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  • Facilitator: Thanks very much Peter and thank you all for coming. I should also thank the

  • Faculty of Science for giving Justin and I the opportunity to tell you a little bit about

  • our research this evening. Yeah, so letís get started. The ocean is arguably the earthís

  • largest habitat. If youíve ever seen a satellite picture or earth from space, itís a blue

  • plant. Thereís 70 per cent of ocean on our - excuse me, that was a bit fast.

  • So if we look at the surface area of the planet, its 500 million square kilometres. If we consider

  • the highest mountain and the deepest ocean trench - we already see some disparity there

  • - and if we consider the average land elevation of 840 metres and the average ocean depth,

  • we can do the maths pretty easily and know that the ocean forms the largest habitat for

  • life on earth. To Australia, as an island continent, the

  • oceanís very important. Our marine territory is larger than our land area. Itís relevant

  • for most of us in Australia because we live so close to the coast. Many Australians live

  • within 50 kilometres and use those coasts for their recreational and other amenities.

  • The ocean is incredibly valuable. The western rock lobster fishery, our largest fishery,

  • is worth up to $350 million a year. You might also be interested to know that our recreational

  • fishery is worth $2 billion dollars if it was sold. Tourism to the Great Barrier Reef

  • contributes over $5 billion to our economy each year and in New South Wales the marine

  • industry contributes $2 billion annually and itís important for jobs here in our local

  • region. Marine microbes do the work in the ocean.

  • Theyíre microscopic so not easily recognised but they constitute up to 90 percent of biomass,

  • of living biomass, in the ocean. Thatís roughly equivalent to 240 billion elephants. You consider

  • that in terms of size. What do they look like? Letís take a view - microscopically and zoom

  • that. This is a cyanobacterium called a Prochlorococcus. It typically grows in low nutrient water.

  • It is - I should say there that itís the most abundant photosynthetic organism in the

  • ocean. There are 10 to the power of 27 cells globally. Synechococcus is somewhat bigger

  • cyanobacterium. It also photosynthesises and is more found in nutrient-rich waters. An

  • Emiliana huxleyi is a coccolithophorids. Itís an organism that has these calcium carbonate

  • scales, which makes it fairly distinctive when you see it in water.

  • ll show you a picture of that a little later. This is a diatom example Fragilariopsis

  • Antarctica. As the name implies itís a polar organism grown below 50 degrees south typically.

  • Gymnodinium catenatum is a toxic dinoflagellate. These cells are somewhat larger, grow in coastal

  • systems and can cause problems for aqua culture and shellfish industries.

  • Lastly, Iíve provided two examples of - I guess theyíre microbes and microscopic as

  • single cells, but when they form these aggregations, here this is called a tuft and here a big

  • colony, this is Trichodesmium and this is Phaeocystis and they are macroscopic, you

  • can see those in the water. Collectively, these organisms are called Phytoplankton and

  • theyíre responsible for photosynthesis in the ocean just as we would consider land plants

  • here. We already know that there are rooted plants

  • in the ocean called seagrasses and you might have also heard about kelp forests. But overwhelmingly,

  • itís these small microbes that are responsible for most of the photosynthesis in the ocean.

  • These phytoplankton can grow and form large accumulations that are observable from space.

  • Here, this is a picture of Emiliana. As I explained earlier, it has these calcium

  • carbonate scales, which are highly reflective. This is the south coast of England and the

  • bloom is almost as large as that whole land area. This is a toxic dinoflagellate, here

  • blooming of the west coast of Tasmania and you can see it forms these what we call red

  • tides. That can be harmful for other organisms growing in the vicinity.

  • [PAUSE] What do they do? These microbes, these phytoplankton

  • are basically providing food for the rest of the food web. So plankton a microscopic

  • animals that consume phytoplankton and the zooplankton in turn are consumed by the higher

  • food webs, the larger animals in the ocean. Typically, our most productive oceanographic

  • systems are those in upwelling areas. Nutrients are brought to the surface of the

  • ocean when prevailing winds, parallel to the coast in this case, cause water to actually

  • move away from the coast and thatís replenished by deep ocean water. So thereís this circulation,

  • this uplift of water that brings nutrients with it, phytoplankton have the opportunity

  • to grow, they are consumed by zooplankton and they basically drive ocean production

  • and produce lots of fish for our marine fisheries.

  • Microbes are also critically important in the carbon cycle. They are basically converting

  • dissolved carbon dioxide in the ocean together with nutrients into particulate organic carbon

  • in the presence of sunlight. In doing so they also produce oxygen. This oxygen is really

  • critical for life on hearth. Humans wouldnít exist without oxygen. So itís the function

  • of these microbes that are actually allowing us to inhabit the earth.

  • This rate of conversion of dissolved or gaseous carbon dioxide into organic carbon is called

  • productivity. The rate of carbon fixation is what we typically measure in the ocean.

  • So weíll come back to that a little later. Each day more than a hundred million tonnes

  • of carbon are fixed in this way by these autotrophic photosynthetic microbes. The organism that

  • is the most abundant photosynthesiser in the ocean is responsible for 20 per cent of the

  • oxygen in the earthís atmosphere, a really significant proportion.

  • So just to summarise that or give you the comparison, the ocean is contributing about

  • half of global photosynthesis. Itís fixing about 50 per cent of carbon dioxide on our

  • planet annually. To show you than in a vertical perspective, here we have carbon dioxide,

  • diffusing into the surface of the ocean. It is taken up by photosynthesisers in the presence

  • of sunlight energy and in the presence of nutrients to form cells and these are then

  • consumed by the food web. Justin will talk further about the details

  • hidden behind this box that end up being very important to the fate of that carbon in the

  • ocean. But essentially, itís what happening here in the surface ocean that then determines

  • what amount of organic carbon gets delivered further down into the ocean sediments. This

  • is what we refer to as the biological pump. So the carbon dioxide in the surface is taken

  • up by the food web and organisms then are dying. Theyíre reproducing and dying as part

  • of their natural life cycles and they contribute then to the dead or decaying organic carbon,

  • this particulate organic carbon in the ocean. Itís comprised of dead phytoplankton cells,

  • zooplankton poo, which is these little oval dots and I guess the [tridal] remains of fish

  • and other larger organisms. Essentially that is slowly sinking through the ocean and some

  • of it reaches the ocean sediments and is buried there for millennia.

  • I do want to mention that diatoms, these organisms I illustrated earlier, and coccolithophorids

  • contribute to this vertical flux as we call it and actually may increase the ballast,

  • the weight of this material, and may cause it to sink faster. So it might matter if we

  • have a change in composition of phytoplankton in the ocean and that may change the rate

  • of sinking of this particulate carbon. Okay so yeah, looking at that in view, itís actually

  • - this biological pump is a natural carbon sequestration mechanism.

  • [PAUSE] So I guess in thinking about productivity

  • and the link between these photosynthetic microbes and climate, we now have very good

  • tools over large scales that can detect this productivity in the ocean. Thereís a satellite

  • sensor called SeaWiFS that was basically optimised to capture signals from the ocean and was

  • able to then quantify productivity quite accurately. Then we were able to link that to environmental

  • factors. This is a seminal study published in nature

  • several years ago that basically examined this productivity data on a global scale and

  • did this over a decade and considered the links between productivity and climate. Here

  • in the upper plot itís describing the pattern of sea surface temperature. Sea surface temperature

  • in red means itís hot, relatively, compared to blue which means itís cooler. In the middle

  • plot, it shows you changes in this primary production, this productivity.

  • This is nice because it actually - this third plot here - shows the change in productivity

  • over the 10-year time period that they did this observation. The parts of the ocean in

  • yellow indicate that with warming thereís a decrease in productivity. Okay, so a large

  • part of the Pacific Ocean here in the middle, when thereís increased warming thereís a

  • decrease in productivity. These observed decreases provide some indication of what will happen

  • with future warming. I want to zoom in now on Australia. To do

  • that I need to give you an oceanographic context. So weíre an island continent and unusual

  • in the global ocean. There are two warm tropical currents that move from north to south along

  • both costs. Typically, in other continents we see the opposite pattern here on the west

  • coast we see the currents move upwards, sorry, towards the north rather than towards the

  • south. Because these currents bring warm nutrient-poor

  • water, it really affects the oceanography in the region and the nutrient-poor water

  • means that we donít necessarily have a lot of productivity, especially on our west coast,

  • which would normally be a large area for upwelling. We know from long-term measurements at three

  • of the longest time series stations in the southern hemisphere - theyíve been collecting

  • data on ocean conditions from the 1940s - we know then from these long-term observations

  • that ocean circulation is changing. East Australia currently forms part of the

  • South Pacific gyre that is responding to changes in salt and temperature of the ocean and itís

  • speeding up. Itís increasing itís southward transport. The speed of this current is faster

  • in summer than it is in winter. So as a result, weíre seeing changes in the temperature profiles

  • in waters, particularly off Eastern Australia. Just to explain a little bit more about this

  • current, it forms in the Coral Sea, it intensifies in Northern New South Wales and at Smokey

  • Cape separates from the coast. Two-thirds of that flow moves across towards New Zealand

  • and the examining southward flow forms what we call eddies and coastal fingers. They can

  • move as far south as Tasmania. So these long-term data show as that the ocean

  • is warming. Hereve shown temperature over the time period 1940 to 2010 for these three

  • different locations. Rottnest Island is shown in red - this is the western station - shows,

  • letís call it a one degree percentary increase in temperature if we just plotted that linearly

  • over time that would be the average rise. Port Hacking, just south of Sydney, is showing

  • a similar rise in temperature, but certainly our most southern station here at Maria Island

  • off the east coast of Tasmania is showing the starkest increase in temperature indicative

  • of more East Australia current water moving southward. So now to link what these investigators

  • found in the global ocean and examining the Australian situation, we did a similar study

  • using the same optical sensor, satellite data. Over the same time period we did the same

  • analysis at Maria Island. What we see here, shown in this plot, is a growth rate of the

  • phytoplankton. So we take that as the difference in the amount of phytoplankton that might

  • have occurred over a three-monthly period in the spring and we see that over this decade

  • there has been a decline in the growth rate of those phytoplankton near Maria Island and

  • also a decline in the total amount of biomass of those microbes.

  • So it mirrors the global picture. Weíre seeing a decline in phytoplankton productivity and

  • increase in sea surface temperature. We know though that remote sensing only captures part

  • of the story. Itís looking at the surface layer of the ocean typically and not able

  • to capture any information at depth. So using other types of sensors that we put into the

  • ocean we can actually look at - excuse me, sorry - we can actually look at patterns in

  • the phytoplankton biomass with depth across large space scales.

  • I guess here similarly we have red as high amounts of phytoplankton and blue as low amounts

  • of phytoplankton. The first thing you might notice then is that we have this mid-range

  • - at 40 metres, we have this maximum chlorophyll. Itís certainly not all clustered up here

  • at the surface. The satellites then are typically only seeing something between zero and 20

  • metres. So thereís a large part of the picture that we still have yet to capture.

  • Just to explain what weíre using here, these are computer-guided underwater vehicles onto

  • which we can put different instrumentation including sensors that measure the amount

  • of phytoplankton in the water. This particular plot shows this transit of the glider from

  • north to south in the Sydney region some years ago. So weíre measuring productivity in the

  • ocean using oceanographic tools and Iím just showing you to estimate this rate of carbon

  • fixation this is a typical plot showing the change in carbon fixed with light intensity.

  • Iím summarising some data that was collected a couple of years ago on an oceanographic

  • voyage by our group and it shows a sea surface temperature plot indicating that weíre in

  • different water masses. Itís a very variable region of the ocean off New South Wales. This

  • red patch indicates the East Australia current, thereís a patch of really warm water relative

  • to the other water next to it and we examined the productivity at three different stations

  • indicative of those water masses. Here on the inner shelf coastal water we get

  • four point six units of productivity here in the East Australia current or just at its

  • edge we get one unit of productivity. But interestingly, when we were in the eddy, which

  • is basically mixing water from great depth and bringing it to the surface providing nutrients

  • for phytoplankton to grow in the surface, we have 14 units of productivity. So weíre

  • seeing a massive contribution perhaps of the eddies in stimulating productivity in this

  • region. [PAUSE]

  • The other thing thatís happened in the ocean over this time period from 1940 to today has

  • been a change in the amount of nutrients. If you remember itís not just the dissolved

  • carbon dioxide in the seawater thatís driving productivity, these cells require nutrients

  • and nitrogen and silicate are two major nutrients these guys need. So from 1940 to 2007 this

  • data set sows that firstly the nitrogen availability hasnít necessarily changed but thereís been

  • a huge decline in silicate. Silicate is essential for these diatoms to grow.

  • You remember I mentioned that theyíre important organisms that basically affect the way that

  • that particular organic carbon sinks into the ocean. So really, from 1970 when we first

  • started measuring silicate we see a potential for a great amount of decline in the potential

  • for diatoms to grow. We think thereís two things that may be happening to drive that

  • pattern, that decrease in silicate. The first is that silicate is introduced into

  • the ocean through weathering of rocks that comes from our continental land run-off. So

  • if thereís decreased rainfall across Eastern Australia then weíre likely to see decreased

  • silicate into the ocean. So this may be indicative of a drying continent. The second hypothesis

  • weíre going out to test is that the East Australia current water is actually going

  • to displace the water that exists on our continental shelf and it may contain low silicate and

  • itís basically driving this pattern - more EAC water, less silicate.

  • So our oceanographic work is really trying to answer this question. So to summarise then,

  • we have a long-term increase in temperature, particularly on our east coast. We have long-term

  • changes in nutrient availability and we have eddies that potentially affect productivity.

  • So this gives us great interest in studying this part of the ocean. We are now blessed

  • with a federally funded program to make more observations in the ocean.

  • This is called the Integrated Marine Observing System and itís funded until 2013 and itís

  • basically increased the number of instruments in the ocean by at least an order of magnitude.

  • So the Port Hacking station, which forms one of the longest time series, as I mentioned,

  • is based on a mooring now that basically is able to measure temperature at different depths

  • in the ocean and a whole bunch of other oceanographic parameters that we can use to better understand

  • the dynamics and productivity in that region. In October of this year UTS together with

  • other partners is going out into the ocean to investigate the EAC and the eddies it produces.

  • Iím going to let Justin now take you from my macro scale into the micro scale and uncover

  • the box. [PAUSE]

  • Facilitator 2: So as Martinaís described, these phytoplankton, photosynthetic microbes

  • are very important for carbon flux in our ocean and also controlling our food web. Iím

  • going to talk to you about another bunch of microbes in the ocean, the bacteria, specifically

  • the heterotrophic bacteria, which are the bacteria, which consume this carbon, which

  • the phytoplankton produce. So as Martina showed us, the phytoplankton

  • are at the base of the food web and they, along with the bottom parts of the food web,

  • control this biological pump, which is essential for the oceanís carbon cycle. So how do the

  • bacteria fit into all of this? So thereís two other parts to this story which we need

  • to consider when we want to look at the importance of bacteria.

  • One is when weíre considering phytoplankton photosynthesis, which Martina described earlier,

  • not all of their photosynthesis ends up being turned into phytoplankton biomass. In fact,

  • a significant proportion of the photosynthesis is released back into the water column in

  • the form of dissolved organic carbon. Now, this is one of the largest pools of carbon

  • on earth so itís very important in that global carbon budget.

  • But for a long time it was thought it was lost from the food web because these larger

  • animals canít consume dissolved forms of carbon. So the big question was what happened

  • to this carbon and how was it recycled? The second question is, what happens to all of

  • this material thatís being exported in the biological pump? Is it all reaching the bottom

  • of the ocean and are we getting a complete 100 per cent transfer of this carbon to the

  • ocean sediments? So the answer to both of these questions lies

  • in the activity of the bacteria in the ocean. So typically, when weíre swimming around

  • at Bondi or somewhere like that we donít like to think that the water weíre swimming