Open Literature Review Summary

Chemical Name: Atrazine

CAS No: 1912-24-9

ECOTOX Record Number and Citation:

deNoyelles, F., S.L. Dewey, D.G. Huggins, and W.D. Kettle. 1994. Aquatic mesocosms

in ecological effects testing: detecting direct and indirect effects of pesticides. In:

Graney RL, Kennedy J.H., Rodgers J.H. Jr. (Eds.). Aquatic mescocosm studies in

ecological risk assessment. Lewis Publishers, Boca Raton, FL. Pp. 577-603 (MRID

47543609).

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 (LOC).

Date of Review:

November 24, 2009

Purpose of Study:

This study examines the potential effects of atrazine to aquatic plants and animals in

experimental ponds (mesocosms).

Summary of Study Findings:

Methods: The study's methods are described in far more detail in other papers by

deNoyelles and colleagues. In particular, this study often references deNoyelles et al.,

1989, reviewed previously.

The study's data are from the 80S-day study (see deNoyelles et al., 1989 review), which

used ten 0.045-ha earthen pond mesocosms. Two replicates each at nominal atrazine

concentration level of 0 (control), 20, 100, 200, and 500 ~g/L were used. Atrazine

application occurred in a single addition at the beginning of each summer to the treatment

ponds, over 3 successive years (1981-1983) for the 20, 100, and 200 ~g/L treatment

ponds and over 2 successive years (1982-1983) for the 500 ~g/L treatment ponds. (The

first application for the 20-200 ~g/L ponds was June 21, 1981, and the first treatment for

the 500 ~g/L ponds was May 30, 1982.) Actual concentrations were measured

'1.1•••111

2087827
immediately after addition (differed by <10% of nominal) and periodically during the

experiment, with declines to 70% and 25% of original measured concentrations after 6

and 12 months, respectively. Four species of fish were stocked to represent different

food web niches: Ctenopharyngodon idella (grass carp, a macrophyte grazer), Dorsoma

cepedianum (gizzard shad, a filter-feeding omnivore), Ictalurus punctatus (channel

catfish, a benthic-feeding omnivore), and Lepomis macrochirus (bluegill sunfish, a visual

predator).

For further details, including statistical analyses ofresults, the authors reference

deNoyelles et af., 1989. Other studies are referenced for further descriptions of particular

methods, including Carney, 1983 (previously reviewed), Dewey, 1986 (review

forthcoming), Huggins, 1990 (a University of Kansas Ph.D. thesis, not presently included

in the literature review), and Huggins, Johnson, and deNoyelles, 1994 (a structural

equation modeling study from the same volume as this study, Ch. 33, not presently

included in the literature review).

Before these study results are presented, the authors summarize a large number of

mesocosm studies that measured direct and indirect effects of various pesticides and were

conducted prior to the issuance ofthe 1988 EPA mesocosm technical guidance document

for pesticide registration studies (EPA-600/4-85/0 13, "Methods for measuring the acute

toxicity of effluents to freshwater and marine ecosystems"). The summary for atrazine

will be presented in this review, before the study results (see below).

Results:

Summary 0/atrazine mesocosm study results prior to 1988

Effects are tabulated for different types of mesocosm studied, with direct or indirect

increases or decreases noted for phytoplankton, periphyton, macrophytes, rotifer and

crustacean zooplankton, macroinvertebrates, insects, and fish, with alteration of physical

or chemical parameters also noted. For atrazine, phytoplankton were generally indirectly

increased, periphyton and macrophytes were directly decreased, and fish were indirectly

decreased, with lack of observations and/or no consistent effects reported for

zooplankton, macroinvertebrates, and insects. Most studies also noted indirect alteration

to physical and/or chemical parameters. See Table I.

Results/rom the 80S-day, 1981-1983 study

In the 80S-day study, declines in phytoplankton occurred within the first few days ofthe

first exposure to atrazine, but returned to (or exceeded) control pond levels within one

month. However, after subsequent treatments no short-term declines occurred. Species

composition remained altered, and the phytoplankton community as a whole was

demonstrated to develop tolerance or resistance to atrazine. See Figure 1 for the study's

depiction ofthe data (graphs a and b show production in mg C/m3

/h for 1982 and 1983,

2
and c and d show biomass in chI a Ilg/L for 1982 and 1983, respectively). DeNoyelles et

aI., 1989 is cited for methods.

Grazing rotifer and crustacean zooplankton, the planktonic insect Chaoborus, and the

filter-feeding gizzard shad all were unaffected by atrazine treatment either directly or

indirectly. These animals all depend on phytoplankton for their food base, and were

apparently unaltered by changes in the species composition ofthe phytoplankton

community. Channel catfish, benthic omnivores, were also unaffected by atrazine

treatment. See Figure 2, graphs a, b, and h (gizzard shad, channel catfish). DeNoyelles

et aI., 1989 is cited for methods.

Macrophytes were strongly affected by atrazine treatment: the submergent macrophyte

community in general, "particular species" (the authors refer the reader to deNoyelles et

aI., 1989 and Carney, 1983), and the emergent community (primarily cattails, Typha

latifola and T angustifolia) all were reduced, especially at concentration at or above 100

Ilg/L, and did not recover. At the 20 and 100 Ilg/L treatment levels, there was a relative

increase of Chara, but no other indications of community tolerance or resistance were

noted. See Figure 1, graphs e andjfor some ofthe data (submersed macrophyte

coverage ofthe pond bottom). DeNoyelles et aI., 1989, Carney, 1983, and Huggins et aI.

from Ch. 33 ofthe same volume as this study are cited for methods.

Grass carp, a macrophyte grazer, declined in both individual biomass and total biomass

per pond at atrazine concentrations at or above 100 Ilg/L, where macrophyte densities

were low. Although macrophyte densities were also lower in the 20 Ilg/L pond, grass

carp did not decline there as much, which the authors attribute to higher macrophyte

growth rates at the low treatment level (thereby maintaining an adequate food supply).

See Figure 2, graph h. Grass carp grazing, in turn, affected the response of both

submergent and emergent macrophytes. With grass carp present, the added grazing

pressure reduced macrophyte densities compared to areas ofthe same ponds fenced off

from the grass carp. Although atrazine alone was enough to maximally reduce

submergent macrophytes at concentrations of 200 Ilg/L or above, at 100 Ilg/L, only the

areas with grass carp achieved similar reductions. At the low 20 Ilg/L concentrations,

grass carp-affected areas had similar macrophyte cover to the control ponds' grass carpaffected areas. In one ofthe control ponds (24C), grass carp were lost in September

1982, "probably due to transient vertebrate predation (snapping turtle)" in the authors'

words. This pond had more macrophyte cover than the other control pond in 1983.

(However, in the 500 Ilg/L pond 26C, grass carp were also lost in September 1982, but

macrophyte reduction in 1983 was still near-total.)

Some insects that did not feed on macrophytes but used them for their habitat or for

epiphytic algal food declined with atrazine treatment. Such insects included

Chironomidae (mostly herbivores and detritivores in the epiphytic microhabitat), in

particular Endochironomus (an herbivore on epiphytic algae) and Ablabesmyia (predator

3
on microcrustacea and Chironomidae including Endochironomus). See Figure 1, graphs

g and h (note: total emerging insects were dominated by Chironomidae) and Figure 2,

graphsjandg. DeNoyelles eta!', 1989, Dewey, 1986, and Huggins, 1990 (Ph.D. thesis)

are cited for methods.

Frog populations naturally colonized the ponds, and declines in tadpole biomass

(primarily Rana catesbeiana) occurred at all atrazine concentrations. The authors

attribute the effect to declines in macrophytes and shoreline vegetation affecting egg

deposition and survival as well as to declines in periphyton feeding sites. See Figure 2,

graph h (tadpoles).

Bluegill sunfish declined in total biomass in all ponds at or above 100 )Jg/L atrazine

concentration. The authors attribute this effect to decline in the emerging insect

population that provide a major feeding base for adult bluegill. See Figure 2, graph h

(note that bluegill >7cm are all adults; not all bluegill <7 cm are adults).

The amphipod Hyallela azteca increased in abundance with atrazine treatment. Other

insects, like Caenis spp., Dicrotendipes simpsoni, Parachironomus spp., and

Glyptotendipes spp. were more abundant at levels of 20, 100, and 200 )Jg/L, but only

when compared to the high macrophyte control pond (24C, the one where grass carp

were lost). At 500 )Jg/L treatment, these species were less abundant but still greater than

the low macrophyte control (pond 26C). The Ceratopogonidae had a similar distribution

over the treatment levels, but did not differ between the two control ponds. The authors

propose several possible indirect mechanisms potentially responsible for these effects.

See Figure 2, graphs c, d, and e. Huggins, 1990 (Ph.D. thesis) and Huggins et a!., 1994

(same volume as this study) are cited for methods.

4
Table 1. Direct and indirect effects of atrazine detected from mesocosm studies conducted prior to the original mesocosm guidance document (Touart,

1988) for pesticide registration studies. From study table 1.

Mesocosm Phyto- Periphyton Macrophytes Rotifer Crustacean Macro- Insects Fish Physical/ References plankton zooplankton zooplankton invertebrates Chemical

farm or natural direct ponds, indirect direct direct not indirect direct decrease, indirect indirect constructed increase decrease decrease monitored increase decrease indirect decrease alteration I

ponds, stocked decrease with fish

experimental direct

earthen ponds, decrease, direct direct not indirect not not indirect indirect 2 stocked with indirect decrease decrease monitored decrease monitored monitored decrease alteration

fish increase

experimental direct

earthen ponds, decrease, not direct not indirect

no effects no effects no effects no effects 3,4 stocked with indirect monitored decrease monitored decrease

fish mcrease

experimental direct indirect earthen ponds, decrease, direct direct

no effects no effects no effects increase & indirect indirect 5,6 stocked with indirect decrease decrease decrease alteration

fish increase decrease

direct direct

limnocorrals decrease, decrease, not not not not not not indirect 7, 8 indirect indirect monitored monitored monitored monitored monitored monitored alteration

increase increase

I Walker, C.R. 1961. Weeds 12:134-139

2 deNoyelles, F., Jr., W.D. Kettle and D.E. Sinn. 1982. Ecology 63: 1285-1293

3 Gunkel, G. 1983. Arch. Hydrobio!. Supp!. 65:235-267

4 Gunkel, G. 1984. Arch. Hydrobio!. Supp!. 69:130-168

5 deNoyelles, F., Jr., W.D. Kettle, C.H. Fromm, M.F. Moffet and S.L. Dewey. 1989. Misc. Pub. No. 75, Entom. Soc. of America, 41-56.

6 Dewey, S.L. 1986. Ecology 67:148-162

7 Hemlan, D., N.K. Kaushik, K.R. Solomon. 1986. Can. J. Fish. Aquat. Sci. 43: 1917-1925

8 Hamilton, P.B. 1987. Environ. Pollut. 46:83-103

5
Ji8

Figure 1. Distribution of aquatic organisms in 0.045-ha pond mesocosms treated with atrazine at 20

/-lg/L (22L, 23L), 100 /-lg/L (11M, 15M), 200 /-lg/L (14MH, 16MH), and 500 /-lg/L (21H, 25H) plus

controls (24C, 26C). Graphs a, c, e, g are from 1982, and b, d,j, h are from 1983.

6
lOOOO

:lOtiO

- 0

Figure 2. Distribution of aquatic organisms in pond mesocosms as described in Figure 1. Results are

all from 1983.

7
Data Summary Table:

Effect Magnitude of Nominal Day of Time Weighted Did Comments

Effect Atrazine Study Average Recovery

relative to Concentration tYrect Atrazine Occur~ if

controls (f.1g/L) Occurred Concentration so, when

from Day 0 to (see

When Effect comment)?

Occurred'

Phytoplankton

biomass and

d . J pro uctlOn

Change in

phytoplankton

species

composition J

Submerged

macrophyte

coverI

Total 85% 20 Ilg/L 464 13.1 Ilg/L Effects and

90% 100 JJg/L 464 65.4 JJg/L dates

emergmg no estimated insects 70% 500 ).1g/L 121' 404.6 ).1g/L from Figure I

>100% 20 ).1g/L 807 12.6 ).1g/L (increase) Effects and

Hyallela (# >100% 100 ).1g/L 764 62.2 ).1g/L not dates

per sampler) (increase) applicable estimated

>100% 500 ).1g/L 464' 326.8 ).1g/L from Figure 2

(increase)

>100% 20 ).1g/L 842 12.7 ).1g/L (increase) Effects and Ceratopo- >100% not dates gonidae (# per (increase) 100 ).1g/L 842 63.4 ).1g/L applicable estimated sampler) >100% from Figure 2

(increase) 500 ).1g/L 499' 328.5 ).1g/L

300% 20 ).1g/L 842 12.7 ).1g/L not Effects and Parachiro- (increase) applicable dates nomus (# per 50% 100 ).1g/L 842 63.4 flg/L no estimated sampler) 100% 500 ).1g/L 499' 328.5 flg/L no from Figure 2

Endochiro- 80% 20 JJg/L 785 12.5 Ilg/L Effects and

90% 100 flg/L 785 62.7 flg/L dates nomus (# per no estimated sampler) 100% 500 flg/L 442' 324.5 flg/L from Figure 2

Ablabesmyia 100% 20 Ilg/L 701 12 flg/L Effects and

100% 100 Ilg/L 701 60.1 Ilg/L dates (# per no estimated sampler) 100% 500 flg/L 358' 303.8 flg/L from Figure 2

~30% 20 Ilg/L 842 12.7 flg/L Effects and Tadpoles ~60% 100 )J.g/L 842 63.4 Ilg/L dates (biomass per ~90% 200 flg/L 842 126.7 flg/L no estimated pond) ~60% 500 )J.g/L 499' 328.5 )J.,g/L from Figure 2

8
Note: * Days are calculated SInce InItial atrazIne addItIOn (5/30/1982 for the 500 f!g/L treatment ponds)

I See Data Summary Table in review of deNoyelles et a!., 1989.

Effect Magnitude of Nominal Day of Time Weighted Did Comments

Effect Atrazine Study Average Recovery

relative to Concentration Effect Atrazine Occur- if

controls (Jlg/L) Occurred Concentration so, when

from Day 0 to (see

When Effect comment)?

Occurret

0% (similar) 201lg/L 842 12.7Ilg/L Effects and Grass carp ~75% 1001lg/L 842 63.4 Ilg/L dates (biomass per ~60% 200 Ilg/L 842 126.7 IlgiL no estimated pond) ~75% 500 Ilg/L 499* 328.5Ilg/L from Figure 2

Bluegill 0% (similar) 201lg/L 842 12.7Ilg/L Effects and

sunfish ~75% 1001lg/L 842 63.4 Ilg/L dates

(biomass per >90% 2OOllg/L 842 126.7 Ilg/L no estimated

pond) ~75% 5001lg/L 499* 328.5Ilg/L from Figure 2 . .. ..

Time weighted average concentrations could not be calculated with confidence. The

effect days are rough estimates, and the study does not provide data on atrazine

concentrations or additions apart from stating that atrazine was added to bring

concentrations up to within 10% of nominal occurred at the beginning of each summer,

and atrazine had reduced to 70% ofthe original concentration after 6 months and 25%

after 12 months. From these statements, and brief examination of Figure 1 in the

deNoyelles et al. 1989 review, the following assumptions were made to allow calculation

oftime-weighted averages:

1. Effect days are accurate (even though concentrations are available from Day 842 of

"80S-day study")

2. Application every 350 days (based on deNoyelles et al. 1989 review, Figure 1)

3. Since most recent application, linear decline in first 180 days to 70% of original

4. Original = 90% of nominal

5. In prior application intervals, piecewise linear decline (70% after 180 days, 25% after

350 days)

See below for the calculated time-weighted average concentrations, and the linked Excel

spreadsheet for more details. 2

2 An important note: in this paper, the authors state the following: "The exposure was a single addition of

atrazine at the beginning of each summer to the same ponds with 20-, 100-, and 200-f!gll treatments for 3

successive years (1981 to 1983), and the 500-f!g/1 treatment for 2 successive years (1982, 1983)." No

further details are provided, or complications to this simple method mentioned. However, Dewey, 1986,

Carney, 1983, and deNoyelles et aI., 1989 all describe a more complex treatment method: the two 500 f!g/L

ponds were created out of20 f!glL ponds previously treated with commercial atrazine, and one ofthe 200

Ilg/L ponds was not created until 1982, and then out of a 100 Ilg/L commercial treatment pond. The TWAs

calculated for this study reflect the information provided in this 1994 study, not the information in these

other studies.

9
Nominal

Cone.

20 IJg/L

20 IJg/L

20 IJg/L

20 IJg/L

20 IJg/L

100 IJg/L

100 IJg/L

100 IJg/L

100 IJg/L

100 IJg/L

200 IJg/L

500 IJg/L

500 IJg/L

500 IJg/L

500 IJg/L

500 IJg/L

Original

Cone.

(lJg/L)

18

18

18

18

18

90

90

90

90

90

180

450

450

450

450

450

No. of

Application Days Effect Day TWA

Intervals Since Last Cone. Cone.

Effect Day Completed Addition (lJg/L) (lJg/L)

464 1 114 14.6 13.1

701 2 1 18.0 12.0

785 2 85 15.5 12.5

807 2 107 14.8 12.6

842 2 142 13.7 12.7

464 1 114 72.9 65.4

701 2 1 89.9 60.1

764 2 64 80.4 62.2

785 2 85 77.3 62.7

842 2 142 68.7 63.4

842 2 142 137.4 126.7

121 0 121 359.3 404.6

358 1 8 444.0 303.8

442 1 92 381.0 324.5

464 1 114 364.5 326.8

499 1 149 338.3 328.5

Reviewer Comments:

One cannot review this study solely on its own merits, because it summarizes and

synthesizes the results of many other studies and refers to these other studies extensively

for technical details of methods and results. Not all studies so referenced are part ofthis

open literature review. For the ones that are, please see those reviews for reviewer

comments. All reviewer comments for those reviews are directly applicable to this study,

insofar as the methods and results are used or discussed in this study.

Reviews applicable to this study: deNoyelles et al., 1989 (everything relating to the 805-

day study), Carney, 1983 (macrophytes in experimental ponds), Dewey, 1986.

Studies referenced that are not part ofthis literature review: Huggins, 1990 (a University

ofKansas Ph.D. thesis), and Huggins, Johnson, and deNoyelles, 1994 (from the same

volume as this study, Ch. 33).

In terms of data presentation, the study was rather unclear. No statistics were presented.

It was difficult to estimate the magnitude ofthe effects from the figures; therefore, effect

magnitudes, day of effect, and (as previously described) time weighted average

concentrations are all extremely crude estimates despite their numeric appearance.

Overall, the emphasis was far more qualitative than quantitative.

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

10
0!l3/tt

Rationale for Use: The paper provides a synopsis and comparison ofthe results of

atrazine mesocosm data from the following studies: Walker (1961), deNoyelles et at.

(1982 and 1989), Gunkel (1983 and 1984), Dewey (1986), Herman et at. (1986), and

Hamilton (1987). In general, the reported data show direct effects via reduction in plant

production and biomass (i.e., phytoplankton, periphyton, and macrophytes); however, in

many ofthe studies recovery of phytoplankton communities was observed within one

month of atrazine application with a shift toward species that are resistant or tolerant to

atrazine. No recovery of macrophytes was observed. Indirect effects were also observed

via reduction in food for grazers followed by reduced prey for predators, altered habitat

structure for particular plants and animals, and reduced competition for unaffected plants.

Limitations of Study: Data summary table results are crude visual estimates from small

three-dimensional graphs and should not be used quantitatively. The study describes

many qualitatively interesting results and possible mechanisms for ecotoxicity in

mesocosms, but the underlying methodology suffers from poorly controlled experimental

design (evidenced by frog colonization and snapping turtles apparently eating fish from

some ponds) with too few replicates. Additionally, no statistics or data tables are

presented.

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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