Darwin Harbour in good health
Westra Van Holthe, Willem
Media Releases for 12th Assembly 2012 - 2016; Media Releases; ParliamentNT
Made available by via the Publications (Legal Deposit) Act 2004 (NT)
Oceans; Marine life
Northern Territory Government
Issued as a Media Release
Northern Territory Government
12 5.1.1. Dissolved Oxygen saturation Median dissolved oxygen ranged from 107% (Shoal Bay) to 88% saturation (Buffalo creek). Values for DO% were generally lower in the upper reaches of the harbour and higher in the outer zones such as the main body to outer harbour reporting zone. Results did not always comply with the WQO, for example elevated DO was observed in Shoal Bay (119%), Middle Harbour (105%) and Buffalo Creek (103%). These higher values were typically short-lived episodes usually driven by algal biomass (particularly for Buffalo Creek) and tidal slack in the upper reaches of systems examined. 5.1.2. Total Suspended Solids Suspended solids remained low in Darwin Harbour over neap dry season conditions. Medians across all reporting zones ranged from 1.2 mg/L (Shoal Bay) through to 10.8 mg/L (Buffalo Creek). Similarly corresponding turbidity across the harbour and Shoal Bay were also low (<10 NTU) with the exception of the upper reaches of Buffalo Creek where the median value was 15.6 NTU and elevations as high as 110 NTU were recorded. 5.1.3. pH Median pH ranged from 7.5 (Blackmore Upper) to 8.1 in the outer harbour zone. This limited range was typical of dry season conditions where negligble to no flow persists with the exception of the Blackmore River. 5.1.4. Salinity Median salinities ranged from 32-36 ppt with lower salinities detected in the upper reaches of the Blackmore River and Buffalo Creek. The freshwater flows continue during the dry season in the Blackmore contributing to lower salinities. The Buffalo Creek system is subject to treated discharge from the Leanyer-Sanderson treatment plant. 5.1.5. Temperature Temperature ranged from 23C to 32C. Systems such as Elizabeth River, Blackmore River, Middle Harbour, Shoal Bay and West Arm had a narrow temperature range. Conversely systems such as Buffalo Creek, Myrmidon Creek and East Arm revealed a wider range of water temperatures. 5.1.6. Chlorophyll a Median Chlorophyll ranged from 0.2 mg/L in Shoal Bay to 10mg/L in Buffalo Creek. Extremely high concentrations were observed in Buffalo Creek particularly in upper reach sites in association with treated wastewater entering the creek. Most systems recorded very low chlorophyll-a values (<4 mg/L) with higher algal biomass generally observed in upper reach sites and tidal creeks.
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