Show simple item record

dc.contributor.advisorSeaman, M. T.
dc.contributor.advisorKok, D. J.
dc.contributor.authorOelofsen, Michiel Jacob
dc.date.accessioned2018-02-28T09:17:43Z
dc.date.available2018-02-28T09:17:43Z
dc.date.issued1982-01
dc.identifier.urihttp://hdl.handle.net/11660/7884
dc.description.abstractEnglish: Wuras Dam is a shallow, suspensoid-rich polymictic impoundment. The turbidity results from the inflow of turbid water from the cathment, as well as from resuspension due to wind action and consequent water movement. On the basis of its chemical composition Wuras Dam can be considered a mesotrophic to eutrophic system. Environmental factors such as temperature, dissolved oxygen concentration, pH, turbidity and conductivity did not vary greatly over the study period, while the water level did. The sediment had a relatively high organic content and the particle size varied from fine silt to coarse sand. In the areas where the sediment was very fine, an ooze layer was indicated. For the benthic fauna, three macrohabitats were studies, viz. the macrophytes, the stones and the sediment. It was found that the high suspensoid load in the water column reduced light penetration and algal growth, resulting in a vertical zonation of organisms on the macrophytes and stones. A large number of taxons were found, with the Molllusca, Chironomidae and Ephemeroptera being numerically dominant. Colonisation on the sprouting macrophytes occured after the winter, and periphyton growth appears to have been the most important factor controlling the presence and distribution of the epifauna on the macrophytes and stones. The epifauna on the macrophytes comprised approximately half of the benthic standing crop of the dam (3260 kg a-1), while the stone epifauna made an insignificant contribution to the total biomass. The dominant organisms in the sediment were the Oligochaeta, Nematoda and Chironomidae. Their numbers and production were largely influenced by the decaying organic material derived from the macrophyte beds. Other factors influenced numbers and production such that a sediment with an organic content of 4 to 8 per cent had the highest zoobenthic production. Sand harboured a higher production than finer particles and a water depth of 60 to 120 cm appeared to be the most productive zone. Periphyton growth in the shallower areas resulted in the development of a different community in the sediments of that region, which was marked by Chironomid community of specific composition. The presence of an ooze layer, particularly in the deeper parts of the dam, affected the occurrence of most organisms adversely, effectively excluding all but Chaoborus, Nematoda, Tubificidae and 3 genera of the Chironomidae. Suspensoids appear to have both direct and indirect effects on all three zoobenthic macrohabitats. In spite of this the production of zoobenthos per ha in Wuras Dam was found to be much higher than that of other South African standing waters.en_ZA
dc.description.abstractAfrikaans: Wurasdam is 'n vlak, suspensoïedryke polimiktiese watermassa. Die troebelheid word veroorsaak deur die invloei van troebelwater uit die opvanggebied, asook deur resuspensie van slik as gevolg van windaksie en waterbeweging. Op gond van die chemiese eienskappe kan Wurasdam as 'n mesotrofiese tot eutrofiese sisteem beskou word. Omgewingsfaktore soos temperatuur, konsentrasie opgeloste suurstof, pH, turbiditeit en konduktiwiteit het nie uitsonderlik baie gewissel oor die tydperk van die studie nie, terwyl die watervlak baie gefluktueer het. Die sediment het 'n relatief hoë organiese inhoud gehad, terwyl die korrelgrootte van 'n fyn slik tot 'n growwe sand wissel. In die gebiede waar die sediment baie fyn is, was daar baie moontlik 'n sliblaag teenwoordig. Ten spyte van die bentiese fauna is drie makrohabitatte ondersoek, nl. die makrofiete, die klippe en die sediment. Dit is gevind dat die hoë belading suspensoïede in die water 'n beperkte ligindringing en alggroei veroorsaak, sodat 'n vertikale sonering van organismes op die makrofiete en die klippe voorkom. 'n Groot hoeveelheid taksons word onderskei, alhoewel die Mollusca, Chironomidae en Ephemeroptera in die littoraal dominant is. Kolonisasie het op die uitgroeiende makrofiete na die winter plaasgevind, en perifitongroei blyk die belangrikste faktor te wees wat die voorkoms en verspreiding van die epifauna op die makrofiete en klippe beïnvloed het. Die produksie op die makrofiete het ongeveer die helfte tot die staande-oes van die soöbentos van die dam (3260 kg jr-1) bygedra, terwyl die organismes op die klippe 'n minimale rol gespeel het. Die dominante organismes in die sediment was die Oligochaeta, Nematoda en Chironomidae. Hulle getalle en produksie is hoofsaaklik beïnvloed deur die dooie organiese materiaal wat van die makrofiete afkomstig was. Ander faktore het die getalle en produksie sodanig beïnvloed dat 'n sediment met 'n organiese inhoud van 4 tot 8 persent die hoogste produksie per eenheidsoppervlak gelewer het. Sand het ook 'n hoër produksie as fyn slik gehad, terwyl 'n waterdiepte van 60 tot 120 cm ook blyk om die hoogste produksie te huisves. Perifitongroei in die vlakker dele het die ontwikkeling van 'n ander soöbentiese gemeenskap veroorsaak, waarby 'n totaal ander Chironomidae-gemeenskap voorgekom het. Die aanwesigheid van 'n sliblaag, veral in die dieper dele van die dam, het die meeste organismes benadeel sodat slegs Chaoborus, die Nematoda, Tubificidae en 3 genera van die Chironmidae daar voorgekom het. Suspensoïede blyk by al drie soöbentiese makrohabitatte beide direkte en indirekte negatiewe invloed uit te oefen. Ten spyte hiervan is gevind dat die produksie van soöbentos per hektaar in Wurasdam baie hoër as die van ander Suid-Afrikaanse staande waters is.en_ZA
dc.language.isoafen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectEutrophication -- South Africa -- Wurasdamen_ZA
dc.subjectSludge bulkingen_ZA
dc.subjectAlgaeen_ZA
dc.subjectDissertation (M.Sc. (Zoology and Entomology))--University of the Free State, 1982en_ZA
dc.title'n Studie op aspekte van die soöbentos van Wurasdamen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record