Nutrient properties of tidal-borne alluvial sediments from a tropical mangrove ecosystem

Abstract

Mangroves are inundated through tidal action, which mobilizes a large quantity of suspended and dissolved particles, including both decomposed mangrove and terrigenous materials. Sediments brought in by tidal water and trapped by mangrove roots contribute to the productivity of coastal, tropical mangrove ecosystems. They play an important role in the nutrient cycling of these ecosystems. However, there is limited information on sediment properties, inclusive of nutrients levels in tidal-borne sediments affecting mangrove ecosystems. Selected properties of sediment, including cation exchange capacity (CEC), texture, organic matter (OM) content, organic carbon (OC) content, and nutrient content (C, N, S, P, K, Ca and Mg) were studied, in a seasonal pattern, in tidal-borne sediment from Sibuti estuary mangrove. Sediment showed a high proportion of sand (range: 60%–65%) with high mean values of CEC 17 cmol/kg, a sediment OM content of 15%, and OC content of 13%. The mean average content of C was 15%, and mean concentrations of N, S, P, K, Ca, Mg and Na were 12, 10, 2, 3, 34, 18 and 16 (mg/kg), respectively. Significant positive relationships were found among nutrient concentrations in sediment and nutrient concentrations in leaf, stipule, flower, propagule, stem, bark, and root of both Rhizophora apiculata (Blume) and Xylocarpus granatum (Koenig) trees and their saplings. Seedlings are indicative of the growth, health, and productivity of the mangrove ecosystem, and are largely dependent on the phenomenon of nutritive aspects of tidal-borne sediments. The results of this study provide baseline information on the roles of nutrient productivity of a less disturbed tropical mangrove forest, adjacent to the South China Sea.