The Sabine River Basin is approximately 300 miles long and extends from northeastern Texas to Sabine Lake and on to the Gulf of Mexico. The Sabine River and watershed provide a wide variety of recreational opportunities, such as fishing, boating, hiking, hunting, etc. to countless residents and visitors each year.
Since 1982, Eastman Chemical Company, Texas Operations has sponsored a series of biological and water-quality surveys on the Sabine River near Longview, Texas, by the Patrick Center for Environmental Research of The Academy of Natural Sciences. The present study was conducted in October of 2000; previous studies were completed in 1982, 1987, and 1995.
The Sabine River surveys are designed to assess the potential impacts of effluent from Eastman's Longview facility on the general "health" of the river. Components of the surveys include environmental chemistry (water, sediments, fish, and clams), attached algae and aquatic plants, macroinvertebrates, and fish. Multiple levels of the aquatic food web are studied because no single group is reliably the best indicator of the health of an ecosystem, and also because it is widely believed that maintaining the integrity of the entire ecosystem is very important.
The study design employed in the Sabine River surveys includes four main sampling zones: three exposed to Eastman's operations (Zones 2, 3 and 4), and an unexposed reference zone (Zone 1) upstream from the facility.
Potential impacts of Eastman operations are assessed by determining whether differences exist between the exposed and reference zones that can't be attributed merely to natural differences among sites or to disturbances originating upstream from the Eastman facility. Signs of impact might include fewer numbers of species and individuals, increased dominance by a small proportion of the species present, or slower individual growth rates.
Determining whether exposed and reference zones differ is complicated by the fact that considerable variation exists even among samples collected on the same day throughout the study area. Any apparent differences between zones may be a function of only collecting a single sample within each zone. For this reason, several components of The Academy's surveys include the collection of multiple samples from each zone.
Another type of variation which The Academy's surveys address is variation over time. As The Academy's Sabine River surveys continue, it will eventually be possible to address this issue. Currently, the are too few studies to assess trends over time or the natural variability that may occur. The present study, however, does include a comparison of the 2000 results with those from the 1982, 1987 and 1995 studies.
Environmental Chemistry
In 2000, samples of water, sediment and fish were collected from all zones. Water sample tests included trace metals, major ions, nitrogen and phosphorus nutrients, suspended solids, dissolved oxygen and biochemical oxygen demand, pH, hardness, alkalinity, conductivity, dissolved organic carbon, and temperature. Sediment and fish samples were analyzed for trace metals (including total mercury), polycyclic aromatic hydrocarbons (PAHs), and assorted organic compounds.
There was a sharp increase in a variety of water quality parameters between Zone 2 and upper Zone 3 (3U), including pH, total alkalinity, conductivity, chloride, sulfate, selenium, nitrite, total Kjeldahl nitrogen, dissolved orthophosphate, total phosphate, and dissolved organic carbon. However, no water quality parameters exceeded Texas water quality criteria.
Sediment samples showed low concentrations of metals at all zones and no clear increases in metals between Zones 2 and 3U. Total PAHs appeared to increase between these zones, but were below levels likely to have adverse effects on benthic macroinvertebrates. Concentrations of chlorinated benzenes were low at all zones and only one, hexachlorobenzene, exceeded the Texas Natural Resources Conservation Commission (TNRCC) screening level (not a regulatory criterion) in lower Zone 3.
Fish samples showed low trace metal concentrations at all four zones, with no clear spatial relationship. Total mercury levels in all fish were well below the US Food and Drug Administration screening level. PAH concentrations in fish were low, but showed an increase between Zones 2 and 3. Chlorinated benzene concentrations were low and showed no clear zone-related pattern.
Water-column concentrations of dissolved and total phosphate have decreased considerably since The Academy's 1982 survey, and dissolved nitrate concentrations have also decreased. Trace metals in sediments and fish show no pronounced changes since 1982, although zinc concentrations in sediment appear to have declined slightly.
In summary, results of the environmental chemistry assessment indicate that several parameters in water, sediments, and fish showed increases that are related to Eastman operations. However, no concentrations exceeded regulatory criteria, and no chemical parameters for which biological-effect guidelines exist were present at concentrations that would be expected to impair biological communities in the river.
Algae attach to vegetation, rocks, and sediments throughout most rivers. Their abundance and diversity are a reflection of the surrounding water quality. Attached algae and aquatic plants were sampled in all four zones during the October survey. Specimens were identified and assessed for their known ecological and pollution-tolerance characteristics.
The composition of attached algal populations in sampling zones above and below the Eastman facility was similar. As in all previous surveys, nutrient enrichment was indicated by low species richness, high abundance, and presence of species known to tolerate high nutrient conditions. Enrichment was apparent in all sampling zones with origins from sources upstream from Eastman's facility.
The 2000 results are similar to those of the 1995 survey, which found greatly reduced differences among stations above and below the Eastman facility, compared to the 1982 and 1987 surveys. No evidence of facility-related organic enrichment was found during this study.
The abundance and diversity of aquatic insects (mayflies, dragonflies, midges, etc.) and non-insect macroinvertebrates (crayfish, shrimp, mussels, etc.), are widely used to monitor water quality in lakes, streams, and rivers throughout the United States. As the link between the base of the food web (algae and detritus) and fish, macroinvertebrates have proven to be excellent indicators of water quality throughout the Sabine River study area. Grazing atop or burrowed within the river bottom, most macroinvertebrate species are constantly exposed to changes in their environment.
Macroinvertebrates were sampled qualitatively in all four zones during October, identified and assessed for known ecological and pollution-tolerance properties. The results of the qualitative hand collections were used primarily to determine the numbers of different forms living on and within a wide range of natural substrates. Aquatic insects were also sampled quantitatively (using a T-sampler) in all zones except Zone 2, which lacked shallow-water riffle habitats.
For the insects, the hand collections yielded higher numbers of forms in each sampling zone than in any of the previous Sabine River surveys, and higher numbers of different types of insects in Zone 3 than in either Zone 1 or Zone 2. The results of the T-sampler collections indicated that no statistically significant variation among zones was found for most parameters examined. However, one statistical test showed significantly higher average pollution tolerance scores in Zones 3 and 4 compared to the upstream reference Zone 1, apparently due to the elevated numbers of one group of midges.
These results suggest that the Eastman effluent has a minor effect on the Sabine River aquatic insect assemblage. However, this effect appears to be restricted to a single midge group and does not appear to be biologically significant.
The results for the non-insects indicated that the number of species was similar to that in 1995 in every sampling zone and was higher in every zone than in 1987. Species numbers were similar among sampling zones but somewhat higher in Zones 3 and 4 (downstream from the main entry point of Eastman effluent) than in Zone 2 (immediately upstream from the main effluent discharge). The primary change from 1995 in the non-insect macroinvertebrate fauna was a substantial decrease in the numbers of freshwater mussel species recorded at all zones (14 species in 2000 versus 21 in 1995) . Taken together, results of the assessment of non-insect macroinvertebrates in 2000 reveal no impacts from any of the Eastman discharge points to the river.
The numbers, types, and growth rates of fish living in the Sabine River are an accurate reflection of water quality and the availability of food and cover. Fish were sampled during October in all four zones using three different sampling techniques (electroshocking, seining, and gill-netting), each appropriate to a different habitat or size-range of fish. Specimens were identified to species, and samples were assessed for species abundance, richness, and diversity. In addition, growth rates of young-of-year red shiners were determined, based on fish length and examination of growth rings within fish ear bones or otoliths.
When results of all collecting techniques were combined, the total number of fish species collected in 2000 was smaller than in 1995 (39 versus 47), but larger than in either 1987 (37) or 1982 (33). The most species were collected in Zone 1, while the fewest were collected in Zone 2. Two species (red shiner and bullhead minnow) made up 92% of the total catch.
(fish ear bone).Statistical analyses of the seining data revealed differences in species richness among zones, but not in Shannon-Wiener diversity. Richness did not differ significantly among Zones 1, 3, and 4, but was reduced in Zone 2, possibly due to lack of riffle habitats.Analysis of growth rates in young-of-year red shiners revealed no significant differences among zones.
Taken together, the results for total species richness, quantitative seine and electroshocking samples, and red-shiner growth rates reveal no impacts on the Sabine River fish assemblage due to Eastman's effluent.
The environmental chemistry component of the 2000 Sabine River survey found that several parameters showed evidence of an Eastman influence, but none exceeded Texas water quality criteria, and all concentrations of chemicals for which biological-effect guidelines exist were below levels likely to impair biological communities in the river.
In the biological components of the survey, only aquatic insects showed evidence of an Eastman impact, but this impact appears to be due entirely to increased abundance of a single pollution-tolerant midge in the two zones exposed to the facility's effluent, with no associated decrease in the abundance of sensitive taxa. Results for attached algae suggest that the system-wide nutrient enrichment observed in the 1995, 1987, and 1982 surveys persists, evidently due to sources upstream from the Eastman facility. As found in the 1995 survey, the degree of enrichment appears much lower than in the 1982 and 1987 surveys.
Overall, the 2000 Sabine River survey indicates that the condition of water quality and biological communities in the river near Longview, Texas, was broadly similar to their condition in 1995 and substantially better than in 1987 or 1982, and there appeared to be little or no significant impact on the aquatic environment from the Eastman facility discharge.
For more information on the Sabine River and it's surrounding watershed.
Tel: 215-299-1000 Email: webmaster@acnatsci.org
