Roots and rhizomes of seagrass play an important role in coastline zone by anchoring the substrate firmly
which prevent resuspension and also controlling sediment biogeochemistry. The aim of this study was to
compare the physical and chemical differences of sediments for 3 seagrass species, which have different
root morphology between summer (February 2013) and the monsoon month (September 2013). Seven
seagrass communities were studied and are: the mono stand of Halophila ovalis, Thalassia hemprichii, and
Cymodocea rotundata, the mixed patches of H. ovalis with T. hemprichii, H. ovalis with C. rotundata, and
T. hemprichii with C. rotundata and the mixed patches of 3 seagrass species. The roots of seagrasses were
the main driver of differences in sediment properties; the branched, long root species, C. rotundata,
showed an increasing redox potential by means of oxygen releasing from their roots. The unbranched,
long root with dense root hair species, T. hemprichii, tended to cause more poorly sorted sediments. The
carbon storage was also estimated and results showed a trend of higher organic carbon density was in
the multispecific patches, the mono specific patches and bare sand, respectively. Season also influenced
the sediment properties; high wave action in the monsoon stirred up the sediments, this led to lower
organic carbon density and high redox potential. Our results suggest that the roots of seagrass species
both increase and decrease sediment properties.