n Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie - Die reaksie van die diatoom gemeenskapstruktuur op endosulfiene blootstelling : 'n Mesocosm benadering : referaatopsomming

Volume 31, Issue 1
  • ISSN : 0254-3486
  • E-ISSN: 2222-4173


Diatoms in South Africa are well studied, with a substantial species database available for use in identification of species. Biomonitoring and water quality analysis using such algae is a useful tool in aquatic health research. Diatom community assemblages and species prevalence shed light on various elements as they are used as indicators for pH, nutrients, salinity and organics. Due to their fast responses to toxicants as well as importance as primary producers they have become a key component of most aquatic health assessments. In this study, epilithic diatoms collected from the Vaal River were exposed to the organochlorine pesticide endosulfan by means of controlled application using mesocosms. Exposure concentrations were calculated using the LC50 value and determining 10%, 25% and 50% of the LC50 value. Endosulfan was added as a once-off application to simulate agricultural spray drift. The mesocosms were run for a 96 hour exposure period before diatoms were sampled using standard methodologies. A higher density of biofilm was observed macroscopically in the control and first exposure. Sixteen species of diatoms were identified in the control experiment, whilst only 13 were identified in the highest exposure concentration. Taxonomic identification showed that species such as and were not significantly affected by the pesticide. Other species like and were more sensitive as they were not found in the third exposure.

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