20 year study finds major changes in Southern Ocean plankton
Continuous Plankton Recorder Project Leader, Dr Graham Hosie:
The continuous plankton recorder is a means of mapping the distribution and abundance of plankton. Very quickly and very consistently and very repeatedly over very large areas.
Plankton are the basis of the food web. They are important not only for the food web. They are important for the rest of us in terms of oxygen production, CO2 absorption and we need to map their distribution and abundance to see if it’s changing. If it changes there are consequences for the food web, there are consequences for us.
The CPR is a very simple device, its 1931 technology, it takes in water through a very small aperture at the front as it’s towed behind a ship and traps plankton between two sheets of silk. We then unravel that silk in the laboratory and we have actually got a continuous record of what the plankton existed in the water column over about 450 nautical miles or about 830 kilometres. And at the same time we are recording environmental data so we can match the two, the distribution of the plankton and distribution of oceanography.
The coverage we have got to date is roughly about 70 % around the Antarctic, and to date we have something like about 230 zooplankton species, and probably I think about this stage 70-80 phytoplankton species that we are also looking at.
We are just starting to see indications that we are not seeing as many krill in the sea ice zone as we used to get. We don’t know why, whether it is a change in numbers, a change in distribution or a change in behaviour.
In the sea ice zone, where most of the predators are found during the summer months, the whales, penguins, flying seabirds, it’s a keystone species. These animals have evolved to feed on an organism like krill which are about 50-60 millimetres in size. Now if they disappear or the animals can’t find them to feed on them, they’ll have to either shift their diet to something else, some of the smaller zooplankton, or maybe fish which feed on smaller zooplankton. So there’s consequences higher up, if you start removing keystone species.
We have also been mapping the biogeography of the species, so we have actually now produced a new Atlas on the distribution of what we call our top 50 species. That’s useful for researchers and other monitoring programs they can look in the Atlas and see what species they can expect to see in a certain area.
We need to continue the project, we’ve just set the foundation and we need to continue to look at the potential changes and the consequences. We can use plankton as a bit of an early warning indicating system of what may be coming and what’s happening. It’s the foundation of the whole Antarctic system, if we are not monitoring that part it’s very hard to explain what’s happening elsewhere.
Setting up to go south
Robb Clifton – Australian Antarctic Division Support and Coordination Manager: On average we’ll move between about 450 and 500 people to and from Antarctica over a summer period and that’s by ship and aeroplane. [Music]
Rob Bryson – Australian Antarctic Division Shipping Manager: Last season we shipped 3000 tonnes of cargo south. [Music]
Steve Daw – Australian Antarctic Division Aviation Manager: Arguably aviation in Antarctica is one of the three most challenging environments in the world. [Music]
Robb Clifton: Preparation for the season starts quite a long way out, effectively for us it’s about 12 months out. What we start looking at is the whole range of projects and activities we have to do and then try to work out how we can fit all of those projects and activities in together across the breadth of the season.
So for example this season we have about 80 different projects going to Antarctica. We’ve got voyages, so ships we are using, probably about 3 different ships. We are flying our aircraft, using our helicopters. So we look at that at a macro level across our four stations and how we slot all of those 80 projects in and in fact if we can, when they best fit and what resources they need on the ground.
So each person needs training before they go, they need to have considered what they need to take with them, the design of their science or their project. You know it might be a media project or a construction project, they need to consider the equipment they need, their power needs, what they need on station, whether they need field support and a field camp. How they are then going to get samples and equipment back to Australia, and all their contingencies. Because of course impacting all of this is the great thing we can’t control, which is the Antarctic weather.
Rob Bryson: The main stay and the back bone of our program shipping wise is the Aurora Australis, which has been doing the Antarctic work for the last 20 years. She is a super 1A ice breaker.
Our season is pretty much dictated by environmental conditions and we like to be at certain stations at certain times, dependent on what the ice is like. At the beginning of the season we will always aim to go to Davis first because we can break into the ice there and do our resupply over the ice. And then at the other end of the season we like to be at Mawson after about Australia Day because that’s when the ice is gone and we can actually get into Horseshoe Harbour and do a mooring with the ship and get in there.
So it’s all about timing people, resources, cargo and all that stuff around the environmental conditions. It’s all about herding cats and everything into the one place at the one time to get them out. So it makes an interesting job.
Steve Daw: The AAD operates an airbus 319 that takes our expeditioners to and from Wilkins airdrome from Hobart. The airbus flies about 75,000 nautical miles a year over about 20 odd flights. Normally about 12 flights-14 flights will be down to Wilkins airdrome, with the rest providing support to our other Antarctic partner nations. We also operate a couple of CASA 212 aircraft. The CASA 212’s undertake about 40,000 nautical miles of flying a year. The helicopters also undertake a large number of flights, sometimes up to 1500 flights a season, providing utility support, support to science and shuttling people to and from the skiway at Davis station as well.
Each season probably the most complicated challenge is ensuring that we are providing the right type of support, overcoming weather issues during the course of the season. For the pilots some of the most significant issues would be weather and waiting for the right weather to get off the ground. The pilots have a white on white environment, almost akin to flying in a ping pong ball which can be very demanding.
Robb Clifton: We have a really great team here at head office, who work with our teams through our station leaders on the ground to adjust who’s going, when they are going, when we are going to send certain flights and how we are going to fit the whole jigsaw together. So it’s a pretty non-stop activity that runs for about 6 months and certainly keeps us on our toes because it seems to changes very regularly. [Music]
Animation of krill mating in the Southern Ocean
Do krill have sex?
Here is what we know:
First there is the Chase.
Second in the Probe.
Third is the Embrace.
Fourth is Flex.
Fifth is Push.
Footage of krill mating in the Southern Ocean
Krill swarm at 507m off East Antarctica
Mertz Glacier under the microscope
Acting Chief Scientist Martin Riddle:
In January this year, 78 kilometres of the Mertz Glacier ice tongue broke off. Now this is a once in a lifetime event. What happened was a very large iceberg approached it from the eastern side, just gave it a little nudge and that sent it off ricocheting westwards.
The Mertz glacier is due south of Tasmania and it’s a very special place because adjacent to the Mertz glacier is the Mertz polynya. So most of the ocean around the Antarctic is covered in sea ice in winter, but polynyas are kept free of sea ice by the wind blowing the ice away from it. Paradoxically although they have no ice covering them, they are actually an ice factory, so they continually form sea ice and then it gets blown out and cleared.
The formation of sea ice creates heavy brine, heavy salt water, its heavy, its cold and so it sinks. In sinking it drives, pushes water in front of it and in fact the polynya areas that form Antarctic Bottom Water drive the ocean circulation.
The main purpose of the voyage this summer is to better understand what the ice tongues role is in the formation of the polynya and what its role is in driving the development of Antarctic Bottom Water. But it also provides an opportunity to better understand the effects on the biological systems in the region. So we’ll been using satellite remote sensing to see whether primary production is still high in the region.
We’ll also be using underwater videos to see what was living in the area that was previously covered by the ice tongue. We are expecting to see some very different communities. When the tongue was covering it, it was dark, it was very remote from open water. In those conditions very special biological communities develop, that are able to exist and thrive under what are very different conditions.
We’ll be visiting the areas where the ice tongue grounded and hit the continental shelf and getting a baseline that will provide us with a better understanding of how the seabed communities recover after a major disturbance. We are also going to revisit some cold water coral communities that we discovered during the International Polar Year. We want to understand just how common or rare these communities are.
This research is very important in understanding global ocean circulation patterns and the role of polynyas in driving those. More locally the work on the biological processes are important because they are very important areas of high biological productivity around the Antarctic.
The investigations of life under the glacier tongue, will inform our understanding of how life in the Antarctic has changed over time. It will also give us a better indication of what might change if we lose some of the ice shelves, the permanent ice shelves, around the Antarctic.