Biological Resources of Big Thicket National Preserve, Texas

Science Center Objects

Innovations in three-dimensional seismic surveying technology spawned an unprecedented wave of oil and gas prospecting throughout Big Thicket National Preserve. The preserve resource managers were concerned about the potential impacts to aquatic resources from these operations. The USGS Texas Water Science Center (TXWSC) provided a baseline assessment of the biological resources in the preserve including channel habitat, fish, benthic invertebrates, and riparian woody vegetation.

The Big Thicket National Preserve (96,669 acres) has a highly fragmented land base of nine units connected by four riparian corridor units. The U.S. Congress recently authorized two additional riparian corridor units and one land-based unit that are expected to become part of the the Preserve in the near future. The two units form a narrow buffer zone around Village Creek, considered one of the best canoeing streams in southeast Texas.

Although the region around the preserve is largely forested, a trend of increased urbanization and industrialization is emerging. Over the past 10 years, there has been a regional decline in dissolved oxygen levels in streams of southeastern Texas. As cities within the region expand, point-source pollutants from increases in sewage treatment plant effluents could further reduce dissolved oxygen levels.

Industrial point-source pollutants also are an issue in the preserve. In 1986-87, as part of the National Bioaccumulation Study, the U.S. Environmental Protection Agency documented toxic levels of dioxin in fish tissue samples from the lower Neches River Corridor Unit in the Big Thicket National Preserve. The Texas Department of Health (TDH) issued a fish-consumption advisory for this reach on the lower Neches River, which remained in effect until 1996. TDH continues to monitor the situation.

Historically, the most important point-source impacts on stream in the preserve have been from oil and gas operations. In 1981, for example, an oil spill adjacent to the Turkey Creek unit flowed into a nearby tributary and eventually into the preserve. Although the spill was quickly contained, it nearly extirpated the benthic marcoinvertebrate community along the entire stream reach. 

Combined with past water-quality monitoring efforts, this study provided a baseline of water-quality information from which to detect future change. TXWSC scientists

  • Provided a baseline assessment of the status of instream biological resources and riparian zone woody vegetation throughout the Big Thicket National Preserve.
  • Established a network of permanent biomonitoring benchmark stations to compliment historical and planned basic water-quality monitoring stations and provided the data to develop a predictive tool for assessing the status of instream biological resources.
  • Provided the Big Thicket Preserve with watershed delineation, basin characteristics and land-use characteristics for all subwatersheds and permanent benchmark monitoring stations.

A synoptic biomonitoring study benefits management of the preserve in several significant ways. The study provided the preserve with a comprehensive and current inventory of aquatic fauna for the existing units and the first-ever inventory of aquatic fauna for the new units. The last fish inventory for the existing units was done 20 years ago, and no comprehensive inventory of aquatic fauna has ever been done. The biomonitoring effort, however, yielded more than just an updated inventory. It was the first step in developing a predictive tool for assessing how changes in land use in the surrounding watersheds can potentially impact the running waters of the preserve. Instead of reacting to degraded waters, the preserve managers may eventually be able to manage proactively by knowing beforehand how land use changes will affect aquatic biota. This information was critical for resource managers to work effectively with stakeholders within the watersheds and reduce impact to aquatic resources. The methods and knowledge gained from this study also are readily transferable to other National Park Service units with similar issues.