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 monitori ng program data collection location.

Table 1 : Peak and 60-day maximum running average concentrations ( μ g/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 c ontribute 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 re served 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. Implicati ons 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 phytoplankt on 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 eug lenophyta 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 comm unities 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 ar e 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 pe ak and average concentrations may contribute to the similarity of the aquati c 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 c hronology 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'