Neches River Monitoring

field crew seining for shoreline fish along an estuarine shipping channel

Introduction

For over 50 years independent academic and scientific institutions have conducted periodic monitoring studies of the lower Neches estuary. During October 2003, the Patrick Center for Environmental Research of the Academy of Natural Sciences completed the sixth in a series of biological and water quality surveys.

Previous studies were performed in 1953, 1956, 1960, 1973 and 1996. For over half a century Patrick Center scientists have been using state-of-the-art biological and chemical surveys to assess water quality in a wide range of rivers, lakes and streams around the world.

In addition to the Academy river surveys, Dr. Richard C. Harrell from Lamar University has also conducted an ongoing series of complementary biological studies of the Neches River. Lamar's close proximity affords a unique opportunity to monitor seasonal changes in water quality over an extended period of time.

The Lower Neches Valley Authority (LNVA), Jefferson County Waterway & Navigation District, ExxonMobil and DuPont jointly sponsored the most recent river survey. The study was designed to assess the general “health” of the river by taking water quality measurements, and sampling the attached algae, macroinvertebrate and fish communities. Many levels of the aquatic food web are studied because no single group can reliably indicate the condition of an ecosystem.

Study Area

The Neches River is more than 400 miles long, extending from near Canton, Texas southeastward to Sabine Lake. Totaling more than 10,000 square miles, the Neches River and its tributaries flow through many miles of picturesque forests including the Big Thicket National Preserve. These heavily wooded areas are one of the sources of naturally occurring organic materials, which, at times, gives the Neches River its distinctive “tea” color.

Two large reservoirs, Sam Rayburn and B. A. Steinhagen, are used to collect and store water as it enters the basin. These reservoirs provide a reliable source of fresh water to the many communities, farms, and industries served by the Lower Neches Valley Authority (LNVA). The Neches River also sustains the region’s deepwater ship channel, the Sabine-Neches Waterway, maintained locally by Jefferson County Waterway & Navigation District.

Chemistry

Many basic water quality parameters were measured and water samples collected and analyzed for nutrients, certain metals and organic compounds. Salinity generally increased with depth at Stations 2-4, indicating limited water column mixing throughout the downstream portion of the study area.

Dissolved oxygen (DO) concentrations throughout the water column were generally favorable at all stations, with the majority exceeding Texas Commission on Environmental Quality (TCEQ) water quality criteria, demonstrating sufficient levels exist for aquatic organisms to live and reproduce. At Stations 2-4, bottom DO values decreased to near zero. Low DO concentrations near the river bed are commonly found in estuarine mixing zones. Microbial activity, in conjunction with limited mixing throughout the water column, can deplete the available DO near the bottom.

Nitrogen, phosphorus and fecal coliform values are commonly used as indicators of human and agricultural activities. All nutrient forms of nitrogen and phosphorus measured were below TCEQ water quality screening levels. Fecal coliform counts however, did exceed the screening level in 10 of 16 samples, most likely due to increased runoff from a large storm event prior to the field sampling.

Concentrations of all metals tested were low and below the tidal screening levels, and concentrations of selected organics in the surface water samples were either undetectable or at low levels above the detection limit.

Overall, the 2003 lower Neches River chemistry study, as in 1996, revealed stable or slightly improved water quality over the past 20 years.

Algae

Algae form the base of the aquatic food chain in rivers, lakes and oceans. They use the sun’s energy during photosynthesis to grow, providing food and oxygen for many larger organisms. Some forms of algae attach to vegetation and sediments located along the banks of rivers and streams, areas that are constantly exposed to environmental change. Their ability to colonize a wide variety of habitats makes them ideal for monitoring the health of aquatic ecosystems. Algae and diatoms (algae with silica shells) serve as living biological indicators of the ecological condition of streams, lakes and rivers.

Samples of attached algae and diatoms were collected by hand from many different habitats such as mud and sand shorelines, aquatic plants and hard substrates like submerged tree roots. Changes in the numbers of algal species at each site, their relative abundance and community dominance (whether there’s a balance of different species or the community is dominated by just a few types), have been used to evaluate water quality on the lower Neches for the past 50 years.

The 2003 results indicate a more balanced algal community, with the presence of more diatoms than blue-green algae, and generally decreased amounts of algae throughout the study area compared with the earlier 1953 and 1973 surveys.

The graph shows the relationship between blue-green algae and diatoms collected at Stations 2-4 during the four lower Neches river surveys. The change in dominance (with an equal or greater proportion of diatoms in 1996 and 2003) reflects the increased water quality throughout the study area since the earlier surveys.

Macroinvertebrates

Macroinvertebrates (shrimp, clams, snails, aquatic insects, etc.) generally provide the link in the aquatic food chain between algae and animals that occupy higher feeding levels, like fish. Their limited mobility, relatively long life spans of some species and responses to a wide range of environmental conditions make them effective in monitoring long-term change. The growth and reproduction of many types are a direct reflection of changes in water quality.

Some macroinvertebrates, like shrimp and blue crabs, are also vital to people who live and work along the Texas Gulf Coast. During 2003, nearly 1 million pounds of blue crabs were harvested from the Sabine Lake system, with a dockside value in excess of six hundred thousand dollars.

All available habitats were sampled to characterize the macroinvertebrate community within each of the four study sites. Important considerations for the macroinvertebrates included the number and relative abundance of species and their habitats and distributions within the estuary.

Macroinvertebrates can be divided into insect and non-insect groups. Insects dominate freshwater environments and become less diverse when salinity increases, while non-insects are common in both fresh and saline waters. Mollusks (clams, snails, etc.), crustaceans (shrimp, crayfish, etc.) and leeches are the dominant freshwater non-insect macroinvertebrate groups. Polychaete worms (clam worms, etc.) and a very diverse crustacean assemblage (crabs, barnacles, etc.) are more common in saline waters. During surveys with higher annual river discharges (e.g., 1973 and 2003) conditions are favorable for freshwater macroinvertebrates to move further downriver. In drier years (e.g., 1996), because of the greater influence of tidal cycles, conditions favor macroinvertebrates that prefer higher salinities.

Compared to the 1996 survey, roughly similar numbers of non-insect species and a greater number of insect species were collected at each station in 2003. The higher percentage of insects is comparable to the results of the 1973 survey, conducted under similar annual river discharge patterns. However, in 2003, more than twice as many insect and non-insect species were recorded at the downriver Stations 2 through 4, and from all stations combined, than in 1973. These increases in diversity are consistent with the Neches River studies conducted under the direction of Dr. Richard C. Harrel, Lamar University, which showed an improvement in water quality in the lower Neches River between his 1971-1972 and 1999 studies.

The chart illustrates the continued increase in the numbers of insect and non-insect macroinvertebrate species collected over time during the Academy's four comprehensive lower Neches River surveys. As water quality improves, macroinvertebrate diversity increases but the number of insect species can decline when salinities get higher, as during the 1996 survey. Non-insect macroinvertebrates become more numerous as salinities increase, displacing aquatic insects along the river bottom.

Fish

Fish occupy a wide range of trophic levels, including herbivores (e.g., menhaden which feed on phytoplankton), invertebrate-feeders (including many bottom fishes), and top predators. Many species are recreationally and commercially important, particularly in southeast Texas, where fishing provides family recreation and is an integral part of the local economy.

The Academy fisheries studies document the numbers and kinds of fish that are found in the range of habitats in the study area, including deeper channels, sand beaches and muddy backwaters. The numbers and diversity of fish are key indicators of the amount and quality of food available, accessible habitats and water quality.

Fish were sampled using a trawl and a variety of seine and dip nets. A total of 51 species was collected in 2003 using all techniques, reflecting the salinity gradient throughout the study area, with freshwater species (e.g., some minnows and channel catfish) relatively common at Station 1, and a number of estuarine species (e.g., gulf menhaden, sailfin molly and bay whiff) found only at Station 4. Juveniles of many important commercial and recreational species, including spot, Atlantic croaker, spotted and sand seatrouts, channel and blue catfish, and spotted bass, were also noted.

Forty-seven species were recorded from various shallow water habitats by seining, with the main species including bay anchovy, sand seatrout and tidewater silverside. Nine species were collected by trawling, with sand seatrout and bay anchovy being most common. As in the seine samples, the trawl catches reflected increased salinity from Stations 1 through 4, with two species (channel catfish and hogchoker) found only at Station 1 and two species (hardhead catfish and darter goby) caught only at Station 4. Numbers of young fish were trawled both in deep and in relatively shallow waters indicating that the area serves as a nursery ground for a variety of fish species.

The number of species recorded during the 2003 fisheries survey equaled the 1996 study. The number at each station was greater in 2003 than in 1973 at all stations: Station 1 (32 vs. 22 species), Station 2 (20 vs. 12), Station 3 (19 vs. 12), and Station 4 (18 vs. 16) with an increase in total numbers of species at all stations (51 vs. 33 species).

The 2003 lower Neches River fish collections reflect a mixture of freshwater and estuarine species found throughout the inland and coastal waters of the northwestern region of the Gulf of Mexico. The varied wetlands and marsh habitats within the lower Neches River basin provide essential nursery areas for numerous fish species. The fish fauna recorded during the most recent survey indicates that the existing water quality and habitat diversity support a productive and substantial fish community.

Conclusions

Compared with earlier Academy studies, the 2003 Lower Neches River study clearly indicates the system-wide improvement in the biological communities within the study area. The Neches estuary supports diverse algal, macroinvertebrate and fish populations, and serves as primary nursery habitat for numerous species of estuarine and marine fish.

Most chemical and water-quality parameters in 2003 were within acceptable limits and were similar to or better than levels in previous Academy studies, especially those in 1953 and 1973. As in past Academy studies, however, there continues to be evidence of elevated fecal coliform levels.

Also as in earlier Academy studies on the lower Neches River, blue-green algal growths were evident at all stations, indicating continued nutrient enrichment throughout the study area. However, overall reductions in algal species dominance, prevalence of blue-greens relative to diatoms, and total algal abundance all indicate improved conditions in 2003 compared to 1953 and 1973.

Total macroinvertebrate species richness in 2003 was by far the highest observed in any Academy study on the lower Neches River to date.

The fish assemblage in the lower Neches River continues to be abundant and diverse. Increased abundance and variety of estuarine species at Stations 2 through 4 were evident in the 2003 and 1996 studies compared to the 1953 and 1973 studies.

Download a pdf version of this Neches River 2003 Studies Report (6MB).

If you have any questions about the 2003 Lower Neches River studies, please contact:

Lower Neches Valley Authority
P.O. Box 5117
Beaumont, TX 77708-5117
(409) 892-4011
www.lnva.dst.tx.us/