Science Show

Andrew McMinn describes the challenges of 24 hours of darkness, and 24 hours of daylight, and the amazing transmission that takes place over about 6 weeks.

Andrew McMinn studies phytoplankton and zooplankton and observes how they cope with the extended darkness.

He suggests these organisms can survive in the darkness in low temperatures. It won't be so easy in the dark at higher temperatures.

Transcript

This transcript was typed from a recording of the program. The ABC cannot guarantee its complete accuracy because of the possibility of mishearing and occasional difficulty in identifying speakers.

Most scientists avoid periods of complete darkness at the poles, but Andrew McMinn makes a virtue of it, going south when it's night to see how plants survive without photons. So isn't it hard to get there at all in winter?

Andrew McMinn: That's true, it's difficult. To go and study in Antarctica, mostly you have to spend the year down there, and most scientists are too busy to do that. So the scientists that have gone down tend to be PhD students and young post docs. Older scientists have tended to avoid these long times away from home.

Robyn Williams: So as a result of it they miss the night.

Andrew McMinn: They do, and the night is very important. What happens subsequently in spring and summer is very, very much determined by what happens during the night. A lot of people have just assumed that everything shuts off, that it's virtually lifeless, but that's not the case. There are a lot of things going on there, and what happens the subsequent spring is really based on what happens and what survives the long, cold winter.

Robyn Williams: Have you been sacrificing your career and spending years there at night yourself?

Andrew McMinn: Well, I'm very fortunate...I've just come back from Antarctica, I've just come back from spending some of winter in Antarctica. The Australian program and most other countries don't allow access during winter. But the American program flies one flight in in the middle of winter, so I flew in in the middle of winter and I've just come out at the beginning of spring. So when I arrived there it was completely night and when I left it was completely day. So in the space of six or seven weeks we had the full transition from all night to all day, so it was wonderful.

Robyn Williams: When it's night, is it really dark so that you can't do very much except with torches and so on?

Andrew McMinn: Yes, it's really, really dark. It's as dark as it is anywhere in Australia in the middle of the night...stars, auroras, all that sort of thing. And when it's light, of course it's very, very light. I've been there lots of times, 12 times in the past, and I've only gone down in summer and we have 24 hours daylight. So it was really nice to see this very rapid transition from total dark to total light.

Robyn Williams: And what were you studying there? Were you watching creatures? Are they out in the night?

Andrew McMinn: I was looking at the little things, the little creatures that live in the ice and under the ice. These are the primary producers, the grasses of the Antarctic. I was looking in particular to see how well they were surviving, dark survival, how many of them are surviving and how active they are during the winter.

Robyn Williams: Which creatures?

Andrew McMinn: These are phytoplankton, there are small single-celled algae, and also small zooplankton, the very small little animals that graze on them.

Robyn Williams: And what did you observe when you were studying these creatures at night? What did you actually see going on?

Andrew McMinn: My hypothesis is that it's going to be a lot harder for these organisms to survive when it gets warmer. It's a lot easier if it's dark and cold than if it's dark and warm, because plants respire, they have to use energy to live, just the same as animals do, but in the light they're able to get their energy from the sun. But if it's dark they're not able to get their energy from the sun, but as it warms up they're running faster so they're using more energy. So we think that it's going to knock out a lot more creatures during the polar night if the temperature gets warmer. So that's what we're really studying when we're down there this time.

So the light-dark cycle isn't going to change with climate change, that's a planetary phenomenon which is going to stay the same, but the temperatures are changing. So this night and warm thing is the thing we're really looking at.

Robyn Williams: Any signs of change already?

Andrew McMinn: Not yet. The ice is still very thick. The ice is two metres thick when we were down there, and the temperatures were still very cold, so it hasn't started happening yet. It has certainly started happening up in the Arctic, and I'm working up in the Arctic as well, and in fact we're looking at what's happening now in the Arctic to understand what will happen in the Antarctic in a few decades.

Robyn Williams: Any results so far that you can actually write up?

Andrew McMinn: We were surprised to find how active the ecosystem was under there. The plants were surprisingly healthy, much more healthy than we had expected them to be. We thought that coming out of the long winter they would be really moribund and struggling to survive. There was very little there but what was there was quite photo-synthetically active, they were quite happily growing at extremely low light levels and of course very cold temperatures.

Robyn Williams: How do you account for that with such dim light? Because you've got to make your food somehow.

Andrew McMinn: That's a good question. These organisms are extremely well adapted to very, very low light, and they're photosynthesising in what to us looks dark. The levels of light...it's difficult to explain...in terms of light units these organisms had half a unit, whereas in a normal sunny day in Australia we would have something like 2,000. So you compare the 2,000 to one-half is the amount of light they're getting to photosynthesise in, and they're doing it relatively well.

Robyn Williams: In circumstances like that do you see any big creatures up on the ice at all wandering around?

Andrew McMinn: No, anything with any sense moves north. So there's virtually nothing there in winter. There are a few emperor penguin colonies but there were none near us, and they're the only large organisms that live on the ice. Only the little things...the microscopic organisms are the only things that are left.

Robyn Williams: And what about for humans? What was it like actually living there for that period? I know it's only about six weeks, but still...

Andrew McMinn: This was really good, this was the first time I've been a winterer. Normally we go down in spring and we arrive there and these people have been isolated then for six months most of the time, and we've always heard these stories about how they resent us and how hostile they are to us, and this time the boot was on the other foot. So I was down there for winter and we felt the hostility of the new scientists coming in in the beginning of spring. It's very unusual.

Robyn Williams: Andrew McMinn is a professor at the University of Tasmania in Hobart and director of the Antarctic Institute there. And on ABC Radio National during this year you can hear a few programs on this theme as we go pole to pole. More soon.

Guests

Andrew McMinn
Director Institute of Antarctic and Southern Ocean Studies Director International Antarctic Institute University of Tasmania Hobart
http://fcms.its.utas.edu.au/scieng/iasos/pagedetails.asp?lpersonId=1475

Presenter

Robyn Williams

Producer

David Fisher

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