Environmental assessment of a mangrove protected area in the southeast Gulf of Mexico through sediment core analysis

Three sediment cores were collected from different regions of the mangrove adjacent to Carmen Island, in Terminos Lagoon, to examine the influence that natural processes, the oil industry and urban development exert upon the mangrove environment. Textural and chemical characteristics were evaluated in each core. The variations among them reflect the different dynamic and depositional conditions for each site. Core C1, located near Puerto Real inlet, presents higher averages of grave l (16%), silt (32.6%), clay (1.48%), organic carbon (4.42%), carbonates (49.9%), CaO (28.96%), MgO (1.7%), P₂O₅ (0.99%) and Cu (4.46 mg/kg), some of these elements linked to the abundance of organisms in the area. Located in a channel with high sand content formed by an ancient delta, core C2 presents the highest average concentration of Al₂O₃ (4.39%), Fe₂O₃ (1.1%), MnO (0.02%), TiO₂ (0.17%), Zn (14.8 mg/kg), Ni (16.9 mg/kg), Cr (293 mg/kg), V (12.3 mg/kg) and Cd (0.14 mg/kg), indicating high concentration of terrigenous sediments associated with heavy minerals. Situated in the lagoon border close to Carmen City, core C3 presents the highest sand (88.3%), SiO₂ (64.5%), K₂O (1.1%) and Pb (2.2 mg/kg) concentration. The location of this core makes it more susceptible to the dynamic processes that take place in the lagoon. The chemical differences observed in C2 are linked to the construction of Federal Highway 180. The drought that affected the basin during El Niño (1997–1998) produced a decrease in the rivers flow and a diminution of terrigenous sediments supply to Terminos Lagoon that is mainly observed in C3.