High macrophyte canopy complexity enhances sediment retention and carbon storage in coastal vegetative meadows at Tangkhen Bay, Phuket, Southern Thailand

摘要

Marine macrophytes help protect coastal habitats by modifying the energy of their environment, attenuating wave action, and stabilizing the sediment. The aim of this research was to examine the effect of the above ground parts of different seagrass and seaweed species on the deposition, retention, physical (dry bulk density and grain size), and chemical properties (organic carbon content and organic carbon density) of sediment. Six seagrass and seaweed communities with different above ground morphologies were studied between the dry (April 2015) and wet seasons (August 2015). The results suggested that the highest canopy complexity index was in the green alga, Halimeda macroloba Decaisne patches, which had the highest canopy score. High canopy complexity patches were likely to retain more sediment and store more organic carbon than lower canopy complexity patches and bare sand, respectively. The sediment retention and percent of organic carbon content were also affected by seasons. The wave action in the wet season affected the sediment through higher sediment deposition and movement, which caused increased sediment instability and led to changes in sediment properties. In addition, shoot density in the dry season was lower than that in the wet season, most likely due to damage from long exposure during low tide. Our results indicate that the canopy complexity of marine macrophytes and seasons influenced both sediment retention and properties of the sediment.