The distribution and origin of aliphatic hydrocarbons in surface sediments of El Morro de Puerto Santo was
evaluated in order to establish an environmental baseline for this coastal environment. For the study, 23 surface sediment
samples were collected from both bays, and some geochemical parameters and the concentrations of extractable organic
material (EOM) of each sample were determined. The West Bay was characterized by a sandy-silt bottom, while the East Bay
is mainly sandy, with a domination of very fine sands in both bays with higher proportions of 90%. The concentrations of
total organic carbon (TOC) and total aliphatic hydrocarbons (TAH) in the West Bay, had average values of 2.59% and 637.64
mg g-1, while in the East Bay these values were 0.12% and 65.65 μg g-1, respectively, with significant differences between the
medians (Kw(TOC) = 11.09 and Kw(TAH) = 11.25; p <0.05) in both bays. The aliphatic organic matter was significantly
correlated with TOC (r = 0.74) and with the silt fraction of the sediment (r = 0.77). The carbon preference index (CPI)
suggests a mixed origin of hydrocarbons in the West Bay, contributed by vascular plants and petroleum derivatives, while in the
East Bay their contribution and origin are anthropic, both behaviors associated to the discharge of Puerto Santo River (West
Bay), the fishing activities and urban settlements located in this coastal margin.