Epilithic diatom flora in contrasting land-use settings in tropical streams, Manyame Catchment, Zimbabwe

The objective of this study was to evaluate the response of stream diatom assemblages to changes in water quality in different land-use settings. Water quality sampling and benthic diatom community data were collected in April and September 2013 at 95 sampling stations in the Manyame Catchment, Zimbabwe. The data collected were subjected to multivariate statistical techniques; CCA and cluster analysis to determine environmental gradients along which the diatom species were distributed as well as to elucidate hypothesized differences in community structure per land-use type. Three land-use categories were identified in this study: commercial agricultural, communal agricultural and urban-mining areas in order of increasing human disturbance. No significant differences in physical and chemical variables were recorded between the two sampling periods. Study sites were grouped into roughly three broad categories based on CCA and cluster analysis. As pollution increased, low to moderate pollution tolerant species such as Cocconeis placentula, Surirella linearis and Surirella robusta were replaced by high pollution tolerant species such as Pinnularia braunii, Tryblionella coarcata, Luticola goeppertiana and Stauroneis smithii. This shows that diatom assemblages are potential indicators of changes in water quality due to changes in catchment land-use