influence between the areas. This study demonstrates that cyanobacteria can accumulate heavy metals, serving as bioindicators of environmental quality in coastal areas, which is crucial for understanding the impact of these metals on aquatic environments, especially in areas with varying levels of anthropogenic influence.