### Open Literature Review Summary

Chemical Name: Atrazine 

### CAS No: 1912-24-9



### ECOTOX Record Number and Citation: Stay, F.S., Larsen, D.P., Katko, A., and Rohm, C.M., "Effects ofAtrazine on Community Level Responses in Taub Microcosms," 

### Validation andPredictability

## 0/ Laboratory Methods/orAssessing the Fate andEffects o/Contaminants inAquaticEcosystems, ATSMSTP 865, T.P. Boyle, Ed., American Society for Testing and Materials, Philadelphia, 1985, pp. 75-90 (MRID 45087419).



### Purpose ofReview: Determine potential effects ofatrazine on an aquatic community. Endpoints from this study contribute to the weight-of-evidence regarding effects ofatrazine on aquatic plant communities and associated determination ofa Level ofConcern (LOC).



### Date ofReview: November 24, 2009



### Purpose ofStudy: This study examines the effects ofatrazine on aquatic plants and animals in Taub mIcrocosms.



### Summary ofStudy Findings:

Methods: An aquatic microcosm bioassay was developed according the protocol ofTaub (as described in Taub, F.B. and Crow, M.E. in

### Microcosms in EcologicalResearch, J.P. Giesy, Jr., Ed., Technical Information Center, U.S. Department ofEnergy, 1978, pp. 69- 104). Initially 30 microcosms were constructed. Each microcosm was constructed in a 3.7-L wide-mouth picklejar, with 3 L ofnutrient-rich Taub and Dollarmedia (see 

### LimnologyandOceanography, Vol. 9, 1964, pp. 61-74), 200g white silica sand, 0.5-g ground chitin, and 0.5-g ground cellulose. Microcosms were autoclaved, cooled to incubation temperature, and then populated with ten species ofalgae (see below) on Day 0. 1 

### Each algal species was addedto achieve an initial microcosm concentration of 10

1N.B.: Throughoutthe review text, Day Xrefers to the day numbers as defined in the study, with atrazine application occurring on Day 7. In the Data Summary Table and related tables and spreadsheets, however, day numbers are listed with Day 0 as the day ofatrazine application (study day numberminus 7). 

# IIIIIIIIII 2087836cells/mL per species. On Day 4, 

### Daphnia magna and other animals were added (Table 1).

Algae species added on Day 0: 

### Anabaena cylindrica, Chlamydomonas reinhardi, Chlorella vulgaris, Nitzschia kutzigiana, Scenedesmus obliquus. Selenastrum capricornutum, Ankistrodesmus sp., 

### Lyngbya sp., 

### Stigeoclonium tenue (tentative species identification), 

### Ulothrixsubconstricta (tentative species identification)

Table 1 Animals added to microcosms on Day 4 Organism Initial NumberperMicrocosm Daphnia magna (Cladoceran) 6 large (3 gravid), 10 small Hyalella azteca (Amphipod) 3 mating pairs, 6 small Cypridopsis sp. (Ostracod) 6 Philodina sp. (Rotifer) 90 Hypotricha (Protozoan) 330

Atrazine stock solution at a concentration of23 mg/L was prepared from reagent grade atrazine and Taub and Dollar media. On Day 7, the 27 of30 microcosms with the most similar dissolved oxygen (DO), algal counts, 

### D. magna counts, and primary productivity
were chosen for the experiment. Appropriate amounts ofatrazine solution were added to achieve given nominal concentrations. Ofthe 27 microcosms used for the experiment, five were used as controls, five for treatment at an atrazine concentration of60 Ilg/L, three at 100 Ilg/L, five at 200 Ilg/L, five at 500 Ilg/L, three at 1000 Ilg/L, and one at 5000 Ilg/L. No additional atrazine was applied to the microcosms after the initial application
on Day 7.

The microcosms were incubated at 20 ± I°C under 900±I00 foot-candle cool-white fluorescent bulbs (GE F96PG17.CW) with a light cycle of 12 hours on and 12 hours off. Twice a week from Day 7 to Day 60, measurements ofDO, 14C-uptake, chlorophyll 

### a, and

### D. magna were made, after scraping periphyton from the walls and mixing the microcosm. All measurements were made from 5 cm below the surface, following scraping ofperiphyton from the containerwalls and mixing ofthe microcosm contents. No additional solute was addedto make up for losses from evaporation and sample collection. Atrazine concentrations in the microcosms were measured on Days 7, 28, 53, and 60.

Analysis methods followed U.S. EPA's "Methods for Chemical Analyses ofWater and Wastes" (1979, EPA-600/4-79-020) or the 1980 American Public Health Association's "Standard Methods for the Examination ofWater and Wastewater" wheneverpossible. Atrazine was extracted from a 100-mL water sample with 20 mL ofpesticide-grade ethyl acetate followed by concentration ofextract and analysis by gas chromatography with a nitrogen-phosphorus flame ionization detector. Algae were filtered from 20-mL samples ofmicrocosm media with glass fiber filters (Millipore AP 40 024 05) and analyzed for

2chlorophyll 

### a according to Lorenzen, 

### Limnology andOceanography, Vol. 12, 1967, pp. 343-346. (Acid concentration used for phaeophytin correction was reduced to 8E-03 

### M HCl to avoid absorption spectra interferences.) 14C-uptake (primary productivity) was measured by the 14C

-HC

### 0 3 method using 15-mL samples incubated for 1 hour at microcosm light intensities. A YSI Model 54 dissolved oxygen meter was used to
measure DO. 

### Daphnia magna counts were made on 100 mL ofwater collected from each microcosm after gentle mixing with a glass rod to evenly distribute the organisms without injuring them (contents settled again in 2-4 hours). Animals were counted immediately and returned to the microcosm.

Net primary productivity and respiration were calculated by estimating the amount ofDO change over a 24-hrlight/dark cycle and correcting for oxygen exchange with the atmosphere. Oxygen exchange with the atmosphere was modeled as a first-order process: 

### dCldt

### = K*(Cs-C), where C is DO concentration, Cs is DO concentration at saturation, with a mass transfer coefficient K that was experimentally determined to be 0.026 1/hrfor a 2 L microcosm and proportionally scaled to the actual microcosm volume. During the dark cycle, the oxygen exchange rate was reduced by respiration, which was assumed to occur at a constantrate for 12 hours. During the light cycle, the oxygen exchange rate was increased by net primary productivity. The solution ofthe resulting set ofequations based on known or measured information allowed respiration, and therefore netprimaryproductivity, to be calculated.

Statistical analyses ofthe data used the folded F and Cochran C tests to determine homogeneity ofreplicate variances among treatment groups. If, for aparticular variable, replicate variances were not significantly different (p-value 

### < 0.05), a 

### t-test with pooled variance was used to find the probability ofdifference between control andtreatment groups; otherwise, non-pooled variance was used with degrees offreedom calculated.



### Results:



### 14C-Uptake At atrazine treatments of500, 1000, and 5000 Ilg/L, primary productivity (14C-uptake)
was almost completely inhibited (no p-value cited). At treatments of60, 100, and 200 Ilg/L, primary productivity was significantly (p-value < 0.05) different from controls through Day 20. However, the controls' primary productivity decreased sharply after Day 14 during a

### D. magna bloom between Days 18 and 35 when nutrients (nitrogen and phosphorus) generally reached minimal concentrations. After the

### D. magna bloom ended, primary productivities were similarbetween the controls and the 60, 100, and 200 Ilg/L treatments (no p-value cited). See Figure 1. Note that ofthe three highest treatment groups, only 500 Ilg/L is shown; the 1000 and 5000 Ilg/L treatmentresults were similar to the 500 Ilg/L treatmentresults. (Magnitudes are not described explicitly in the study text but are shown in the figure.)

3

### DissolvedOxygen Dissolved oxygen was measured at the end ofthe dark and lightperiods on measurement days. DO concentrations in the 500, 1000, and 5000**~g/L** 

### treatment microcosms decreased sharply untilafterD. 

### magna bloom afterboth light and darkperiods (no pvalues cited); afterthe bloom ended, the DO after darkperiods approached control levels, but the DO after lightperiods gradually approached DO saturation (9.07 mg/L) while remaining significantly (p-value < 

### 0.01) less than the controls for the rest ofthe experiment. The microcosms treated with 60, 100, and 200**~g/L** 

### atrazine had DO concentrations between the highertreatment levels and the controls (on Day 11, DO concentrations were lowerthan controls withp-value < 0.01 afterboth light and dark periods), and had recovery ofDO afterbothphotoperiods to control levels (no significant difference atp-value < 0.05). On the maximum primary productivity day, Day 14, DO afterthe lightperiod was similarto the controls for treatments of60 and 100**~g/L,** 

### but 200**~g/L** 

### treatments had lowerDO afterthe lightperiod than the controls (p-value < 

### 0.01). During the D. 

### magna bloom, DO in the 100 and 200**~g/L** 

### treatments were generally significantly less than controls (p-value < 0.05), whereas DO in the 60**~g/L** 

### treatments was significantly (p-value < 

### 0.01) less than controls only on Day 21. See Figure 2 for DO after lightperiods and Figure 3 for DO after dark periods. Note that of the threehighesttreatment groups, only 500**~g/L** 

### is shown; the 1000 and 5000**~g/L** 

### treatment results were similar to the 500**~g/L** 

### treatment results. (Magnitudes are not described explicitly in the study textbut are shown in the figures.)



### NetProductivity andRespiration Netproductivity andrespiration were estimated from DO changes overthe light/dark cycle and corrected based on the deviations ofmeasured DO from saturation. The correctionresulted in maximum changes of1.8 and 1.5 mg 02/L/12 h for netproductivity and respiration, respectively. Netproductivity for the highertreatment groups (500, 1000, and 5000**~g/L)** 

### was significantly (p-value < 

### 0.01) less than controls and did not
recover during the experiment, often falling below zero (respiration greaterthan production). Forthe 200**~g/L** 

### treatments, netproductivity remained significantly (pvalue < 

### 0.01) less than controls until afterthe D. 

### magna bloom had passed, then recoveredto near control levels (no p-value cited). Forthe 60 and 100**~g/L** 

### treatments, netproductivity was similar to controls both before and afterthe

### D. magna bloom (no pvalue cited), but during the bloom were lowerthan controls, particularly during the growth phase ofthe bloom when differences were significantatp-value < 

### 0.01. See Figure 4. Note that ofthe three highesttreatment groups, only 500**~g/L** 

### is shown; the 1000 and 5000**~g/L** 

### treatmentresults were similarto the 500**~g/L** 

### treatment results. (Magnitudes are not described explicitly in the study textbut are shown in the figure.)

Respiration for the highertreatment groups remained atpretreatment levels immediately following atrazine treatment and then gradually increased for the rest ofthe experiment. Respiration for the 200**~g/L** 

### treatment group remained lowerthan controls until the end ofthe D. 

### magna bloom, then recovered to near control levels (no p-values cited). Forthe

460 and 100 /lg/L treatments, respiration was similarto controls both before and afterthe 

### D. magna bloom (no p-values cited), but during the bloom were generally lowerthan controls (although these differences were not statistically significant atp-value 

### < 0.05 due to high variation among the replicate microcosms). See Figure 5. Note that ofthe three highest treatment groups, only 500 /lg/L is shown; the 1000 and 5000 /lg/L treatment results were similarto the 500 /lg/L treatmentresults. (Magnitudes are not described explicitly in the study text but are shown in the figure.)



### P,/Rni

### Ratio The ratio between primary productivity and respiration was also examined. This measure remained above 1 in the control for the first 20 days ofthe experiment, and remained near 1 for the restofthe experiment. In the highertreatment groups (500, 1000, and 5000 /lg/L), the Pn/Rni ratio decreased sharply to under0.4 and remained significantly (p-value


### < 0.01) less than controls for much ofthe remainder ofthe experiment. The Pn/Rni ratio for the 200 /lg/L treatment group also remained significantly (p-value 

### < 0.01) less than the controls until afterthe

### D. magnabloom, when itrecovered to near 1. Forthe 60 and 100 /lg/L treatments, the Pn/Rni ratio did not differ significantly from control levels at pvalue 

### < 0.05 throughoutthe experiment. See Figure 6. Note that ofthe three highest treatment groups, only 500 /lg/L is shown; the 1000 and 5000 /lg/L treatment results
were similarto the 500 /lg/L treatmentresults. (Magnitudes are not described explicitly in the study text but are shown in the figure.)

14

### C-Uptake/Chlorophyll a 

### Ratio The 14C-uptake/chl 

### a ratio, an index ofthe effectiveness ofthe algal photosynthetic systems, was the most sensitive measure ofthe effects ofatrazine. Throughoutthe experiment, the 14C-uptake/chl 

### a ratio was significantly (p-value 

### < 0.01) lowerin all treatment groups than in the controls, with somewhat strongereffects noted for the higher treatment groups (500, 1000, and 5000 /lg/L) compared to the lowertreatment groups. The ratio did not seem to be significantly affectedby the

### D. magna bloom. Low numbers for the ratio resulted from a combination ofreduced 14C-uptake as well as increased chlorophyll 

### a perunit biomass. See Figure 7. Note that ofthe three highest treatment groups, only 500 /lg/L is shown; the 1000 and 5000 /lg/L treatmentresults were similar to the 500 /lg/L treatmentresults. (Magnitudes are not described explicitly in the study text but are shown in the figure.)

5'2.00 

## .c -0 ug/r L 60 ug/l 1.76 

### 0-'" 100 vg/I U 6--6200 UA/I 01 01:l 500 ug/l E 1.60**~.** 1.25 

### ;:; f= 

### u 1.00 ;:j Cl 0 0.76 

### a: Q. >- 0.60 a: <t 

## :e 0.25 

### a: l1.

20 25' 30 35 40 45 50 55 60 65 DAY NUMBER Figure 1. Mean primary productivity

# e 4C-uptake) ofmicrocosms exposed to atrazine. Points of significant (p-value < 0.05) linear contrast from control are presented with darkened symbols. The shaded region represents the D. magna bloom.

12.0 _0 ug/l 0-<> 60 VV/I

, 1.0 0--0 100**\.I~/~** """0 200 ugrJ



# - o--<J 500 uo"\ 10.0 01 E 9.0 Z 8.0 w C) )0- 7.0 X 0 6.0 Cl 6.0 W 

### >



### .... 4.0 0 <I) 3.0 <Il 

### 0 2.0
1.0
0.00 6 10 16**~o** 25 30 35 40 46 60 Sf> 60 66 DAY NUMBER Figure 2. Mean DO concentration at the end ofthe 12-hourdark cycle in microcosms exposed to atrazine. Symbols as in Figure I.



### 618.0 17.0 16.0 :r:. 15.0 Ql 14.0 E·13.0 

### i 12.0 11.0 >- 10.0 9.0 o 8.0 w 7.0 6.0 

### o 5.0 4.0 

# o 3.0 2..0 1.0 0.00 Figure 3. atrazine.

9.5 86
.r:. 7.5 N



# ... 6.5



# - <5 5.5

1;71 4.5 E 3.5 )0' 2.5 I- 

### :; 1.5 i= U 0.5 ;:) 0 ·0.5 0 IX: ·1.5 D- ·2.5 .3.6 0 Figure 4. Figure 1. - 0 vg/l 0-0 &0 vQII 0--0 100 ug/l 6--0 200 u011 500 Ugll

5 10 15 20 2.6 30 35 40 45 50 65 60 65 DAY NUMBER Mean DO concentration atthe end ofthe 12-hourlight cycle in microcosms exposed to Symbols as in Figure 1.

- 0 vgll 0-<> 60 vgll 0--<> 100 vgll 6-- -0 200 ug/l 0-0 500 vgll

5 10 15 20 25 30 36 40 45 60 65 60 6,6 DAY NUMBER Mean net primary productivity (Pn) in microcosms exposed to atrazine. Symbols as in

79,0
8,0 

## .c N 7,0 L 

### 0 6.0
Ol 

## e 6,0 Z 0 4.0
et 3.0 IX: 0: (I) 2.0 w IX: 1.0

0.00 Figure 5. Figure 1. - 0 ug/l 0-<> 60 ug/l 

## 0-.., 100 "Il/l ll--l> 200 Ug/l o-<J 500 ug/l

5 to 15 20 26 30 36 40 46 60 56 60 66 DAY NUMBER Mean 12-hourdark respiration (Rni) in microcosms exposed to atrazine. Symbols as in



### o 4.0 j: c:t: a: 3.0 Z 

### o 2.0 j: 

### < 1,0 (I) 0.0 "- -1.0 

### > j: U -2.0 :I. 

### o ·3,0 0.. -4,0

.......**..LU~UJ.J'-"** o - 0 ug/l C>-O 60 ug/l 0--0 100 ug/l b--€> 200 uglJ 0--0 500 ug/l

50 55 60 65

Figure 6. Mean netprimary productivity/respiration (Pn/Rni) ratios in microcosms exposed to atrazine. Symbols as in Figure 1.

8**o.ou.........u.~~** o 5 10 1& 20 25 30 35 40 45 60 155 60 66 DAY NUMBER Figure 7. Mean primary productivity/chlorophyll a e 4C-uptake/chlr a) ratios in microcosms exposed to atrazine. Symbols as in Figure 1.



### Data Summary Table:

Nominal Time. Atrazine Weighted Magnitude of Concen- Day of Study Average Did Effect Effectrelative tration Effect Atrazine Recovery Comments to controls (initial Occurred) Concentration Occur- 

### if

testcone) fromDayOto so, when?

(pg/L) When Effect Occurred 4 Recovery after (less than D. magna bloom.**~40%** 60 (53) controls at 52 Ilg/L Yes

- Day Magnitude of p<0.05 28 effects through Day estimated from 20) Figure 1.
4 Recovery after Primary (less than D. magna bloom. productivit**~55%** 100 (84) controls at 82.1 Ilg/L Yes

- Day Magnitude of ye4C p<0.05 28 effects uptake) through Day estimated from 20) Figure I. 4 Recovery after (less than D. magna bloom.**~70%** 200 (170) controls at 164.1 Ilg/L Yes

- Day Magnitude of p<0.05 28 effects through Day estimated from 20) Figure I.



### 9Time Nominal Weighted Atrazine Average Did Magnitude of Concen- Day of Study Atrazine Recovery Comments Effect Effectrelative tration Effect Concentration Occur- if to controls (initial Occurredl fromDayOto so, when? test cone) When Effect

(pg/L) Occurred Magnitude of effects 500 (430) 4 414.3Ilg/L No estimated from**~90%** Figure 1. Magnitude of effects 1000 4 790.2Ilg/L No estimated from**~90%** (820) Figure 1. Magnitude of effects 5000 4 3781 Ilg/L No estimated from**~90%** (3980) Figure 1. Recovery after D. magna 4 (lowerthan bloom.**~15-20%** 52 Ilg/L Yes

- Day Magnitude of after both 60 (53) controls at 28 effects photoperiods p<O.OI) estimated from Figures 2-3. Recovery after D. magna**~20%** after 4 (lowerthan bloom. Yes

- Day Magnitude of darkperiod, 100 (84) controls at 82.1 Ilg/L 28 effects**~30%** after p<O.OI) estimated from light period Figures 2-3. Recovery after D. magna**~45%** after 4 (lowerthan bloom. Dissolved Yes

- Day Magnitude of oxygen dark period, 200 (170) controls at 164.1 Ilg/L 28 effects**~55%** after p<O.OI) estimated from light period Figures 2-3. Magnitude of**~60%** after effects dark period, 500 (430) 4 414.3Ilg/L No estimated from**~70%** after Figures 2-3. light period Magnitude of**~60%** after effects darkperiod, 1000 4 790.2Ilg/L No estimated from**~70%** after (820) Figures 2-3. light period Magnitude of**~60%** after effects dark period, 5000 4 37811lg/L No estimated from**~70%** after (3980) Figures 2-3. light period

10Nominal Time Atrazine Weighted Magnitude of Concen- Day of Study Average Did Effect Effectrelative tration Effect Atrazine Recovery Comments to controls (initial Occurred] Concentration Occur- 

### if

testcone) from Day Oto so, when?

(pg/L) When Effect Occurred Yes-Day Recovery after 21 (less than D. magna controls at bloom peaked.**~60%** 60 (53) 14 51.1 flg/L p<O.OI Magnitude of during effects growth estimated from period) Figure 4. Yes

- Day Recovery after 28 (less than D. magna controls at bloom.**~55%** 100 (84) 4 82.1 flg/L p<O.OI Magnitude of during effects growth estimated from period) Figure 4.
Net Recovery after primary Yes

- Day D. magna 28 (less than bloom. productivit**~100%** 200 (170) 4 164.1 flg/L controls at Magnitude of y p<O.O1 until effects afterbloom) estimated from Figure 4. No (less Magnitude of <100% (went 500 (430) 4 414.3 flg/L than controls effects negative) atp<O.OI for estimated from duration) Figure 4. No (less Magnitude of <100% (went 1000 4 790.2 flg/L than controls effects negative) (820) at p<O.OI for estimated from duration) Figure 4. No (less Magnitude of <100% (went 5000 4 3781 flg/L than controls effects negative) (3980) at p<O.OI for estimated from duration) Figure 4. Recovery after D. magna Yes

- Day bloom. <10% 60 28 49.3 flg/L Magnitude of 32 effects estimated from Respiration Figure 5. Recovery after D. magna Yes

- Day bloom. <20% 100 28 73 flg/L Magnitude of 32 effects estimated from Figure 5.



### 11Nominal Time Atrazine Weighted Magnitude of Concen- Dayof Study Average Did Atrazine Recovery Effect Effectrelative tration Effect Concentration Occur- 

### if Comments to controls (initial Occurred! from Day 0 to so, when? testcone) When Effect

(J-lg/L) Occurred Partial recovery after D. magna 200 4 164.1 Ilg/L Somewhat

- bloom.**~55%** Day 35 Magnitude of effects estimated from Figure 5. Magnitude of
500 4 414.3Ilg/L No effects**~65%** estimated from Figure 5. Magnitude of
1000 4 790.2Ilg/L No effects**~65%** estimated from Figure 5. Magnitude of
5000 4 3781 Ilg/L No effects**~65%** estimated from Figure 5. Recovery after D. magna Yes

- Day bloom peaked.**~25%** 60 14 51.1 Ilg/L 21 Magnitude of effects estimated from Figure 6. Recovery after D. magna Yes

- Day bloom peaked.
Ratio ofnet**~35%** 100 14 77 Ilg/L 21 Magnitude of effects primary estimated from productivity Figure 6. to Recovery after respiration Yes

- Day D. magna (Pn/Rni) 28 (less than bloom.**~100%** 200 4 164.1 Ilg/L controls at Magnitude of p<O.OI until effects afterbloom) estimated from Figure 6. No (less Magnitude of >100% (went 500 4 414.3Ilg/L than controls effects negative) at p<O.Ol for estimated from most days) Figure 6. >100% (went 1000 4 790.2Ilg/L No (less Magnitude of negative) than controls effects

12Nominal Time Atrazine Weighted Magnitude of Concen- Day of Study Average Did Effect Effectrelative tration Effect Atrazine Recovery Comments to controls (initial Occurred J Concentration Occur- 

### if from Day Oto so, when? testconc) When Effect

(pg/L) Occurred atp<O.OI for estimated from most days) Figure 6. No (less Magnitude of >100% (went 5000 4 3781 flg/L than controls effects negative) atp<O.OI for estimated from most days) Figure 6. No (less Magnitude of**~50%** 60 (53) 4 52 flg/L than controls effects atp<O.OI for estimated from most days) Figure 7. No (less Magnitude of**~55%** 100 (84) 4 82.1 flg/L than controls effects at p<O.OI for estimated from most days) Figure 7. Ratio of No (less Magnitude of primary**~65%** 200 (170) 4 164.1 flg/L than controls effects productivit atp<O.OI for estimated from y to most days) Figure 7. chlorophyll No (less Magnitude of
a

# e 4C-**~80%** 500 (430) 4 414.3 flg/L than controls effects uptake / atp<O.OI for estimated from chlra) most days) Figure 7. No (less Magnitude of**~80%** 1000 4 790.2 flg/L than controls effects (820) atp<O.OI for estimated from most days) Figure 7. No (less Magnitude of -80% 5000 4 3781 flg/L than controls effects (3980) atp<O.OI for estimated from most days) Figure 7.
I Only atrazIlle effects that occurred pnorto the daphmd bloom (pnorto Day 18) are consIdered III the "Cosm DataPoints and Exposure Profiles" spreadsheet. Bolded values are those datapoints specified in the "Cosm DataPoints and Exposure Profiles" spreadsheet.



### The table below is alinked object showing the calculations for the time weighted averages used in the Data Summary Table. Effect day concentrations didnot occuron days when atrazine concentrations were measured, and were interpolated in apiecewise linear fashion (see "Stay 1985 TWA.xls", sheet "Stay1985

_Attach5" for calculations and
a graph showing the results for the nominal 60 /lg/L case).

13

### Nominal Day 0 Effect TWA Cone. Day of Cone. Day Cone.** Endpoint (ug/L) 

### Effect (ug/L) 

### Conc.* (ug/L) 

### primaryprod. 60 4 52.4 51.6 52.0 primaryprod. 100 4 84.1 80.0 82.1 primaryprod. 200 4 169.3 158.8 164.1 primaryprod. 500 4 430.2 398.5 414.3 primaryprod. 1000 4 820.3 760.2 790.2 primaryprod. 5000 4 3980 3581.9 3781.0 DO 60 4 52.4 51.6 52.0 DO 100 4 84.1 80.0 82.1 DO 200 4 169.3 158.8 164.1 DO 500 4 430.2 398.5 414.3 DO 1000 4 820.3 760.2 790.2 DO 5000 4 3980 3581.9 3781.0 NPP (Pn) 60 14 52.4 49.7 51.1 NPP (Pn) 100 4 84.1 80.0 82.1 NPP (Pn) 200 4 169.3 158.8 164.1 NPP (Pn) 500 4 430.2 398.5 414.3 NPP (Pn) 1000 4 820.3 760.2 790.2 NPP (Pn) 5000 4 3980 3581.9 3781.0 Respiration 60 28 52.4 46.3 49.3 Respiration 100 28 84.1 62.0 73.0 Respiration 200 4 169.3 158.8 164.1 Respiration 500 4 430.2 398.5 414.3 Respiration 1000 4 820.3 760.2 790.2 Respiration 5000 4 3980 3581.9 3781.0 Pn/Rni 

### 60 14 52.4 49.7 51.1 Pn/Rni 

### 100 14 84.1 69.9 77.0 Pn/Rni 

### 200 4 169.3 158.8 164.1 Pn/Rni 

### 500 4 430.2 398.5 414.3 Pn/Rni 1000 4 820.3 760.2 790.2 Pn/Rni 

### 5000 4 3980 3581.9 3781.0 14C/ch1r

### a 60 4 52.4 51.6 52.0 14C/ch1r

### a 100 4 84.1 80.0 82.1 14C/chlr

### a 200 4 169.3 158.8 164.1 14C/chlr

### a 500 4 430.2 398.5 414.3 14C/ch1r

### a 1000 4 820.3 760.2 790.2 14C/ch1r

### a 5000 4 3980 3581.9 3781.0
* interpolated from chemograph in Stay85

_Attach5 (piece-wise linear
** average ofDay 0 and Effect Day concentrations

14

### Reviewer Comments:

The methodology is well documented. All analytical methods as well as statistical procedures are fully described. The few instances where the authors deviate from published standard practice are supported with clearexplanations.

The study uses highly controlled microcosms as opposedto the mesocosms ofprimary interest for the literature review. Because ofthe more controlled conditions, there is little chance ofconfounding from environmental factors; however, it is likely that communitylevel responses are unrealistic in such a controlled setting. In particular, the

### Daphnia bloom, which occurred between Day 18 and 35, interacted significantly with the effects ofthe atrazine to create the effects observed in the aquatic communities. Therefore, only atrazine-related effects that occurredbefore the daphnid bloom on Day 18 ofthe study
were considered. Given the highly controlled nature ofthe experiment, the relevance of the study results to mesocosms ornatural field systems is uncertain.

The authors note two factors making the Taub microcosms different from the seminatural pond communities ofdeNoyelles et al. (Ecology 63:5, pp. 1285-1293, 1982 as well as the 1985 study in the same volume as this study). First, the microcosms are very nutrient-rich and could be considered hypereutrophic, whereas the ponds are roughly mesotrophic and have much lower oxygen demand. Second, reaeration is different between the two systems. They also note thatthe 14C-uptake/chl 

### aratio, the most sensitive measure to atrazine they found, is the measure that is least similarbetween their results and deNoyelles et al (1982).

Description ofUse in Document (QUAL, QUAN, INV): Qualitiative

Rationale for Use: Although the study has limitedutility, given the

### Daphnia magna bloom occurring between Days 18 and 25 (in all controls and treatment groups), the results document decrease in community-level endpoints forphytoplankton at all atrazine treatment levels (:::: 60 ug/L) with no recovery at atrazine concentrations of500, 1000, and 5000 ug/L and recovery within 32 days attreatmentlevels of60, 100, and 200 ug/L.

Limitations ofStudy: The use ofmicrocosms allowed ahighly controlled setting; however, the 

### Daphnia magna bloom occurring between Days 18 and 35 strongly interacted with the effects ofatrazine treatments and is notto be commonly expected in the real world. According to the study authors; the nutrient status ofthe control and treated microcosms could not be assessed because samples collected priorto day 30 of

15

### the study were contaminated. Further details on the "contamination" issue were not provided. Given the uncertainties associated with the daphnid bloom on Days 18-35, only those atrazine-related effects that occurred priorto Day 18 ofthe study were considered. Additionally, the reaeration regime ofapicklejar is much differentthan that ofapond. Results, therefore, have limited applicability to mesocosms ornatural aquatic systems.

Primary Reviewer: Sara Hendrix, M.S., StaffScientist, Cambridge Environmental Inc

Secondary Reviewer: Anita Pease, M.S., SeniorBiologist, Environmental Fate and Effects Division, U.S. Environmental Protection Agency.**{}X(t~** 

# 0/t3/1\

16