Open Literature Review Summary 

Chemical Name: Atrazine

CAS No: 1912-24-9

PC Code: 080803

ECOTOX Record Number and Citation: 

Andrus, J.M., D. Winter, M. Scanlan, S. Sullivan, W. Bollman, J.B. Waggoner, A.J. Hosmer, R.A. Brain. 

2013. Seasonal synchronicity of algal assemblages in three Midwestern agricultural streams having 

varying concentrations of atrazine, nutrients and sediment. Science of the Total Environment 458-460: 

125-139.

Date of Review: February 18, 2016

- This research article describes the seasonal and environmental factors that were found to 

be potentially influencing changes in aquatic plant communities that have recorded 

atrazine exposures. 

- The study sites were selected from a few of the AEEMP monitoring program watersheds 

(IA-03, IL-10, MO-05). Community sampling sites were selected at one location at the 

point closest to the AEEMP monitoring program data collection location. 

Table 1: Peak and 60-day maximum running average concentrations (μg/L) of measured atrazine 

concentrations reported in the AEEMP monitoring program (EPA calculated averages). 

Year IA-03 IL-10 MO-05 

Peak 60-day Avg Peak 60-day Avg Peak 60-day Avg 

2010 50.6 10.5 5.0 0.4 84.2 12.9 

2011 39.8 4.9 11.5 1.4 70.5 6.2 

- The study collected data relevant to assessing the diversity and community composition, 

as well as abiotic factors that may contribute to changes in the community. 

- The study adequately sampled for abiotic environmental factors. 

- The algal community sampling was primarily done in a robust manner given the study 

objectives, with the following concerns: 

o Different volumes of water were taken to evaluate phytoplankton samples, thus it 

is unclear how changes in the phytoplankton diversity, AFDM, chl-a, and 

community composition may be impacted by the different sample sizes. 

o Periphyton collection using periphytometers submerged at a depth of 5 cm may 

not reflect changes in the stream bed periphyton communities. 

o It was not reported how often or in which localities the periphytometers were 

found above the water surface (dried out), damaged, or incorrectly positioned. 

The authors briefly mention the sue of the reserved periphytometer in those but it 

is not clear in the report how often the reserved periphytometers were relied upon 

or if they showed different communities from the primary periphytometers at the 

same site locations. 
o It is unclear how selection of periphyton samples for chl-a, AFDM and taxonomic 

identification was made to avoid potential sampling bias. 

o Chl-a levels for phytoplankton were below detection limits. The report indicates 

that instream optical chlorophyll probes were relied upon for two streams, but 

these were not identified, and impacts on comparisons between the glass fiber 

filters and the optical probes were not provided to evaluate potential sampling 

method differences. 

o Different water volumes were used to evaluate the taxonomic phytoplankton 

composition of the non-diatom (10 ml subsample) and diatoms (250 ml 

subsample) components. Implications of this difference are unknown. 

Results 

- Abundance 

o Periphyton was most abundant at the MO-05 site and least at the IA-03 site. 

o All three sites were dominated by diatom taxa in periphyton. 

o Periphyton diatom densities were greatest at MO-05 and least at IL-10. 

o In phytoplankton, densities of diatoms were similar to total non-diatom taxa, but 

were the most abundant compared to any individual group of non-diatom taxa. 

o Non-diatom taxon densities in phytoplankton were highest at IA-03 and least at 

MO-05. 

o Non-diatom groups were dominated by chlorophyta, cyanophyta, cyanophyta, and 

euglenophyta. 

o Cyanophyta, raphidophyta and dinophyta were much less abundant.

o Abundance of individual groups changed temporally

o Increased flow rates reduced euglenophyta and cyanophyta densities.

o Potential decreased productivity (measured by DO) was observed at MO-05 after 

the atrazine runoff events.

- Diversity

o No differences in univariate diversity metrics between sample replicates, 

o Statistically significant differences between three sites

 This was reported to not be associated with atrazine concentration

 High flow events attributed to the differences

- Patterns in communities

o Greatest similarity in phytoplankton communities is shared between IA-03 and 

MO-05.

o Significant changes within each site over time, thus a seasonality of the 

community structure was observed

o Substantial changes in the communities are not observed after the atrazine peaks, 

suggesting the 2011 exposures may not have been a major factor in the 

community structure or seasonal pattern of changes (synchronicity) in these 

streams in 2011.
Author Conclusions 

- Abundance 

o IA-03 and MO-05 similar atrazine peak and average concentrations may 

contribute to the similarity of the aquatic plant compositions in these sites as 

compared to IL-10. 

o High flow at IL-10 could also explain the difference of this site from the other 

two. 

- Seasonality 

o The algal communities are changing with the seasons, and these changes are 

similar across the study sites 

o Stream flow, NO2+NO3, total phosphorus, solar radiation, pH, wind speed, 

alkalinity and hardness, and atrazine concentration showed substantial vector 

projection in the direction of the chronology CA plots for all sites. 

o Attribute primary changes in community changes to seasonality and flow. 

- Atrazine Effects 

o Major deviations in overall abundance and diversity metrics and community 

structure did not follow atrazine peak exposures 

o No decreases in chlorophyta cell density immediately following atrazine pulses at 

any site. 

o Lack of response to atrazine pulses in the evaluated systems may be a result of 

community composition and sensitivity. Sites are dominated by diatoms which 

tend to be less sensitive than the green algae and cyanophyta. Many of the 

diatoms identified are known as pollution tolerant species suggesting that these 

communities are less sensitive to anthropogenic disturbances. 

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

Rationale for Use: The study contributes to the understanding of aquatic plant community 

composition and seasonal dynamics within streams exposed to atrazine at various concentrations 

and durations. 

Limitations: The primary limitation in this study is the lack of a set of reference streams which 

have had limited or no atrazine exposure. The three streams selected have some of the lowest 

atrazine concentrations of the AEEMP program (see table 1). The streams have peak values that 

reach toxic levels for individual species, and 60-day average concentrations for IA-03 and MO05 exceed the 2009 CELOC of 3 ug/L for the 2010 and 2011 monitoring years. However, these 

exceedances of the CELOC represent a 50% chance of an effect on the communities, so not 

seeing a strong and direct atrazine influence in the study results is not unanticipated. 

Primary Reviewer: Frank T. Farruggia Ph.D., EPA/OCSPP/OPP/EFED/ERB3 

Digitally signed by FRANK 

FARRUGGIA 

DN: c=US, o=U.S. Government, 

ou=USEPA, ou=Staff, cn=FRANK 

FARRUGGIA, 

dnQualifier=0000048865 

Date: 2016.03.24 08:58:02 -04'00'