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.

Iíll 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. Here Iíve 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.