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 impact of

atrazine on lake periphyton communities including carbon uptake dynamics using track

autoradiography. Environ. Poll. 46:83-103 (MRlD 47543616).

Purpose of Review:

Determine potential effects of atrazine on an aquatic community. Endpoints from this

study contribute to the weight-of-evidence regarding effects of atrazine on aquatic plant

communities and associated determination of a Level of Concern (LaC).

Date of Review:

November 24, 2009

Purpose of Study:

This study examines the potential effects of atrazine to aquatic plants (periphyton) in

experimental mesotrophic lake enclosures (limnocorrals) during the autumn growing

season in Ontario, Canada.

Summary of Study 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 carried out, from August to December 1982 and from August

1983 to June 1984, in Lake St. George, a 10.3 ha mesotrophic lake (coordinates are

provided, but surrounding land use is not described). Aquatic enclosures (125 m3

, 5 m x

5 m x 5 m deep) constructed of nylon reinforced polyvinyl chloride (PVC) were

previously installed in 1980 (other articles are cited for details). Each enclosure isolated

a complete water column, including lake sediment. In April 1982, the walls were litted to

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, manufacturer not

III1IIIIII

2087861
provided) 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 other two, 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 similar initialization 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 of 3 enclosures using a backpack sprayer to achieve nominal

concentrations of 0.1 mg/L (100 /lg/L), and the other 3 enclosures were used as controls.

A second application of 0.1 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 state that in both 1982 and 1983 experiments, periphyton communities were

not introduced to the enclosures until 90-125 days after atrazine application. (However,

based on the dates provided, the 1982 experiments placed the periphyton communities in

the enclosures 53 days after atrazine application, and the date of periphyton 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 rubber cement. The

slides were then glued 20 mm apart on baked clay bricks (8 slides per brick). 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 and resuspended at 1 m depth, with 2 bricks placed in each

enclosure. Sampling began on the first day of brick transfer (what the 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 serum bottles

were inoculated with 0.5 mL ofstandardized NaH14C03 (2.5 /lCi) using a Hamilton

syringe and resuspended at 1 m depth for 3-4 hours. Subsequently, the periphyton was

scraped from the strip, blended in a Waring mixer for 5 seconds at low speed, and divided

into 3 aliquots. One aliquot was filtered through a Whatman GF/C filter using 69 kPa

pressure and immediately frozen. Later, chlorophyll a was extracted with 90% acetone

and analyzed using the technique of Lorenzen (1967, Determination ofchlorophyll and

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 a 2-methoxyethanol-toluene scintillation cocktail.

Fractionation separated the larger filamentous and colonial algae from the smaller cells

and fragmented material. Assimilation rates for the periphyton samples were calculated

following the method of Smythe (1973, MSc thesis at University ofWaterIoo). The third

aliquot was preserved with Lugol's solution and later the cells were counted (minimum

count 300 cells) using Utermohl's transect technique. The initial blending fragmented

2
the 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 weight biomass in the method ofJanus

(1976, MSc thesis at University of Waterloo). Volumetric conversion to biomass

assumed that cell density was the same as water. Numbers and fresh weight biomass

were transformed by loglo(x+1) to fulfill normality and homogeneous variance

requirements, and then the data were analyzed by sampling day using fixed block

ANOVA (specific tests used are not described). Also, in addition to counts, individual

cell production levels were examined using nuclear track autoradiography, in the method

of Duthie and Hamilton (1983, Studies on periphyton community dynamics in acid

stressed streams using track autoradiography). Photosynthesis ofselected species was

expressed as pg C/fixed cell/hr.

In 1983, the experiment was repeated. Glass slides holding PVC strips were attached to 9

cm plastic Petri dishes (4 per dish) and suspended in the lake at 1 m depth for 39 days

before transfer to the enclosures. Sampling commenced just prior to transfer and

continued for 223 days. (The date oftransfer is not specified, and it is not reported on

what day after atrazine application the transfer took place. Later in the article, November

18, 170 days after atrazine addition, is reported as "day 49" after periphyton addition in

1983, which would imply that periphyton were added 121 days after atrazine was first

applied; however, this is several days off from another estimate based on the caption in

Table 3.) The collected samples were divided into two aliquots, with one used for

determination of ash free dry weight (AFDW) using a 0.45 Jim Millipore filter, and the

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-values will 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 and diversity), but this 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, et al. (1988), Hamilton, et al. (1989), and Herman, et al. (1986). Similar water

quality measures are provided in Herman, et al. (1986) and are summarized differently

(and more completely) in Hamilton, et at. (1989). Many ofthe periphyton measures

appear similar to those of Herman, et al. (1986), but the methods described in Herman, et

al. are different and appear to be separate periphyton investigations within the same

enclosures.

3
No 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 (after periphyton addition)

were 1.56 mg/L and 0.14 mg/L in the high and low treatments, respectively. By 56 days

after periphyton addition, mean atrazine levels had dropped to 1.39 and 0.11 mg/L,

respectively. Throughout the 1982 experiment, most water quality parameters (nitrogen,

phosphorus, dissolved organic carbon, silicon, temperature, most major ions) were

similar in control and treatment enclosures, but significantly (p-value < 0.05) higher

values of dissolved 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

after periphyton addition was 0.08 mg/L (80 Jlg/L). As with the 1982 experiment, most

water quality parameters (nitrogen, phosphorus, silicon, temperature, most major ions,

oxygen) were similar in control and treatment enclosures, but significantly (p-value <

0.05) higher values of dissolved 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 lower after

exposure to treatment (as Figure I is apparently meant to show). Although chlorophyll a

levels were consistently lower in treatments, only on days 10 and 21 after periphyton

addition were statistically significant (p-values < 0.05) differences found between

controls and the high (1.56 mg/L) treatments. There were no significant differences

between controls and the low (0.14 mg/L) treatments. In community biomass and cell

density, significant differences 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

Chlorophyta Mougeotia sp. was the dominant species throughout the study at relative

abundances ranging from 10.7-63.4% by biomass, and showed lower biomass and cell

density after treatment without recovery to control levels. Other noticeably 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 after periphyton 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.

4
decline, 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 it declined significantly from day 10-35 (p-value < 0.05). Another

common diatom, Achnanthes minutissima, at 1.5-16.1 % of control biomass, showed

significant reductions in cell numbers and biomass from high treatment on days 21 and

35, but no significant differences from controls in the low atrazine treatments. There was

no significant reduction in cyanobacterial numbers or biomass, due to 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 Chrysophyta were 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 at both treatment levels (Figure 2).

Overall, the total number ofspecies in the periphyton community was decreased in both

the atrazine treatments, with green algae and diatoms showing the greatest losses,

particularly after day 21.

The carbon assimilation in 1982 ranged from 0.5-4 mg C/m2

/hr in the >5 11m size class

(fraction A), and from 0.5-2 in the 0.22-5 11m size class (fraction B). See Figure 4. In all

enclosures, both fractions showed increasing production in the first 10 to 21 days, and

then declined, a pattern explainable by seasonal effects (late summer turning into fall and

winter). Fraction A contributed 73-84% ofthe total production in the first 21 days, but

by the end ofthe study both fractions were contributing equally. Fraction A net

productivity declined initially after placement in the treatment enclosures, with a

significant (p-value < 0.05) difference from control values at day 10 at the high treatment

level, which recovered by day 21. Fraction B was actually more productive in the

treatment enclosures than the controls, especially the high treatment level, where carbon

uptake was approximately 4 times higher than 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-specific production in 1982, large filamentous Chlorophyta had the highest

cell production rates. 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 100 pg C/cell/hr throughout the study in both controls

and treatment enclosures. All common taxa showed seasonal decline from day 3 to 56,

with the largest declines in the filamentous greens, which had reductions of 77.2-90.0%,

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 atrazine treated enclosures,

all common taxa except Scenedesmus acutiformis had significantly lower carbon fixation

rates (see Table 4), but by day 21, Tolypothrix limbata was the only taxon that had not

recovered. Two initially affected taxa, M. sp. and S. sp., became significantly more

productive in the treated enclosures. By day 35, S. sp. was still more productive in the

treatment enclosures, while O. sp., E. turgida, and A. minutissima had returned to

5
significantly lower production rates. By day 56, all production levels had become

similar. See Figure 4 for details at the high treatment level.

In the 1983 study, AFDW, fresh weight biomass, and total numbers declined significantly

(p<O.05) with atrazine treatment, but recovered by day 49 after being placed in the

enclosures. See Figure 1. As with the 1982 experiment, green algae and diatoms

dominated the biomass ofthe control periphyton communities (Figure 5). Chlorophyta

cell numbers and biomass declined in treatment enclosures from days 4 to 49, with

significant (p<O.05) differences between days 12 and 49; by the next spring (day 223),

recovery had occurred. In controls, M sp. was dominant with 19.4-55.8% ofthe total

biomass, and in treatments, it had significant reductions (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, and biomass was also lower in that time,

although significant differences only occurred on day 4 and 12. As in 1982, diatoms

increased in relative percent abundance due to treatment, since they were not affected by

treatment as much as Chlorophyta (Figure 2). The diatom Rhopalodia gibba, which

contributed 11.7-29.3% ofthe total biomass (Figure 3), significantly declined in biomass

from day 4 until the end ofthe study, although in percent abundance it remained similar

in controls and treatments. Gomphonema gracile, Gomphonema augustatum, Cymbella

cis/ula, and E. turgida were other common diatoms showing declines in treatment,

though their (and R. 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, but recovered by day 34 to become the dominant species in total numbers,

reaching a percent abundance of>34% after day 23. Cyanobacteria numbers 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 Nostoc punct!forme

and Lyngbya sp. persisted until day 49.

The number ofspecies present in the periphyton in the 1983 experiment was affected by

atrazine treatment, as is apparently meant to be shown in Figure 1. The cyanobacteria,

Chlorophyta, Chrysophyta, and Bacillariophyceae communities 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 by day 49.

Coefticients of variation in the measured variables in the two studies were rather high,

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
J..-._j , ,

HI

1933

t:""~-"::;r"'-'_-~--"-'-"-'''-' "-•.

--,-~_.._"._...... _.._- 'i

--.

o

e;.-+--

"-r--r----r-~...,~--...-___,r___ ---,-

no

l III

4,1)

:J 3.0

f

4( 2.0

1.0

60 eo

- 0-

10 :10 30 40

O~ ·It

'1'.0

.l

"".. !i.0 ;l;

Il.

0 :l.t} . II'

0

..:r

U t,O

12

l/) 011 lit

<C

::I 0.11

0.3

0

.'" 11,0 e

II) 4,0

ec:

l.l.I

lD 2..0 ::I

;l

Z

Q

'"...

u

'1 ....

a. '0 l1)

30 ...

0 20

=: 10 ...

• (I :I

:::> 0 %

DAYS AFTER TREAnl.ENT

Figure 1. Mean changes in chlorophyll a (mg/cm2), fresh weight biomass (mg/cm2), total numbers

(lIcm2), ash-free dry weight (AFDW, mg/cm2

) and total number ofspecies, after atrazine exposure of

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)

7
DAVS 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. Percent composition of biomass by major phyla after exposure to atrazine in 1982.

Cyanophyta represents the cyanobacteria. (study figure 2)

8
1982

BIOtlASS

10 21 35 56 2 4 12 23 34

DAYS AFTER TREATMENT

I

r., 1.,.·'1

lilFigure 3. Changes in IOglO numbers (lIcm2

) and IOglO fresh weight biomass (mg/cm2

) for the common

taxa. Open bars represent controls; slashed bars represent the 0.4 mglL treatment in 1982; and solid

bars represent the 1.56 mglL treatment in 1982 and the 0.08 mg/L treatment in 1983. Standard

deviation bars are shown, except for the control enclosure on day 56 of 1982. (study figure 3)

9
)5.0 lJm

• CONTROL

A 0, j4 rng l; .... 1,56 mg C

+-t~1 0.22 - 50 ~m

t==t~ <:A~=~---:::1

.......

_ 4.0

1:

C\J

E 3.0

o

E2.0

z

o

..--

u

:::>

a

2.0

CL 1.5

1.0

05

500

i:300

100

LIGHT

o 10 20 30 40

DAYS AFTER TREATMENT

50 60

Figure 4. Net production of the 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) at the time of the productivity experiments are presented in the bottom graph in units

of /lEinsteins/m2/s. (study figure 4)

10
DAYS 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 of biomass by major phyla after exposure 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 of colonization.

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

Chlorophyta 5.53 i 0.487 0.429 I 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 of the 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, except for temperature. (from study table 2)

O. J4 mg/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)

12
Table 3. Physical characteristics of the 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

10 7.9 7.6

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

13
Table 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 ofStudy

Effect

Occurred

2,0001lg/L

Nominal

Atrazine

Concentration

(pg/L)

Effect Magnitude of

Effect relative

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:s

ft 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 Decrease in 20% I

i 100 I!g/L .

I ~---+-I 80 I!g/L I

--------~-gni-tudes~l 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 data points specified in the "Cosm Data Points and Exposure Profiles" spreadsheet.

15
Time weighted average concentrations are assumed equal to the measured levels on day 1

after periphyton addition because that was 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 of atrazine 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 concurrent with atrazine addition confounded the determination of

effect and recovery days~ many techniques were not summarized sufficiently, and at two

points the methodological references were MSc theses from the University of Waterloo

that were over 10 years old at the time ofthe study's publication; the nutrient additions to

the enclosures, which the reviewer recalls from the 1989 paper by the same group, were

not mentioned, despite some discussion of data on nutrient levels and water quality

variables in the enclosures; and finally, the caption on Figure 1 fails to define which lines

correspond to the various treatment levels, forcing the reader to make inferences based on

discussion in the text or else ignore the data entirely. The most clearly interpretable data

in the whole study are the species composition data (percent relative composition by

biomass), Figures 2 and 5.

The experimental setup for these two experiments was unconventional in that precolonized periphyton strips were added into the enclosures months after the atrazine had

been applied. Therefore, the pre-existing water quality 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

same periphyton shifts in species composition observed in this study would have

occurred if an atrazine pulse was applied to a pre-existing system with established

periphyton.

Some ofthe results, for example the chlorophyll a determination, scem questionable,

although the methods are not described in sufficient detail to make an informed

judgment. The authors mention a number of artifacts that may have occurred in the

productivity measurements due to the filtration technique. In these variables, the

coefficients of variation approach 100%. Random error due 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.

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Description of Use in Document (QUAL, QUAN, INV): Qualitative

Rationale for Use: Results confirm a shift in periphtyon community structure at atrazine

concentrations of 80 and 140 f.tg/L.

Limitations of Study: The study results are difficult to interpret due to poor presentation

of methods and results, high variability caused by small number ofreplicates and

potentially questionable measurement methods, lack of data on the potential presence of

atrazine in the control enclosures, and the choice of applying periphyton strips to the

enclosures months after the atrazine was added. In addition, the "high" treatment level

from the 1983 study of 2,000 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., Staff Scientist, Cambridge Environmental Inc

Secondary Reviewer: Anita Pease, M.S., Senior Biologist, Environmental Fate and

Effects Division, U.S. Environmental Protection Agency.

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