Source,distribution and influencing factors of sediments on Luhuitou fringing reef, Northern South China Sea

Sediment traps were used for monitoring sedimentary processes on the Luhuitou fringing coral reef. Sedimentation rates, grain sizes and the composition of the collected sediments were then analyzed in this paper. The results indicate that (1) the average sedimentation rate varied from 5.70 mg cm-2d-1 in spring to 97.41 mg cm-2d-1 in summer, averaging at 29.9 mg cm-2 d-1 ; (2) the sediments were composed of organic (～9.5%), authigenic (～44.5%) and terrigenous (～45.9%) materials; (3) the average grain size of the collected particles was dominated by small and fine sediments (80%), this is because the reef is located at a leeward bay and the waves are relatively weak; and (4) the spatial and temporal patterns of sediments were directly related to the reef’s hydrodynamic condition, for example, the sedimentation rate at a stormy season was about 10 times higher than the stormless period; and the lower reef slope had more fine sands deposited than that of the upper reef slope where the hydrodynamic conditions was relatively stronger. Based on the above data, the calculated total terrigenous input was about 1900 mg cm-2 a-1 , which would have a sustainable effect on the coral communities at this reef through suspension/re-suspension.