Galveston Bay

Roosting-Birds-Silhouette-from-Gene-Fisseler

Overview

Galveston Bay Watershed Courtesy of Galveston Nature Tourism . Find your watershed with this tool .
Galveston Bay Watershed Courtesy of Galveston Nature Tourism. Find your watershed with this tool.

Galveston Bay is the state’s largest bay. The San Jacinto and Trinity Rivers (in addition to bayous and creeks) drain fresh water, sediments and nutrients into this semi-enclosed system, which mixes with salt water from the Gulf of Mexico. Estuaries are among the most productive ecosystems in the world, and 95% of fish species in the gulf are dependent upon the bay.

Abiotic factors include water and air temperature, pH (acidic or basic), dissolved oxygen, salinity (affected by freshwater inflows), nitrogen and phosphorus levels, and turbidity/transparency. A biotic factor is fecal indicator bacteria, in addition to wildlife population surveys.

There are many types of ecosystems in Galveston Bay. Healthy ecosystems provide food, clean water, shelter and nurseries to wildlife.

An estuary is a place where rivers, like the Trinity and San Jacinto, meet the ocean. There is a mixing of fresh and salt water.

Brown Pelican numbers are rebounding. The long beak acts like a net, enabling it to catch fish. Photo courtesy of Houston Audubon and Greg Lavaty
Brown Pelican numbers are rebounding. The long beak acts like a net, enabling it to catch fish. Photo courtesy of Houston Audubon and Greg Lavaty

A salt marsh lines the landward side, touches the salty water of the bay, and is home to cordgrasses like Spartina alterniflora that slow the flow of water, allowing sediments and pollutants to settle out. It’s a muddy, mucky place with changing salinity, temperature and water levels. Birds here have wide feet for walking through the mud. To learn about their benefits, check out the Texas Coastal Exchange.

A brackish, or intermediate, marsh is characterized by plants that tolerate both salt and fresh water conditions due to occasional strong storm surges that flood inland areas with salt water.

A bay is a broad mud flat, usually always covered in water, partially enclosed by land and directly connected to the ocean. Underwater seagrass beds stretch to the gulf, and oyster reefs grow in deeper water with a current.

History

Galveston Island and Bolivar Peninsula formed from shoreline deposited sediments thousands of years ago, and have been inhabited by people ever since. Akokisa (Orcoquisa) tribes lived here 7,000 years ago, followed by the Karankawa, Coco and Tonkawa tribes. Cabeza de Vaca was stranded on the Texas coast in 1528. Jose Antonio Evia surveyed the entire Gulf coast in the late 1700’s and named the area “Galveston Bay” in honor of his patron, the Spanish Governor of Louisiana, Bernardo de Galvez.

The deciding battle in Texas’ war for independence from Mexico was fought at the confluence of the San Jacinto River and Buffalo Bayou, and later Texas was annexed to the United States. In 1850, Galveston was identified as the largest town in Texas due to its navigational improvements. Industrialization and oil refineries soon followed, as did a widening and deepening of the Houston Ship Channel and a degrading ecosystem. Today, half of the population of Texas lives in the Galveston Bay watershed - and even more people depend upon its extensive resources.

Conservation

Organizations like the Galveston Bay Foundation are focused on five key issues facing the bay:

  1. loss & degradation of habitat
  2. need for lands under conservation
  3. insufficient fresh water inflows from rivers, bayous and creeks
  4. poor water and sediment quality
  5. lack of public awareness

Wildlife

Estuaries are like a nursery for young finfish and shellfish. As freshwater flows in from rivers and bayous, the nutrients feed seagrass and plankton. These autotrophs, or producers, turn sunlight into energy through photosynthesis and form the base of the food web.

Oysters filter water in order to eat plankton, and oyster reefs provide habitat for small fish. Oysters also filter out detritus and sediment, helping to clean the bays. Red drum and spotted seatrout, two popular finfish, are predators in the system. They spawn in the bay but often return to the open ocean when bay temperatures are too cold. Other predators include birds like brown pelicans and herons.

Aquatic Food Web. A web is a model that shows the interconnectedness of a system; a chain, however, only shows one piece of the puzzle. Photo courtesy of Texas Aquatic Science
Aquatic Food Web. A web is a model that shows the interconnectedness of a system; a chain, however, only shows one piece of the puzzle. Photo courtesy of Texas Aquatic Science
A Yellow-Crowned Night Heron, the official Bird of Houston, has wide feet and long legs. These adaptations allow it to walk and hunt with its sharp beak in the marshes. Photo courtesy of Wild South Florida.
A Yellow-Crowned Night Heron, the official Bird of Houston, has wide feet and long legs. These adaptations allow it to walk and hunt with its sharp beak in the marshes. Photo courtesy of Wild South Florida.
Aquatic Food Pyramid. Due to the Second Law of Thermodynamics, up to 10% of the energy at each trophic level is lost as heat. Courtesy of Texas Aquatic Science
Aquatic Food Pyramid. Due to the Second Law of Thermodynamics, up to 10% of the energy at each trophic level is lost as heat. Courtesy of Texas Aquatic Science

To check on the health of this interconnected system, scientists monitor many different populations.

  • One is shellfish (blue crabs, oysters and shrimp). Currently, populations are stressed by decreasing habitat. To help, you can volunteer to remove abandoned crab traps, reduce your consumption of shellfish and conserve water to protect freshwater inflows.
  • A second monitored population is finfish, like Atlantic croaker, bay anchovy, drum, seatrout and catfish. Finfish numbers have remained stable since 2004; to protect them, reduce runoff pollution and support the protection of habitat.
  • A third monitored population is birds, and most of the species numbers have remained the same. Especially hopeful are the rebounding numbers of Brown pelicans. You can learn more about coastal bird species from Houston Audubon. To help, you can pick up trash in the habitat.

Invasive species can ruin an ecosystem because they disrupt feeding patterns and outcompete native species. Once established, especially in aquatic environments, they are very difficult to remove. Search for invasive species in the bay with this tool from HARC. It’s important for recreational boaters to clean, drain and dry their boat, trailer and gear in order to remove invasive hitchhikers. Pet owners should never release plants or animals into the environment.