From: Castaneda and Contreras, 2001
Laguna Tamiahua is the third largest coastal lagoon in Mexico. It has brackish waters and is located in the coastal plains of the state of Veracruz. Some of its most notable characteristics are the presence of numerous streams such as La Laja, Cucharas, Carbajal, Tancochin, Tampache, Milipas and San Lorenzo, among others, the majority of which have a seasonal flow. Islands like Juan A. Ramirez (also cited as Juana Ramirez on several documents, maps and nautical charts), Toro and Idolo are present, as well as a great sandy barrier called Cabo Rojo. Channels connect its waters with the Panuco River to the north, the Tuxpan River to the south, the Laguna de Tampamachoco and the Corazones Barrier or Corazones Mouth, which connects it to the Gulf of Mexico. A chain of live and dead coral reefs are also a distinctive characteristic of Tamiahua. They are located on the lagoon’s bottom near the Isla del Toro and around Cabo Rojo’s subsoil, which seem to have great importance in the origin of the sandy barriers and the development of the lagoon.
Tamiahua has a humid climate with strong rains during summer and dry conditions during winter, with relatively low evaporation. With shallow waters, the lagoon registers 2 to 3 m in depth, while the channel located leeward of the Corazones Barrier registers higher depths due to the constant tidal flow. The Cabo Rojo Barrier is formed by quartzite sand, with big active dunes to the north and diminishing towards the south, where they are small and stabilized. The Corazones Mouth, the only communication with the Gulf of Mexico and the only actual mouth of the lagoon, is small and narrow, but evidence of three old mouths also exists: The Tampamachichi Mouth, located on the north side of the barrier, and the Galindo and the Tanhuijo Mouths, which are located on the south side of the barrier.
There are three different hydrological environments in the lagoon: the north area with a strong marine influence, a central region with a strong continental influence and a south region with similar characteristics as those of the north area, except during some times of the year when it is influenced by the central region. Salinity in Tamiahua is governed by tides, precipitation and river discharge, and although the waters are primarily brackish, there are two distinct phases: An ultrahaline phase with greater than 30 ppt salinity, and a polyhaline phase with salinity between 16 and 30 ppt. The first, directly affected by the tides, is restricted to the mouth and neighboring areas, and the second is influenced by indirect tidal activity.
The lagoon plays a significant role in the fishing and ecologic development of the region. It is considered the most productive lagoon of the state of Veracruz and an important breeding, feeding and reproductive zone for many species of fish. Among the most dominant are the Anchoa mitchilli, Aripsis felis, Bairdiella chrysoura, Cathorops melanoppus, Eucinostomus fula, Hyporhamphus roberti, Lagodon rhomboides, Mugil cephalus, M. curema, Orthopristis crysoptera and Strongylura notata. Oysters and crustaceans are also big contributors to the local economic development.
Several surrounding and distant villages discharge their untreated domestic waste into the Tamiahua lagoon and the rivers that empty their waters into the lagoon. This fact and the high temperatures that the area can reach during certain times of the year, contribute to elevated levels of fecal bacteria, putting near dwellers at high risk given their direct dependency on the lagoon.