Transported hundreds of kilometres by rain, rivers and ocean currents, toxic chemicals are finding their way into the Indian Ocean and building up in the fragile coral reefs between Lake St Lucia and Kosi Bay.

High levels of pesticides and herbicides -- including several banned chemical compounds -- are accumulating in coral reefs in one of South Africa's largest marine protected areas.

The numerous chemical compounds detected in coral reef animals within the iSimangaliso World Heritage Site in KwaZulu-Natal include residues of DDT (banned in farming in most of the world, but still used in SA for malaria control) as well as several other organochlorine pesticides (OCPs) that have been banned globally because of their long-lasting and harmful impacts on people, wildlife, fish and other aquatic fauna.

The detection of at least 18 OCP contaminants in corals and sponges in several places along the northern KZN coast is part of an ongoing research project by scientists from the Durban-based Oceanographic Research Institute (ORI) and Wits University in Johannesburg.

"The levels of DDT we have found at iSimangaliso are among the highest levels recorded in corals around the world," said ORI senior scientist Dr Sean Porter, noting that these chemical compounds build up progressively as the corals grow older.

Apart from their role as a major tourist attraction, coral reefs are one of the richest and most valuable marine ecosystems. Home to more than...