Andaman mangrove sediments: source of nutrients and sink of heavy metals

Abstract

Andaman Islands (AI) of India is a biodiversity hotspot of mangroves but biogeochemical dynamics of AI is less understood. We collected sediment samples from four AI mangrove sites and one site without mangroves for nutrients and trace metal analysis. Samples were collected from each site at the inlet of seawater (Zone A) and the other 500 m into the mangrove creek (Zone B). Nutrients (sulphate, ammonium, nitrite and nitrate) level, organic matter (OM) and carbon content were higher at Zone B of mangrove ecosystem due to the higher OM content from mangrove leaf litter decomposition and microbial degradation. Metal (Pb & Cd) content of zones with and without mangroves were similar and Igeo values indicated moderate contamination of mangrove zones of AI due to lack of anthropogenic pollution. Our results suggest mangrove ecosystems of AI are uncontaminated from heavy metals and are source of nutrients to the oligotrophic coastal ecosystems of Andaman Sea.