Seasonal variation of heavy metals in seagrasses along Thondi coast, Palk Bay, India.

The present study deals with the bioaccumulation of heavy metals in different seagrass species (Syringodium isoetifolium, Halodule pinifolia, Cymodocea serrulata, Halophila ovalis) along Thondi coast and decaying seagrass offshore. Heavy metal concentrations in the seagrass samples were analysed during the period of April 2019 to March 2020 using atomic absorption spectrophotometry. Among the heavy metals assayed, the level of manganese was higher (15.62 ± 1.02 mg/kg) and chromium was the least metal observed (0.002 mg/kg). One-way ANOVA revealed significantly higher level of heavy metals in summer season, while it gradually decreased through pre-monsoon to monsoon season (P < 0.05). Cadmium and chromium were observed to be below detectable levels in the seagrass species. S. isoetifolium was found to bioaccumulate higher levels of heavy metals than the other seagrass species studied. Elucidation of heavy metal levels in the dead and decayed seagrass offshore revealed a higher level of heavy metals than live seagrass species.