Organic and metal contamination in surface mangrove sediments of South China.

Mangrove forests, the intertidal wetlands of the tropics and subtropics, are key ecological habitats that link terrestrial and marine environments. Mangrove forests and adjacent mudflats are increasingly impacted by urban/industrial development in the tropical coastal zone, suffering pollution from multiple sources including but not limited to municipal waste, aquaculture, mariculture and shipping as well as onshore industries and run-off from urban centres (Cuong et al. 2005; Huang et al. 2003; Zheng et al. 2000). Sediments that accumulate in mangroves are potential repositories of anthropogenic pollution because of high total organic carbon content, anaerobic properties and rapid turnover and burial (Marchand et al. 2005; Tam and Yao, 2002). The world wide denigration and loss of mangrove habitats is of global concern given they account for an estimated 11 % of the input of terrestrially-derived carbon into the ocean and about 10 % dissolved organic carbon (DOC) sourced from land; the long term effect of altering the carbon cycle is uncertain (Dittmar et al. 2006; Jennerjahn and Ittekkot, 2002). It has been widely postulated that mangroves afford physical protection against catastrophic storm events such as hurricanes and tsunamis (Alongi, 2007). Recent post-impact surveys along the Tamil Nadu coast follwing the 2004 Indian Ocean tsunami confirmed this notion and demonstrated that man-made structures built behind mangroves were significantly less damaged than their unprotected counterparts (Alongi, 2007).