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The habitats of La Mancha Lagoon, located midway along the coast of Veracruz, Mexico, are responding to the change of sediment supply reaching its primary inlet at the Gulf of Mexico. Until several decades ago, an abundant alongshore supply of sediment created a periodic opening and closing of the La Mancha inlet. The hydrologic regime of the lagoon consisted of raised water level and lower salinity during the closures, whereas the open inlet favored lower water level, higher salinity, and sediment accumulation in the flood tidal delta. Currently, diminished alongshore sediment supply has affected the inlet morphology and the discharge regime. Associated with the reduced sediment supply, the inlet is open longer in its periodic cycle, the water level variation is reduced, the salinity contrasts are reduced, and the rate of sedimentation in the flood-tide delta is increased. This combination of alterations to the inlet area is changing the flooding regime and affecting the conditions in a very well-developed mangrove habitat at the lagoon margins as well as conditions within the aqueous portions of the lagoon. Management options produce a conflict between supporting the direction of change or preserving the existing habitats. [ABSTRACT FROM AUTHOR]

The largest Gulf coast alluvial plain in Mexico lies primarily in the state of Tabasco. Although predominantly a fluvial-deltaic plain the coastal landforms contribute beach-ridge topography which extends inland up to twenty miles. Beach ridges attain fullest development adjacent to distributory channels and reflect periods of active discharge. Trenching of the ridges disclosed their internal stratification to comprise forest units which suggest sequences of washover deposits. [ABSTRACT FROM AUTHOR]