09 July 2010
Darwin Harbour and Beaches
There are no public health risks associated with E.coli at Darwin beaches and DHF has continued to monitor beach water quality since the beaches were reopened. Latest tests continue to show that the water quality remains high and in compliance with NT Recreational Microbiological Water Quality Guidelines, with E.coli test result levels being between 20 - 300 E.coli per 100ml. This means the sea water quality is open for swimming. In addition, fish and mudcrab have been tested and indicated no evidence of E coli or enterococci.
Beach monitoring testing is now being carried out on a fortnightly basis. Results from the next round of sampling will be available mid next week and will be published on DHF's Environmental Health website, along with previous results of other beach monitoring tests carried out by DHF since 07 June 2010.
An integrated monitoring plan is being developed on future monitoring and management of Darwin Harbour, including beach monitoring.
Origin of E. coli
The E. coli is likely to have originated from a number of sources, which are still subject to an extensive environmental and sanitary survey, including discharges from stormwater and effluent drains. However, while these surveys are not finalised, there appears to be a high association between the algae and E. coli outbreaks. Results of deep water sampling in Darwin Harbour indicate there is no link to high levels of E. coli identified in beach monitoring and Power and Water Corporation sewage discharges.
Other water testing
Other water channels that are not considered to be recreational water bodies include Little Mindil Creek, the Gardens Park Golf Course Lake and Vesteys Lake.
On 8 June 2010, DHF took an initial sample from the golf course storm water channel, which is not a recreational water body, that indicated elevated bacteria levels of 560 000 E.coli and in excess of 2005 enterococci per 100 ml. This was a one-off sample and could be anomalous.
The Little Mindil water quality results indicated in excess of 2005 E.coli per 100ml on 9, 10, 11 and 15 June 2010.
Subsequent beach testing close to the Little Mindil Creek inlet indicated continually improving water quality. The water is now very clear at Little Mindil Creek and in the shallows along Mindil Beach.
On June 11, interim results of testing undertaken by NRETAS for nutrients and metals in Little Mindil Creek showed high levels of nitrogen and phosphorus that exceeded the national water quality guidelines.
Follow-up testing by NRETAS was conducted on 24 and 29 June 2010 for nutrients and metals, with the results expected by the end of July 2010. The results of which will be made public.This follow-up testing also included an algal biomass survey of Little Mindil Creek.
These test results form part of the environmental monitoring and testing program being undertaken by NRETAS that is expected to take some time to complete.
There is no evidence of any runoff from the construction site at the Skycity Little Mindil development, into Little Mindil Creek. Recent Little Mindil Creek sampling results indicate very high quality water and the presence of fish.
Blue Green Algae
Fifty Tonnes of Blue-green (cyanobacteria) algae (Lyngbya majuscule) was removed from the Little Mindil and Mindil Beaches, and the stretch of beach between the Trailer Boat Club and the Darwin Sailing Club last month.
The public is reminded of the health risks this algae poses and to avoid direct contact with it, which may still persist in the environment. A fact sheet containing general information and health and safety advice is available on the DHF website.
The website address for the fact sheet is: http://www.health.nt.gov.au/Environmental_Health/Water_Quality/index.aspx#FactSheetsWaterQuality
Final water testing results of nutrients, metals and algal biomass from Little Mindil Creek have not come back yet, so the cause/reason for algal outbreak are not yet determined. These test results are due at the end of the month.
Blue-green (cyanobacteria) algae (Lyngbya majuscule) has not previously been detected or identified in Darwin Harbour. However, algal blooms of blue-green (cyanobacteria) algae have previously been reported in Queensland and other areas of the Northern Territory coastline such as Port Bradshaw, a stretch of the East Arnhem coast.
Blue-green (cyanobacteria) algae is responsive to high levels of nutrients in waterways and is a naturally-occurring algae.
