### Open Literature Review Summary

Chemical Name: Atrazine CAS No: 1912-24-9

ECOTOX Record Number and Citation: Van den Brink, PJ., E. van Donk, 

### R Gylstra, SJ.H. Crum, and T.C.M. Brock. 1995. Effects ofchronic low concentrations ofthe pesticides chlorpyrifos and atrazine in indoor freshwater microcosms. Chemosphere. 31 :3181-3200. (MRID 47543516)

Purpose ofReview: Determinepotential effects ofatrazine on an aquatic community. Endpoints from this study were also used to parameterize the Comprehensive Aquatic SystemModel (CASM) and establish the model-associated LOC for atrazine.

Date ofReview: January 15,2009

Purpose ofStudy: This studyexamines the potential effects ofatrazine to aquaticplants and animals in laboratory aquaria (microcosms).

Summary ofStudy Findings:

Methods: This study examinedpotential effects ofexposure to low concentrations ofan insecticide, chlorpyrifos, as well as to atrazine. Only methods pertaining to atrazine will be described here.

Two groups offour microcosms each were designed to receive 0 (controls) or 5jlg/L atrazine, and then dynamics in waterquality, zooplankton, phytoplankton, and macroinvertebrates were studied overan 8-weekperiod (treatmentoccurring afterthe first week), from May 3, 1993 to June 28, 1993. Each microcosm consisted ofaglass aquarium (1.1 m x 

### 1.1 m x 

### 0.7 mhigh, watervolume 600 L) filled with 2 cm oflake sedimentand a 50 cm water column. (Source oflake sedimentand waternot described.) The microcosms wereplaced in aroom atconstanttemperature, 19 ± 

### 2°C, with high pressure metal halide lamps (Philips HPL-T, 400W) lighting them with an intensity of 120jlE/m2/s 

### atthe water surface and adaily photoperiod of14 hours light, 10hours dark. (Anotherpaperis cited for more details.) Plankton and macroinvertebrates were



# \111111111 2087834

### introduced to the microcosms (sources oforganisms not described) togetherwith the natural sediment and anutrient addition ofphosphorus and nitrogen at initial concentrations of0.05 

### mg/L and 0.30 

### mg/L, respectively. The microcosms were then allowed 3 months to stabilize theirbiotic communities, during which time they were all connectedby tubes (2.6 cm internal diameter) with a circulation flow rate of3.5 Llmin to achieve uniformity.

The initial dose ofatrazine was distributed evenly over the water surface ofeach microcosm and mixed as rapidly as possible. Aeration stones maintained water movement. Atrazine was added twice aweekto compensate for losses, which were calculated from concentration measurements. Atrazine concentrations were measured by combining duplicate 100 mL watersamples (taken at mid-depth with aglass pipette), shaking the water samples for two hours with 30 mL dichloromethane in 250 mL bottles to extract the atrazine, and analyzing the atrazine concentration in the dichloromethane by splitless injection of3 !J.L on an HP 5890 gas chromatograph. A wide-bore WCOT fused silicacapillary column (25 m long) coatedwith CP Sil 5 CB stationary phase (film thickness was 4.75 !J.m) was used. Operating parameters were: 205°C oven temperature, 10 mLimin helium carrierflow, 240°C injection blocktemperature, NDP detector, 280°C temperature, 3.5 mLimin hydrogen flow, 90 mLimin air flow and 20 mLimin auxiliary nitrogen gas flow, with a retention time of3.5 min. The detection limitwas 6pg, and recovery from waterwas 99.9 ± 

### 2.8% (mean ± 

### standard error, n=4).

Zooplankton were sampledweekly (week -1 to 7) by taking a depth-integrated water sample with a40 cm long, 1 L volume Perspex tube, with at least 5 samples per microcosm. The samples were then concentrated on a nylon zooplankton net (55 !J.m), preserved in 4% formalin, stainedwith Lugol, and then a subsample was counted at 25x using a counting chamber.

Phytoplankton were analyzed from week-1 to week4. Ofa2.1 Lsample as taken above, 1 L was used to study species composition, and 1.1 L was used for analysis of chlorophyll 

### a and nutrients. Phytoplankton samples were stainedwith 3.5% Lugol and stored in bottles for sedimentation. After 6 days, 90% ofthe waterofeach sample was extracted and the remaining sample preserved with 4% formalin. Cell counts were made with BurkerTurkcounting chambers (0.04 mm2 

### x 0.10 mm).

Macroinvertebrates were sampled every two weeks (weeks -1, 2, 4, and 6) in two litter bags permicrocosm. (A paperheaded by a coauthoris cited for details.) The litterbags consisted ofaglass Petri dish (diameter 11.6 em), closed with a coverofstainless steel wire (0.7 mm mesh), in which two 0.5 em diameterholes allowedpassage of macroinvertebrates. Each litterbag was filled with 2 g driedPopulus 

### leaves as substratum. Aftertwo weeks ofcolonization, the contents ofthe litterbags were transferred to a tray to separate macroinvertebrates from leafmaterial. The

2macroinvertebrates were identified and counted alive, then released backto theirhome microcosm.

Water quality measurements (dissolved oxygen [DO], pH, conductivity, and alkalinity)
were taken once a week in the afternoon throughoutthe experimental period. Measurements were performed at 10 cm depth using a WTW oxygen meter (Oxi 196) and oxygen probe (EO 196), a Metrohm Herisan pH meter (E-488), and a WTW conductivity meter (LF 191). Alkalinity estimation was done by titration of100 mL of water sample with 0.05 M HCl down to pH 4.2. From week -1 through week 6, plankton chlorophyll 

### a and soluble inorganic nitrogen and soluble reactive phosphorus (SRP) were determined, the lattertwo quantities with a Skalar5100 Autoanalyser. Chlorophyll 

### a was estimated by concentrating alL water sample over a Whatman 

### GF/C glass fiber filter (1.2 11m) and analyzing with spectrophotometry (as described in a cited 1978 paper). The remaining 100 mL ofthe subsample was filtered and stored at -20°C.

Bioassays were performedwith crustaceans 

### (Gammaruspulex and

### Asellus aquaticus) inside each microcosm in cages, 10 individuals per species in a 10 cm x lO cm x 50 cm cage with separate cages for each species, with the cage bottom45 cm below water level and one side ofthe cage consisting of55 11m gauze mesh to allow waterexchange. The cages were stocked with

### Populus leaves, providing the organisms with their own separate food supply. Bioassays lasted 24 days, from week 3 to week 7, with surviving individuals countedregularly and dead removed. Neonates were counted at the end of the experiment.

Data analysis was carried out with both univariate methods (for effects oftreatment on individual taxa orphysicochemical parameters) and multivariate methods (for community-level ormulti-componentwaterquality effects). Univariate analyses used analysis ofvariance (ANOVA) with the Dunnetttestto detect significant differences between treatment and control, as implemented by the computerprogram TOXSTAT Release 3.2. Where necessary to meet assumptions ofhomogeneous variance and normal distribution, the data were natural-log (In) transformed, and ifthat failed, the nonparametric Steel's rank sum test was used. Statistical significance wasjudged at a pvalue::; 0.05.

Multivariate analyses used the Redundancy Analysis (RDA) ordination technique, and significance tested by Monte Carlopermutation testing. (Sources are cited for details on the theory and application ofthese methods.) RDA produces a diagram where samples with similar species combinations lie close together, andthose with dissimilar species combinations lie far apart. Points are shown for each species, and samples where that species was abundant will lie close to that species' point.

3

### RDA and the Monte Carlo pennutation tests were performed with the CANOCO version 3.14 computerprogram, forthe zooplankton, phytoplankton, macroinvertebrate, and physicochemical data. Waterquality was expressed as the "community" ofthe physicochemical parameters (DO, pH, alkalinity, conductivity). Forplankton and macroinvertebrates, defaultRDA options were chosen, butwith the physicochemical data, parameters were standardized to make them commensurate. Before analysis, however, the plankton and macroinvertebrate communities' species abundance values
were In(IOx+I) and In(2x+I) transformed, respectively, to better analyze low abundance values. Sample points were defined by all data on a specific community, from a specific pesticide (treatment), and on a specific sampling day. For each ofthese sample point datasets, the total variance in the variables is only partly expressed by the two axes ofthe RDA diagram, and this "percentage ofvariance explained" is commonly 30-40% in ecological applications. ForMonte Carlo tests (performed underthe RDA option), each sampling time and pesticide treatment was permuted againstthe control microcosms. Pvalues 

### < 0.05 were considered "significant" andp-value between 0.05 and 0.10 were considered "atrend ofsignificance".



### Results: This study examinedpotential effects oflow concentrations ofan insecticide, chlorpyrifos, as well as atrazine. Only results pertaining to atrazine will be described in this review.

Atrazine concentrations in the microcosms varied between 4.2 and 6.0 Ilg/L (see Figure 1). Mean concentration (determined from the area underthe curve) was 5.08 Ilg/L, with
a standard error of0.03 Ilg/L.

The most abundant zooplankton taxa in the microcosms were Copepoda andthe rotifer 

### Keratella quadrata (Table 1). The only zooplankton showing a significant (but brief) response to atrazine was Cyclopoida, which increased in week 3 relative to controls (see also Figure 2). The mostabundantphytoplankton taxa in the microcosms were: 

### Botryococcus spp., 

### Chlamydomonas spp., 

### Choomonas spp. (Chlorophyceae) 

### Navicula spp., 

### Cocconeis spp., 

### Achnanthes minutissima (Bacillariophyceae) 

### Cryptomonas spp. (Cryptophyceae) 

### Gymnodinium spp. (Dinophyceae) Ofthese, only one showed significant differences from controls in the atrazine microcosms: 

### Botryococcus spp. was significantly less abundant in treatment microcosms in week-1 (which was priorto treatment). See Table 2. Macroinvertebrate communities
were dominated by Gastropoda and Crustacea, the former increasing in abundance with time and the latterdecreasing. See Table 3. No significant effects ofatrazine treatment on macroinvertebrates were found.

4

### In the water quality parameters, there were no significant differences in any parameter due to atrazine treatment. DO andpH in the atrazine treated microcosms were somewhat lower, and conductivity and alkalinity somewhathigher, comparedto controls, but not significantly so (p>0.05). See Table 4. In all microcosms, nutrient and chlorophyll a 

### concentrations were very low, and there were no significant (p<0.05) differences between treatments and controls. Ranges were: SRP: 0.000 0.009 mg/L 

### Inorganic N: 0.000 0.093 mg/L 

### chlorophyll a: 

### 0.00 6.22 Jlg/L



### In multivariate analyses, no significant differences due to atrazine treatmentwere found in zooplankton, phytoplankton, ormacroinvertebrate communities. Inthe zooplankton community RDA diagram, 75% ofthe total variance was explained (see Figure 3), and in the macroinvertebrate community RDA diagram, 77% ofthe total variance was explained (see Figure 4). (The phytoplankton community RDA diagram is not provided in the article because no significantdifferences were found.) There was a "trend ofdifference" (p-value < 0.10) in the physicochemical parameters in week 5 (see Figure 5; 90% ofthe total variance is explained in this RDA diagram).

No significant effects ofatrazine were found in the crustacean bioassays. SeeTable 5.**!J'JIO~I_~,a!~.!_~OI1** _" 1 ? J ••A.IR 1 , AlR;?,

-- ATR 4**n~e** after start of exposure (wlJBks)

Figure 1. Mean atrazine concentrations (J.lg/L) over time at mid-depth in the four treatment microcosms. (from study figure])



### 5.., 5 II HI'r**,~~ -~--'--~------~--~-~-** 

-I 0 7 

### A

5 4 3 10



### 't

t 

### ; I**O.1L-~** .j 0 ...I 

# -

..Q E :::'l :z

Time aUer**at~ut** expolure (we.ka) Time after 8tart exposure (weeki)

....... Con .-- Cpf

-- Atr

-- Con -<0- Cct

Figure 2. Dynamics in numbers (mean ± standard error, n=4) ofcyclopoida (A) and Keratella quadrata (B) in the control (Con, small solid diamonds), chlorpyrifos (Cpf, closed squares), and atrazine (Atr, open squares) treated microcosms. (study figure 2)

6cpfS" / 

## + (p16 cpf7 tL



# • Cali.U"lIt>t:.;.**~;** (on3,

Figure 3. Ordination diagram (RDA) showing effects ofchlorphyrifos (cpf, dotted line), atrazine (atr, dashed line), and control (con, solid line) treatments on the zooplankton community. Lines represent changes overtime. 

### * indicates significantdifferences from controls atp::;O.05. (study figure 3)



### 7cpfGU 

# + ;'cpf2

, ,

jl**~-I-;rt** ..... 4

...

, 

### .....-"

....'.-'

## .

.."'....

Figure4. Ordination diagram (RDA) showing effects ofchlorphyrifos (cpf, dotted line), atrazine (atr, dashed line), and control (con, solid line) treatments on the macroinvertebrate community. Lines represent changes over time. 

### * indicates significant differences from controls at**p~O.05** (no such differences were found); 

### ** indicates "trends ofdifference"**(O.05<p~O.10).** (study figure 4)

8**AIk:~iflltY** • atr4* I tonSI 

### 1 I \ 

### ;(.. \ atrS U \ 

### \ 1

at.r3

. : [ ' (on1 ••••

## ..f-

" •••-.. cpf1

### c~1--' .-'

..-",

# I
i I cpf"

# t ;.c.on.4

" I' 

## .' cpf:5; : 

# .+

,



# . 

# .

cen3 (on2 C>O.

Figure 5. Ordination diagram (RDA) showing effects ofchlorphyrifos (cpf, dotted line), atrazine (atr, dashed line), and control (con, solid line) treatments on the waterquality parameters. Lines represent changes overtime. 

### * indicates significant differences from controls at**p~O.05** (no such differences were found); 

### ** indicates "trends ofdifference"**(O.05<p~O.lO).** (study figure 5)



### 9Table 1. Abundance (individuals/L, mean and standard error [Slq with n=4) ofthe zooplankton taxa and the macroinvertebrateBothromesostoma esseniisummarized over3 periods: week -1 (pretreatment), week 0-3, and weeks 4-7. Only the taxa present in more than 10% ofsamples are shown. No significant differences between atrazine treatment and control microcosms were found, except for an increase in Cyclopoida spp. abundance in treatment microcosms in week 3 (significant at p<0.05). (from study table lA)

Taxon ! Control I Mean 

### SE**~---** ---**--~---** Daphnia galeata Sars 1.5 1.1 1.4 0.7 

# I 1.5 1.0 2.9 0.9 0.6 0.3 2.0 0.6 Simocephalus vetulus (Muller) 0.0 0.0 0.1 0.1 0.4 0.3 1.5 0.8 0.2 0.\ 0.8 0.6 Acroperus harpae (Baird) 0.1 0.1 0.0 0.0 

## I 0.0 0.0 0.1 0.0 0.\ D.\ 0.0 0.0 Ceriodaphnia sp. 0.0 0.0 0.0 0.0 0.3 0.3 0.9 0.9 D.l D .\ 0.1 0.\**~QlLeIJoda** Cyclopoida spp. 46.5 \4.5 24.7 6.1 1 22.7 4.5 27.7 3.8 3.0 0.5 2.8 0.7 Calanoida spp. 1.8 0.\ D.7 0.3 \O.D 3.5 \2.4 0.7 17.5 7.5 16.4 2.7 52.6 9.3 53.\ 16.71 35.2 12.5 31.8 4.4 28.2 4.4 30.7 4.7 Ostracoda spp. 0.\ 0.\ 0.0 0.0 0.4 0.2 0.3 0.\ 0.3 0.2 0.\ 0.1 Rotifera Keratel/a quadrata (Muller) 

### I J35.D 32.8 TurbeIlaria I Bothromesostoma essenii Braum ! 4.0 1.2

10Table 2. Abundance (individuals/L except Volvox spp. in 1,000 indiv.lL, mean and standard error (SE) with n=4) ofthe phytoplankton taxa summarized over3 periods: week -1 (pretreatment), weeks 0-3, and week4. Only the taxa present in more than 10% ofsamples are shown. No significantdifferences between atrazine treatmentand control microcosms were found, except for a decrease in Botryococcus spp. abundance in treatmentmicrocosms in week -1 (significantatp<0.05). (from study table lB)

Taxon

1.1
0.0 0.6 0.2 0.0 0.3 0.0 0.0

0.2 0.0 0.17 0.7 0.6 1.0 0.0 0.0 0.0

1.7

3.9 0.0 0.7 0.0 0.0 0.3

0.3 0.0

2.2 0.0 0.2 0.5 0.2 0.0 0.0 0.2 0.0

5.4 0.0 0.3 0.0 0.9 1.0 0.0 0.0 0.3

3.1 0.9 I 3.8 1.0 0.1 0.1 

# I 0.3 0.2 0.2 0.2 0.1 0.1 3.4 0.6 4.3 1.2 1.5 0.2 1.8 0.7 0.9 0.2 1.1 0.5 1.0 0.4 1.4 0.5 0.4 0.2 0.5 0.2 0.3 0.2 0.3 0.3 0.13 0.10 0.01 0.00 3.2 0.7 2.2 0.5 3.3 0.3 2.7 0.3 1.6 0.4 4.1 l.l 0.7 0.3 0.0 0.0 0.3 0.1 0.0 0.0 0.1 0.1 0.0 0.0

0.5 0.2

0.6 0.7 1 1 0.9 0.8 0.3 0.3 0.00 27.4 1.1 0.8 0.0 0.0 0.0

2.3 2.3

2.8 1.7 1.4 0.5 0.3

0.7 0.2 0.00 60.2 3.9 2.2 0.0 0.0 0.0 SE SE**~-----+** 0.07 0.05 0.28 2.0 1.3 1.5 1.9 7.0 0.9 0.3 0.2 1.6 0.0 0.0 0.0 0.0 0.0**I~** 0.0 0.0 0.0 0.0

3.4 1.0 2.1 0.5 2.0 0.6 0.9 0.3 0.8 0.6 0.4 0.2 0.3 0.2

1.0 0.7 0.2 0.2 0.01 0.00 177.8 44.5 5.4 1.1 1.6 0.5 0.7 0.3 0.4 0.4 0.1 O. Chlorophyceae Volvox spp. Botryococcus spp. Chlamydomonas spp. Chroomonas spp. Kirchneriella spp. Monoraphidium spp. Oocystis spp. Bacillariophyceae Navicula spp. Cocconeis spp. Gomphonema spp. Achnanthesminutissima Synedra spp. Epithemiazebra Cyanophyceae Phormidium spp. Anabaena spp. Cryptophyceae Cryptomonas spp. Dinophyceae

11Table3. Abundance (individuals/L, mean and standard error [SE] with n=4) ofthe macroinvertebrate taxa summarized over3 periods: week -1 (pretreatment), week2, and weeks 4 and 6. Only the taxa presentin more than 10% ofsamples are shown. No significant (p<O.05) differences between atrazine treatment and control microcosms were found. (from study table Ie)

Weeks 4 & 6 Taxon 

## I Control Control AtrazilJe Mean 

### SE lv/ean 

### SE j\1ean 

### SE Mean 

### SE Mean 

### SE**~~~--** Dugesia lugubris (Schmidt) 0.0 0.0 0.0 0.0 1.3 0.5 0.3 0.3 1.5 1.2 0.0 0.0 Polycelis tenuis Ijima 1.5 0.3 1.5 0.5 5.5 1.2 3.5 0.7 11.1 2.9 

# I 7.9 1.9 Bothromesostoma esseniiBraum 1.3 0.8 0.8 0.5 6.0 0.7 7.0 2.2 3.1 0.6 3.9 0.4 Nemertea 2.0 0.7 1.5 0.3 0.0 0.0 0.0 0.0 1.5 0.6 

## I 0.3 0.1

Lumbriculus variegatus (MUller) 0.0 0.0 0.0 0.0 0.3 0.3 0.5 0.5 0.0 0.0 0.6 0.6 Turbificidae 5.0 1.8 ,., ,., 1.0 0.3 0.3 0.0 0.0 0.4 0.4 1.0 1.0 .:l•.:l Dero digitata (MUlier) 0.8 0.5 1.5 1.5 0.0 0.0 2.0 1.7 0.0 0.0 8.6 8.1 Hirudinae I 0.0 

## I I 1.9 

# I Glossiphonia heteroclita (Linnaeus) i 0.0 0.0 0.0 I 2.3 0.0 0.0 

### I 0.8 0.8 

### I 0.0 0.0 GastroIJoda Physaacuta (Draparnaud) 6.3 3.8 14.5 13.5 37.5 18.2 23.5 10.0 50.9 28.9 55.6 4.2 Potamopyrgus antipodarum (Gray) 5.3 2.7 3.0 1.2 38.8 30.9 14.3 10.0 21.8 10.3 8.5 2.9 Bithynia tentaculata (Linnaeus) 22.8 6.6 16.0 2.5 11.0 2.8 4.3 1.8 6.8 1.0 6.0 1.5 Lymnaeastagnalis (Linnaeus) 0.0 0.0 0.0 0.0 0.0 0.0 2.8 2.8 0.3 0.1 

# I 7.8 5.5 Valvatapiscinalis (MUlier) 8.5 3.4 3.3 1.7 4.8 3.8 

## I 1.3 1.0 3.5 1.3 1.5 0.9

Gammaruspulex (Linnaeus) 12.8 1.9 11.0 3.1 6.3 2.5 5.3 2.9 Asellus aquaticus Linnaeus 6.0 0.6 7.0 2.0 3.5 1.3 7.5 4.9 Proasellus meridianus (Raeovitza) 1.5 0.9 1.5 1.0 2.0 I.l 2.0 1.7 2.3 0.9

12Table 4. Measurement results on the physicochemical parameters (mean and standard error [SE) with n=4) summarized over3 periods: week -1, weeks 0-3, and weeks 4-7. All parameters were not measured in week6, and pH was not measured in week 7. No significant (p<O.05) differences between atrazine treatment and control microcosms werefound. (from study table 1D) 

# I Week-l**~~WeeksO=3~~--1··** Weeks 4-7 I Parameter Control [Atrazine Control Atrazine Control Atrazine I Mean SE Mean SE Mean SE Mean SE Mean SE 

## I Mean SE I Dissolved oxygen (mg/L) 

## I 9.4 0.2 9.2 0.1 9.9

# j

9.3 0.2 9.9 OJ! 9.7 0.1 1 pH 8.4 0.2 8.4 0.1 9 0.2 8.6 0.2 8.8 0.2 

## I 8.4 0 

## I Conductivity (JlS/cm) 1189.3 2.8 189.5 1.2 175.1 6.5**18~** 159.3 4.21169.3 2.3. Alkalinity (mL) 2.2 0 2.2 0 1.9 0.1 2.1 0.1 1.4**~~~** -**._~** ..**~-_** ...._. ..•..- 0.1 1.7 0.1 

# I

13Table 5. Results ofbioassays (in numbers, mean and standard error 

### ISED with Gammaruspulex and Asellus aquaticus. No significant (p<O.05) differences between atrazine treatments and controls were found. (from study table 2)**Gammaru:>Jl!!1<:~** Asellus aquaticus 

### I**t1tDl~ne** Con!!:Ql I Afrazine Alean SE i Alean SE Afean SE i Alean SE I 10.0 0.0 10.0 0.0 10.0 0.0 10.0 0.0 2 10.0 0.0 10.0 0.0 9.3 0.4 9.5 0.3 3 10.0 0.0 10.0 0.0 9.0 0.4 9.5 0.3 4 10.0 0.0 10.0 0.0 8.8 0.2 9.5 0.3 5 10.0 0.0 10.0 0.0 8.5 0.4 9.5 0.3 6 9.8 0.2 9.8 0.2 8.3 0.4 9.5 OJ 7 9.5 OJ 9.8 0.2 8.3 0.4 8.8 0.5 10 9.5 0.3 9.3 0.2 8.0 0.4 8.0 0.4 13 9.5 0.3 9.0 0.4 6.5 0.8 7.0 0.4 17 9.5 0.3 8.5 0.6 5.0 1.2 6.0 0.6 20 0.4 8.8 0.4 4.0 1.3 4.8 0.4 24 0.4 3.8 1.1 0.4 24 10.6 29J 12.8 5.8

14

### Data Summary Table:
Comments

[ Effect Magnitude of Nominal Day of Time Did Effect Atrazine Study Effect Weighted Recovery relative to Concentration Occurred Average Occur

- if controls (flg/L) Atrazine so, when Concentration (see from Day 0 to comment)? I

I! When Effect 

# 1

Occurred**-C-h-a-ng-e~in---I---------i-~"---~'---I--~--~"-----II--=-'::"'::"'::::":":-=----l-**----**~:~; t~u~~d** 

, phytoplankton No effect 5Ilg/L NA NA NA , study textp.

community! i 3193.
Change in zooplankton community (increase in Cyclopoida spp.) No adverse effect (22% increase observed) , 5Ilg/L I 21 NA NA From study table lAo Effect magnitude is based on Week 0-3 averages. Change in
macroinvertebrate community No effect NA From study table IC and Fig. 4.

I From study table 2.

From Figure 3

Effectonly reported for Week 5 NA NA

5 ug/L Week5(no subsequent evaluations) 

## I

5 ug/L Slight No effect Change in chlorophyll a concentration Change in I crustacean 

# IN f"' t . I ( I ' 1 0 e lee survlva extema I food provided)----.J --l-. t- +- -t.

__. 

### + --i "Trendof difference" for water chemistry (DO, pH, alkalinity, conductivity) Note: NA=Not ApplIcable



### Atrazine concentrations were maintained very close to nominal during the experimentby multiple analyses and corrective additions. By visual inspection ofFigure 1, it was determined thatthe above-nominal fluctuations were roughly balanced outby the belownominal fluctuation from Day 0 to Day 21 (week 3). The figure is somewhat illegible due to the separate lines for each microcosm. Therefore, it was assumed thatDay 21 time weighted average atrazine concentrations were equal to nominal, 5 Jlg/L. 

### It 

### is expected thatthis is accurate to ±O.5 Jlg/L.



### Reviewer Comments: Fourreplicates were used for treatments and controls; the study had areasonably long time for microcosms to stabilize (3 months, during which time they were hydraulically



### 15

### connected); and the data analysis techniques used are appropriate, sophisticated and welldescribed. The results are presented clearly and completely, with many tables.

Several study limitations were noted. The sources ofsediment, water, and organisms used to create the microcosms are not described, so results may be confounded by prior atrazine exposure in the biotic community. The use of

### Populus leaves in both the
macroinvertebrate litterbags and inthe bioassay cages distorts the ability ofthe experimentto capture indirecteffects ofatrazine on non-producerelements ofthe aquatic food chain. Finally, as a microcosm experimentwith a limited artificial ecosystem (no macrophytes, fish, seasonality, 

### etc.), the results may not scale up directly to a largerand
more complex natural environment



### Description ofUse in Document(QUAL, QUAN, INV): QUAL.



### Rationale for Use: The study contributes to the weight ofevidence regarding potential for atrazine to affect aquatic communities. However, some limitations were noted, and the study did notprovide a sensitive endpoint (no effects were observed in this study).



### Limitations ofStudy: The macroinvertebrate and crustacean bioassay results are limited because they provided

### Populus leaves as substrate/food source, thus preventing potential indirecteffects ofatrazine on food ordetritus availability. As a whole, the microcosms
were oversimplified in comparison to natural aquatic ecosystems: they containedno macrophytes orfish, the climate was artificially stable, and the sources ofthe organisms used to populate them were notprovided and may have given the biotaprevious exposure to atrazine.



### Primary Reviewer: SaraHendrix, M.S., StaffScientist, Cambridge Environmental Inc



### Secondary Reviewer: Brian Anderson /

16