Variation partitioning of benthic diatom community matrices: Effects of multiple variables on benthic diatom communities in an Austral temperate river system Tatenda Dalu a,b, ⁎, Ryan J. Wasserman c,b , Mandla L. Magoro b,d,e , Tongayi Mwedzi f , P. William Froneman a , Olaf L.F. Weyl b a Zoology and Entomology, Rhodes University, Grahamstown 6140, South Africa b South African Institute for Aquatic Biodiversity, Grahamstown 6140, South Africa c School of Science, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor Darul Ehsan, Malaysia d DST/NRF Shallow Water Ecosystems Laboratory, Nelson Mandela Metropolitan University, Port Elizabeth 6031, South Africa e Botany, Nelson Mandela Metropolitan University, Port Elizabeth 6031, South Africa f Department of Wildlife Ecology and Conservation, Chinhoyi University of Technology, P Bag 7724, Chinhoyi, Zimbabwe HIGHLIGHTS • We explored diatom dynamics in modi- fied river system with inconsistent river flow. • Seasonal diatom composition was driven by nutrient loads and metal con- centrations. • Temporal variation in communities was observed in smaller systems over time. • Differences in stream and mainstream sites were pronounced than canals and streams. GRAPHICAL ABSTRACT abstract article info Article history: Received 24 March 2017 Received in revised form 17 May 2017 Accepted 17 May 2017 Available online xxxx Editor: D. Barcelo This study explores diatom community dynamics in a highly modified semi-arid temperate region river system characterised by inconsistent river flow. Various water and sediment environmental variables were assessed using a multi-faceted analysis approach to determine the spatio-temporal drivers of benthic diatom communities in the river system. Overall, the diatom community was generally dominated by pollution tolerant species, reflecting the anthropogenic intensity and activities on the river system. Diatom community composition was found to be largely determined by water column chemistry variables particularly nutrient concentrations in com- parison to sediment chemistry and physical variables. Strong seasonal diatom species composition was also ob- served and this was driven by strong seasonal variations in nutrient loads and metal concentrations, a result of the variable water flow across the two seasons. However, the greater temporal variation in communities was ob- served in the smaller systems with the mainstream river system being more homogenous over time. In addition, diatom community composition and environmental variables were found to be different and more pronounced between streams and mainstream sites, than between canals and streams. The study highlights the complex in- teraction between water column, sediment and physical variables in determining the diatom species Keywords: Benthic diatom Community composition Indicators River flow inconsistency Urban Science of the Total Environment 601–602 (2017) 73–82 ⁎ Corresponding author at: Zoology and Entomology, Rhodes University, Grahamstown 6140, South Africa. E-mail address: dalutatenda@yahoo.co.uk (T. Dalu). http://dx.doi.org/10.1016/j.scitotenv.2017.05.162 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