Potential Bioremediation of Heavy Metals in Offshore Waters Using Natural Sponges

The heavy metal contamination in aquatic environments is a critical hazard to biota and human health, yet simple, low-cost remediation measures remain insufficient. This study focused on natural and synthetic sponges, monitoring 12 heavy metals (As, Co, Cr, Cu, Mn, Ni, Zn, V, Ba, Mo, Cd, Pb) in offshore seawater and sponge tissues to identify factors regulating sponge adsorption capacity. Natural sponges showed significant bioaccumulation of heavy metals with distinct interspecific differences in accumulated metal profiles. Temporal variations in sponge metal concentrations were strongly associated with environmental nutrient levels, as well as sponge density and porosity—with sponge morphology being the dominant intrinsic factor. Spongia officinalis had a high removal rate of metallic copper, which was 84 ± 0.6%, 90.6 ± 1.6%, and 74.9 ± 0.2%, in seawater exposed to an initial concentration of metallic copper of 0.05 mg/L, 0.1 mg/L, and 1 mg/L, respectively.