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Ecotoxicological information

Toxicity to other aquatic organisms

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Endpoint:
toxicity to other aquatic vertebrates
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study.
Qualifier:
no guideline available
Principles of method if other than guideline:
An integrated model stream ecosystem.
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
Sampling was done two to three times weekly at both the head and tail of each stream. Sampling was done in triplicate.
Test organisms (species):
other:
Details on test organisms:
other: Baetis sp. (mayfly), Isonychia sp. (mayfly), Stenonema sp. (mayfly), Thienemannimyla sp. (chironomid), Tanytarsus sp. (chironomid), Cricotopus sp. (chironomid), Polypedilum sp. (chironomid), Reotanytarsus sp. (chironomid), Naididae (aquatic worm)
Test type:
other: out-door experimental streams
Water media type:
freshwater
Limit test:
no
Total exposure duration:
56 d
Remarks on exposure duration:
Exposures ranged from 126 to 2978 ¿g/L
Nominal and measured concentrations:
Exposures ranged from 126 to 2978 ¿g/L
Details on test conditions:
An integrated model stream ecosystem fate and effects study of a C12LAS homologue, with a high content (35.7%) of its most hydrophobic and toxic 2-phenyl isomer, was performed in the summer and fall of 1996 in Procter and Gamble's Experimental Stream facility. The study addressed responses of periphytic microbes, immature benthic fauna including abundance and drift, and emergence of adult insects in a 56-day exposure.
Duration:
56 d
Dose descriptor:
NOEC
Effect conc.:
268 µg/L
Basis for effect:
other: bioavailailability model
Details on results:
Microbial heterotrophs acclimated to C12LAS exposure quickly (14 days) and biodegraded C12LAS at all concentrations. Blue-green algae responded by increasing in abundance with increasing C12LAS concentration. Invertebrates responded by increased drift and reduced benthic abundances at concentrations exceeding 293 µg/L. Emergence at 927 µg/L also declined relative to the control. Adverse responses for mayflies and chironomids were indicated using univariant statistical techniques. Multivariant techniques indicated these taxa plus molluscs, aquatic worms, caddisflies, and stoneflies were impaired at some concentrations. Bioavailability of C12LAS was investigated in streams as a function of the total suspended solids load in the water column driven by local weather and watershed patterns. A continuous bioavailability model indicated exposure was reduced by an average of 8.5 ± 8.9%. A model ecosystem NOEC (no-observed-effect-concentration) was concluded to be 293 µg/L based on measured water column exposure and adjusted to 268 µg/L by the bioavailability model. A summary of selected population and community responses at 8 weeks from the current study is shown in the table below.

Community/Measure

Dose Response

Temporal

NOEC (µg/L)

Heterotrophic microbial

Biomass (total lipid phosphate/mm2)

Amino acid uptake (3H dpm/mm2/min)

Phospholipid fatty acid (PLFA) distr.

Surfactant mineralization (% CO2)

NS

NS

Shift at >293 µg/L

Acclimation at all conc.

Autotrophic microbial

Bicarbonate uptake (14C dpm/mm2/min)

Algal density (cells/mm2)

Algal biovolume (µm3/mm2)

Blue-green algal density (cells/mm2)

Green algal density (cells/mm2)

Diatom algal density (cells/mm2)

Algal richness

Dominant taxa (cells/mm2)

  Cocconeis placentula

  Melosira varians

  Chrococcus sp.

  Nitzschia dissipata

  Navicula salinarum v. intermedia

  Pleurosira (= Biddulphia) laevis

  Nitzschia inconspicua

  Nitzschia palea

  Diatoma vulgare

  Gyrosigma acuminatum

+

NS

NS

++

NS

NS

-

-

NS

+

NS

NS

NS

++

+

--

-

+

++

-

-

+

++

+

--

-

927

927

927

927

Invertebrates

Richness

Diversity (Shannon-Weaver)

Total abundance (No./m2)

Insect abundance (No./m2)

EPT abundance (No./m2)

Mayfly abundance (No./m2)

Caddisfly abundance (No./m2)

True fly abundance (No./m2)

Chironomid abundance (No./m2)

Mollusk abundance (No./m2)

Oligochaete abundance (No./m2)

Dominant populations (No./m2)

  Baetis sp. (mayfly)

  Isonychia sp. (mayfly)

  Stenonema sp. (mayfly)

  Thienemannimyla sp. (chironomid)

  Tanytarsus sp. (chironomid)

  Cricotopus sp. (chironomid)

  Polypedilum sp. (chironomid)

  Reotanytarsus sp. (chironomid)

  Naididae (aquatic worm)

NS

NS

--

NS

-

NS

NS

NS

NS

NS

--

b

---

NS

---

++

+

+

NS

NS

--

-

--

---

---

++

+

+

293

927

293

927

293

a Plus (+) and minus (-) signs indicate whether the response significantly increased or decreased from the control condition (± = 0.05). The strength to the response was graded as slight (+/-), moderate (++/--), or great (+++/---) based on statistical analyses.  NS indicates not significant. bTaxon too low in abundance, emerged.

Conclusions:
A model ecosystem NOEC (no-observed-effect-concentration) was concluded to be 293 ¿g/L based on measured water column exposure and adjusted to 268 ¿g/L by the bioavailability model.
Executive summary:

An integrated model stream ecosystem fate and effects study of a C12LAS homologue, with a high content (35.7%) of its most hydrophobic and toxic 2-phenyl isomer, was performed in the summer and fall of 1996 in Procter and Gambles Experimental Stream facility.  The study addressed responses of periphytic microbes, immature benthic fauna including abundance and drift, and emergence of adult insects in a 56-day exposure.  A model ecosystem NOEC (no-observed-effect-concentration) was concluded to be 293 microgram/L based on measured water column exposure and adjusted to 268 microgram/L by the bioavailability model.

Endpoint:
toxicity to other aquatic vertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication/study report which meets basic scientific principles
Qualifier:
no guideline followed
Principles of method if other than guideline:
Tests were conducted as an aqueous fraction in the presence of sediment.
GLP compliance:
not specified
Analytical monitoring:
yes
Vehicle:
not specified
Details on test solutions:
Natural stream sediments (71% clay, 19% fine silt, 4% medium sand, 6% fine sand) were collected from a pristine site in Rapid Creek, SD. Before testing, wet sediment was autoclaved for 40-60 minutes to reduce microbial populations and minimize initial rates of surfactant biodegradation.
Test organisms (species):
other: Chironomus riparius
Test type:
other: flow-through closed system
Water media type:
not specified
Limit test:
no
Total exposure duration:
24 h
Remarks on exposure duration:
average
Hardness:
"monitored frequently"
Test temperature:
"monitored frequently"
pH:
"monitored frequently"
Dissolved oxygen:
"monitored frequently"
Nominal and measured concentrations:
Test concentrations were control, 8, 42, 146, 319, and 993 ppm.
Details on test conditions:
LAS was added to a sediment slurry at a nominal concentration and stirred overnight, then 350 g was poured into each test chamber and allowed to settle. The organic carbon content of the test sediment was 4.2% prior to testing. A flow-through diluter system delivered test material in water to glass containers with 120-140 cm² bottom surface area each. Intact egg masses were incubated in Petri dishes containing 20-30 mL of dilution water at 22 °C until hatching commenced. Newly hatched larvae were allowed to mature 72 hours before testing. Twenty larvae were randomly distributed to each duplicate test chamber for each of five test concentrations plus the controls. Larvae were fed daily until emergence of the first adult in each chamber. Tests were continued until each midge emerged as an adult or larvae were determined to be dead.
Reference substance (positive control):
yes
Dose descriptor:
NOEC
Effect conc.:
319 other: ppm in sediment
Basis for effect:
other: emergence
Dose descriptor:
LOEC
Effect conc.:
993 other: ppm in sediment
Basis for effect:
other: emergence
Details on results:
Adults typically emerged 12-14 days after hatching. Control values for adult emergence were similar to or exceeded the historical average observed in their laboratory (>90%). Percent emergence was 98, 95, 90, 90, 90, and 73 for the control, 8, 42, 146, 319, and 993 ppm concentrations, respectively. For comparison, additional flow-through studies were conducted without sediment.

Results indicate that sorption onto sediment significantly mitigates LAS bioavailability.

Conclusions:
The NOEC for Chironomus riparius in sediment was 319 ppm, and the LOEC was 993 ppm based on emergence.
Endpoint:
toxicity to other aquatic vertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication which meets basic scientific principles
Qualifier:
no guideline followed
Principles of method if other than guideline:
Collected and placed in net tubes in a tank for 7 days in contact with 50 mg/L continuously suspended LAS-spiked sediments. Mussels were fed an algal suspension and water, food, and sediment were renewed daily.
GLP compliance:
no
Analytical monitoring:
yes
Vehicle:
no
Test organisms (species):
other: Mytilus galloprovincialis
Details on test organisms:
Thirty mussels (5.8 cm average main axis length) collected from a mussel cultivation area of the Lagoon of Venice, Italy
Test type:
semi-static
Water media type:
not specified
Limit test:
no
Total exposure duration:
7 d
Nominal and measured concentrations:
50 mg/L continuously suspended LAS-spiked sediments
Details on test conditions:
Mussels were divided into groups of 10 and placed in net tubes in a 60-L tank for 7 days in contact with 50 mg/L continuously suspended LAS-spiked sediments. Mussels were fed an algal suspension and water, food, and sediment were renewed daily.
Reference substance (positive control):
not specified
Dose descriptor:
NOEC
Effect conc.:
32.19 other: mg/kg dry weight (geometric mean of initial [132 mg/L] and final [7.85 mg/L] LAS concentration)
Basis for effect:
other: filtration rate, oxygen uptake, nitrogen excretion
Details on results:
No significant differences in survival or physiological responses between treatments and controls were observed.

The LAS concentration in treated sediments decreased by about 90% over the duration of the study (mean 132 mg/kg at initiation to mean 7.85 mg/kg at completion).

Description of key information

Belanger et al. 2002 determined the effect of C12LAS on an ecosystem in an indoor flowing stream mesocosm (model ecosystem). The stream mesocosm drew water from a high-quality stream (a National Scenic River) in southwestern Ohio, USA. Stream channels were naturally colonized by algae and invertebrates for 56 days prior to dosing. Five stream channels were dosed with the test substance at measured concentrations of Control, 0.126, 0.293, 0.927, and 2.978 mg active ingredient/L (84, 98, 93, 99% of nominal, respectively) for an additional 56 days.

Invertebrate endpoints measured included densities of the invertebrate community, sensitive taxa (EPT), dominant taxa, selected ecologically important families (mayfly, caddisfly, true fly, midges, aquatic worms), emerging insects, and drifting invertebrates. Taxonomic richness, Shannon diversity, functional feeding group composition, and community-level multivariate response were derived. For algal populations and communities, algal cell and biovolume density for each dominant taxa and the algal community were determined. Taxonomic richness, Shannon diversity, and community-level multivariate response were assessed. Ecological functional endpoints included heterotrophic activity and acclimation (amino acid uptake and surfactant mineralization) and autotrophic activity (bicarbonate uptake). Sorption, microbial biomass, and microbial diversity shifts using phospholipid fatty acids (PLFA) were also evaluated. Assessments were conducted weekly to bi-weekly depending on the endpoint.

Collectively, results for all taxa and endpoints were considered in determining the 56-day NOEC for the model ecosystem exposed to C12LAS. This NOEC was 0.293 mg/L total active ingredient (0.268 mg/L soluble active ingredient adjusted for bioavailability). In general, algae were not affected by C12LAS or increased in density, particularly blue-green algae, and autotrophic activity increased with increasing C12LAS. In contrast, some invertebrates declined in density at concentrations >0.293 mg/L, as a result of increasing drift from the shock of the initial dose or from long-term toxicity and habitat changes. Microbes acclimated to mineralizing C12LAS. Overall, the heterotrophic periphyton community remained robust and did not change their food (amino acid) uptake rate.

Two additional studies are available that provide additional detail regarding aquatic toxicity. A sediment toxicity test of LAS (linear alkylbenzene sulfonate) was conducted following the OECD 218 guideline (Pittinger et all. 1989), using the midge Chironomus riparius.  All results are based on the measured concentration of the test substance. The LAS had an average alkyl chain length of 11.9, and was comprised of C10 -C14 alkyl chains. Natural stream sediments (71% clay, 19% fine silt, 4% medium sand, 6% fine sand) were collected from a pristine site in Rapid Creek, SD. Before testing, wet sediment was autoclaved for 40-60 minutes to reduce microbial populations and minimize initial rates of surfactant biodegradation. Tests were conducted as an aqueous fraction in the presence of sediment. Results indicate that sorption onto sediment significantly mitigates LAS bioavailability. The NOEC for Chironomus riparius in sediment was 319 ppm, and the LOEC was 993 ppm based on emergence. Finally, Marin et al., 1994, reported the study results from thirty mussels (5.8 cm average main axis length) collected from a mussel cultivation area of the Lagoon of Venice, Italy. Following collection, they were placed in net tubes in a tank for 7 days in contact with 50 mg/L continuously suspended LAS-spiked sediments. Mussels were fed an algal suspension and water, food, and sediment were renewed daily.The LAS concentration in treated sediments decreased by about 90% over the duration of the study (mean 132 mg/kg at initiation to mean 7.85 mg/kg at completion). No significant differences in survival or physiological responses (filtration rate, oxygen uptake, nitrogen excretion) between treatments and controls were observed. The NOEC for mussels was 32.19 mg/kg dry weight, based on the geometric mean of the initial and final LAS concentrations.

Additional information

In general, algae were not affected by C12LAS or increased in density, particularly blue-green algae, and autotrophic activity increased with increasing C12 LAS. In contrast, some invertebrates declined in density at concentrations >0.293 mg/L, as a result of increasing drift from the shock of the initial dose or from long-term toxicity and habitat changes. Microbes acclimated to mineralizing C12 LAS. Overall, the heterotrophic periphyton community remained robust and did not change their food (amino acid) uptake rate.