Diatoms as water quality indicators in the upper reaches of the Great Fish River, Eastern Cape, South Africa
Abstract
This study focused on the spring-fed upper reaches of the economically important Great Fish River with the aim of
determining if diatoms could be used for biomonitoring in semi-arid conditions in southern Africa. Five sites were
monitored monthly from 2010 to 2012. Of the 269 diatom taxa belonging to 51 genera identified, the dominant taxa
were mostly those considered to be pollution-tolerant: Amphora pediculus, Craticula buderi, Fragilaria biceps,
Nitzschia frustulum, Nitzschia paleacea, Planothidium lanceolatum and Rhopalodia gibba. A number of diatombased
numerical indices were used to infer water quality, including the generic diatom index, the specific pollution
sensitivity index, the biological diatom index, and percentage pollution-tolerant valves, which forms part of the
UK trophic diatom index. All index scores showed the Great Fish River to be impacted, and showed significant
correlations of diatom species abundance with pH, NO3-N, electrical conductivity, NH4-N and CaCO3. Analysis
revealed EC and NO3-N as the main environmental drivers affecting diatom community composition, followed by
pH and PO4-P. The percentage of diatom deformities at all sites was high, at 3.5%. Diatom indices showed the river
to be impacted by decades of agricultural activity, which was confirmed by chemical water analysis. Thus diatom
indices can be used for biomonitoring in semi-arid areas
URI
http://hdl.handle.net/10394/18607https://doi.org/10.2989/16085914.2015.1086722
https://www.tandfonline.com/doi/abs/10.2989/16085914.2015.1086722