APPENDIX D: 

Bibliography of Microcosm and Mesocosm Studies and Criteria Used to 

Screen Studies for Analysis of Atrazine Risks to Aquatic Plant Communities 

(49 pages)

 

1 
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION

 Date: August 25, 2011

 Chemical: Atrazine 

 PC Code: 080803 

 DP Barcode: 382803

MEMORANDUM

Subject: Bibliography of Microcosm and Mesocosm Studies and Criteria Used to Screen 

Studies for Analysis of Atrazine Risks to Aquatic Plant Communities 

 

TO: Melanie Biscoe, Chemical Review Manager 

 Anne Overstreet, Team Leader 

 

 Pesticide Re-evaluation Division (7508P) 

 Office of Pesticide Programs 

From: Michael Lowit, Ph.D., Ecologist 

 Anita Pease, Associate Division Director 

 Dana Spatz, Branch Chief 

Brian Anderson, Branch Chief 

Environmental Fate and Effects Division (7507P) 

Potential effects of atrazine on plant communities have been evaluated using available 

microcosm and mesocosm studies (referred to as cosm studies hereafter). Initially, a literature 

search was conducted to identify a set of cosm studies that was ultimately used in preparation of 

the 2003 Interim Reregistration Eligibility Decision (IRED, U.S. EPA, 2003). Subsequent to the 

IRED, Scientific Advisory Panel (SAP) meetings were held on scientific issues associated with 

the ecological significance of atrazine on primary producers in surface water streams in 

December, 2007 and May, 2009. Documents from these SAPs can be found at the following url: 

http://www.epa.gov/oscpmont/sap/meetings/2007/index.htm 

http://www.epa.gov/oscpmont/sap/meetings/2009/index.htm 

One recommendation of these SAPs was to consider a number of additional cosm studies, many 

of which were published since the 2003 IRED, for the evaluation of potential effect levels of 

atrazine on aquatic plant communities. Cosm studies included in the 2003 IRED and those 

recommended by the SAP were considered in the current analysis. 

2 
First, all studies were prescreened. A study was excluded from further consideration if four 

criteria were not met: (1) treatments were exposed to only atrazine, that is, not mixtures or multiactive ingredients, (2) exposure concentrations were reported, (3) measured effects were specific 

to aquatic plant communities (defined as two or more species), and (4) the study was written in 

English. 

Studies that met the basic elements of the prescreen criteria were further screened using a quality 

criteria. The accepted studies were then used as the basis for deriving the initial atrazine Level 

of Concern (LOC). The acceptance criteria are included in Attachment 1 and were intended to 

identify studies with minimal study design and performance elements to allow greater confidence 

in the study results. Criteria included basic elements such as use of controls and use of at least 

two replicates per treatment group. The criteria were derived using peer reviewed sources from 

U.S. EPA, SETAC (Society of Environmental Toxicology and Chemistry), and OECD 

(Organization for Economic Co-operation and Development) (Giddings et al. 1999; OECD, 

2004; U.S. EPA, 2004). 

A total of 35 cosm studies were originally included in the 2003 IRED, and an additional 38 cosm 

studies were identified in the May 2009 SAP for a total of 73 studies. Applying the prescreening 

and acceptance criteria to the 73 studies resulted in including 31 of the original 35 studies 

presented in the IRED and 15 of the 38 studies recommended for consideration in the May 2009 

SAP report (46 total studies). Citations of all 73 cosm studies considered are in Attachment 2. 

A total of 87 endpoints were used in the analysis to develop the level of concern for atrazine. 

These endpoints came from the 46 studies that passed the prescreening and acceptance criteria. 

These endpoints are depicted in Figure 1. Figure 1 distinguishes effects endpoints (blue 

squares) from no effect endpoints (hollow triangles). Effects observed in the cosm studies 

included changes in aquatic plant biomass, chlorophyll a concentration, photosynthesis rate (14C 

uptake, oxygen production), and shifts in aquatic plant community structure (e.g. species 

composition and diversity) relative to a control. 

Effects in the cosm studies were scored using a binary effect/no effect score. In previous 

analyses, the cosm studies were assigned Brock scores, which is a 5-point effects scoring system. 

A Brock score of 1 was assigned to studies that did not produce an effect and a Brock score of 5 

was assigned to studies that produced clear effects without recovery. Studies with Brock scores 

of 1 (no effect) or 2 (slight or transient effect) were distinguished from studies assigned 3 (clear 

effect with recovery) or higher for the LOC analysis. Functionally, the binary effects scoring is 

identical to the manner in which Brock scores were used (Brock scores of 1 and 2 were 

considered no effects and Brock scores of 3 or higher were considered to be effects). However, 

all Brock scores (particularly those with a score of “2” indicating slight or transient effects) were 

re-evaluated to ensure that each endpoint was categorized into the appropriate “effect” or “no 

effect” group. Using a binary effect/no effect system was considered to be more clear and 

transparent, which is the reason for adopting it for this analysis. A summary of all cosm 

endpoints used in the analysis is in Attachment 3. 

3 
Figure 1: Exposure duration and average atrazine concentrations for endpoints from cosm studies 

that met the prescreening and acceptance criteria. Blue squares are endpoints with effects; 

hollow red triangles are endpoints with no effects. 

0.01

0.1

1

10

100

1000

10000

1 10 100 1000

Average Study Concentration (ug/L atrazine)

Exposure duration (days)

Effect

No Effect

4 
Attachment 1. Criteria for Acceptance and Review of Atrazine Aquatic Micro/Mesocosm 

Open Literature Study Reviews 

In an effort to address recommendations from the May 12-14, 2009 Scientific Advisory Panel 

(SAP) on Scientific Issues Associated with “The Ecological Significance of Atrazine Effects on 

Primary Producers in Surface Water Streams in the Corn and Sorghum Growing Regions of the 

United States (Part II)”, EFED has developed quality criteria specific for the re-evaluation of 

atrazine aquatic micro- and meso-cosm (cosm) studies that were used as a basis for deriving the 

initial atrazine Level of Concern (LOC). These same criteria were also applied to the review of 

38 additional atrazine cosm studies, which were provided to EPA by an SAP member as 

Appendix 2 of the SAP report, and would be applied to any new atrazine cosm data that the 

Agency considers based on the best available information. 

These criteria were derived based on information contained in the Community Level Aquatic 

System Studies-Interpretation Criteria (CLASSIC) Society for Environmental Toxicology and 

Chemistry (SETAC) publication (Giddings et al., 1999), as well as the 2004 Draft Organization 

of Economic Cooperation and Development (OECD) Guidance Document on Simulated 

Freshwater Lentic Field Tests (Outdoor Microcosms and Mesocosms) (OECD, 2004). While the 

study acceptance and evaluation criteria described below are based on available guidelines for 

interpretation of community-level aquatic toxicity data, it is important to note that best 

professional judgment is necessary to ultimately determine the appropriate use of atrazine cosm 

data in defining the LOC. The acceptance criteria should be used as a first screen to determine 

the validity of the study, whereas the evaluation criteria should be applied in the context of the 

entire study design and quality, rather than as absolute and independent measures of acceptance. 

The approach used to derive the LOC for atrazine is unique in that it makes use of the robust set 

of atrazine cosm data to identify various exposure-duration concentrations where effects are 

observed in primary producers of the aquatic plant community. Therefore, the traditional 

approach of using a pre-defined LOC, as specified in the Agency’s Overview Document 

(USEPA, 2004), with a specific exposure concentration and endpoint value, is not used for 

atrazine. The aquatic cosm acceptance and review criteria specified below are specific for only 

atrazine because derivation of the LOC for this chemical is dependent on the identification of 

exposure-concentration profiles where aquatic plant community-level effects are observed and 

not on the identification of a single endpoint value. 

Study Acceptance Criteria:

A study would be rejected as invalid, if any of the following acceptability criteria are not 

met: 

1. Controls 

A. Controls must be present and run concurrent with the study. 

B. The presence of other stressors (physical, chemical, biological) in 

controls/treatments must not be at levels that would be expected to compromise the 

interpretation of atrazine (degradates) as the causal stressor. 

5 
2. Quantification of Exposure 

A. The amount of test material applied and the exposure concentration in the water 

column should be determined analytically at the start of exposure (t=0). Minimally, 

nominal exposure concentrations of atrazine must be provided. 

3. Experimental Design 

A. At least two replicates per treatment and controls must be included regardless of the 

statistical method used (e.g., regression, hypothesis testing). 

B. If a solvent is used, it must be < 0.5 ml/L in static-renewal or static testing or <0.1 

ml/L in flow-through testing and at the same concentration across treatments and 

solvent and/or negative controls. 

4. Statistical Methods and Data Interpretation 

A. If a regression-based approached is used, at least three treatments (with a minimum 

of two replicates/treatment) in addition to the controls must be tested. In the event 

that two replicates/treatment are not tested, the study design must contain a 

minimum sample size “N” of 5 including the control in order to fit a nonlinear 

regression curve. 

B. Statistical analysis of the data (univariate and/or multivariate) including numerical 

and/or graphical presentation of the results must be clearly described and presented. 

Study Evaluation Criteria:

If a study passes the acceptability criteria stipulated above, further evaluation of the study 

results relative to study performance and interpretation of the effects data will be 

conducted according to the following evaluation criteria: 

1. Controls 

A. Ideally, no detectable atrazine and/or degradate concentrations should be present in 

the controls. Atrazine levels in control water, based on measurements during the 

study or on other information, should be “negligible or low enough” such that 

conclusions regarding atrazine effects concentrations are not compromised. It is 

expected that determination of what is considered “negligible or low enough” will 

involve some level of interpretation regarding effects observed at treatment levels 

relative to the control. Factors to be considered in determining whether atrazine 

levels are “negligible” include, but are not limited to: (1) dose-response within the 

same study; (2) magnitude of contamination relative to effects levels in other 

studies under similar environmental conditions; and (3) magnitude of control 

contamination relative to effects in the study being evaluated. It should be noted 

that studies with chemical contamination in controls would normally be invalidated 

under the Agency’s review process; however, these studies are being considered as 

part the atrazine cosm review because: (1) data from these studies are being used in 

a weight-of-evidence approach as part of a larger data set to identify the occurrence 

of effects associated with various atrazine concentration-duration profiles; (2) low 

levels of atrazine are not uncommon in natural waters and may occur in field study 

6 
control samples, regardless of whether its presence was evaluated; and (3) these 

studies are not being used to satisfy specific data requirements. 

2. Quantification of Exposure 

A. Analytical measurements should be documented and of sufficient quality (if 

reported) so as to not compromise interpretation of the study results (e.g., % 

recoveries, blanks, QA standards, etc.). 

B. Preferably, the amount of parent compound and principal degradates (if reported) 

should be quantified at regular time intervals throughout the study in both the water 

column and sediment (pore water and bound residues). If such time-series 

measurements are not provided, information should be available to estimate 

exposure time trends, such as a reported half-life from the study or time-trends from 

similar systems.

3. Experimental Design 

A. All exposure levels and controls should be analyzed for chemical contaminants 

(particularly pesticides), nutrients, pH, hardness, temperature, dissolved oxygen 

(DO), and turbidity. 

B. If a solvent is used, both a solvent and a negative control should be tested. 

C. If DO is used as a measure of primary productivity, then those measurements 

should be sufficient to characterize diurnal fluctuations and must be recorded at 

relatively similar times across study units. 

D. The purity of the test material should be stated. 

E. Acclimation period should be described. 

F. Source of the water, sediment and biota and containers used in the study should be 

clearly described. 

G. How treatments are assigned to mesocosms should be clearly described; ideally, 

treatments should be assigned randomly. 

H. Study designs should adequately describe and evaluate/account for potential 

confounding effects of non-chemical stressors, e.g., habitat condition, prey 

availability, nutrient loading. 

I. Controls should be representative of treatment units and should describe the basis of 

their selection. 

J. Exterior mesocosm studies should include a description of the weather during the 

study and how water levels were maintained during the study. 

K. Study should describe whether treatment units were screened, i.e., covered to limit 

immigration and emigration of biota.

L. Exposure regime should reflect the objectives of the study and should be based on 

expected routes of entry of the chemical into aquatic systems and relevant 

frequency and timing of the entry of the chemical. 

M. The duration of the study should be appropriate to the life-cycle of the organisms of 

interest and the time needed for their recovery if these are stated objectives. 

7 
4. Statistical Methods and Data Interpretation

A. For hypothesis testing, sufficient information should be available from which to 

evaluate the statistical power of the comparisons (e.g., minimum significant 

difference that can be detected). 

B. Regarding the description of statistical analysis based on mean values, information 

on the variability within replicates (i.e., statistics representing the experimental 

variation among replicates, reporting of the standard deviation, etc.) should be 

provided and considered in the overall quality of the study. 

5. Other 

A . Where the review of a study indicates that a departure from this document’s criteria 

is scientifically warranted, the reviewer should provide the rationale for the action 

taken. 

References

Giddings et al. 1999. Community-Level Aquatic System Studies – Interpretation Criteria 

(CLASSIC). SETAC Press. 

Organization of Economic Cooperation and Development (OECD). 2004. Draft Guidance on 

Simulated Freshwater Lentic Field Systems (Outdoor Microcosms and Mesocosms). 

U.S. EPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of 

Pesticide Programs. Office of Prevention, Pesticides, and Toxic Substances. Office of 

Pesticide Programs. Washington, D.C. January 23, 2004. 

8 
Attachment 2. Micro- and Mesocosm Study Citations

A. Studies Previously Used for Cosm Endpoint Selection that Met Usability Criteria 

1. Berard, A., T. Pelte, et al. (1999a). Seasonal variations in the sensitivity of Lake Geneva 

phytoplankton community structure to atrazine. Archiv Fur Hydrobiologie 145(3): 277-

295. (MRID 48261103) 

2. Brockway, D.L., P.D. Smith, and F.E. Stancil. (1984). Fate and effects of atrazine on 

small aquatic microcosms. Bull. Environ. Contam. Toxicol. 32:345-353. (MRID 

47543602) 

3. Carney, C.E. (1983). The effects of atrazine and grass carp on freshwater communities. 

Thesis. University of Kansas, Lawrence, Kansas (MRID 47543604) 

4. deNoyelles, F. Jr., and W.D. Kettle. (1980). Herbicides in Kansas waters – evaluations of 

effects of agricultural runoff and aquatic weed control on aquatic food chains. 

Contribution Number 219, Kansas Water Resources Research Institute, University of 

Kansas, Lawrence, Kansas (MRID 47543605) 

5. deNoyelles, F., Jr., W.D. Kettle, and D.E. Sinn. (1982). The responses of plankton 

communities in experimental ponds to atrazine, the most heavily used pesticide in the 

United States. Ecology. 63 (5):1285-1293 (MRID 47543607) 

6. deNoyelles, F. Jr., and W.D. Kettle. (1983). Site studies to determine the extent and 

potential impact of herbicide contamination in Kansas waters. Contribution Number 239, 

Kansas Water Resources Research Institute, University of Kansas, Lawrence, Kansas. 

(MRID 47543606) 

7. deNovelles, Jr., F., W.D. Kettle, C.H. Fromm, M.F. Moffett, and S.L. Dewey. (1989). 

Use of Experimental Ponds to Assess the Effects of a Pesticide on the Aquatic 

Environment. Department of Systematics and Ecology, University of Kansas. 

Entomological Society of America. Miscellaneous Publications No. 75: 41 – 56 (MRID 

47543608) 

8. 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) 

9 
9. Detenbeck, N.E., R. Hermanutz, K. Allen, and M.C. Swift. (1996). Fate and effects of 

the herbicide atrazine in flow-through wetland mesocosms. Environ. Toxicol. Chem. 

15:937-946 (MRID 47543610) 

10. Dewey, S.L. (1986). Effects of the herbicide atrazine on aquatic insect community 

structure and emergence. Ecology. 67:148-162 (MRID 47543611) 

11. Gruessner, B. and M.C. Watzin. (1996). Response of aquatic communities from a 

Vermont stream to environmentally realistic atrazine exposure in laboratory microcosms. 

Environ. Toxicol. Chem. 15:410-419 (MRID 47543613) 

12. Gustavson, K. and S. Wängberg. (1995). Tolerance induction and succession in 

microalgae communities exposed to copper and atrazine. Aquat. Toxicol. 32:283-302 

(MRID 47543614) 

13. Hamala, J.A. and H.P. Kollig. (1985). The effects of atrazine on periphyton communities 

in controlled laboratory ecosystems. Chemosphere. 14:1391-1408 (MRID 47543615) 

14. Hamilton, P.B., G.S. Jackson, N.K. Kaushik, and K.R. Solomon. (1987). The impact of 

atrazine on lake periphyton communities including carbon uptake dynamics using track 

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

15. Hamilton, P.B., G.S. Jackson, N.K. Kaushik, K.R. Solomon, and G.L. Stephenson. 

(1988). The impact of two applications of atrazine on the plankton communities of in situ 

enclosures. Aquat. Toxicol. 13:123-140 (MRID 47543617) 

16. Hamilton, P.B., D.R.S. Lean, G.S. Jackson, N.K. Kaushik, and K.R. Solomon. (1989). 

The effect of two applications of atrazine on the water quality of freshwater enclosures. 

Environ. Pollut. 60:291-304 (MRID 47543501) 

17. Herman, D., N.K. Kaushik, and K.R. Solomon. (1986). Impact of atrazine on periphyton 

in freshwater enclosures and some ecological consequences. Can. J. Fish. Aquat. Sci. 

43:1917-1925 (MRID 47543502) 

18. Johnson, B.T. (1986). Potential impact of selected agricultural chemical contaminants on 

a northern prairie wetland: A microcosm evaluation. Environ. Toxicol. Chem. 5:473-

485. (MRID 47543503) 

10 
19. Jurgensen, T.A. and K.D. Hoagland. (1990). Effects of short-term pulses of atrazine on 

attached algal communities in a small stream. Arch. Environ. Contam. Toxicol. 19:617-

623. (MRID 47543504) 

20. Kettle, W.D. (1982). Description and analysis of toxicant-induced responses of aquatic 

communities in replicated experimental ponds. Ph.D. Thesis. University of Kansas, 

Lawrence, KS. (MRID 48273504) 

21. Kettle, W.D., F. deNoyelles, B.D. Heacock, and A.M. Kadoum. (1987). Diet and 

reproductive success of bluegill recovered from experimental ponds treated with atrazine. 

Bull. Environ. Contam. Toxicol. 38:47-52 (MRID 47543506) 

22. Kosinski, R.J. (1984). The effects of terrestrial herbicides on the community structure of 

stream periphyton. Environ. Pollut. (Series A). 36:165-189. (MRID 47543507) 

23. Kosinki, R.J., and M.G. Merkle. (1984). The effect of four terrestrial herbicides on the 

productivity of artificial stream algal communities. J. Environ. Qual. 13:75-82. (MRID 

47543508) 

24. Krieger, K.A., D.B. Baker, and J.W. Kramer. (1988). Effects of herbicides on stream 

Aufwuchs productivity and nutrient uptake. Arch. Environ. Contam. Toxicol. 17:299-

306. (MRID 47543509) 

25. Lampert, W., W. Fleckner, E. Pott, U. Schober, and K.U. Storkel. (1989). Herbicide 

effects on planktonic systems of different complexity. Hydrobiologia. 188/189:415-424. 

(MRID 47543511) 

26. Lynch, T.R., H.E. Johnson, and W.J. Adams. (1985). Impact of atrazine and 

hexachlorobiphenyl on the structure and function of model stream ecosystems. Environ. 

Toxicol. Chem. 4:399-413. (MRID 47543512) 

27. Moorhead, D.L. and R.J. Kosinski. (1986). Effect of atrazine on the productivity of 

artificial stream algal communities. Bull. Environ. Contam. Toxicol. 37:330-336. 

(MRID 47543513) 

28. Pratt, J.R., N.J. Bowers, B.R. Niederlehrer, and J. Cairns, Jr. (1988). Effects of atrazine 

on freshwater microbial communities. Arch. Environ. Contam. Toxicol. 17:449-457. 

(MRID 47543514) 

11 
29. Stay, F.S., Larsen, D.P., Katko, A., and Rohm, C.M., (1985) Effects of Atrazine on 

Community Level Responses in Taub Microcosms. Validation and Predictability of 

Laboratory Methods for Assessing the Fate and Effects of Contaminants in Aquatic 

Ecosystems, ATSM STP 865, T.P. Boyle, Ed., American Society for Testing and 

Materials, Philadelphia, pp. 75-90 (MRID 45087419) 

30. Stay, E.F., A. Katko, C.M. Rohm, M.A. Fix, and D.P. Larsen. (1989). The effects of 

atrazine on microcosms developed from four natural plankton communities. Arch. 

Environ. Contam. Toxicol. 18:866-875. (MRID 47543515) 

31. Van den Brink, P.J., E. van Donk, R. Gylstra, S.J.H. Crum, and T.C.M. Brock. (1995). 

Effects of chronic low concentrations of the pesticides chlorpyrifos and atrazine in indoor 

freshwater microcosms. Chemosphere. 31:3181-3200. (MRID 47543516) 

B. Studies Previously Used for Cosm Endpoint Selection that Failed Usability Criteria 

1. Carder, J.P. and K.D. Hoagland. (1998). Combined effects of alachlor and atrazine on 

benthic algal communities in artificial streams. Environ. Toxicol. Chem. 17(7):1415-

1420. (MRID 47543603) 

2. Fairchild, J.F., T.W. LaPoint, and T.R. Schwarz. (1994). Effects of a herbicide and 

insecticide mixture in aquatic mesocosms. Arch. Environ. Contam. Toxicol. 27:527-533 

(MRID 47543612) 

3. Juttner, I., A. Peither, J.P. Lay, Al. Ketrup, and S.J. Ormerod. (1995). An outdoor 

mescosm study to assess ecotoxicological effects of atrazine on a natural plankton 

community. Arch. Environ. Contam. Toxicol. 29:435-441. (MRID 47543505) 

4. Lakshminarayana, J.S.S., H.J. O’Neill, S.D. Jonnavithula, D.A. Legerand, P.H. Milburn. 

(1992). Impact of atrazine-bearing agricultural tile drainage discharge on planktonic drift 

of a natural stream. Environ. Pollut. 76:201-210. (MRID 47543510) 

C. New Studies Incorporated into Analysis as Recommended by the Science Advisory 

Panel 

1. Berard, A., C. Leboulanger, et al. (1999b). Tolerance of Oscillatoria limnetica 

Lemmermann to atrazine in natural phytoplankton populations and in pure culture: 

Influence of season and temperature. Archives of Environmental Contamination and 

Toxicology 37(4): 472-479. (MRID 47543601) 

12 
2. Berard, A. and C. Benninghoff (2001). Pollution-induced community tolerance (PICT) 

and seasonal variations in the sensitivity of phytoplankton to atrazine in nanocosms. 

Chemosphere 45(4-5): 427-437. (MRID 48261101) 

 

3. Boone, M. D. and S. M. James (2003). Interactions of an insecticide, herbicide, and 

natural stressors in amphibian community mesocosms. Ecological Applications 13(3): 

829-841. (MRID 48261104) 

4. Diana, S. G., W. J. Resetarits, et al. (2000). Effects of atrazine on amphibian growth and 

survival in artificial aquatic communities. Environmental Toxicology and Chemistry 

19(12): 2961-2967. (MRID 48261107) 

5. Downing, H. F., M. E. Delorenzo, et al. (2004). Effects of the agricultural pesticides 

atrazine, chlorothalonil, and endosulfan on South Florida microbial assemblages. 

Ecotoxicology 13(3): 245-260. (MRID 48261110) 

6. Knauert, S., B. Escher, et al. (2008). Mixture toxicity of three photosystem II inhibitors 

(atrazine, isoproturon, and diuron) toward photosynthesis of freshwater phytoplankton 

studied in outdoor mesocosms. Environmental Science & Technology 42(17): 6424-

6430. (MRID 48261119) 

7. Knauert, S., U. Dawo, et al. (2009). Effects of Photosystem II Inhibitors and Their 

Mixture on Freshwater Phytoplankton Succession in Outdoor Mesocosms. Environmental 

Toxicology and Chemistry 28(4): 836-845. (MRID 48261120) 

8. Leboulanger, C., F. Rimet, et al. (2001). Effects of atrazine and nicosulfuron on 

freshwater microalgae. Environment International 26(3): 131-135. (MRID 48261121) 

9. McGregor, E. B., K. R. Solomon, et al. (2008). Effects of planting system design on the 

toxicological sensitivity of Myriophyllum spicatum and Elodea canadensis to atrazine. 

Chemosphere 73(3): 249-260. (MRID 48261124) 

10. Relyea, R. A. (2009). A cocktail of contaminants: how mixtures of pesticides at low 

concentrations affect aquatic communities. Oecologia 159(2): 363-376. (MRID 

48261129) 

11. Rohr, J. R. and P. W. Crumrine (2005). Effects of an herbicide and an insecticide on pond 

community structure and processes. Ecological Applications 15(4): 1135-1147. (MRID 

48261130) 

12. Rohr, J. R., A. M. Schotthoefer, et al. (2008). Agrochemicals increase trematode 

infections in a declining amphibian species. Nature 455(7217): 1235-1239. (MRID 

48261131) 

13 
13. Seguin, F., J. C. Druart, et al. (2001a). Effects of atrazine and nicosulfuron on periphytic 

diatom communities in freshwater outdoor lentic mesocosms. Annales De LimnologieInternational Journal of Limnology 37(1): 3-8. (MRID 48273501) 

14. Seguin, F., C. Leboulanger, et al. (2001b). Effects of atrazine and nicosulfuron on 

phytoplankton in systems of increasing complexity. Archives of Environmental 

Contamination and Toxicology 40(2): 198-208. (MRID 48261134) 

15. Seguin, F., F. Le Bihan, et al. (2002). A risk assessment of pollution: induction of 

atrazine tolerance in phytoplankton communities in freshwater outdoor mesocosms, using 

chlorophyll fluorescence as an endpoint. Water Research 36(13): 3227-3236. (MRID 

48261133) 

D. New Studies Recommended by the Science Advisory Panel that Failed the Usability 

Criteria 

1. Berard, A., T. Pelte, et al. (1998). Characterisation of phytoplankton from two limnic 

systems contaminated by a herbicidal photosynthetic inhibitor. The PICT method 

(Pollution-Induced Community Tolerance): application and significance. Annales De 

Limnologie-International Journal of Limnology 34(3): 269-282. (MRID 48273502) 

2. Berard, A., U. Dorigo, et al. (2003). Comparison of the ecotoxicological impact of the 

triazines Irgarol 1051 and atrazine on microalgal cultures and natural microalgal 

communities in Lake Geneva. Chemosphere 53(8): 935-944. (MRID 48261102) 

3. Bouldin, J. L., J. L. Farris, et al. (2005). Evaluated fate and effects of atrazine and 

lambda-cyhalothrin in vegetated and unvegetated microcosms. Environmental 

Toxicology 20(5): 487-498. (MRID 48261105) 

4. DeLorenzo, M. E., J. Lauth, et al. (1999). Atrazine effects on the microbial food web in 

tidal creek mesocosms. Aquatic Toxicology 46(3-4): 241-251. (MRID 48261106) 

5. Dorigo, U. and C. Leboulanger (2001). A pulse-amplitude modulated fluorescence-based 

method for assessing the effects of photosystem II herbicides on freshwater periphyton. 

Journal of Applied Phycology 13(6): 509-515. (MRID 48261108) 

6. Dorigo, U., X. Bourrain, et al. (2004). Seasonal changes in the sensitivity of river 

microalgae to atrazine and isoproturon along a contamination gradient. Science of the 

Total Environment 318(1-3): 101-114. (MRID 48261109) 

7. Graymore, M., F. Stagnitti, et al. (2001). Impacts of atrazine in aquatic ecosystems. 

Environment International 26(7-8): 483-495. (MRID 48261111) 

8. Guasch, H., I. Munoz, et al. (1997). Changes in atrazine toxicity throughout succession of 

stream periphyton communities. Journal of Applied Phycology 9(2): 137-146. (MRID 

48261115) 

14 
9. Guasch, H., N. Ivorra, et al. (1998). Community composition and sensitivity of 

periphyton to atrazine in flowing waters: the role of environmental factors. Journal of 

Applied Phycology 10(2): 203-213. (MRID 48261113) 

10. Guasch, H. and S. Sabater (1998). Light history influences the sensitivity to atrazine in 

periphytic algae. Journal of Phycology 34(2): 233-241. (MRID 48261116) 

11. Guasch, H., W. Admiraal, et al. (2003). Contrasting effects of organic and inorganic 

toxicants on freshwater periphyton. Aquatic Toxicology 64(2): 165-175. (MRID 

48261112) 

12. Guasch, H., V. Lehmann, et al. (2007). Influence of phosphate on the response of 

periphyton to atrazine exposure. Archives of Environmental Contamination and 

Toxicology 52(1): 32-37. (MRID 48261114) 

13. Gustavson, K., F. Mohlenberg, et al. (2003). Effects of exposure duration of herbicides 

on natural stream periphyton communities and recovery. Archives of Environmental 

Contamination and Toxicology 45(1): 48-58. (MRID 48261117) 

14. Hoagland, K. D., R. W. Drenner, et al. (1993). Fresh-Water Community Responses to 

Mixtures of Agricultural Pesticides - Effects of Atrazine and Bifenthrin. Environmental 

Toxicology and Chemistry 12(4): 627-637. (MRID 48261118) 

15. Lytle, J. S. and T. F. Lytle (2002). Uptake and loss of chlorpyrifos and atrazine by Juncus 

effusus L. in a mesocosm study with a mixture of pesticides. Environmental Toxicology 

and Chemistry 21(9): 1817-1825. (MRID 48261122) 

16. Lytle, T. F. and J. S. Lytle (2005). Growth inhibition as indicator of stress because of 

atrazine following multiple toxicant exposure of the freshwater macrophyte, Juncus 

effusus L. Environmental Toxicology and Chemistry 24(5): 1198-1203. (MRID 

48261123) 

17. Munoz, I., M. Real, et al. (2001). Effects of atrazine on periphyton under grazing 

pressure. Aquatic Toxicology 55(3-4): 239-249. (MRID 48261125) 

18. Navarro, E., H. Guasch, et al. (2002). Use of microbenthic algal communities in 

ecotoxicological tests for the assessment of water quality: the Ter river case study. 

Journal of Applied Phycology 14(1): 41-48. (MRID 48261126) 

19. Nelson, K. J., K. D. Hoagland, et al. (1999). Chronic effects of atrazine on tolerance of a 

benthic diatom. Environmental Toxicology and Chemistry 18(5): 1038-1045. (MRID 

48261127) 

15 
16 

20. Nystrom, B., M. Paulsson, et al. (2000). Evaluation of the capacity for development of 

atrazine tolerance in periphyton from a Swedish freshwater site as determined by 

inhibition of photosynthesis and sulfolipid synthesis. Environmental Toxicology and 

Chemistry 19(5): 1324-1331. (MRID 48261128) 

21. Rimet, F., M. H. De Lacotte, et al. (1999). Atrazine and Nicosulfuron effects on 

phytoplanktonic communities of Lake of Geneva. Archives Des Sciences 52(2): 111-122. 

(MRID 48273503) 

22. Schmitt-Jansen, M. and R. Altenburger (2005). Predicting and observing responses of 

algal communities to photosystem II-herbicide exposure using pollution-induced 

community tolerance and species-sensitivity distributions. Environmental Toxicology and 

Chemistry 24(2): 304-312. (MRID 48261132) 

23. Van den Brink, P. J., S. J. H. Crum, et al. (2009). Effects of a herbicide-insecticide 

mixture in freshwater microcosms: Risk assessment and ecological effect chain. 

Environmental Pollution 157(1): 237-249. (MRID 48261135) 
17 

Attachment 3. Summary of Cosm Endpoints Used to Evaluate Potential Effects of Atrazine on Aquatic P

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Carney, 1983; Kettle et al., 1987; deNoyelles et al., 1989; deNoyelles et al., 1994 

500 365 Single 

Mesocoms, experimental ponds 

Decrease in cover by emerged, floating, and submerged aquatic plants (>90% decline in 

Typha; 100% decline in SAV). 

Macro 

> 1 yr (no recovery observed) 

Carney, 1983; Kettle et al., 1987; deNoyelles et al., 1989; deNoyelles et al., 1994; deNoyelles and Kettle, 1980; Dewey, 1986 

20 365 Single 

Mesocoms, experimental ponds 

Decrease in cover by floating and submerged aquatic plants (40% decline in Typha; 50% decline in SAV; 50% decline in Najas). 

Macro 

> 1 yr (no recovery observed) 

deNoyelles et al., 1982; deNoyelles et al., 1989 

500 63 Single 

Mesocoms, experimental ponds 

Decrease (> 90% decline) in phytoplankton 14C-uptake and biomass. 100% decline in SAV. Change (observed after 14 days) in species composition of phytoplankton. 

Phyto and Macro 

 > 63 d (no recovery reported for shift in species composition; recovery in phytoplankton biomass and production occurred > 3 

weeks) 
18 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

deNoyelles et al., 1989; Carney, 1983 

100 365 Single 

Mesocoms, experimental ponds 

Decrease in cover by emerged and submerged aquatic plants (75% decline in Typha; 80% decline in SAV). 

Macro 

> 1 yr (no recovery observed) 

deNoyelles et al., 1989; Carney, 1983 

200 340 Single 

Mesocoms, experimental ponds 

75-80% decline in Typha; >90% 

decline in SAV. 

Macro 

> 1 yr (no recovery observed) 

Hamilton et al., 1987 80 56 Multiple Lake enclosure 

60% decrease in density; 20% decrease in number of periphyton species; 80% decrease in periphyton biomass. Change (shift observed after 2nd day of exposure) in species composition. 

Peri 

49-50 d recovery for periphyton density and biomass; no recovery for periphyton numbers and shift in species composition. 

Hamilton et al., 1987 140 56 Multiple Lake enclosure 

60% decrease in density; 30% decrease in number of periphyton species; 75% decrease in biomass. Change (shift observed after 3rd day of exposure) in species composition. 

Peri 

>56 d recovery for periphyton density and biomass; no recovery for periphyton numbers and shift in species composition. 
19 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

 Hamilton et al., 1988 100 96 Multiple Lake enclosure 

Change in species composition (93% change in phytoplankton composition occurring on day 49 of study). 

Phyto >323 days 

Herman et al., 1986; Hamilton et al., 1989 

100 96 Multiple Lake enclosure 

40% decrease in POC at day 34; 80% decline in 

14C-uptake at day 

57; 10% - 20% decrease in DO, periphyton biomass (50%), chlorophyll (50%), productivity (70%), and community composition (100% decrease in Cyanophyta). Increase in secchi depth (30%), dissolved inorganic carbon (60%), and nitrite nitrogen (100%). 

Peri 

90 d; 14 d; >294 d; >294 d (POC recovery at 99 d; 14C-uptake 

recovery at 135 d; species comp recovery at >323 d) DO, secchi depth, and dissolved inorganic carbon recovered by the next spring (329 days); no recovery was observed for the other parameters evaluated. 
20 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Stay et al., 1985 430 53 Single 

Microcosms, laboratory Taub (pickle jars) 

60-70% decrease in DO; 90% decrease in 14Cuptake; <100% 

decrease in primary productivity (went negative); and 80% decrease in ratio of 14C to 

chl-a. 

Phyto 

> 53 d (no recovery observed) 

Stay et al., 1985 820 53 Single 

Microcosms, laboratory Taub (pickle jars) 

60-70% decrease in DO; 90% decrease in 14Cuptake; <100% 

decrease in primary productivity (went negative); and 80% decrease in ratio of 14C to 

chl-a. 

Phyto > 53 d 
21 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Stay et al., 1985 3980 53 Single 

Microcosms, laboratory Taub (pickle jars) 

60-70% decrease in DO; 90% decrease in 14Cuptake; <100% 

decrease in primary productivity (went negative); and 80% decrease in ratio of 14C to 

chl-a. 

Phyto > 53 d 

Brockway et al., 1984 100 7 Single Microcosms, lab stagnant 40% decrease in net oxygen production. Phyto > 7 d Brockway et al., 1984 500 12 Single Microcosms, lab stagnant 90% decrease in net oxygen production. Phyto >12 d Brockway et al., 1984 5000 12 Single Microcosms, lab stagnant 100% decrease in net oxygen production. Phyto > 12 d Detenback et al., 1996 15 15 Constant 

Artificial flowthrough swamp 

Decrease in DO and gross productivity (23% decrease in DO; reduction in gross productivity (p<0.05) not reported). Increase in nutrients (15% increase in PO4; 

15% increase in ammonium). 

Peri Recovery not reported. 
22 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Detenback et al., 1996 25 43 Constant 

Artificial flowthrough swamp 

Decrease in periphyton respiration and net productivity (reduction in respiration and net primary productivity (p<0.05) not reported). 

Peri Recovery not reported. 

Detenback et al., 1996 50 32 Constant 

Artificial flowthrough swamp 

Decrease (reduction in net productivity (p <0.05)) not reported. Increase in nutrients (40% increase in PO4; 

100% increase in ammonium). 

Peri Recovery not reported. 

Detenback et al., 1996 79 17 Constant 

Artificial flowthrough swamp 

Decrease (reduction in net productivity (p <0.05)) not reported. Increase in nutrients (50% increase in PO4; 

250% increase in ammonium). 

Peri Recovery not reported. 
23 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Hamala and Kollig, 1985 100 14 Constant Microcosm, lab flowing 

Decrease in primary production (100% reduction in productivity (became negative); 25% reduction in number of species; 50% reduction in biomass). Change in species composition (35% decrease in chlorophyta abundance observed at day 14). 

Peri >14 d to > 21 d 

Johnson, 1986 1000 30 Single Microcosm, lab stagnant 

Decrease in macrophyte biomass (50%); primary production (90%); increase in alkalinity (approx. 2-fold). Slight decrease in pH (10%) and increase in conductivity (20%). 

Macro >30 d 
24 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Kosinski, 1984; Kosinski and Merkle, 1984 

10 21 Single 

Artificial streams, recirculating 

40% decrease in apparent primary productivity; slight decrease in biovolume. 

Peri 

>21 d (primary production); <7 days (biovolume) 

Kosinski, 1984; Kosinski and Merkle, 1984 

1000 21 Single 

Artificial streams, recirculating 

50% decrease in apparent primary productivity; 10% reduction in biovolume. 

Peri 

> 21 d (primary productivity); 14 d (biovolume) 

Kosinski, 1984; Kosinski and Merkle, 1984 

10000 21 Single 

Artificial streams, recirculating 

70% decrease in apparent primary productivity; 20% to 25% reduction in biovolume. 

Peri > 21 d 
25 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Krieger et al., 1988 24 12 Constant 

Artificial streams, recirculating 

Decrease in biomass (24% reduction) and chlorophyll-a (30% reduction). Slight decrease (21%, not statistically significant) in nitrate uptake. No effect on dissolved silica uptake or phosphorus uptake rate. 

Peri None 

Krieger et al., 1988 134 12 Constant 

Artificial streams, recirculating 

Decrease in biomass (31% reduction), chlorophyll-a (44% reduction), and nitrate uptake (25%). No effect on dissolved silica uptake; possible slight effect (8%) on phosphorus uptake rate. 

Peri None 
26 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Moorhead and Kosinski, 1986 10000 7 Single 

Artificial streams, recirculating 

Community productivity was decreased by approximately 18-fold relative to controls and Nitzschia abundance was reduced by approx. 60%. Water quality parameters (conductivity, alkalinity, soluble reactive phosphorus, and pH), respiration, and changes in non-Nitzschia algal abundance were not affected. 

Peri >7 d 

Pratt et al., 1988 337 21 Constant 

Microcosms, laboratory flowing 

Statistically significant decreases in DO (30%), number of species (15%), chlorophyll-a (90%), protein biomass of protozoa (40%), potassium (45%), magnesium (20%), and calcium (15%). 

Peri > 21 d 
27 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Stay et al., 1989 204 (initial measured) 42 Single Microcosms, laboratory Leffler 

30% decrease in pH; 80% decrease in primary production; no effect on dark respiration or heterotrophic activity. 

Phyto 42 - >42 d 

Stay et al., 1989 500 42 Single 

Microcosms, laboratory Leffler 

30% decrease in pH; 120% decrease in primary production; no effect on dark respiration or heterotrophic activity. 

Phyto > 42 d 

Stay et al., 1989 1000 42 Single 

Microcosms, laboratory Leffler 

Decrease in pH and primary production (magnitude not specified); no effect on dark respiration or heterotrophic activity. 

Phyto > 42 d 

Stay et al., 1989 5000 42 Single 

Microcosms, laboratory Leffler 

Decrease in pH and primary production (magnitude not specified); no effect on dark respiration or heterotrophic activity. 

Phyto > 42 d 
28 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Brockway et al., 1984 50 55 Constant 

Microcosms, lab continuous flow 

Approx. 30% decrease in oxygen production and 50% increase in dissolved nitrate concentration. 

Phyto >55 d 

Brockway et al., 1984 100 15 Constant 

Microcosms, lab continuous flow 

Approx. 40% decrease in oxygen production and approx. 65% increase in dissolved nitrate concentration. 

Phyto >15 d 
29 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

deNoyelles et al., 1989 100 360 Single 

Mesocoms, experimental ponds 

Decrease (>90% decline) in 14Cuptake and 

biomass of phytoplankton. 

Phyto > 21 d 

deNoyelles et al., 1989 200 360 Single 

Mesocoms, experimental ponds 

Decrease (>90% decline) in 14Cuptake and 

biomass of phytoplankton. 

Phyto > 21 d 

Kosinski, 1984; Kosinski and Merkle, 1984 

100 21 Single 

Artificial streams, recirculating 

30% decrease in apparent primary productivity; no affect on biovolume. 

Peri < 3 d 

Moorhead and Kosinski,1986 100 7 Single 

Artificial streams, recirculating 

Community productivity was decreased by approximately 8-fold relative to controls. Water quality parameters (conductivity, alkalinity, soluble reactive phosphorus, and pH), respiration, and changes in algal abundance were not affected. 

Peri 7 d 
30 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Moorhead and Kosinski, 1986 1000 7 Single 

Artificial streams, recirculating 

Community productivity was decreased by approximately 8-fold relative to controls. Water quality parameters (conductivity, alkalinity, soluble reactive phosphorus, and pH), respiration, and changes in algal abundance were not affected. 

Peri >7 d 

Stay et al., 1985 53 53 Single 

Microcosms, laboratory Taub (pickle jars) 

40% reduction in 

14C-uptake; 15-

20% reduction in DO; 60% reduction in net primary productivity; and ~50% reduction in 

14C-uptake/chl-a. 

Phyto 21 - 32 d; 53 d 
31 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Stay et al., 1985 84 53 Single 

Microcosms, laboratory Taub (pickle jars) 

55% reduction in 

14C-uptake; 20-

30% reduction in DO; 55% reduction in net primary productivity; and ~55% reduction in 

14C-uptake/chl-a. 

Phyto 28 - 32 d; 53 d 

Stay et al., 1985 170 53 Single 

Microcosms, laboratory Taub (pickle jars) 

70% reduction in 

14C-uptake; 45-

55% reduction in DO; 100% reduction in net primary productivity; and ~65% reduction in 

14C-uptake/chl-a. 

Phyto 28 - 32 d; 53 d 
32 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Stay et al., 1989 100 42 Single 

Microcosms, laboratory Leffler 

Decrease in pH (20%) and primary production (50%). Dark respiration and heterotrophic activity were not affected by treatment. 

Phyto 7 - >42 d 

Brockway et al., 1984 50 12 Single Microcosms, lab stagnant 

Approx. 25% reduction in oxygen production. 

Phyto > 12 d 

deNoyelles et al., 1982; deNoyelles et al., 1989 

20 63 Single 

Mesocoms, experimental ponds 

Decrease (50% decline) in 14Cuptake and 

biomass of phytoplankton. 

Phyto 

 > 3 wks for 

biomass and 

14C-uptake 

Johnson, 1986 10 30 Single Microcosm, lab stagnant 

No effect on macrophyte biomass, conductivity, pH, or alkalinity. Slight (20%) decrease in gross primary productivity at the first measurement. However, this observation did not appear to be related to atrazine treatment. 

Macro 7 d 
33 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Johnson, 1986 100 30 Single Microcosm, lab stagnant 

No effect on macrophyte biomass, conductivity, pH, or alkalinity. Slight (30%) decrease in gross primary productivity. However, this observation did not appear to be related to atrazine treatment. 

Macro 7 d 

Lampert et al., 1989 1 18 Single Lake enclosure 50% decrease in chlorophyll-a and oxygen saturation. Phyto >18 d Lampert et al., 1989 0.1 21 to 42 Single Lake enclosure 

Decrease in photosynthesis rate (1 of 2 replicates in coldwater experiment only, 60% decline) and oxygen saturation (approx. 40% reduction). No clear effect on chlorophyll-a levels. 

Phyto 

>42 d (oxygen) >25 d (photosynthetic rate) 
34 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Pratt et al., 1988 32 (mean measured) 21 Constant Microcosms, laboratory flowing 

35% decrease in DO (statistically significant); slight reductions in magnesium and calcium levels. No effect on number of species, chlorophyll-a, protein biomass of protozoa, or potassium. 

Peri > 21 d 

Pratt et al., 1988 110 (mean measured) 21 Constant Microcosms, laboratory flowing 

35% decrease in DO; 60% reduction in chlorophyll-a (not statistically significant); slight reductions in magnesium and calcium levels. No effect on potassium, number of species, or protein biomass of protozoa. 

Peri > 21 d 

Stay et al., 1989 20 42 Single 

Microcosms, laboratory Leffler 

Slight (10%) decrease in primary production. No effect on pH, respiration, or heterotrophic activity. 

Phyto 1-10 d 
35 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

van den Brink et al., 1995 5 35 Constant Microcosms, laboratory 

Slight decrease in photosynthetic activity, as indicated by higher conductivity and alkalinity, and lower DO and pH. 

Phyto Not applicable 

Brockway et al., 1984 0.5 7 Single Microcosms, lab stagnant No effect on oxygen production. Phyto Not applicable Brockway et al., 1984 5 7 Single Microcosms, lab stagnant No effect on oxygen production. Phyto Not applicable Brockway et al., 1984 0.5 29 Constant 

Microcosms, lab continuous flow 

No effect on oxygen production. 

Phyto Not applicable 

Brockway et al., 1984 5 70 Constant 

Microcosms, lab continuous flow 

Oxygen production was slightly reduced from days 10 to 45. Oxygen production was typically within 90% of controls, but was approximately 80% of controls for about 7 days during the first month of the study. 

Phyto Approx. 45 d 
36 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Gruessner and Watzin, 1996 5 14 

Single with decreasing conc. 

Microcosm, lab 

No effect on chl-a of periphyton on artificial substrate. 

Peri Not applicable 

Gustavson and Wängberg, 1995 1 20 Single Lake enclosure No effect on community tolerance. Phyto and Peri Not applicable Gustavson and Wängberg,1995 20 20 Single Lake enclosure No effect on community tolerance. Phyto and Peri Not applicable Gustavson and Wängberg, 1995 10 20 Single Lake enclosure No effect on community tolerance. Phyto and Peri Not applicable Jurgensen and Hoagland, 1990 2 28 

2 short pulses of 24-hours @ day 1 and 14 

Stream enclosures 

No effect on cell density or biomass. 

Peri Not applicable 
37 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Jurgensen and Hoagland, 1990 30 28 

2 short pulses of 24-hours @ day 1 and 14 

Stream enclosures 

No effect on cell density or biomass. 

Peri Not applicable 

Jurgensen and Hoagland, 1990 100 28 

2 short pulses of 24-hours @ day 1 and 14 

Stream enclosures 

No effect on cell density or biomass. 

Peri Not applicable 

Lynch et al., 1985 25 

30 (4 30-d 

exposures 

with 60-d 

intervals 

b/w 

exposures) 

Constant/ Multiple (see comment) 

Artificial streams, laboratory 

No effect on standing biomass, rate of primary production, or community respiration. 

Peri Not applicable 
38 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Pratt et al., 1988 3.2 (mean measured) 21 Constant Microcosms, laboratory flowing 

No effect on DO, chlorophyll-a, protein biomass of protozoa, number of species, magnesium, calcium, or potassium. 

Peri Not applicable 

Pratt et al., 1988 10 (mean measured) 21 Constant Microcosms, laboratory flowing 

No effect on DO, chlorophyll-a, protein biomass of protozoa, number of species, magnesium, calcium, or potassium. 

Peri Not applicable 

Rohr and Crumrine, 2005 25 30 Multiple 

Mesocosms, experimental ponds 

Reduction in periphyton chlorophyll-a 

(15.2%). 

Peri Recovery not reported 
39 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Rohr et al., 2008 117 28 Single 

Mesocosms, experimental ponds 

Reduction in phytoplankton chlorophyll-a (65%) and increase in periphyton chlorophyll-a (49%). 

Peri and Phyto 

Recovery not reported 

Relyea, 2009 6.4 36 Single 

Outdoor mesocosms, experimental ponds 

No effect to phytoplankton chlorophyll-a, periphyton biomass, and dissolved oxygen. 

Peri and Phyto 

Not applicable 
40 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Knauert et al., 2008; Knauert et al., 2009 

84 173 Multiple 

Outdoor mesocosms, experimental ponds 

Inhibition of phytoplankton photosynthetic activity (51.4%) at day 2. Average inhibition of photosynthetic activity from day 0-34 was 45.6%. Change in phytoplankton community structure. 

Phyto 

No recovery (compared to control ponds, atrazine resulted in statistically significant effects on photosynthesis and differences in phytoplankton species composition until the end of the experiment at day 173). 
41 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Berard et al., 1999a, Berard et al., 1999b, Berard and Benninghoff, 2001, Sequin et al., 2001b, Leboulanger et al., 2001 

10 10 to 23 Single 

Experimental outdoor microcosms 

Change in phytoplankton biomass and community structure (species and higher taxonomic groupings composition, species diversity (Shannon index), and Bray-Curtis index). 

Phyto Recovery not reported 
42 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Seguin et al., 2001a 30 40 Single 

Outdoor mesocosms, experimental ponds 

Increase (61%) in periphyton chlorophyll-aconcentration at Day 40. 

Peri Recovery not reported 

Seguin et al., 2001a 2 40 Single 

Outdoor mesocosms, experimental ponds 

No effect Peri Not applicable 

Seguin et al., 2001b 30 40 Single 

Experimental outdoor mesocosms 

Change in phytoplankton community structure (change in Bray-Curtis index starting on day 2 and increased Chrysophyceae abundance of unknown magnitude on day 40). 

Phyto Recovery not reported 

Seguin et al., 2001b 2 40 Single 

Experimental outdoor mesocosms 

Increased Chrysophyceae abundance on day 40 (unknown magnitude). 

Phyto Recovery not reported 
43 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Seguin et al., 2002 30 25 Single 

Experimental outdoor mesocosms 

Decrease in chlorophyll-a(22%) and dry weight (30%); change in community structure and Bray-Curtis similarity index; decrease in DO (20%). 

Phyto No 
44 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Downing et al., 2004 148 7 Single Laboratory microcosms 

Decrease in chlorophyll-a (30-40%), primary productivity (~60%), and change in phytoplankton composition (~20% decrease in diatoms, ~25% decrease in bluegreen algae, ~30% decrease in green algae, ~75% decrease in brown algae, ~30% decrease in total phytoplankton). 

Phyto Recovery not reported 

Downing et al., 2004 24.3 7 Single Laboratory microcosms 

Decrease in chlorophyll-a(~35%) and change in phytoplankton composition (~15% decrease in diatoms, ~5% decrease in green algae, ~25% decrease in brown algae, ~10% decrease in total phytoplankton). 

Phyto Recovery not reported 
45 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Boone and James, 2003 207 25 Single 

Outdoor mesocosms, experimental ponds 

No clear treatment-related effects. 

Phyto Not applicable 
46 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Diana et al., 2000 20 51 Single Outdoor microcosms No clear treatment-related effects. Macro and Phyto Not applicable Diana et al., 2000 196 51 Single Outdoor microcosms 

98% decrease in macrophyte biomass; 3-fold increase in phytoplankton chlorophyll-a on day 14; approximate 60% reduction in predusk DO levels at day 1. 

Macro and Phyto 

No – chlorophyll-a increase was observed from day 14 to study termination; DO did not recover, and biomass was only measured at study termination. 
47 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

Diana et al., 2000 2036 51 Single Outdoor microcosms 

99% decrease in macrophyte biomass; 2-fold increase in phytoplankton chlorophyll-a; approximate 80% reduction in predusk DO levels at day 1. 

Macro and Phyto 

No - biomass was only measured at study termination, and DO levels did not recover. However, chlorophyll concentrations were similar to control by day 42. 

McGregor et al., 2008 25 42 Single Outdoor microcosms No effect on dissolved oxygen. Macro and Phyto Not applicable 
48 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

McGregor et al., 2008 50 42 Single Outdoor microcosms No effect on dissolved oxygen. Macro and Phyto Not applicable McGregor et al., 2008 100 42 Single Outdoor microcosms 35% decrease in DO at day 1. Macro and Phyto No 
49 

Reference(s) 

Initial Test 

Concentration 

(μg/L) 

Duration 

(d) 

Single / Constant / Multiple 

Ecosystem Results Plant Group Recovery 

McGregor et al., 2008 250 42 Single Outdoor microcosms 50% decrease in DO at day 1. Macro and Phyto No