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The influence of temperature and metaphyton on non-biting midges (Diptera: Chironomidae) at Lake Joondalup

Lamb, Cho (2001) The influence of temperature and metaphyton on non-biting midges (Diptera: Chironomidae) at Lake Joondalup. Honours thesis, Murdoch University.

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Problems of nuisance midge (Diptera: Chironomidae) swarms are common at enriched Perth Wetlands. This project sought to investigate the following hypotheses: Environmental parameters are not limiting to larval chironomid density; larval chironomid density is related to environmental temperature; metaphyton provides both a food source and habitat for larval chironomids.

The following variables were measured at three sites over the period April to September, 2001: conductivity, pH, gilvin, turbidity, dissolved oxygen, chlorophyll a, total nitrogen, total phosphorus, ambient temperature and temperature of the sediment, water column and metaphyton. The three sampling sites provided contrasting habitats and potential food resources for chironomid larvae: bare sediment with dense stands of the algae Chara sp. and sediment covered by a layer of metaphyton.

Larval densities reached 6817 larvae m-2 during the sampling period, however no nuisance swarms were recorded. Of the environmental variables measured, only conductivity, dissolved oxygen and temperature appeared to limit larval chironomid density. Comparison of the ambient temperature for 2000 (when a nuisance swarm occurred) and 2001, suggests that temperature was important for triggering the emergence rates of pupa required for nuisance swarm densities.

Food resources were found to be non-limiting to the development of chironomid larvae. Furthermore, the diet of larvae reflected the composition of food resources found at each of the three micro habitats.

A mathematical model was constructed to examine the interaction between water column phytoplankton, phosphorus concentrations, temperature and larval chironomid densities. The results obtained suggested that temperature had the greatest influence on larval chironomid densities. Further modifications might include factors such as metaphyton and detritus as food sources.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Engineering
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Davis, Jenny and Hocking, Graeme
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