Hicks, Brendan J.Bryant, Nicholas2026-07-092026-07-092003https://hdl.handle.net/10289/18440The water quality, phytoplankton, zooplankton, fish, nutrient regimes, and mixing regimes of three small, shallow, hypertrophic, urban lakes situated on the University of Waikato campus, Hamilton were investigated. The lakes are spatially very close, in the same soil type, subject to the same climatic influences, and have similar nutrient concentrations. However, two of the lakes are shallow (Oranga and Knighton lakes - maximum depth 0.7m) and one of the lakes is slightly deeper (Chapel Lake - maximum depth 1.8m). The lakes experienced strong temperature induced mixing. The water columns of the lakes were less stable at night than during the day. They were more stable in summer than in winter. The water column of Chapel Lake was significantly more stable than Oranga and Knighton Lakes. Oranga Lake was significantly more stable than Knighton Lake. The concentrations of PO₄, NH₄, NO₂, and NOₓ varied over the sampling period but were generally similar in all three lakes. Peaks of NH₄ occurred in Knighton and Chapel lakes. It is possible that low levels of dissolved oxygen caused nitrogen to be released from the sediment in the form of NH₄, which was converted to NO₂ and NOₓ once oxygen levels increased. The exact mechanisms causing the changes in nutrient concentrations are unclear. Water quality varied between seasons. Chapel Lake had consistently better water quality than Knighton and Oranga lakes. This was especially pronounced in summer when there were marked blooms of zooplankton and phytoplankton in Oranga and Knighton lakes but not in Chapel Lake. Significant differences were also found in the phytoplankton and zooplankton diversity and abundance between the lakes. Cyanobacteria and Euglenoids dominated the phytoplankton communities in Oranga and Knighton lakes while Chrysophytes and Chlorophytes were dominant in Chapel Lake. Rotifers and small cladocerans dominated the zooplankton communities in all of the lakes. The differences in phytoplankton communities between lakes were more pronounced than the differences in zooplankton communities. Brown bullhead catfish (Ameiurus nebulous) and shortfinned eels (Anguilla australis) dominated the benthivorous fish communities of the lakes. There was a marked seasonal trend in catch rates with more fish being caught in the warmer months. There were significantly more catfish and eels caught in the two shallow lakes than in Chapel Lake, but significantly fewer common bullies (Gobiomorphus cotidianus). In addition, there were small eels caught in Knighton Lake and Oranga Lake in December but not in Chapel Lake. This indicates that shortfinned eels are able to navigate the stormwater system from the Waikato River to reach the lakes. The catch rates of catfish were lower than previous studies and the populations were dominated by fish aged 1-2 years. The catfish populations have the potential to increase. The greater depth of Chapel Lake appears to protect it from the more extreme effects of hypertrophy experienced by Oranga and Knighton lakes. Artificial deepening is the option that is likely to provide the longest lasting improvements to water quality.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.Thesis