Abstract:
Mangrove forests are unique coastal ecosystems that play an important role in reducing
pollution, especially from heavy metals. These pollutants, including lead (Pb), cadmium (Cd),
copper (Cu), and zinc (Zn), often enter coastal waters from industries, aquaculture, and urban
development. Mangrove roots act as major sinks for Pb, Cd, Cu, and Zn, with metals concentrated
in roots rather than aerial parts, reducing ecological risks. Avicennia marina effectively immobilizes
Zn and Cu, Rhizosphere microdata accumulates higher Cu and Zn, while Kandelia candel shows
strong Cd and Pb retention. Sediment properties such as grain size, organic matter, and redox
potential regulate metal availability, and ecological studies confirm mangroves also act as bio
indicators of contamination severity. Heavy metal retention in mangroves happens through several
processes such as trapping sediments, changes in soil chemistry around roots, and natural barriers
in roots that block metals from moving upward. Laboratory studies explain how metals are stored
at the cellular level, while field studies show that factors like salinity, water flow, and seasonal
changes affect how metals behave in real ecosystems. Studies from around the world, including Sri
Lanka, show that the ability of mangroves to filter metals depends on soil chemistry, tidal flows,
and human activities. Protecting and restoring mangrove ecosystems is therefore vital for
sustainable coastal management, bioremediation, and long-term environmental safety.
