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Is turbidity in a shallow Tasmanian lake controlled by wind or by the extent of macrophyte coverage?


Watson, A and Barmuta, LA and Proemse, B and Visby, I and Hogan, CM and Maxwell, C, Is turbidity in a shallow Tasmanian lake controlled by wind or by the extent of macrophyte coverage?, Abstracts for the Australian Society for Limnology Conference 2017, 24-28 September, Sydney, pp. #51. (2017) [Conference Extract]

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Historically, Woods Lake in the Central Highlands of Tasmania has been considered a turbid (normal range 20 40 NTU) and meso-eutrophic lake. Woods Lake was impounded in 1962, largely to supply irrigation water to downstream agriculture. The turbidity has been a concern, since this lake contains a significant population of the threatened Galaxias tanycephalus. However, Crook (1995) showed that high turbidity was persistent and strongly linked to low water levels and strong winds. This correlated with small particle size and high phytoplankton biomass. Macrophyte coverage was limited to sheltered areas (Hydro Tasmania, unpublished). A series of sediment traps were used to determine sediment resuspension rates at a range of depths. Initial results indicate that resuspended sediment is largely composed of organic material and rapidly falls out of the water column. Maintenance of higher water levels and expansion of macrophyte beds across the lake may have reduced sediment resuspension. Chlorophyll a concentrations were generally low during the study period. Nitrogen and phosphorus concentrations indicate that the lake is oligotrophic. Our conclusion, based on the sediment trap data, is that turbidity levels in the lake are no longer a concern, unless there are major changes to macrophyte persistence or water levels.

Item Details

Item Type:Conference Extract
Keywords:shallow lake, turbidity, macrophytes
Research Division:Environmental Sciences
Research Group:Environmental management
Research Field:Environmental management
Objective Division:Environmental Management
Objective Group:Fresh, ground and surface water systems and management
Objective Field:Measurement and assessment of freshwater quality (incl. physical and chemical conditions of water)
UTAS Author:Watson, A (Dr Anne Watson)
UTAS Author:Barmuta, LA (Associate Professor Leon Barmuta)
UTAS Author:Proemse, B (Dr Bernadette Proemse)
UTAS Author:Hogan, CM (Dr Chad Hogan)
ID Code:121678
Year Published:2017
Deposited By:Zoology
Deposited On:2017-10-10
Last Modified:2017-10-10

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