Open Literature Review Summary Chemical Name: Atrazine 

### CAS No: 1912-24-9
ECOTOX Record Number and Citation: Hamilton, P.B., G.S. Jackson, 

### N.K Kaushik, and 

### KR. Solomon. 1987. The impactof atrazine on lake periphyton communities including carbon uptake dynamics using track autoradiography. Environ. Poll. 46:83-103 (MRlD 47543616). Purpose ofReview: Determine potential effects ofatrazine on an aquatic community. Endpoints from this study contribute to the weight-of-evidenceregarding effects ofatrazine on aquatic plant communities and associated determination ofaLevel ofConcern (LaC).
Date ofReview: November24, 2009 Purpose ofStudy: This study examines the potential effects ofatrazine to aquatic plants (periphyton) in experimental mesotrophic lake enclosures (limnocorrals) during the autumn growing season in Ontario, Canada. Summary ofStudy Findings:
Methods: The basic experimental design ofthis study is also reported in Hamilton, et

### at. (1987), Hamilton, et

### at. (1988), and Herman, et

### at. (1986). This study, however, reports results from 1982 experiments which are not described in the other 3 related articles.
Two experiments were carriedout, from August to December 1982 and from August 1983 to June 1984, in Lake St. George, a 10.3 hamesotrophic lake (coordinates are provided, but surrounding landuse is not described). Aquatic enclosures (125 m3

, 5 m x 5 m x 5 m deep) constructed ofnylon reinforced polyvinyl chloride (PVC) were previously installed in 1980 (otherarticles are cited for details). Each enclosure isolated acomplete water column, including lake sediment. In April 1982, the walls were littedto the water surface, and then dropped down and fixed to the lake bottom again one month later, and checked by divers for leakage. On June 16, four weeks after lowering the walls, the enclosures were treated with atrazine (80% active ingredient, manufacturernot 

# III1IIIIII 2087861provided) using an injection pump to mix the herbicide in the water. A nominal concentration of2 mg/L (2,000 /lg/L) was applied to two enclosures and 0.2 mg/L (200 /lg/L) was applied to the othertwo, with an additional two kept as controls. (The authors state that a fixed block experimental design was used for treatment). In the 1983 experiments, a similarinitialization procedure (lifting the walls in April, dropping them one month later) was applied, and atrazine was applied on June I. In 1983, atrazine was applied to the surface of3 enclosures using a backpack sprayerto achieve nominal concentrations of0.1 mg/L (100 /lg/L), and the other 3 enclosures were used as controls. A second application of0.1 mg/L (100 /lg/L) was applied 35 days later, on July 6.
Water quality measurements (nutrient, oxygen, temperature, major ions) were performed (they are not described in the article, but an article headed by the last co-author is cited). The authors statethat in both 1982 and 1983 experiments, periphyton communities were not introduced to the enclosures until 90-125 days after atrazine application. (However, based onthe dates provided, the 1982 experiments placedthe periphyton communities in the enclosures 53 days after atrazine application, and the date ofperiphyton addition is not directly provided for the 1983 experiments.)


### In 1982, 7.5 cm x 2.5 cm nylon reinforced PVC plastic strips, made from the same material as the enclosure walls, were cut, acid washed with 0.1 N HCl, and thoroughly rinsed with deionized water, then glued to microscope slides with rubbercement. The slides were then glued 20 mm apart on baked clay bricks (8 slides perbrick). On August 8, the bricks with PVC covered slides were suspended in Lake St. George at a depth of 1 m and allowed to colonize for 53 days in the natural lake waters. The bricks were then transferred to the enclosures andresuspended at 1 m depth, with 2 bricks placed in each enclosure. Sampling began on the first day ofbricktransfer (whatthe authors call day 0, which was Day 53 after atrazine application) and continued for 56 days (until Day 109).
For sampling, individual strips were randomly removed from each enclosure and immediately placed in 250 mL serum bottles filled with lake water. The serumbottles were inoculatedwith 0.5 mL ofstandardizedNaH14C03 (2.5 /lCi) using a Hamilton syringe andresuspended at 1 m depth for 3-4hours. Subsequently, the periphyton was scraped from the strip, blended in a Waring mixerfor 5 seconds at low speed, and divided into 3 aliquots. One aliquot was filtered through a Whatman GF/C filterusing 69 kPa pressure and immediately frozen. Later, chlorophyll a was extractedwith 90% acetone and analyzed using the technique ofLorenzen (1967, Determination of chlorophylland phaeopigments: Spectrophotometric equations). The second aliquot was size fractionated onto 5.0 and 0.22 /lm Millipore filters, washed in 0.1 N HCl and deionized water, and radioactivity determined in a2-methoxyethanol-toluene scintillation cocktail. Fractionation separatedthe larger filamentous and colonial algae from the smallercells and fragmented material. Assimilation rates for the periphyton samples were calculated following the method ofSmythe (1973, MSc thesis at University ofWaterIoo). The third aliquot was preserved with Lugol's solution and laterthe cells were counted (minimum count 300 cells) using Utermohl's transect technique. The initial blending fragmented

2the prostrate and filamentous algae, and with these fragments the individual cells were counted. Natural colonial forms, such as Scenedesmus, were counted as colonies. Length, width, and depth (where necessary) measurements were randomly taken for each taxon and, using the counts, converted to fresh weightbiomass in the method ofJanus (1976, MSc thesis at University ofWaterloo). Volumetric conversion to biomass assumed that cell density was the same as water. Numbers and fresh weightbiomass were transformed by loglo(x+1) to fulfill normality and homogeneous variance requirements, and then the data were analyzedby sampling day using fixed block ANOVA (specific tests used are not described). Also, in addition to counts, individual cell production levels were examinedusing nucleartrack autoradiography, in the method ofDuthie and Hamilton (1983, Studies onperiphyton communitydynamics in acid stressedstreams using trackautoradiography). Photosynthesis ofselected species was expressed as pg C/fixed cell/hr.

In 1983, the experiment was repeated. Glass slides holding PVC strips were attachedto 9 cm plastic Petri dishes (4 perdish) and suspended in the lake at 1 m depth for 39 days before transfer to the enclosures. Sampling commencedjustprior to transfer and continued for 223 days. (The date oftransfer is not specified, and itis not reported on what day after atrazine application the transfertook place. Laterin the article, November 18, 170 days after atrazine addition, is reported as "day 49" afterperiphyton addition in 1983, which would imply that periphyton were added 121 days after atrazine was first applied; however, this is several days offfrom another estimate based on the caption in Table 3.) The collected samples were divided into two aliquots, with one used for determination ofash free dry weight (AFDW) using a 0.45 Jim Millipore filter, andthe second preserved with Lugol's solution and later counted. No chlorophyll or primary production measurements were taken during the 1983 periphyton sampling. Cell density, fresh weight biomass, and AFDW were transformed by 10glO(x+l) to fulfill normality and homogeneous variance requirements, and then the data were analyzed using one-way ANOVA "with a 95% probability level" (which likely means determination ofthe 95% confidence intervals, so p-valueswill be assumed <0.05) (specific tests used are not described).
Nutrient additions, described in related articles, are not mentioned in this article. The results describe Morista Similarity Coefficients at one point, citing Wolda (1981, Similarity indices, sample size anddiversity), butthis index is not defined in the article or mentioned in the Materials and Methods section.
Results: The 1983 results presented in the article are also described in the related articles, Hamilton, etal. (1988), Hamilton, etal. (1989), and Herman, etal. (1986). Similarwater quality measures are provided in Herman, etal. (1986) and are summarized differently (and more completely) in Hamilton, etat. (1989). Many ofthe periphyton measures appear similar to those ofHerman, etal. (1986), butthe methods described in Herman, et al. are different and appear to be separate periphyton investigations within the same enclosures.

3No significant differences in density and fresh weight biomass in the pretreatment communities were found in the 1982 or 1983 experiments. See Table 1. These similarities were also demonstrated by Morista Similarity Coefficients that ranged from 0.90-0.99. In 1982, the mean atrazine concentrations at day 1 (afterperiphyton addition) were 1.56 mg/L and 0.14 mg/L in the high and low treatments, respectively. By 56 days afterperiphyton addition, mean atrazine levels had dropped to 1.39 and 0.11 mg/L, respectively. Throughoutthe 1982 experiment, mostwater quality parameters (nitrogen, phosphorus, dissolved organic carbon, silicon, temperature, most major ions) were similarin control and treatment enclosures, but significantly (p-value < 0.05) higher values ofdissolved inorganic carbon, calcium, and oxygen were observed in treatment enclosures. See Table 2.

In the 1983 experiment, the mean atrazine concentration in the treatment enclosures 1 day afterperiphyton addition was 0.08 mg/L (80 Jlg/L). As with the 1982 experiment, most water quality parameters (nitrogen, phosphorus, silicon, temperature, mostmajor ions, oxygen) were similar in control and treatment enclosures, but significantly (p-value 

### < 0.05) higher values ofdissolved inorganic carbon, calcium, and sodium were observed in treatment enclosures, and dissolved organic carbon levels were significantly lower. See Table 3.

In 1982, chlorophyll a, fresh weight biomass, and total cell numbers were lowerafter exposure to treatment (as Figure I is apparently meantto show). Although chlorophyll a levels were consistently lower in treatments, only on days 10 and 21 afterperiphyton addition were statistically significant (p-values < 0.05) differences found between controls and the high (1.56 mg/L) treatments. There were no significantdifferences between controls and the low (0.14 mg/L) treatments. In communitybiomass and cell density, significantdifferences were observed on days 10 and 21 with the high concentration and on day 21 with the low concentration.' Figure 2 shows that dramatic changes in 1982 periphyton community composition (relative species abundances) occurred in treatments relative to controls. The ChlorophytaMougeotia sp. was the dominant species throughout the study at relative abundances ranging from 10.7-63.4% by biomass, and showed lowerbiomass and cell density aftertreatment withoutrecovery to control levels. Othernoticeably affected species were Oedogonium sp., Spirogyra sp., Stigeoclonium sp., and Coleochaete orbicularis. The diatoms were also affected by atrazine, with significant (no p-value provided) declines in numbers and fresh weight biomass on days 21 and 35 in the high treatments and on day 35 in the low treatments (see Figure 3). Despite this absolute

I Day numbers cited as "day X" (lower-case d in day) are numbered afterperiphyton addition, as in the article. Day numbers cited as "Day X" (upper-case D in Day) are numbered after atrazine addition. In this study, however, it is more appropriate to measure endpoints from day 0 as the day ofperiphyton addition, since that was the day that the exposure actually began.


### 4decline, the group's relative abundance increased by 3-43% over controls. 

### Epithemia turgida was the most dominant diatom in the controls at 9.8-34.2% ofthe biomass, but with treatment itdeclined significantly from day 10-35 (p-value 

### < 0.05). Another common diatom,

### Achnanthes minutissima, at 1.5-16.1 % ofcontrolbiomass, showed significantreductions in cell numbers and biomass from high treatment on days 21 and 35, but no significantdifferences from controls in the low atrazine treatments. Therewas no significantreduction in cyanobacterial numbers orbiomass, dueto high variability within treatments. 

### Cylindrospermum stagnale was the most abundant cyanobacterium at 1.4-4.9% ofthe total biomass, and showed some eventual reductions due to treatment which were not detected as significant. The Chrysophytawere dominated by small «2**~lm)** unidentifiable forms that were not affected by treatment, which resulted in an increase in relative abundance on days 35 and 56 atboth treatment levels (Figure 2). Overall, the total numberofspecies in the periphyton community was decreased in both the atrazine treatments, with green algae and diatoms showing the greatest losses, particularly afterday 21.
The carbon assimilation in 1982ranged from 0.5-4 mg C/m2/hrin the >5 11m size class (fraction A), and from 0.5-2 in the 0.22-5 11msize class (fraction B). See Figure4. In all enclosures, both fractions showed increasing production inthe first 10 to 21 days, and then declined, apatternexplainable by seasonal effects (late summerturning into fall and winter). Fraction A contributed 73-84% ofthe total production in the first 21 days, but by the endofthe studyboth fractions were contributing equally. Fraction A net productivity declined initially afterplacementin the treatment enclosures, with a significant(p-value < 0.05) difference from control values atday 10 atthe high treatment level, which recovered by day 21. Fraction B was actually more productive in the treatmentenclosures than the controls, especially the hightreatmentlevel, where carbon uptake was approximately 4 times higherthan controls on days 3 and 10; these returned to control levels at day 21. The authors speculate that perhaps the carbon molecules in the smaller size class were not incorporated into viable cells, but formed complexes with ruptured cells or organic colloids on the filter.
For species-specificproduction in 1982, large filamentous Chlorophytahad the highest cell productionrates. On day 3, control populations 

### ofStigeoclonium sp., 

### Oedogonium sp., and

### Mougeotia sp. 'had fixation rates from 143.8-803.6 pg C/cell/hr, and the large diatom E. 

### turgida fixed well over 100pg 

### C/cell/hrthroughoutthe study in both controls and treatment enclosures. All common taxa showed seasonal decline from day 3 to 56, with the largestdeclines in the filamentous greens, which hadreductions of77.2-90.0%, and the 

### Tetraspora cylindrical (which appeared in the treated enclosures from day 21 to 56) declined for 94.4 to 17.1 pg C/cell/hr. After 3 days in the atrazinetreatedenclosures, all common taxa except

### Scenedesmus acutiformis had significantly lowercarbon fixation rates (see Table 4), butby day 21, 

### Tolypothrix limbata was the only taxon that had not recovered. Two initially affectedtaxa, 

### M. sp. and S. sp., became significantly more productive in the treated enclosures. By day 35, S. sp. was still moreproductive in the treatment enclosures, while O. sp., E. 

### turgida, and

### A. minutissimahad returned to

5significantly lowerproductionrates. By day 56, all production levels hadbecome similar. See Figure 4 for details atthe high treatment level.

In the 1983 study, AFDW, fresh weightbiomass, and total numbers declined significantly (p<O.05) with atrazine treatment, butrecovered by day 49 after being placed in the enclosures. See Figure 1. As with the 1982 experiment, green algae and diatoms dominatedthe biomass ofthe control periphyton communities (Figure 5). Chlorophyta cell numbers and biomass declined in treatmentenclosures from days 4 to 49, with significant (p<O.05) differences between days 12 and 49; by the nextspring (day 223), recovery had occurred. In controls, M sp. was dominant with 19.4-55.8% ofthe total biomass, and in treatments, it had significantreductions (p<O.05) (Figure 3), with a greater percent abundance decline than other species. Bacillariophyceae were prominent in percent abundance in both control and treatment enclosures (Figure 5). Diatom numbers were lower in the treatment enclosures from days 4 to 34, with significant (p<0.05) differences between days 12 and 34, andbiomass was also lower in that time, although significant differences only occurred on day 4 and 12. As in 1982, diatoms increased in relative percentabundance due to treatment, since they were not affectedby treatment as much as Chlorophyta (Figure 2). The diatomRhopalodiagibba, which contributed 11.7-29.3% ofthe total biomass (Figure 3), significantly declined in biomass from day 4 until the end ofthe study, although inpercent abundance itremained similar in controls and treatments. Gomphonemagracile, Gomphonema augustatum, Cymbella cis/ula, and 

### E. turgida were othercommon diatoms showing declines in treatment, though their (andR. gibba's) total numbers did not often significantly (p<0.05) differ from controls. A. minutissima showed an initial decline in numbers and biomass on days 12 and 23, butrecoveredby day 34 to become the dominant species in total numbers, reaching apercent abundance of>34% afterday 23. Cyanobacterianumbers and biomass were generally low in both treatment and control enclosures, although there was a significant (p<0.05) reduction in cyanobacterial biomass from day 12 to 49 in the treatment enclosures. Tolypothrix limbata, Cylindrospermum stagnale, and 

### Osciliatoria tenuis were absent in treatment enclosures from day 12 to 223, while Nostocpunct!forme andLyngbya sp. persisted until day 49.
The number ofspecies present in the periphyton in the 1983 experiment was affected by atrazine treatment, as is apparently meanttobe shown in Figure 1. The cyanobacteria, Chlorophyta, Chrysophyta, and Bacillariophyceaecommunities all had signitkant species losses, and the diatoms, which contributed 40-50% ofthe total species, had an average of 10.7 fewer species in treatment enclosures byday 49.
Coefticients ofvariation in the measured variables in the two studies were ratherhigh, ranging from: 4.5-29.0 for total number oftaxa; 7.9-50.0 for AFDW; 0.3-67.7 for total cell numbers; 21.2-75.4 for fresh weight biomass; 4.9-99.2 for total chlorophyll a; and 0.06-99.0 for net production.

6

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## • (I :I :::> 0 % DAYS AFTER TREAnl.ENT Figure 1. Mean changes in chlorophyll a (mg/cm2), fresh weightbiomass (mg/cm2), total numbers (lIcm2), ash-free dry weight (AFDW, mg/cm2) and total numberofspecies, afteratrazine exposureof the periphyton communities. Standard deviation bars are shown for each measurement day, except day 56 in 1982. The different lines, which should correspond to different treatment levels, are not identified in the original article. (study figure 1)

7DAVS AFTER TREATMENT (19821 3 10 21 35 56

CONTROL

ATRAZINE 0.14 mg L- 1

ATAAZINE 1.56 mg L-"

r'".'_J CHLOROPHYTA c:::, CUPfOPIH'U**C~** UCILLAflIOPH'l'Cr;,U

_ CHIt'l'80PHYf,ll. C-.:J**OTH~R** Figure 2. Percentcomposition ofbiomass by majorphyla after exposure to atrazine in 1982. Cyanophyta represents thecyanobacteria. (study figure 2)

81982

BIOtlASS

10 21 35 56 2 4 12 23 34 DAYS AFTER TREATMENT I 

# r., 1.,.·'1



# lilFigure3. Changes in IOglO numbers (lIcm2) and IOglO fresh weight biomass (mg/cm2) forthe common taxa. Open bars representcontrols; slashed bars represent the 0.4 mglL treatment in 1982; and solid bars representthe 1.56 mglL treatment in 1982 and the 0.08 mg/L treatmentin 1983. Standard deviation bars are shown, except for the control enclosure on day 56 of1982. (studyfigure 3)

9

## )5.0 lJm • CONTROL A 0, j4 rng

# l;

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### C

# +-t~ 1 0.22

- 

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### 1.5 

## 1.0 

## 05
500 

## i:300 100 LIGHT


# o 10 20 30 40 

# DAYS AFTER TREATMENT 50 60

Figure4. Net production ofthe periphyton community (mg Clm2 /hr) in fraction A (>5.0 /lm) and fraction B (0.2-5.0 /lm), after atrazine exposure in 1982. The photosynthetically available radiation (light energy) atthe time ofthe productivity experiments are presented in the bottom graph in units of/lEinsteins/m2 /s. (study figure 4)

10DAYS AFTER TREATNENT (1983) 2 4 12 23 34 49 223
CONTROL

AfRAZINE 0.08 mg L- 1**~,** CIft.ORoP+tnlll n::::J C"fAJlO,"H'YtA

_ CHIlYllOJIKYTA r-:J OTHER lBD IJACILLARIOl'HYCI!""

Figure 5. Percent composition ofbiomass by majorphyla afterexposure to atrazine in 1983. Cyanophyta represents the cyanobacteria. (study figure 5)

Table 1. LoglO transformed mean cell numbers (lIcm2) and fresh weight biomass (l-lg/cm2) for the 1982 and 1983 pretreatment periphyton communities, after 53 and 39 days ofcolonization. respectively. (n=2, SD=standard deviation) (study table 1) 1982 /983 I

n Numbers Biomass

"" ., Mean SD I Mean SD Mean S1J Mean ! SD Cyanophyta 5.033 I 0.062 I 0.266 0.05 5.053 0.016 0.159 i 0.064
i 0.429 I Chlorophyta 5.53 0.487 I 2.208 I 0.177 4.839 0.1 1.577 Chrysophyta 6.075 0.546 i 1.449 0.575 5.943 0.075 1.049 0.163 I I Bacillariophyceae 5.025 0.485 2.266 0.315 5.163 0.065 1.684 0.125

! Cryptophyta 0 0 r 0 0 

## L--.J

Pyrrophyta 1.436 2.031 0.306 0.433 1.577 2.146 0.389 I 0.55 I Total 6.249 I 0.498 2.571 0.27] 6.082 0.058 2.023

11

----- ------ ------ ----Table 2. Physical characteristics ofthe control and treated enclosures during 1982, on day 7 (October 12, 1982) and day 21 (October 26). Low and high values for two samples are shown, exceptfor temperature. (from study table 2) O.J4mg/L Treatment Day 2] Low 0.703 0.799 0.0112 0.0139 0.0115 8 7.3
.2 .1 42.3 55.2 1 0.7 .59
9 10 0.0082 0.0113 0.0168

7.1 8.7 7.6 19.9 21 21.1 32.6 32.9 0.9 0.63 1.66 8.7 I 9
6 Calcium (mglL) Total**WU"5~H** (Kjeldahl, mg/L) Total phosphorus (filtered, mg/L) Dissolved organic carbon (mg/L) f-- ----=---=------1-----1

----

Dissolved inorganic carbon (mg/L)

i Silicon (mg/L)

# ~xygen (0.5 m

depth, mg/L) Temperature (OC)

12Table3. Physical characteristics ofthe control and treated enclosures in the 1983 experiment, on days -4 (September 22, 1983) and 210 (April 27, 1984). (n=3; Min.=minimum, Max.=maximum) (from study table 3)

2.5

3.13 8.5 added Treatment (0.08 mg/L) Mean 

## I Min. Max. 0.881 

# I 0.853 0.896 I I I· J .. .. 0.0122 

### I 0.0118 - 0.0128 2.4 2.4 2.4 31.5 30.9 31.8 49.2 45.4 51.4 I

## 2~. 2.99

i 10.7 I 9.2 I 12.5

# 1~ 14.2 14.9**~9** I 3.82
7.6 7.9 10 2.8 7.8 1.65**~calcium** (mg/L) 

## I 41.9 

### sm",n**(mgIL~**

# -f!27
Oxygen (0.5 m 9 2 denth,

. Temperature (0C) 10.7

13Table 4. Species-specific carbon uptake rates for the common taxa found in the 1982 high atrazinc treatment (1.56 mg/IJ) and control enclosures' periphyton communities. Mean production is shown with CI defined such that Mean +/- CI represents the 95% confidence interval. Data are expressed in pg C1celllhr. (study table 4)

14

### Data Summary Table: Comments

From Fig. 2 and 5 Did Recovery Occur- 

### if so, when (see comment)?

1,560 llg/L Day 3 after exposure Day of Study Effect Occurred

2,0001lg/L Nominal Atrazine Concentration (pg/L) Effect Magnitude of Effectrelative to controls Time Weighted Average Atrazine Concentration from Day 0 to

When Effect Occurred**I--~-_._--+ ------+----~·-+----·----l807C** 

### - NR-- 

### I Decrease 140 IL -NA 

### I**M~gmtudes** pcriphyton**f-'---'-"""'-'-'-'---1-.:c---'-...l-.Io'c..::::..--+'-:-:..:::...:-----f-~- ~-~**  eshmated productivity Day 3 after \

# i: s

## ~~::i I from FigA I (Ie uptake) >95% 2,000

## ~g/L exposure 1 1,560

## ~~L 

# I**~~~1~~~1'** (la<geoelbj 

### I Day 11 after Day 50**M~gnitudes** I Decrease in 60% I00**~g/L** 80 I!g/L f estImated exposure , a ter, 

### I periphyton exposure I from Fig.l, 

### I algal cell**~-------+------+--CY-'----(~** as interpreted density 60% 200 I-tg/L Day 36 after 140 I!g/L 5:sft ay with text info exposure a er from p. 93

____**~60%** 

### _----+ 2,000 Ilg/L

I 1,560 Ilg/L

i exposure)

Change in Qualitative! 

# I Day 2 after

. 

### I periphyton

### ~t I 100

### ~g/L exposure 80

### ~g~-----i community Qualitative Day 3 after 't' f"' 200 I!g/L 140 I!g/L ' Nc) composl Ion e leet exposure (% biomass by major Qualitative phyla) effect**r·.L-"'---£----t-~·------+------_+_-----i_-----+_---------r___-------** Yes (Day Magnitudes 80% 100/lg/L Day 23 after 80 I!g/L 49 after estimated Decrease in exposure periphyton 

# +- +_e_xp'-lO_s_u_re-"'C)--j from Fig.l biomass I**_~_** (Biomass), as (fresh I 75% 

# i 200 Ilg /L Day 20 after 140 I!g/L Yes (Day interpreted 

# F 56 after with text info weight) I exposure exposure) from p. 90 & 75% 2,000 Ilg /L 1,560 IlglL 96 Change in 

# 1--- Day -4 (pre- -'------+--F-ro--m-T-a-b·-le--- nutrien:

. I 40% «0.05) 100 IL exposure, 80 IL Yes (Day 3. Recovery avallablhty 

### I P Ilg post- Ilg i 210) noted the (increase in treatment) next spring.

# ~~~~;~:~~ : 50% (p<0.05) , 200 Ilg /L

# ~::o;u~:,er**~40** Ilg /L

I No (>21 From Tablel carb.on and r 500/< ( <0.05) l2 000.'

. IL Day 60 after I 560 IL 

# I days) 2. calcIUm) ! 0 P , llg treatment ' J-lg 

# '---1

i

.

## ~---+-I**--------~-gni-tudes ~l** 

Decrease in 20% I 100 I!g/L I 80 I!g/L

I estimated number of 

### I D 20 fit i , fi F' 1 ay a er rom Ig. , species in 30% 200 I!g/L \140 I!g/L

i No . h t I

. exposure as interpreted penp y on I**.~** 

## r:-=- 

# -l with text info community

. 30% 2,000 Ilg/L I I**1,560~Il_g/_L** .L1**l--=tr-,o~Jl-J** Note: NR=Not Reported; NA=Not Applicable Balded values are those datapoints specified inthe "Cosm DataPoints and ExposureProfiles" spreadsheet.



### 15Time weighted average concentrations are assumed equal to the measured levels on day 1 afterperiphyton addition because thatwas the only atrazine concentration information provided in this study.
Reviewer Comments: This study, the first article to be published with Hamilton as the lead author, was poorly designed and presented. However, it is the only article in this literature review providing data from the] 982 experiment, where very high (200 and 2,000**~tg/L,** nominally) concentrations ofatrazine were examined.
Problems with the presentation, which interfered with interpretation ofthe results, included: watershed land use and background atrazine in Lake St. George was not described; the exact dates ofperiphyton addition to the enclosures was unclear, and the fact that this was not concurrentwith atrazine addition confounded the determination of effect and recovery**days~** many techniques were not summarized sufficiently, and attwo points the methodological references were MSc theses from the University ofWaterloo that were over 10years old at the time ofthe study's publication; the nutrient additions to the enclosures, which the reviewerrecalls from the 1989 paper by the same group, were not mentioned, despite some discussion ofdata on nutrient levels andwaterquality variables in the enclosures; and finally, the caption on Figure 1 fails to define which lines correspond to the various treatmentlevels, forcing the readerto make inferences based on discussion in the text or else ignore the dataentirely. The most clearly interpretable data in the whole study are the species composition data (percentrelative composition by biomass), Figures 2 and 5.
The experimental setup for these two experiments was unconventional in thatprecolonizedperiphyton strips were added into the enclosures months after the atrazine had been applied. Therefore, the pre-existing waterquality impacts ofthe atrazine had already been established, and the periphyton community was introduced to this previously altered system in an artificial fashion. In addition, it is unclear whether the sameperiphyton shifts in species composition observed in this study would have occurred ifan atrazine pulse was appliedto apre-existing system with established periphyton.
Some ofthe results, for example the chlorophyll a determination, scem questionable, although the methods are not described in sufficientdetail to make an informed judgment. The authors mention anumberofartifacts that may have occurred in the productivity measurements due to the filtration technique. In these variables, the coefficients ofvariation approach 100%. Random errordue to the methods used may account for some ofthis variability, although in a sample size 

### 01'2 (as used in the 

### 1982 experiment), such statistics are necessarily limited.

16Description ofUse in Document (QUAL, QUAN, INV): Qualitative
Rationale for Use: Results confirm a shiftin periphtyon community structure at atrazine concentrations of80 and 140 f.tg/L.
Limitations ofStudy: The study results are difficultto interpret due to poorpresentation ofmethods andresults, high variability caused by small numberofreplicates and potentially questionable measurement methods, lackofdata on the potential presence of atrazine in the control enclosures, and the choice ofapplying periphyton strips to the enclosures months afterthe atrazinewas added. In addition, the "high" treatment level from the 1983 study of2,000 f.tg/L exceeds environmentally relevant concentrations. Species composition data are the most easily interpreted set ofresults in the study and could be qualitatively usefuL Primary Reviewer: Sara Hendrix, M.S., StaffScientist, CambridgeEnvironmental Inc Secondary Reviewer: Anita Pease, M.S., SeniorBiologist, Environmental Fate and Effects Division, U.S. Environmental Protection Agency. 

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