Assessment of potentially toxic element accumulation in octocoral from Todos os Santos Bay in northeast of Brazil

Coastal ecosystems are increasingly threatened by potentially toxic element (PTE) contamination, highlighting the need for reliable biomonitors capable of assessing spatial patterns of metal pollution. Although octocorals exhibit a high capacity to accumulate PTE from the marine environment, their application in environmental monitoring remains poorly explored. Considering this gap, in the present study we developed and optimized an analytical method based on inductively coupled plasma optical emission spectrometry (ICP OES) for the determination of Ba, Cr, Cu, Mn, Pb and Zn in tissues of the octocoral species Neospongodes atlantica , sampled at six locations across Todos os Santos Bay (BTS), northeastern, Brazil. Following a 2 5-1 factorial design, the optimal acid digestion conditions for 1.2 g of octocorals samples were 4 mL of HNO 3 (65% m m -1 ), 0.8 mL of H 2 O 2 (35% m m -1 ), 3.6 mL of ultrapure water, and 80 minutes digestion time. The method demonstrated satisfactory analytical performance, with good precision and accuracy. Element concentrations (μg g -1 ) ranged 8.0–18.8 for Ba, 0.6–4.3 for Cr, 2.7–5.0 for Cu, 16.3–67.4 for Mn, 5.8–8.8 for Pb, and 12.2–31.6 for Zn. Principal component and hierarchical cluster analysis distinguished sites subjected to greater anthropogenic influence from relatively unimpacted areas, revealing clear spatial differences in PTE accumulation across BTS. This study provides the first optimized ICP OES protocol for multi-element determination in N. atlantica and demonstrates its potential as a biomonitor of coastal metal contamination, offering a practical tool for environmental monitoring and management in tropical marine ecosystems.