Gladstone Harbour in November 2011.
Gladstone Harbour in November 2011. David Sparkes

Toxic chemical not monitored during state harbour testing

A HIGHLY toxic chemical that may have exacerbated fish disease problems in Gladstone Harbour during the 2011 floods was not monitored in toxicology tests during the state government's response to the environmental crisis.

But while the chemical, tributyltin, was not included in the extensive tests, there was only a remote possibility it could have entered the marine life food chain, according to several monitoring reports and a CSIRO scientist.

According to various international groups, including the United States Environmental Protection Agency, TBT is highly toxic to most fish and marine animals, but the best and cheapest indicator of contamination is testing imposex levels in molluscs.

A key effect of TBT on marine life is immunosuppression - a symptom cited in several government reports on fish and other marine animals during and after the flood.

The chemical was primarily used in anti-fouling paints on the hulls of marine vessels to prevent barnacles and molluscs from sticking to the boats and creating drag problems, but it was banned worldwide in 2008.

Despite the ban, numerous studies into the effects of the chemical on molluscs in Gladstone Harbour in the past 10 years showed TBT was a "contaminant of concern".

A 2009 study of the effects of TBT on mud whelks in the harbor, part-funded by the port corporation, showed rising levels of imposex at several areas including the harbour's coal port and marina.

Central Queensland University's Dr Scott Wilson conducted the study, finding levels of imposex at the Clinton Coal Wharf rose 50% between the previous study in 2003 and 2009.

The study also found the levels of imposex in mud whelks rose significantly at the marina and near Picnic Island, opposite the coal wharf.

Dr Wilson said the most likely reason for the rise at the coal wharf and Picnic Island was international coal ships entering the area with TBT on their hulls, as the international ban was still being implemented in many countries.

You can't rule it out, I think - in a system where you've got stressors from abnormal climatic events then any added stressor to that system... could push animals over and make them more susceptible to disease

He also said the rise at the marina was more likely residual effects of TBT use on smaller boats, with a ban on the use of TBT on vessel smaller than 25 metres introduced in the late 1980s.

Despite the rise in levels at sites with high shipping activity, most other areas studied in 2009 had only low to moderate levels of imposex recorded, indicating the international ban was starting to take effect.

Dr Wilson said while the levels of TBT in sediments and water were below levels likely to impact fish and other species, it could not be ruled out as an additional stressor on marine species already under the pressure of the effects of the flood and various metals in the harbor.

"You can't rule it out, I think - in a system where you've got stressors from abnormal climatic events then any added stressor to that system, whether it be a chemical or something else, could push animals over and make them more susceptible to disease," he said.

Dr Wilson said it was possible TBT was not considered as an issue in the response to the fish disease crisis due to the ban, but it "should be considered as one of a range of factors".

A 600kg catch of diseased fish in Gladstone in October, 2011.
A 600kg catch of diseased fish in Gladstone in October, 2011. Chris Chan

However, despite the evidence of TBT contamination in the harbor, the chemical was not among the 160 chemicals, metals and organic compounds tested for in toxicology tests completed on marine life by the Queensland Government in response to the fish disease crisis in 2011.

The toxicology tests completed assessed crustaceans, fish , sharks and other species including molluscs - the key species which indicates TBT contamination - for the 160 other chemicals and metals.

But while tests were reported as having been completed on molluscs, the results of the toxicology analysis were not reported by Biosecurity Queensland.

The chemical was, however, tested for in sediments and water quality surveys done before and after the harbor closure, and only very low levels were found in a small number of those tests.

An environmental impact assessment of the Western Basin Dredging and Disposal Project also found little evidence of TBT in sediments; however, government reports show the size of the samples taken may have underestimated the real levels of contamination.

The state government's update on sediment quality released in May 2012 said the Queensland Government monitoring was more likely to detect recent sediment contaminants than the deep and large sediment cores assessed in the dredging EIS.

But that report also showed little evidence of high levels of TBT in sediments, with only a "small number" showing contamination, and none above the interim sediment quality guidelines.

While several independent sources with knowledge of marine ecology and ecotoxicology confirmed TBT should have been considered among the factors in the response to fish diseases, CSIRO contaminant expert Dr Simon Apte believed it was only a "very remote possibility" TBT was a contributing factor.

Dr Apte co-authored a detailed independent analysis of sediment in the harbor, funded by the Gladstone Ports Corporation, which analysed the levels numerous metals in the harbor, but not TBT levels.

He said while he knew TBT was a contaminant in the harbor, the key question was whether it could mobilise out of sediments it was attached to and actually enter the marine food chain in the harbor.

"Nothing's impossible, but it's a very remote possibility and there are other contaminants I'd be more concerned about like the metals we've measured," he said.

"It's a very remote chance that TBT would've increased post flood."

While the levels of imposex in molluscs was clearly rising at some sites in the harbor in 2009, Biosecurity Queensland said the levels of contamination found in sediments were lower than similar ports internationally.

A Biosecurity Queensland spokesman said the report of the independent scientific advisory panel which looked into the harbor issues did not recommend any expansion of testing of TBT.

"A literature review of potential chemicals that may cause the observed signs in fish did not suggest that TBT at environmentally relevant concentrations was a specific concern for fish health in Gladstone Harbour," he said.

"The focus of the study is fish health and water quality. The species selected for the study are those species with observed fish health issues and other species considered appropriate."

The literature review - a review of academic studies of immunosuppression and disease susceptibility - did not specifically recommend TBT be tested.

Nothing's impossible, but it's a very remote possibility and there are other contaminants I'd be more concerned about like the metals we've measured

But it did recommend any testing take a "multi-factory approach", which should include all potential contaminants that could be linked to immunosuppression in marine life.

Despite the results of mollusc tests completed not being released to date, the spokesman said a report including all of the findings of toxicology tests would be released by the state government in mid-2013.

Read Biosecurity Queensland's full statement here.

A key panel, the Ecosystem Research and Monitoring Panel, established as part of the federal approval for the WBDDP, was tasked in 2009 with "protect sensitive marine ecosystems" through a range of monitoring and reporting.

But a port spokesman said the panel was conditioned to be specific to marine megafauna and species listed under the Environmental Protection and Biodiversity Conservation Act, which did not include molluscs or any other species not listed.

In response to a question of why the panel did not order such an investigation, the port spokesman said the lack of molluscs being listed under the act, and there being "no or very little contamination", meant such an investigation was not ordered.

"As there was no or very little TBT detected in the dredging footprint, TBT contamination in the dredging footprint in the Gladstone harbour was not needed to be considered," he said.

Read Gladstone Ports Corporation's full response here.

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