Laguna Madre (United States)

The Laguna Madre is a long, shallow, hypersaline lagoon along the western coast of the Gulf of Mexico in Nueces, Kenedy, Kleberg, Willacy and Cameron Counties in Texas, United States. It is separated by the roughly 20-mile (32 km) long Saltillo Flats land bridge into Upper and Lower lagoons. The two are joined by the Intracoastal Waterway, which has been dredged through the lagoon. Cumulatively, Laguna Madre is approximately 130 miles (209 km) long, the length of Padre Island. The main extensions include Baffin Bay in Upper Laguna Madre, Red Fish Bay just below the Saltillo Flats, and South Bay near the Mexican border.

The lagoon's ecosystem is protected by the Laguna Atascosa National Wildlife Refuge and the Padre Island National Seashore, as well as the privately owned King Ranch. The human history predates the formation of the Laguna Madre, and settlements have been established at Port Isabel and Port Mansfield on the lagoon's shores.

History

Laguna Madre was formed about 3,000 years ago, after the stabilization of the sea level on the Texas Coast, culminating in the rise of Padre Island. The Baffin Bay extension is considerably older than Laguna Madre, and formed as a river valley during the Pleistocene epoch, over 12,000 years ago. Early peoples obtained oysters from the bay, which were eliminated due to changes in salinity after the full formation of Laguna Madre. The first people to encounter the new lagoon were most likely the nomadic Karankawa and Coahuiltecan Indians. The Spanish explorer Alonso Álvarez de Pineda is believed to be the first European to come in contact with Laguna Madre in the early 16th century, and is credited with giving it the name, which is Spanish for "mother lagoon".

Laguna Madre (Mexico)

The Laguna Madre extends well into Mexico, to the mouth of the Río Soto la Marina in the state of Tamaulipas. It is separated from the Gulf of Mexico on the east by a number of barrier islands, including Barra Los Americanos, Barra Jesús María, and Barra Soto la Marina, and is bounded on the west by mainland Tamaulipas. It is located in the municipalities of Matamoros, San Fernando, and Soto la Marina.

Characteristics

The Laguna Madre is very shallow, with an average depth of only 0.9 m. The lagoon is connected to the ocean by only two narrow inlets, so the tidal range – which is already minor in this part of the Gulf of Mexico – is negligible.Atmospheric effects are much more important than tides in its circulation; its weak currents generally follow the prevailing winds, and these winds can influence the water level by as much as a meter.

Oceanographically, the Laguna Madre is considered a hypersaline lagoon; this indicates that it is usually much saltier than the ocean, due to being nearly landlocked in a semiarid environment This is because its salinity can vary wildly depending on rainfall and freshwater inflow, from as high as 120 ppt (12%) – over three times saltier than the ocean – to as low as 2 ppt (0.2%) after a heavy rain.