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Sea Grass Beds
The sea grass beds are the second largest habitat. The bright Texas sun encourages a mixture of marine grasses to grow where the water is clear and 3 to 7 feet deep, salinity is low to medium, and wind and waves don’t stir up bottom sediments. Turtle Grass (Thalassia testundinum), Shoal Grass (Halodule wrightii), Widgeon Grass (Ruppia maritima) and several other species provide food, shelter and a place to settle for a wide variety of creatures, ranging from sea turtles to baby shrimp. These underwater meadows are the most productive and diverse areas of the south Texas marine environment.
Sand and Mud Flats
These stretches of unstable sediments are the third largest habitat in the South Texas estuary system. They are too low for marshes to form yet too shallow for all but the hardiest creatures to survive. Temperatures and salinity are typically at the extremes of either high or low. Tides and winds can leave the surface dry, or shift sediments around to smother the inhabitants. Yet there are a number of mollusks, particularly clams that successfully make their homes here. |
South Texas Shells/Hall of Marine Science
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South Texas Shells/Hall of Marine Science
Click Image to Enlarge |
Open Bottom Bay
Most of our estuary system is classified as open bay bottom. Few plants grow in this empty expanse of flat sand, mud and clay. The water is turbid, full of plankton, larvae, nutrients and sediment. Relatively shallow depths average about 13 feet. Exceptions are the ship channel, which is dredged to 45 feet deep and naturally occurring scour holes up to 65 feet deep. In bays salinity tends to be low because of river run-off from the land. The Laguna Madre and Baffin Bay have a high salt content. This is due to not having direct river flow for 4000 years and to limited exchange with the Gulf of Mexico. Otherwise there is little difference between the two areas.
Sandy Beach
The barrier islands that run the full length of the coast of Texas are actually giant sand bars that grew until they emerged from the sea. Long shore drifts bring more sand constantly, and wind and storms distribute it, making the islands dynamic, unstable and fascinating. We often think of the sandy beach as being the area along the edge of the water, where we walk and play. It actually extends form the dunes all the way out past the underwater sand bars to the broad reaches of the sand in the shallows of the Gulf of Mexico. Beyond this lie the mud-bottomed offshore shrimp grounds. |
Jetties and Groins
The only rocky intertidal habitats along the Texas coast are granite boulders of the jetties at Port Aransas and concrete sea wall in Corpus Christi, along with various other concrete, wood and stone piers and groins. These habitats are also the youngest. They were all made or put in place by human hands less than 100 years ago. Yet in that time these habitats have been colonized by far drifting larvae, producing a distinct ecosystem in South Texas.
Reefs and Rigs
The continental shelf off South Texas is marked by numerous mounds, knolls, salt domes and remnants of ancient reefs. These, along with oil platforms, form hard-surfaced habitats where depth, salinity, distance from shore, clearness of the water and minimum winter temperature control living conditions. Tropical mollusks not found elsewhere in Texas are able to secure a foothold here. |
South Texas Shells/Hall of Marine Science
Click Image to Enlarge |
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