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additional ecotoxicological information
Type of information:
experimental study
Adequacy of study:
weight of evidence
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference Type:
Direct and indirect ecotoxicological effects of alkyl sulfate and alkyl ethoxysulfate on macroinvertebrates in stream mesocosms
Belanger SE, Meiers EM, Bausch RG
Bibliographic source:
Aquatic Toxicology 33 (1995) 65-87

Materials and methods

Principles of method if other than guideline:
AS stream mesocosm experiments were conducted at the Procter & Gamble Experimental Stream Facility (ESF) near Cincinnati, Ohio. The ESF location, source water and basin, and operational environment is described in detail by Belanger et al. (1994) and will only be briefly reviewed here. The source water for the ESF is the Lower East Fork of the Little Miami River, Clermont County, Ohio. This river is rated as an exceptional warmwater fishery by the Ohio EPA (OEPA, 1985) and drains into a national and state scenic river. ESF stream channels are 12 m in length and are divided into five sections: a head box, an upper reach which is used mostly for periphyton investigations, a flared section that leads to the invertebrate reach, and a tail pool. A total of seven stream mesocosms was used in these studies. Current velocity was approximately 0.5 m/s at a volume of 166 l/min per stream. Average hydraulic residence from entry into the headbox to exit from the tail pool is approximately 3.5 min. Lighting is accomplished by 30, 1000-watt metal halide arc lamps that provide daylight quality radiation at 68 pmolls m-2. Lights are staged up and down to simulate dawn and dusk. Natural photoperiods specific to the latitude and longitude are used and are adjusted daily through on-site computer control systems. Test chemical is individually delivered to each of the seven streams from large stock reservoirs located at the head of each stream. Water quality is monitored by a cluster of electronic devices in the tail pool and at the river water head tank where water is first delivered to the ESF. Dissolved oxygen, temperature, pH, and conductivity are continuously monitored. Environmental control and monitoring of flow rates to each system, lighting, and water quality data are logged into electronic data bases by an on-site mini-computer.

Invertebrate communities were evaluated in the lower 4.5 m reach of the stream channels. The sampling unit used in this stream section was a polypropylene tray (dimensions of 26.0 cm long, 15.9 cm wide, 6.4 cm deep) filled with cobble. Forty-five trays arrayed in 3 columns by 15 rows were placed in each stream. Trays were held in place by a lexan holder which was machine-grooved to provide a near water-tight seal between trays and the holder. Thus, water flows over the surface and percolates through the trays. Trays were filled with cobble (2.0 cm typical diameter, range of 1300&1800 mm2 surface area) substrate prior to colonization. At the intersecting corners of trays a 25 cm7 square tile was placed to diffuse the flow of water which otherwise tends to channel along the edges of the trays. Water depth varied from 2.0 to 3.0 cm through the invertebrate reach.

Invertebrates were sampled after 0, 4, and 8 weeks of exposure in ESF stream mesocosms. Five replicate trays were sampled on week 0 and 9 replicate trays were sampled at weeks 4 and 8 from each stream. Trays were selected using a randomization program developed using SAS (1990). In addition to benthic samples, invertebrate drift was also monitored. Drift nets (253 ,um mesh net, 63 µm mesh cod-end) were inserted at a chute placed at the entry to the stream pool. The opening to the drift net was 29 x 18 cm and accommodated 100% of the flow to the pool. Drift was collected for 30 min immediately prior to the initiation of chemical dosing and for 15 min after 1, 2, 4, and 5 h of exposure. Volume of water flowing through the streams (and drift collections) was determined using data collected from the computer logging and data acquisition system timed with the insertion and removal of the drift nets. Invertebrate tray samples were initially sorted by sieving all of the tray through a sequential series of sieves terminating with two 250 pm mesh standard sieves. All contents of the trays retained were preserved in 250 ml bottles filled with 10% buffered formalin. Samples were transferred to 70% ethanol for processing in the laboratory. Quantitative sorting and subsampling followed standard operating procedures developed at the Academy of Natural Sciences of Philadelphia. Identifications for all taxa were made to lowest practical taxon by available taxonomic keys. Once taxonomic identity was recorded and individuals enumerated, all the individuals for a taxonomic group were blotted dry and placed in a petri dish (excluding molluscs described below). Samples were dried in a drying oven at 40°C for 48 h and weighed on a Cahn model 25 electrobalance to kO.05 mg. Bivalve, snail and limpet biomass was determined by dissolving the mollusc shell using a 5% solution of Rid-Lime (Ohio Valley Chemical Corporation, Cincinnati, Ohio) followed by rinsing the remaining mass in distilled water and drying. Very small individuals (< 5 mm shell length) were dried whole. Oligochaete biomass was estimated by pooling 100-1000 individuals from each taxon. A simple scalar multiplier for each taxon was applied to abundance data for all streams and times. It is recognized that more elaborate estimates could be made, but the procedure used was appropriate for these investigations. Mollusc and aquatic worm samples were dried at 60°C for at least 24 h and weighed on a Mettler PE360 balance to +/-0.05 mg.

Invertebrate endpoints
Compilation of the taxonomic information obtained resulted in the use of the following indices and endpoints: total and population abundance, total and population biomass, relative abundance, taxa richness, Shannon diversity, trophic functional feeding group abundance and biomass, drift rate and density (community and population level), drift richness and drift Shannon diversity.

Surfactant chemistry
AS was measured in stream and stock tank samples on a weekly basis. Stream measurements were taken both at the head and tail of each stream . AS (GC-FID) surfactant-specific techniques for stream samples used previously published validated methods (Fendinger et al., 1992; Popenoe et al., 1994). The results are based on measured concentrations.
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
Sodium dodecyl sulphate
EC Number:
EC Name:
Sodium dodecyl sulphate
Cas Number:
Molecular formula:
sodium dodecyl sulfate

Results and discussion

Any other information on results incl. tables

Responses to alkyl sulfate

Total invertebrate density increased with AS exposure. The large majority of the increased density was associated with increased numbers of oligochaetes at 224-1586 µg AS/l. The number of oligochaetes at 1586 ,ug AS/l was approximately 1000x that of controls. Non-oligochaete invertebrates were not affected in the same manner with relatively consistent densities during the experiment. A decline in the highest exposure was noted, but differences were not significant. Total biomass of non-oligochaete invertebrates was also not affected at any concentration, but certain groups exhibited increases or decreases. For example, gastropod biomass increased with increasing AS exposure concentration and differences were significant at 582-1586 µg AS/l. Gastropods were numerically dominated by the limpetFerrisseuand the snailPhysella.Total mayfly biomass and density were affected in the opposite manner. Although differences were not significant, the trend was to reduce mayfly abundance at high AS levels.BaetisandStenonemawere greatly reduced at 1586 and 582-1586 µg/l, respectively. Other mayflies, such asIsonychiaandTricorythodes,were reduced, but not significantly at any concentration.Corbiculu$uminea,the Asian clam, was also reduced in density at 1586 ug AS/l. These taxon-specific responses were reflected in diversity analyses. When oligochaetes were excluded from diversity calculations, Shannon diversity based on biomass was not affected, but diversity based on abundance was reduced at 224-1586 µg AS/l. This reduction in diversity reflected the increased numbers ofPhysellnandFerrisseain AS-exposed streams which were numerically the most abundant organisms other than aquatic worms. When proportional densities were corrected withFerrisseaabsent, diversity was reduced only at 1586 µg AS/l. Trophic functional feeding groups directly reflected absolute and proportional density or biomass of aquatic worms (collector-gatherers) and gastropods (scrapers). The reductions ofBaetisandStenonemapopulations, which are scraper taxa, were offset by the larger proportional increases of gastropods. Thus, as the experiment progressed, both scraper and collector-gatherer feeding groups significantly increased in dominance.

Drift density, rate, and diversity during the initial stages of AS exposure were not affected. Control values after 5 h of dosing were: 13.6 individuals/m3 (drift density), 124 individuals/h (drift rate), and 2.457 (drift diversity).

Applicant's summary and conclusion

AS C12 stream ecosystem NOEC: 0.224 mg/L
Executive summary:

Stream mesocosm experiments were conducted with the anionic surfactants alkyl sulfate (AS) to determine the ecotoxicological effect thresholds on stream communities. Autotrophic and heterotrophic periphyton, protozoan, and invertebrate population and community effect assessments were conducted over an 8 week exposure period in the summer to fall seasons following a 2- to 3-month colonization period. Concentrations spanned environmentally low to unrealistically high concentrations to challenge the sensitivity of the test system and to understand the potential array of effects. Mayfly taxa and clam populations were significantly impaired at high concentrations (582-1586 µg surfactant/l). Indirect effects, associated with increased heterotrophic periphyton biomass in surfactant-treated streams at 224-1586 µg surfactant/l, supported increased densities of oligochaetes and gastropods. Mayfly habitat may have become sub-optimal during the AS experiment as a result of the heterotrophic biofilm at concentrations above 224 µg/l. These experiments resulted in ecotoxicological no-observed-effect-concentrations (NOECs) of 224 µg AS/l.

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