Evaluation of carbon stock in the sediment of two mangrove species, Avicennia marina and Rhizophora mucronata, growing in the Farasan Islands, Saudi Arabia

•Avicennia marina and Rhizophora mucronata locations showed significant differences in SBD.•Avicennia marina and Rhizophora mucronata locations showed significant differences in SOC concentration.•SOC concentration and SBD had a significant and inverse relationship.•SOC stock of Avicennia marina was greater than that of Rhizophora mucronata by 114.3%.•Greater mean CSR was noted for Avicennia marina than for Rhizophora mucronata locations.