Trace metal distribution in seawater, brown algae, and seagrasses from Guanahacabibes National Park, Cuba.

Trace metals are contaminants in marine ecosystems, and their distribution and bioaccumulation inform environmental quality assessment. Baselines in tropical protected areas are essential for detecting changes in trace metal availability. We quantified Zn, Cd, Pb, and Cu in seawater, five brown algae (Padina pavonica, Turbinaria tricostata, Dictyota dichotoma, Sargassum buxifolium, and Sargassum natans), and two seagrasses (Thalassia testudinum and Syringodium filiforme) from four beaches in Guanahacabibes National Park, Cuba. Seawater metals were determined by square-wave anodic stripping voltammetry, whereas macrophytes were analyzed by ICP-OES. Bioaccumulation factors (BAFs), principal component analysis (PCA), and log-log regressions assessed spatial and species-specific accumulation and relationships between dissolved metals and BAFs. Seawater concentrations ranged from 12.7 to 40.1 μg L⁻1 for Zn, 0.39-1.3 μg L⁻1 for Cd, 0.69-3.6 μg L⁻1 for Pb, and 1.3-5.5 μg L⁻1 for Cu, with highest concentrations at Los Cayuelos. Macrophyte concentrations followed Zn > Cu > Cd > Pb; maximum values were 52.5 mg kg⁻1 Zn in D. dichotoma and 5.97 mg kg⁻1 Cu in P. pavonica. Brown algae showed higher BAFs than seagrasses, varying by species and site. PCA explained 83.4% of variance, distinguishing Zn-associated patterns at El Perjuicio from Cu-associated patterns at La Barca. Significant inverse relationships between dissolved metals and BAFs were found for all four metals (p < 0.05). Overall, low concentrations and absence of widespread enrichment indicate limited anthropogenic influence. The integrated use of macrophyte species, dissolved metal concentrations, and BAFs provides a baseline for monitoring trace metal bioavailability in tropical protected coastal ecosystems.