Sabine River Monitoring
Introduction
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 2005; previous studies were completed in 1982, 1987, 1995 and 2000.
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 among 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, there 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 2005 results with those from the 1982, 1987, 1995, and 2000 studies.
Environmental Chemistry
In 2005, samples of water, sediment, freshwater mussels and fish were collected from all zones. Water sample tests included, major ions, nitrogen and phosphorus nutrients, suspended solids, dissolved oxygen and biochemical oxygen demand, pH, hardness, alkalinity, conductivity, dissolved organic carbon, temperature, and total selenium. Sediment, mussels 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, total alkalinity, conductivity, chloride, sulfate, nitrite, total phosphorus, and dissolved organic carbon. However, no water quality parameters exceeded Texas water quality criteria.
Sediment samples showed low concentrations of trace metals at all zones with no clear trends. Total PAHs appeared to increase between Zones 2 and 3U, but all PAH compounds were below levels likely to have adverse effects on benthic macroinvertebrates. Concentrations of all chlorinated compounds were below Texas screening levels.
Trace metal concentrations in mussels collected in all four zones were low and most metals showed no spatial patterns. Copper and nickel concentrations appeared to increase in Zone 3. PAHs appeared to also increase in 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. However, if fish consumption (mostly longnose gar) equaled three 8-oz. meals per month then screening levels would be exceeded. PAH concentrations in fish were low, but values were slightly higher in Zones 3 and 4. Concentrations of chlorinated compounds 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. Concentrations of most trace metals in sediments were lower in 2005 compared to the 1987 study.
In summary, results of the environmental chemistry assessment indicate that several parameters in water, sediments, freshwater mussels, 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 and Aquatic Plants
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 2005 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 2005 results are broadly similar to those of the 1995 and 2000 surveys, 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.
Macroinvertebrates
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 Zones 1, 2, and 4 than in previous Sabine River surveys. Twenty taxa identified in 2005 had not been collected by Academy staff in previous surveys. The results of the T-sampler collections indicated that Zone 1 was the most impaired.
The results for the non-insects indicated that the number of species was highest ever recorded at three of the four (1, 2, and 4) zones and highest for the entire study area (44) compared to past surveys (28-43). Several new species were recorded during the 2005 survey. The numbers of freshwater mussel species recorded also increased substantially between Zones 2 and 3, due principally to the increased mussel habitat throughout Zone 3. Taken together, results of the assessment of non-insect macroinvertebrates in 2005 reveal no impacts from any of the Eastman discharge points to the river.
Fish
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 a variety of sampling techniques including 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 number of individuals per species and total number of species per sample. 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 2005 was smaller (34) than in 2000 (39), 1995 (47), or 1987 (37), but larger than in 1982 (33). The most species were collected in Zones 2 and 3 (26), while the fewest were collected in Zone 4. Three species (red shiner, bullhead minnow, and ghost shiner) made up 91% of the total catch. (See Fish Surveys for 1982-2005.)
Statistical analyses of the seining data revealed no significant differences in numbers of species recorded in each zone, or in the five most common species collected from each zone. Growth rates in young-of-year red shiners were also similar 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.
Conclusions
The environmental chemistry component of the 2005 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. Mercury levels in fishes collected from all zones were below screening levels but additional monitoring may be warranted.
The results of the attached algae collections suggest that the system-wide nutrient enrichment observed in the previous surveys persists, evidently due to sources upstream from the Eastman facility. As found in the 2000 and 1995 surveys, the degree of enrichment appears much lower than in the 1982 and 1987 surveys. The macroinvertebrate and fisheries studies do not indicate Eastman impacts on the Sabine River study area.
Overall, the 2005 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 2000 and 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 discharges.