Browsing by Author "Grainger, Cole Vincent"
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- ItemPatterns in periphyton biomass and community structure in foothill rivers: A comparison between winter and summer rainfall regions(Stellenbosch : Stellenbosch University, 2017-12) Grainger, Cole Vincent; Ewart-Smith, Justine; Jacobs, Shayne Martin; Simaika, John; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.ENGLISH ABSTRACT: South Africa has a semi-arid climate with seasonal rainfall whose runoff is jeopardised by high rates of evapotranspiration. These conditions decrease the ability of rivers to dilute point and non-point sources of pollution, which leads to enrichment and the subsequent eutrophication of water bodies. Eutrophication occurs when periphyton communities proliferate through a shift in community structure, accompanied by greater biomass accrual that deteriorates water quality and impairs aquatic ecosystem functioning. The National Eutrophication Monitoring Programme (NEMP) has set water quality guidelines for concentrations of phosphorous and Benthic chlorophyll a, but periphyton are understudied in South African waters, which explains their exclusion from the River Eco-Status Monitoring programme (REMP). To underpin the causes of eutrophication, this study aimed to broaden the knowledge on periphyton-environmental relationships in terms of patterns in peripyton biomass and community structure on a regional scale across seasons in a winter (Western Cape) and summer (KwaZulu-Natal) rainfall region. Periphyton biomass and community structure were observed across flow and enrichment categories and a suite of environmental metrics comprising flow, nutrients, water temperature, sunlight and macroinvertebrates. An in situ tool known as the Benthotorch® was validated to potentially be used in future rapid assessments of trophic status. Periphyton samples from sites representing a range in environmental conditions were collected in autumn and spring which mark the beginning and end of the periphyton growth seasons. Periphyton biomass in the Western Cape was found to be influenced predominantly by the availability of TIN in autumn and WTMAX in spring. In KwaZulu-Natal, periphyton biomass was influenced mostly by flow metrics and WTCV. Periphyton community structure in the Western Cape was influenced mostly by TIN and the length of the growing season in autumn and by EC and the duration of class 1 floods in spring. In KwaZulu-Natal, periphyton community structure was influenced mostly by water temperature and flow metrics in autumn and by the length of the growing season (Since≥2), the duration of class 2 floods and PO4-P in spring. The flow regime is regarded as the primary regulator of flood prone rivers, which was not the case in this study, and calls for future research. Nutrients accounted minimally towards spatial variation in periphyton communities in KwaZulu-Natal possibly due to sites with similar nutrient ranges, or because nutrients are not a key driver of periphyton communities here. The importance of water temperature metrics in both regions stresses the need for water temperature monitoring programmes, that are currently lacking in South Africa. The Benthotorch® estimated periphyton biomass and community structure more accurately at sites that were dominated by diatoms, overestimated cyanobacteria and did not consistently recognize green algae.