Texas has five seagrasses, all of which occur in the Laguna Madre , . TPWD's species page uses two older names, Halodule beaudettei for shoal grass and Cymodocea filiforme for manatee grass; most current sources, including the monitoring program cited below, use Halodule wrightii and Syringodium filiforme , .
Shoal grass (Halodule wrightii) — near South Padre Island, resident. The most abundant seagrass on the Texas coast. Flat, narrow, blade-like leaves about an eighth of an inch wide and three to fifteen inches long with three-pointed tips; grows in one to three feet of water, colonizes disturbed bottom quickly, and tolerates wide swings of temperature and salinity . In the 2014–2015 Lower Laguna Madre survey it was the leading species, dominating from the north end of the lower lagoon to just south of the Arroyo Colorado, with its greatest cover near the arroyo's mouth and north toward Port Mansfield .
Manatee grass (Syringodium filiforme) — near South Padre Island, resident. Cylindrical, spaghetti-like leaves in clusters of two or three, in two to five feet of water on the lower coast, usually mixed with other species . It had the tallest canopy in the lower lagoon survey (about 26 centimeters) but only about 1.7 percent mean cover . Seven research-grade records exist for the island polygon, most with Gulf-side place names, presumably wrack .
Turtle grass (Thalassia testudinum) — near South Padre Island, resident. Broad, flat, ribbon-like leaves in clusters of three to seven, up to fourteen inches long, on mud-sand bottoms in two to five feet of water on the lower coast; it forms extensive beds where conditions suit it and is named for the green sea turtles that eat it . The 2014–2015 survey found it confined to the southernmost Lower Laguna Madre and the waters just outside Laguna Atascosa NWR, where it was the second species by cover (18 to 20 percent) . Nine research-grade records exist in Cameron County, including one from Port Isabel in 1980 .
Star grass, clover grass (Halophila engelmannii) — near South Padre Island, resident. Short, elliptical, finely toothed leaves in rosettes of four to eight, a very small plant of sheltered water that lives in the understory of mixed beds . It registered under one percent cover in the lower lagoon . One research-grade county record, coordinates obscured .
Widgeon grass (Ruppia maritima) — near South Padre Island, resident. Thin, pointed leaves on long branched stems, a single root at each node, and flower stalks that reach the surface; primarily a freshwater plant that tolerates salt and so turns up across Texas estuaries . In the Upper Laguna Madre it is the second most abundant species ; in the lower lagoon it was nearly absent in 2015 . One county record, from the South Texas Ecotourism Center in 2023 .
Observe responsibly
Wildlife, tides and access conditions change. Keep a respectful distance, do not feed wildlife, stay out of dunes and marked nesting areas, and use current official rules before fishing or handling any catch.