A widely observed pattern in nature is a positive relationship between local abundance and spatial distribution. This study investigates this relationship amongst three taxa namely rodents, millipedes and trees on regenerating and unmined coastal dune forests at Richards Bay, KwaZulu-Natal. No sensible analyses were possible on the rodent data. Both millipedes and trees had a positive relationship between local abundance and distribution (measured as species incidence). Millipedes showed no changes in the relationship with changes in habitat regeneration time. For trees, the regression slope decreased with time due to changes in abundance and incidence of Acacia karroo. Lack of bimodality in incidence frequency distributions ruled the core-satellite metapopulation hypothesis out as a mechanism producing the positive abundance-incidence relationship. The resource availability hypothesis was a most likely mechanism. This study confirmed that rare species tend to be restricted in both abundance and incidence. / Dissertation (MSc (Zoology))--University of Pretoria, 2007. / Zoology and Entomology / unrestricted

Phosphorus is an essential element since it controls primary productivity in aquatic ecosystems and its excess can lead to eutrophication in receiving systems. The aim of this project was to determine phosphorus distribution in biotic and abiotic nutrient pools of two KwaZulu-Natal estuaries. Samples of dissolved inorganic phosphorus (DIP), particulate phosphorus (PP), phytoplankton, microphytobenthos, zooplankton, macrozoobenthos and sediment were collected in the temporarily open/closed Mpenjati (MP) and permanently open Mlalazi Estuary (ML) during May (ML), September (MP) and November (ML+MP) using standard methods. Chlorophyll a concentrations as well as species richness, abundance and biomass of zooplankton and macrozoobenthos were analysed. Living and non living nutrient pools were analysed for phosphorus and were compared between stations, sampling sessions, estuaries and taxa. Zooplankton abundance and biomass in the Mlalazi Estuary was higher during May than November. In the Mpenjati Estuary highest zooplankton abundance and biomass was recorded during September than November. No significant differences were apparent in abundance (p = 0.217) and biomass (p = 0.974) of zooplankton between the two estuaries. Macrozoobenthos abundance and biomass in the Mlalazi Estuary was higher during May than November. In the Mpenjati Estuary macrozoobenthos abundance and biomass was higher during November than September. Significant differences in abundance (p = 0.003) and biomass (p = 0.020) were apparent between the estuaries. Sediment to a depth of 10 cm comprised the highest phosphorus biomass than any other nutrient pool in both Mlalazi (4871.1 mgP·m⁻² ± 5888.9 SD) and Mpenjati (2578.6 mgP·m⁻² ± 1828.0 SD) estuaries followed by DIP (120.5 mgP·m⁻² ± 177.7 SD and 5.9 mgP·m⁻² ± 6.1 SD respectively). In both estuaries, the lowest phosphorus biomass was contained in zooplankton with both estuaries containing zooplankton P biomass of 0.001 mgP·m⁻² ± 0.002 SD. Particulate phosphorus and DIP concentrations were higher in the upper reaches in both estuaries indicating that rivers were the main sources of this nutrient in these systems. The Mlalazi Estuary had higher nutrient levels than the Mpenjati Estuary. Such elevated nutrients can be enhanced by the continuous river flow into the permanently open estuary. In both estuaries, no significant differences were apparent in zooplankton and macrozoobenthos P content between different taxa. / M.Sc. University of KwaZulu-Natal, Durban 2013.