Sekere aspekte van die abioties-biotiese verwantskappe van 'n troebeldam
| dc.contributor.advisor | Keulder, P. C. | |
| dc.contributor.advisor | Toerien, D. F. | |
| dc.contributor.author | Janse van Vuren, Carel Johannes | |
| dc.date.accessioned | 2020-12-03T14:23:11Z | |
| dc.date.available | 2020-12-03T14:23:11Z | |
| dc.date.issued | 1979-09 | |
| dc.description.abstract | English: Wuras Dam is a shallow, turbid polymictic impoundment. The turbidity of the water is influenced by the silt-laden flood water entering the dam from the catchment area, and by re-suspension of silt as a result of wind action and consequent water agitation. The dam has a maximum depth of 5 m and an average depth of 2,8 m. Average chorophyll α values indicate that Wuras Dam falls into the late mesotrophic to early eutrophic category. Temperature stratification did not occur and there was little temperature difference between bottom and surface water. More significant were the differences in oxygen concentration between surface and bottom water. Anaerobic conditions as such, however, did not occur and the lowest oxygen concentration registered was 2 mg l-1. The pH, alkalinity and mineral salts gradually increase as the water level falls, reaching a maximum during the dry season. This may be as a result of evaporation from the dam. The inflow of mineral-rich ground water from the catchment area may also be a contributing factor. Flood water which is low in mineral concent has a diluting effect on the water in the dam and consequently results in a decrease in the pH, alkalinity and mineral concentration. Furthermore growth in Wuras Dam appears to be limited to nitrogen, whereas the low Si-concentrations may from time to time inhibit diatom growth. The orthophosphate concentration (PO4-P) fluctuates largely and could possibly be attributed to biological assimilation and release and/or chemical reactions and to input from flood water. Five species of fish, all breeding during the summer months. inhabit Wuras Dam. The dam yields approximately 900 fish ha-1 and the fish production amoutns to approximately 452,5 kg ha-1. The figures must be regarded as provisional as the study on the biomass of fish has not yet been completed. Twenty seven zooplankton species were found in Wuras Dam, sixteen of which are more common. Mesocyclops schuurmanae and Asplanchna were the two main predators, whereas Chaoborus larvae were seldom encountered. The zooplankton is dominated by Mesocyclops schuurmanae which constitutes more than 20% of the total zooplankton population. Five other species, Metadiaptomus meridianus (Copepoda), Daphnia longispina/puler and Moina dubia (Cladocera) and Brachionus calyciflorus and Hexarthra (Rotifera), make with Mesocyclops schuurmanae the greater part of the zooplankton. According to the linear and logartihmic classifications in terms of correspondence analysis five zooplankton groups can be identified. The classification of the various groups depends more on reaction of the zooplankton to environmental factors than on their feeding habits. The two statistical procedures that were applied to the results, viz. the correlation coefficient matrix and the correspondence analysis led to the same results. Correspondence analysis appears to be a very suitable procedure for dividing the zooplankton into groups. Four groups of environmental parameters influenced the density of the zooplankton, namely: silt content of the water, water temperature, chlorophyll α concentration and pH and conductivity of the water. Whereas most chemical parameters were related to the distribution of zooplankton, the others were not as significant as the abovementioned. Furthermore it is clear that the organisms in the dam are subject to wide fluctuations in the concentrations of minerals, plant nutrients, pH, conductivity, alkalinity and suspensoids in the water. Consequently, if they are to survive, the organisms must be adapted to these fluctuations or have the ability to recover rapidly from catastrophical population declines. From the results of this study it can be determined whether the silt content of the water does in fact influence the distribution of zooplankton. Although the results are suggestive, the precise influence of silt on the zooplankton has not yet been established and consequently warrants further research. | en_ZA |
| dc.description.abstract | Afrikaans: Wurasdam is 'n vlak, suspensoiedryky polimiktiese watermassa. Die troebelheid van die water word deur die vloei van slikryke vloedwater uit die opvanggebied asook deur die resuspensie van slik deur waterbeweging as gevolg van windaksie, beinvloed. Die maksimum diepte van die dam is ongeveer 5 m en die gemiddelde diepte 2,8 m. Op grond van gemiddelde chlorofil waardes wil dit voorkom asof Wurasdam in die laat mesotrofe - begin eutrofe toestand verkeer. Geen temperatuurstratifikasie het voorgekom nie en die verskil tussen bodem- en oppervlaktemperature was deurgans klein. Grotere verskill tussen bodem- en oppervlak suurstofkonsentrasies het voorgekom en by die bodem was daar soms tekens van hoe suurstofverbruik. Geen werklike anaerobiese toestande het egter voorgekom nie en die laagste suurstofkonsentrasie was 2 mg l-1. Die pH, alkaliniteit en minerale soute bou stadig op namate die watervlak daal en bereik 'n maksimum gedurende die droe tydperk. Dit is moontlik as gevolg van die verdamping van die water. Die invloei van mineraalryke grondwater uit die opvanggebied kan ook hierin 'n rol speel. Vloedwater, laag in minerale verdun die water van die dam en het tot gevolg dat die pH, alkaliniteit en die konsentrasies van minerale soute afneem. Wurasdam blyk verder stikstof groeibeperkend te wees, terwyl die lawe Si-konsentrasies die diatoomgroei van tyd tot tyd mag beperk. Die ortofosfaatkonsentrasies (PO4-P) fluktueer grootliks en kan moontlik toegeskryf word aan biologiese opname en uitskeiding en/of chemiese reaksies en word blykbaar deur vloedwaters verhoog. Vyf vissoorte, wat almal in die somer broei, kom in Wurasdam voor. Ongeveer 900 vis ha-1 water kom in die dam voor, terwyl die visopbrengs ongeveer 453,5 kg ha-1 is. Hierdie syfers moet as voorlopig beskou word aangesien 'n studie na die visbiomassa nog nie voltooi is nie. Sewe en twintig sooplanktonsoorte is in Wurasdam aangestref waarvan sestien soorte meer algemeen was. Twee predatore naamlik Mesocyclops schiurmanae en Asplanchna is aangetref, terwyl 'n derde predator, die Chaoborus-larwe, baie min voorgekom het. Die sooplankton word deur Mesocyclops schuurmanae gedomineer en maak meer as 20% van die totale sooplankton uit. Vyf ander soorte maak, saam met Mesocyclops schuurmanae, die grootste deel van die sooplanktonbevolking uit, naamlik Metadiaptomus meridianus (Copepoda), Daphnia longispina/pulex en Moina dubia (Cladocera), en Brachionus calyciflorus en Hexarthra (Rotifera). Volgens die liniere- en logaritmiese indeling, volgens die korrespondensie-analise, word onderskeidelik vyf groepe onderskei. Die indeling van die groepe berus blykbaar meer op die reaksie van die sooplankton op die invloed van die omgewingsparameters, as op die voedingsgewoontes van die sooplanktonsoorte. Die twee statistiese prosedures wat gebruik is by die verwerking van die resultate, naamlik die korrelasie koeffisientmatriks en die korrespondensie-analise toon baie min verskille. Die korrespondensie-analise blyk verder 'n baie handige metode te wees, waarvolgens die sooplankton in groepe ingedeel kan word. Vier groepe omgewingsparameters kan uitgesonder word, wat die voorkoms van die sooplankton beinvloed, naamlik die slikinhoud van die water, die watertemperatuur, die chlorofil α konsentrasie en die pH en konduktiwiteit van die water. Daar bestaan 'n verband tussen die meeste chemiese parameters en die sooplankton, hoewel dit nie so belangrik as bogenoemde parameters geag word nie. Dit is verder duidelik dat die organismes in die dam onderhewig is aan wye fluktuasies in die konsentrasies van minerale, plantvoedingstowwe, pH, konduktiwiteit, alkaliniteit en die suspensoiede in die water. Die organismes moet gevolglik vir suksesvolle oorlewing daarby aangepas wees of instaat wees om vinnig te kan herstel van katastrofale populasietuimelings. Uit hierdie studie kan daar vasgestel word of die slikinhoud van die water 'n invloed op die voorkoms van die sooplankton het. Hoewel dit uit die resultate wel so blyk, was dit nie moontlik om vas te stel wat die definitiewe invloed daarvan op die sooplankton was nie en behoort verder ondersoek te word. | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11660/10855 | |
| dc.language.iso | af | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Dissertation (M.Sc. (Plant Sciences))--University of the Free State, 1979 | en_ZA |
| dc.subject | Wurasdam - Bloemfontein | en_ZA |
| dc.subject | Zooplankton species | en_ZA |
| dc.subject | Physico-chemical water conditions | en_ZA |
| dc.subject | Suspensoid concentration - zooplankton | en_ZA |
| dc.title | Sekere aspekte van die abioties-biotiese verwantskappe van 'n troebeldam | en_ZA |
| dc.type | Dissertation | en_ZA |