Queensland's Great Barrier Reef catchments will serve as a living laboratory.

Research to reduce sedimentation to the GBR lagoon.

Turning the tide on reef water quality

Evidence of coastal ecosystem degradation in the Great Barrier Reef has been linked with increased land-based runoff of suspended solids, nutrients and pesticides resulting from clearing and agricultural land use.

  • 9 September 2011 | Updated 17 June 2013

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Learn more about Baseline pollutant loads to the Great Barrier Reef.

Glen Paul: G'day, and welcome to CSIROpod. I’m Glen Paul. The long term survival of Australia’s world heritage listed Great Barrier Reef is under threat from various pressures including declining water quality in the reef lagoon. Pollutants such as sediment, nutrients, and pesticides in waters that flow from agricultural lands in the catchments adjacent to the reef have been found to be the major cause of the decline.

In an effort to combat this, CSIRO is conducting research in the Great Barrier Reef region to ensure the long term protection and restoration of reef ecosystems, and the sustainability of agricultural land uses.

To discuss it I'm joined by Dr Frederieke Kroon from CSIRO Ecosystems Sciences. Frederieke, I’ve seen the satellite images detailing plumes of brown river water flowing out into the Great Barrier Reef Lagoon, and while you could say well, there’s the evidence, there’s obviously a lot more to it in establishing just what sort of pollutants are in the water.

Dr Kroon: That’s part of the work that we’re doing. We’re certainly looking at remote sensing images to see where flood plumes travel to during the wet season from the rivers to the reef, but an important part of our work is to determine what pollutants may be present in those flood plumes, and where they’re actually coming from in the GBR catchment.

Glen Paul: Right. So what sorts of pollutants are being carried in with these run-off waters?

Dr Kroon: Well, there’s suspended sediments that come from the land basically, like are mainly caused by processes like erosion. There's nutrients such as nitrogen and phosphorus, and whilst they’re naturally present in waterways in the GBR catchment, they’ve increased significantly since European settlement, due to agricultural development and industries – for example due to the use of fertilizers.

And the third pollutant of interest to us are pesticides, and of course they were never present naturally, and they’re used in various agricultural settings, as well as urban and private settings as well.

Glen Paul: And obviously they’re going to have some major impacts. What kind of affects are you seeing on the reef ecosystem?

Dr Kroon: Well, the scientific consensus between, or amongst several research institutions that work in the reef, is that water quality is still have a detrimental effect on the reef ecosystems, and some examples are sediment can smother coral reefs, particularly closer to the coast, and if that is not washed away or removed then covers will eventually die – they cannot survive when they’re covered by sediment.

Another effect of the pollutants that we’re looking at is increased growth of phytoplankton. These are small microscopic sized plants which thrive on nutrients in the water, just like plants on the land, and we’ve seen higher concentrations than you would expect in tropical reef ecosystems, and this is related to an increased concentration of nutrients coming down from the rivers to the reef.

Glen Paul: And what of herbicides and pesticides?

Dr Kroon: Herbicides and pesticides have certainly been detected right throughout the GBR Lagoon, as well as in the rivers that drain into the reef lagoon. The effects in the ecosystem itself in the wild are only now started to be studied by scientists, including myself and people from other institutions.

But in the lab we’ve certainly documented effects of herbicides on the zooxanthellae, the small algae that co-exists with coral polyps, and because they’re herbicides, obviously they affect plants, and so they affect these little microscopic plants that live with the corals as well. And so it affects the survival and the condition of coral polyps, because they affect the organisms that they co-exist with, and that they rely on for nutrients.

Glen Paul: Absolutely. What about the techniques that you use to analyse the water?

Dr Kroon: Ooh, we use several techniques. As I already mentioned, the remote sensing is one technique to look at where the flood plumes travel to in the reef. In the rivers itself, and in the agricultural landscapes, we have several monitoring stations that can sample the water automatically, particularly during floods when most of the pollutants are mobilised and transported to the rivers and the reefs.

We also do, where possible – because obviously when there’s floods it’s very difficult to get access to the rivers and their associated systems – we also try to do manual sampling where possible, and where required. For some pollutants we can’t use automatic stations for example, because they need to be frozen straight away, or processed straight away for proper analysis. So we use a combination of manual sampling and automatic sampling.

Glen Paul: OK. And this has led to CSIRO producing the first comprehensive estimation of pollutant loads in all rivers draining into the Great Barrier Reef. How will this report by used by authorities?

Dr Kroon: Yeah, our monitoring is part of a larger monitoring program in the reef that has resulted in quite a large water quality database that, indeed like you said, we’ve used to estimate pollutant loads in certain rivers of the Great Barrier Reef. In other rivers, where such data is not available, we have relied on the most recent modelling estimates of pollutant loads, and combined that has a result in the first comprehensive estimate of pollutant load estimates to the Great Barrier Reef.

Now these load estimates, it’s an estimate of a particular point in time, and it will be used to track progress in water quality improvement in the future, as a result of changed management practices in agricultural industries, such as sugarcane and grazing.

Glen Paul: And what is the mood then among farmers, and how is it being sold to them to work to reduce the run-off?

Dr Kroon: The farmers have been collaborating with research organisations and Government agencies to, for example, develop new practices that reduce fertilizer run-off, or pesticide run-off, or minimise erosion on their properties. And working collaboratively on these projects, the researchers get an understanding of the improvements in water quality that can be made by changing practices, as well as at the same time look at the effects on productivity in these agricultural industries.

And in a lot of cases there are win/win situations, where both the productivity for the farmers’ increases, as well as water quality improves, and obviously in those cases farmers are very interested in taking up those practices.

Glen Paul: OK. So then what of the added affects of global warming and ocean acidification – are they inclusive in the conservation strategy?

Dr Kroon: Climate change is seen as the biggest threat to the Great Barrier Reef and its ecosystems. The other threats that have been identified to the reef are the decline in water quality, and a couple of other ones. So, management of water quality is seen as a way to improve the resilience of the reef in the face of climate change.

There's certainly additive affects that have been demonstrated, where the affects of climate change and a decline in water quality result in detrimental affects to coral reef health. So when you add them up the total effect is actually more than the sum of the two. 

So by managing water quality we can certainly reduce the stress on the Great Barrier Reef, and as such improve the resilience of the reef in the face of climate change.

Glen Paul: OK. So what then do you think should be the next step in the conservation of the Great Barrier Reef?

Dr Kroon: I think an important part of that is to determine what Great Barrier Reef we actually want – what sorts of ecosystems do we like to see, and what sort of organisms would we like to see living in those ecosystems.

The Great Barrier Reef is obviously a world heritage area, and was declared as such because of its universal natural values. But when you go to the level of managing the Great Barrier Reef, more detailed information is needed about what we like to see out there – is it coral reefs or is it seagrass beds?

And having that information on what sort of ecosystems we’re actually keen to have will certainly inform management in the climate change arena, as well as in the water quality arena, and in other threats.

As far as the water quality issue is concerned, what I’m keen to see myself is to get a good understanding of what we need to do in the catchments to achieve the water quality guidelines that have been set for the Great Barrier Reef Lagoon.

And that would allow us to look at where exactly we need to change management practices, and possibly land use, to achieve the water quality improvement in the rivers, and at the end of rivers, and to the reef, to have the greatest chance for a healthy and resilient reef into the future.

Glen Paul: Right. Well I hope so. I’d hate to see it turn into a giant patch of kelp. Thank you very much for talking to me about the research today, Frederieke.

Dr Kroon: OK. No problem at all. My pleasure.

Glen Paul: Dr Frederieke Kroon. For more information find us online at csiro.au. You can like us on Facebook, or follow us on Twitter at CSIROnews.