Latest monthly water quality testing in Port Curtis have continued to find no evidence to link water quality with any adverse impacts on fish health.
The Department of Environment and Heritage Protection (EHP) today released the results of February and March water sampling in Gladstone Harbour.
Director-General Andrew Chesterman said the monthly monitoring program, which began last September, was expanded in February from 32 to 47 sites, in line with recommendations made by the Gladstone Fish Health Scientific Advisory Panel.
The monitoring program was expanded to determine any impact of existing large industrial activities on water quality in Gladstone, and also includes sites across the broader region including the Fitzroy catchment and sites closer to the coastline within the Gladstone Harbour area.
“The water quality results from the extended sampling are similar to those in previous reports, and based on the evidence, there remains no clear link between water quality and fish health in Gladstone waterways,” Mr Chesterman said
In February, the water quality tests found dissolved metals were within Australian and New Zealand Water Quality Guideline trigger values at all but one of the 47 sites monitored. This site, at South Trees Inlet, was one of the new sites included for metal analysis. The concentrations of aluminium, arsenic and molybdenum at South Trees exceeded the trigger values. There had been no previous exceedance of trigger values for arsenic and molybdenum.
In March, there were 18 exceedances of guideline trigger values which is similar to observations in November last year. Trigger value for aluminium was exceeded at 10 at the 36 sites sampled, trigger value for copper was exceeded at four sites, molybdenum at two sites, while arsenic and zinc were each exceeded at one site.
Mr Chesterman said it was important to understand that exceeding trigger values in the Australian and New Zealand Water Quality Guidelines did not necessarily mean that water quality is harmful to marine life.
“It triggers the need for action, such as follow up sampling or further investigation of sources,” Mr Chesterman said.
“These sites will therefore continue to be monitored for metals in future sampling rounds to assess whether the latest results are replicated in future months.”
There was no consistent pattern in the results of turbidity sampling. In March, turbidity increased at more than 20 sites and decreased at more than 20 sites.
The very high turbidity seen at Boat Creek in November and January was again seen in March. This was not associated with dredging operations and indicates that high turbidity levels do occur naturally in Port Curtis waters.
Salinity levels also varied in line with climatic conditions. In February salinity levels were lower following January’s high rainfall, but increased in March when there was no major rainfall in the Port Curtis region in the days leading up to the sampling.
The January rainfall also caused higher nutrient concentrations in many parts of the region which in turn caused higher levels of phytoplankton. This often occurs in summer after rainfall, but in March these concentrations generally decreased with the exception of areas near Curtis Island, offshore and at the mouth of the Calliope estuary.
Dissolved oxygen levels were lower in March than February, however all measurements were greater than 65 per cent with readings greater than 79 per cent across Gladstone Harbour, which means that fish health is unlikely to have been adversely affected.
Dredging Today Staff, May 2, 2012; Image: westernbasinportdevelopment