Colonisation and community structure of benthic diatoms on artificial substrates following a major flood event: A case of the Kowie River (Eastern Cape, South Africa)

Abstract

A major flooding event that occurred during October-November 2012 caused major changes in the Kowie River hydromorphology and aquatic communities. The aim of our study was to identify the environmental variables that structure riverine benthic diatom communities at upstream and downstream locations 25 km apart on the Kowie River, South Africa. This was undertaken using tiles as artificial substrates so that we could study how the communities developed after the flood disturbance. The diatom community structure was assessed over a 28-day period following a flood event in October 2012. The Mann Whitney test indicated that there was a statistically significant difference (p < 0.05) in total dissolved solids, salinity, pH and oxygen reduction potential between the two sites. In total, 58 diatom species belonging to 30 genera were identified over the 28-day study. Achnanthidium minutissimum, Fragilaria biceps, F. ulna var. acus, Pinnularia borealis and P. acrosphaeria were the most numerically dominant on Day 7 and were considered as early colonisers, while on Day 28, Achnathidium minutissimum, F. capucina, Craticula buderi, C. vixnegligenda, Diploneis subovalis and Gomphonema venusta, the late colonisers, were dominant. The species richness increased from 13 (upstream location) on Day 7 to 22 (both locations) by Day 21. A redundancy analysis showed that total suspended solids, salinity, resistivity, pH and oxygen reduction potential were the most significant physico-chemical variables explaining diatom composition. The results from this relatively smallscale tile experiment indicate the complexity of freshwater benthic diatom community structure and development.

Assessment of water quality based on diatom indices in a small temperate river system, Kowie River, South Africa

“…In addition to nutrient availability, water flow was also identified as an important factor in structuring diatom communities in this study, which again is consistent with previous studies conducted both locally and internationally (e.g. Ruth, 1977;Biggs et al, 2005;Song, 2007;Tan et al, 2014b;Bere et al, 2013;Dalu et al, 2014a).…”

Assessment of the spatial and temporal variations in periphyton communities along a small temperate river system: A multimetric and stable isotope analysis approach

“…Citrus (pineapples, citrus and chicory) and livestock (fodder crops, beef cattle and goats) farms occur mostly in the middle to the lower sections of the river. A major flooding event in October-November 2012 produced a record discharge of 699.14 m 3 s −1 , changing the geomorphology of the Kowie River; a detailed description of the flooding is highlighted in Dalu et al (2014a).…”

Coastal Climate Change Adaptation and Disaster Risk Reduction: A Review of Policy, Programme and Practice for Sustainable Planning Outcomes

“…It has been revealed that Africa would experience extreme climate events which would affect people's adaptation to climate change and increase disaster risk in the future giving South Africa as a case study, for example there were recorded events of devastating flooding in year 1994-1995, 2000, 2011 and 2012 in the Western Cape, Limpopo, Kwazulu-Natal and the Eastern Cape respectively [20,21]. These are scientific evidences of climate events that have affected South Africa and its population [22].…”