The contribution of volunteer-based monitoring data to the assessment of harmful phytoplankton blooms in Brazilian urban streams Davi Gasparini Fernandes Cunha a, ⁎, Simone Pereira Casali a , Patrícia Bortoletto de Falco b , Ian Thornhill c , Steven Arthur Loiselle c a Departamento de Hidráulica e Saneamento, Escola de Engenharia de São Carlos, Universidade de São Paulo, Avenida Trabalhador São-Carlense, 400, CEP 13566-590 São Carlos, SP, Brazil b Departamento de Ciências Ambientais, Universidade Federal de São Carlos, Rodovia Washington Luiz, km 235, CEP 13565-905, São Carlos, SP, Brazil c Earthwatch Institute, Mayfield House, 256 Banbury Rd, Oxford OX2 7DE, United Kingdom HIGHLIGHTS • Data from Brazilian urban streams were successfully collected by trained volun- teers. • Relatively high nutrient and turbidity levels were observed in the streams. • Pollution sources and riparian vegeta- tion were related to phytoplankton abundance. • Phytoplankton densities and phosphate (not nitrate) were positively correlated. • Thresholds for Cyanobacteria blooms were established based on volunteers' data. GRAPHICAL ABSTRACT abstract article info Article history: Received 11 August 2016 Received in revised form 12 January 2017 Accepted 13 January 2017 Available online xxxx Editor: Jay Gan Urban streams are vulnerable to a range of impacts, leading to the impairment of ecosystem services. However, studies on phytoplankton growth in tropical lotic systems are still limited. Citizen science approaches use trained volunteers to collect environmental data. We combined data on urban streams collected by volunteers with data obtained by professional scientists to identify potential drivers of phytoplankton community and determine thresholds for Cyanobacteria development. We combined datasets (n = 117) on water quality and environmen- tal observations in 64 Brazilian urban streams with paired data on phytoplankton. Sampling activities encompassed dry (July 2013 and July 2015) and warm (February and November 2014) seasons. Volunteers quantified phosphate (PO 4 3- ), nitrate (NO 3 - ) and turbidity in each stream using colorimetric and optical methods and recorded environmental conditions in the immediate surroundings of the sites through visual observations. We used non-parametric statistics to identify correlations among nutrients, turbidity and phytoplankton. We also looked for thresholds with respect to high Cyanobacteria abundance (N 50,000 cells/mL). The streams were characterized by relatively high nutrient concentrations (PO 4 3- : 0.11 mg/L; NO 3 - : 2.6 mg/L) and turbidity (49 NTU). Phytoplankton densities reached 189,000 cells/mL, mainly potentially toxic Cyanobacteria species. Moder- ate but significant (p b 0.05) correlations were observed between phytoplankton density and turbidity (ρ = 0.338, Spearman) and PO 4 3- (ρ = 0.292), but not with NO 3 - . Other important variables (river flow, temperature and light) were not assessed. Volunteers' observations covaried with phytoplankton density (p b 0.05, Kruskal- Wallis), positively with increasing number of pollution sources and negatively with presence of vegetation in Keywords: Citizen science Cyanobacteria Eutrophication Nutrients Urban water bodies Science of the Total Environment xxx (2017) xxx–xxx ⁎ Corresponding author. E-mail address: davig@sc.usp.br (D.G.F. Cunha). STOTEN-21793; No of Pages 9 http://dx.doi.org/10.1016/j.scitotenv.2017.01.080 0048-9697/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Please cite this article as: Cunha, D.G.F., et al., The contribution of volunteer-based monitoring data to the assessment of harmful phytoplankton blooms in Brazilian urban streams, Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.01.080