Abstract
Giralang Pond was a water body, with little emergent or submerged vegetation, designed to trap fine sediment and buffer input of rising water to Ginninderra Wetland downstream. Ginninderra Wetland was designed to retain and use sediment nutrients and other potential hazardous materials in urban run-off. Water in the Wetland was more turbid and had lower magnesium concentration, redox potentials and dissolved oxygen concentration than did Giralang Pond. Water temperature was a minimum of 4 °C in the winter and reached a summer maximum of 30 °C.Giralang Pond had more organisms but fewer taxa than Ginninderra Wetland. The greatest abundance in the pond resulted principally from high numbers of two numerically dominant species Calamoecia sp. and Micronecta sp.. More organisms were found in vegetated habitats of Ginninderra Wetland than open water habitats. The number of invertebrates and the number of taxa found in Typha domingensis did not differ significantly from similar estimates for Schoenplectus validus.
Gambusia affinis was the dominant predator in both water bodies. On one occasion, G. affinis reached population densities of 35 individuals per m . G. affinis was five times more abundant in Gininnderra Wetland than in Giralang Pond and also showed a preference for vegetated areas.
G. affinis over-grazed it’s prey on several occasions.
G. affinis, invertebrate predators and prey followed a pattern of a community in a stable predator-prey cycle. Prey in early spring increased population numbers and then decreased when G. affinis and other predators increased their numbers. The pattern was further strengthened by occurring in both areas of open water and vegetated habitat types.
| Date of Award | 1989 |
|---|---|
| Original language | English |
| Supervisor | Richard NORRIS (Supervisor) & Arthur GEORGES (Supervisor) |
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