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    Conducted under the Coast and Clean Seas program of the Natural Heritage Trust fund, this study provides a summary and assessment of water quality parameters, as indicators of estuarine health, in 22 selected Tasmanian estuaries. The estuaries are: Duck Bay, East Inlet, Black River, Don River, Mersey River, Port Sorell, Boobyalla Inlet, Little Musselroe River, Ansons Bay, Grants Lagoon, Douglas River, Great Swanport, Meredith River, Little Swanport, Earlham Lagoon, Browns River, Cloudy Bay Lagoon, Catamaran River, Cockle Creek, Pieman River, Nelson Bay River and Arthur River (for location, see Fig. 1 in the attached report). Information is summarised on both a State wide and individual estuary basis.

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    Water quality and biological data was collected from four tide-dominated river estuaries indicative of catchments with varying levels of human impacts to: 1) assess draft indicator levels for water quality, and 2) investigate biological indicators of estuarine health in NW Tasmania. This data includes sampling from Detention River, Duck Bay, Montagu River and Black River

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    A 12-month program was developed and implemented in order to obtain baseline information on water quality (salinity, water temperature, dissolved oxygen, turbidity, pH, dissolved nutrients, silica), ecological condition as shown by Chlorophyll a, benthic macroinvertebrates, pathogens, and habitat extent determined from habitat mapping. Five key estuaries and coastal waters were assessed in the Southern NRM Region of Tasmania. This data includes sampling from Pitt Water / Orielton Lagoon, North West Bay, Port Cygnet, Little Swanport, Moulting Lagoon / Great Swanport.

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    Biologically relevant macronutrients, nitrate + nitrite, silicate, phosphate and ammonia, were measured at all sites throughout the study. Nitrate + nitrite values (NOx) at the surface showed clear seasonal trends, peaking over winter and drawing down to near zero in summer and autumn. Phosphate concentrations also reached a peak in winter, which was associated with Southern Ocean influence. Median ammonium concentrations at all sites were generally <0.5 μM, with no clear peaks in any season or month. Overall, the lowest values were measured in August and other months showed reasonable spread around the median. Median silicate concentrations were consistently highest at sites 1 and 9, followed by site 5. Water from the River Derwent flows through site 1, then tracks east towards site 9 then site 5. Seasonally, silicate was generally highest in winter when the River Derwent outflow is also greatest.

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    Physical and chemical parameters at five Pacific oyster (Crassostrea gigas) growing areas in Tasmania - Pittwater, Pipeclay Lagoon, Little Swanport, Georges Bay and Simpsons Bay - were measured as part of a study to determine the carrying capacity of the areas for oyster farming. This has provided valuable environmental data for these areas. The hydrodynamic regimes at each area except Simpsons Bay were studied, including high and low water volumes, flushing rates, flow rates and depth contours. Temperature, salinity and concentrations of nitrates, phosphates, silicates and chlorophyll a were measured monthly at several sites in each area. The change in these parameters over different time scales also was examined at two sites in Pittwater and indicated temporal and spatial variability in the environmental parameters measured.

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    This study considered a range of water-column and sediment (benthos) based variables commonly used to monitor estuaries,utilising estuaries on the North-West Coast of Tasmania (Duck, Montagu, Detention, and Black River). These included: salinity, dissolved oxygen, turbidity, nutrient and chlorophyll a levels for the water-column; and sediment redox, organic carbon content, chlorophyll a and macroinvertebrate community structure amongst the benthos. In addition to comparing reference with impacted estuaries, comparisons were also made across seasons, commensurate with seasonal changes in freshwater river input, and between regions within estuaries (upper and lower reaches) - previously identified in Hirst et al. (2005). This design enabled us to examine whether the detection of impacts (i.e. differences between reference and impacted systems) was contingent on the time and location of sampling or independent of these factors. This data includes sampling from Duck River, Montagu River, Detention River, and Black River.

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    We implemented a monitoring program developed by Crawford and White (2006), which was designed to assess the current condition of six key estuaries in NW Tasmania: Port Sorell, the Leven, Inglis, Black, Montagu and Arthur River estuaries. This study considered a range of water quality and ecological indictors commonly used to monitor estuaries. These included: salinity, temperature, dissolved oxygen, turbidity, pH, nutrients (nitrate + nitrite, dissolved reactive phosphorus and ammonia), silica molybdate reactive and chlorophyll a for the water column; chlorophyll a and macroinvertebrate community structure amongst the sediments.