NARRATION
Gladstone in Central Queensland, major industrial hub, gateway to the Great Barrier Reef. Its harbour of Port Curtis is being transformed by a massive dredging project.

Mark Horstman
Gladstone has been an industrial port for several decades now. And there's evidence from other ports in the world that marine life can get sick if the heavy metals and mud are stirred up from the sea floor of harbours like this. So here's the question - could all the dredging that's going on here to expand the port cause disease in fish and crabs?

NARRATION
One one side of Port Curtis, a deeper channel is being dug for six new terminals to load giant ships with coal seam gas. The dredged mud is pumped behind a bund wall to reclaim more than 200 hectares of land for the Gladstone Ports Corporation. The rest of the mud is dumped outside the harbour, into the Coral Sea. Fish veterinarian, Dr Matt Landos believes marine life is being contaminated.

Dr Matt Landos
We're moving the metals out of the sediments, into the food web, into the animals.

NARRATION
Dr Leonie Andersen also trained as a veterinarian and runs the monitoring program for the Gladstone Ports Corporation.

Dr Leonie Andersen
All I can say from the results that we've taken, that the dredging hasn't made a difference to the water quality in the harbour, apart from some elevated turbidity. And people have the misconception that turbidity is toxic, and it's not.

NARRATION
There are two sides to every story, so I'm boarding boats from opposite sides of the debate. We're heading past the bauxite refinery and the coal loaders, into the industrial zone of Port Curtis. The turbidity here - that is how muddy the water is - varies naturally between wet and dry seasons. But Matt worries all the man-made changes in the harbour are enough to put the fish off having sex.

Dr Matt Landos
It's really the equivalent to having your mother come in and turn the light on. You only get one shot at it for fish in the year, and if they lose that opportunity, we've lost a whole year class of fish.

Mark Horstman
At this time of year in Gladstone Harbour, it's winter, there's no rainfall, the tides are really small. You'd expect the water to be really clear. In fact, normally, the visibility is about 3 metres.

Mark Horstman
What's your visibility reading?

Dr Matt Landos
10 centimetres of visibility in the water.

Mark Horstman
10 centimetres? Is that normal for this time of year?

Dr Matt Landos
No, it's totally abnormal. So this has deteriorated even further from when we were doing sampling just six months ago. And now the dredging has escalated further.

Dr Leonie Andersen
This sort of dredge is considered quite a clean operation, so the material that it is dredging is actually being sucked up and taken to a reclamation area.

NARRATION
Nevertheless, satellite images show plumes of turbidity extend as far as 35km from the main dredging site. The long plumes can't be explained only by natural forces, like tides or river discharge. On her boat, Leonie's job is to make sure the water quality meets Australian environmental standards. Her fleet maintains 18 automatic buoys that measure water chemistry every 15 minutes.

Dr Leonie Andersen
The breadth of parameters that we measure and the frequency of sampling and the extent of the sites that we cover is bigger than any monitoring project that I've heard of in Australia. It is quite extensive.

NARRATION
Downstream of the dredges, this boat carries an acoustic Doppler current profiler that bounces sonar off mud particles in the water column.

Dr Leonie Andersen
It sends a ping every so many minutes as they're motoring along at a slow pace. It's important to track dredge plumes and also to calculate the concentration of those plumes. And that helps us make sure that we're monitoring in the right locations.

NARRATION
While the mud particles are visible, the metals they carry are harder to find. After the dredging started, Leonie's team began monthly sampling for the metals that get dissolved.

Dr Leonie Andersen
They're the ones that are most important because they're the ones that are potentially bioavailable to the food chain.

NARRATION
There are few labs in Australia able to detect trace metals in marine waters. This is one of them - CSIRO at Lucas Heights in Sydney.

Dr Brad Angel
There's a whole suite of metals that we analyse for. Some of them include aluminium, cadmium, copper, cobalt, nickel, lead and zinc.

NARRATION
It doesn't take much dissolved metal to trigger affects in marine life. Measuring it needs sensitive techniques that can detect minute concentrations.

Dr Brad Angel
Parts per trillion.

Mark Horstman
Parts per trillion?!

Dr Brad Angel
Yeah. We need to be able to measure down to that kind of range to be able to measure the real concentrations in the environment.

NARRATION
Since the dredging started in Port Curtis, CSIRO has sampled dissolved metals for three days and didn't find any contamination hotspots. However, they were able to compare their samples with what they collected nearly ten years ago.

Dr Simon Apte
We saw a slight increase in dissolved copper and zinc concentrations in the harbour, compared to back then. We found detectable concentrations of aluminium in most locations across the harbour, which are above the environmental concern level that applies in Australia.

NARRATION
To know when metal levels become toxic, water quality standards set limits called 'trigger values'.

Dr Leonie Andersen
The fact is that the dissolved metals haven't gone above those triggers. And those triggers are set based on a lot of science.

NARRATION
But not yet for aluminium. There's currently no water quality standard for aluminium in marine waters because the research is still being done. CSIRO is exposing algae to different levels of aluminium to discover how much is toxic.

Mark Horstman
Are algae often neglected?

Dr Lisa Golding
They can be. They're not often seen so it's important to look at them because they drive a lot of the processes that are going on with an ecosystem.

NARRATION
It's crucial to have reliable toxicity data, because when algae die from metal poisoning the whole food chain suffers.

Mark Horstman
Port Curtis is a beautiful estuary full of life. In fact, where I am right now is inside the Great Barrier Reef World Heritage area. So you'd expect a place like this to support a productive fishery.

voice off camera
Can you tell what's going on on the skin there?

NARRATION
And it did, until a year ago, when fishermen reported sick fish with cloudy eyes, rashes, eroded fins and sores. Fisheries Queensland banned all fishing in the harbour for three weeks and launched an investigation four months after dredging commenced.

Dr Matt Landos
Well, there's an important thing in investigating an outbreak, is you need to try and sample at the time of the outbreak.

NARRATION
So Matt started his own independent research, funded by donations from the public and the seafood industry, working with fishermen to try and figure out what was happening.

Dr Matt Landos
We had a look at the gills of the fish for damage to the gills. We then did a full necropsy on the animal, examining all of the internal organs.

NARRATION
Matt took bacterial swabs and organ samples from a number of species.

Dr Matt Landos
We identified skin disease in a whole range of fish. We also identified problems internally in the fish with parasites - what appears to be increased intensities of parasitic infection.

NARRATION
Bob Appo has seen this before. Over the 36 years he's been a crab fishermen here, the harbour has been dredged three times.

Bob Appo
Every time it dredged, the fishing just went down - the prawns, the fish, the mud crabs, everything. I've gone from 150kg to about 50kg on a good day. And this is only just the start of it. There's another three years, at least, dredging to go on.

NARRATION
He's helping Matt investigate a disease in mud crabs called 'rust spot' that ulcerates their shells.

Dr Matt Landos
That one actually has a rust spot on it.

Mark Horstman
Are you right there, Bob? (Laughs)

Bob Appo
Yeah, I'm right, yeah. I'm watching me toes. (Laughs)

Dr Matt Landos
This little orange spot here is what is unique as a disease to the crabs in Gladstone Harbour. And that becomes a weak spot and bacteria like to invade weak spots. When crabs get increased rates of exposure to metals, like copper and zinc, their shell doesn't re-form properly. And so after they've moulted, they don't end up with a nice hard shell to protect themselves. They end up with these deformed shells. It progresses in many of the crabs to actually go right through the shell.

NARRATION
This disease was first studied by Leonie back in 1998.

Dr Leonie Andersen
I don't think the prevalence of disease has changed at all since I last investigated. I think that people are just more observant and now are seeing things that they might not have noticed before.

Mark Horstman
So looking at the bigger picture, do metals have anything to do with the shell disease?

Dr Leonie Andersen
I can't... We didn't find conclusively that that was the case.

NARRATION
Matt's theory is that the immune systems of harbour animals are being overwhelmed by multiple stressors, like noise, turbidity and mixtures of heavy metals.

Dr Matt Landos
On this case, we should be looking, first, at the animals. They're telling the story. If they're sick, there's something wrong with their environment.

Mark Horstman
Is it not conceivable that dredging could be one of the factors that are contributing to what people are seeing in fish and crabs?

Dr Leonie Andersen
I just don't see that, when, by default, by maintaining the water quality within Australian standards, we are maintaining ecological health. You wouldn't include fish disease monitoring in a standard dredge project. And particularly when you know your water quality is of a high standard, you're sort of going, 'Well, you know, is there anything more we should do?'

NARRATION
Solving the mystery of the disease means following the trail of dissolved metals to see how much ends up in the animals of Port Curtis.

Dr Simon Apte
Well, I think it's quite important to look at metal concentrations in fish tissues, and we've certainly recommended that as a follow-up to our study.

Mark Horstman
Has it been happening?

Dr Simon Apte
Not that I'm aware of. No.

Mark Horstman
Why is that?

Dr Simon Apte
I don't know. It's up to the regulators that look after the system to really prioritise the research studies that need to be done.

NARRATION
As the dredging continues, Queensland Government agencies are yet to release all their results from the first 12 months of studies. But Bob Appo has had enough of catching fewer crabs that are too sick to sell.

Bob Appo
It's lucky I'm at the age where I can say, 'Well, that's enough.' But I still love it, that's the thing. It is heartbreaking that this is happening. I just don't even wanna come near it.

STORY CONTACTS

Dr Matt Landos 
Future Fisheries Veterinary Service
East Ballina, NSW

Dr Leonie Andersen 
Vision Environment Queensland 
Gladstone, QLD

Dr Brad Angel 
Ecotoxicologist, CSIRO Land & Water,
Lucas Heights, NSW

Dr Simon Apte 
Environmental analytical chemist
CSIRO Land & Water
Lucas Heights,NSW

Dr Lisa Golding 
Aquatic ecotoxicologist,
CSIRO Land & Water
Lucas Heights, NSW

Bob Appo 
Crab fisherman, 
Gladstone