Efficacy of Metal
Accumulation and Bioremediation Potential of Ascidians from the Thoothukudi Coast
Subashini N. and Tamilselvi M.
Res. J. Biotech.; Vol. 20(11); 195-204;
doi: https://doi.org/10.25303/2011rjbt1950204; (2025)
Abstract
This study investigated the accumulation of trace metals in ten ascidian species
collected from pollution-impacted zones along the Thoothukudi coast, Southeast India.
Using atomic absorption spectroscopy (AAS), we quantified seven metals K, Ca, Mg,
Fe, Cu, Zn and V across three ascidian suborders: Aplousobranchia, Stolidobranchia
and Phlebobranchia. The whole-body tissues of the selected ascidians were digested
following EPA Method 3050B and analysed via AAS. The results revealed clear taxon-specific
metal accumulation profiles: Didemnum psamathodes (Aplousobranchia) exhibited exceptionally
high iron accumulation (780.68 ppm/g), Microcosmus squamiger (Stolidobranchia) concentrated
calcium (>1062 μg/g) and Phallusia arabica (Phlebobranchia) sequestered vanadium
(55.1 ppm/g). One-way ANOVA indicated significant interspecies differences (F(9,54)
= 42.44, p < 0.0001), further supported by Principal Component analysis. Transplantation
experiments confirmed site-dependent accumulation patterns with P. arabica vanadium
levels increasing to 48.7 ppm/g at industrial sites over 60 days.
Biofiltration trials demonstrated about an 84% reduction in vanadium from synthetic
wastewater, confirming the biofiltration potential of ascidians. Protein-binding
assays revealed the presence of vanadium- and iron-affinitive proteins with high
stability constants (log K > 6.8), suggesting species-specific metal retention.
Desorption studies further highlighted differences in metal lability: P. arabica
retained 78.4% of vanadium after 28 days in clean seawater, while D. psamathodes
released over 60% of its iron. These findings underscore the utility of ascidians
as effective biomonitors and biofilters, offering promising avenues for marine environmental
monitoring and trace metal recovery.
