title: Seasonal synchronicity of algal assemblages in three Midwestern agricultural streams having varying concentrations of atrazine, nutrients, and sediment.
abstract: Numerous studies characterizing the potential effects of atrazine on algal assemblages have been conducted using micro- or mesocosms; however, few evaluations focused on in situ lotic algal communities, potentially confounding risk assessment conclusions. This exploratory study, conducted at several sites in the midwestern United States where atrazine is commonly used, presents in situ observations of native algal communities relative to atrazine exposure and other parameters. Planktonic and periphytic algae from three streams in three Midwestern states, having historically differing atrazine levels, were sampled over a 16-week period in 2011 encompassing atrazine applications and the summer algal growth period at each site. Changes in abundance, diversity, and composition of algal communities were placed in the context of hydrological, climatic, and water quality parameters (including components sometimes present in agricultural runoff) also collected during the study. Diatoms dominated communities at each of the three sites and periphyton was much more abundant than phytoplankton. As expected, significant variations in algal community and environmental parameters were observed between sites. However, correspondence analysis plots revealed that patterns of temporal variation in algal communities at each site and in periphyton or phytoplankton were dominated by seasonal environmental gradients. Significant concordance in these seasonal patterns was detected among sites and between phytoplankton and periphyton communities (via procrustes Protest analysis), suggesting synchronicity of algal communities across a regional scale. While atrazine concentrations generally exhibited seasonal trends at the study watersheds; no effects on algal abundance, diversity or assemblage structure were observed as a result of atrazine pulses. This lack of response may be due to exposure events of insufficient concentration or duration (consistent with previously reported results) or the composition of the algal assemblages present. This was in contrast to the effects of elevated flow events, which were associated with significant changes in periphyton abundance, diversity and assemblage.
authors: Waterborne Environmental, Inc., 2001 South First Street, Suite 109, Champaign, IL 61820, USA. andrusm@waterborne-env.com
authors: J Malia
authors: JM
authors: Andrus
authors: Diane
authors: D
authors: Winter
authors: Michael
authors: M
authors: Scanlan
authors: Sean
authors: S
authors: Sullivan
authors: Wease
authors: W
authors: Bollman
authors: J B
authors: JB
authors: Waggoner
authors: Alan J
authors: AJ
authors: Hosmer
authors: Richard A
authors: RA
authors: Brain
mesh_terms: D018533:Biomass; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D017377:Diatoms / Q000254:growth & development*; D017753:Ecosystem; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D007087:Illinois; D007484:Iowa; D008923:Missouri; D009566:Nitrates / Q000032:analysis; D010100:Oxygen / Q000032:analysis; D010839:Phytoplankton / Q000254:growth & development*; D011157:Population Dynamics; D045483:Rivers / Q000737:chemistry / Q000382:microbiology*; D012621:Seasons; D013696:Temperature
chemical_list: D009566:Nitrates; D002734:Chlorophyll; D010100:Oxygen; D000077194:Chlorophyll A