Ponds of Bratina Island no match for Waikato University student
2 August 2011
Welcome to Scott Base: The University of Waikato's Stephen Archer at Scott Base, Antarctica.
There can be fewer environments for life that are harsher than the ponds on Bratina Island, near New Zealand’s Scott Base in Antarctica, and there is no shortage of diversity, as Waikato University student Stephen Archer is finding.
Frozen solid for most of the year, the biological communities of these ponds are among the simplest known, consisting almost entirely of bacteria and other microorganisms. In just one pond, Stephen recorded 583 distinct microbial varieties, which distributed themselves according to depth.
“It’s really interesting being able to see these differences,” he says. “This pond was 48cm top to bottom, and over that distance we saw a huge change in the geochemistry and the microbial populations, which matched up quite nicely with each other.”
The ponds, which are mostly only a few metres across, vary hugely in their physical properties – some are freshwater, some are highly saline, and they also differ in pH and oxygen levels. There are even gradients within individual ponds. The annual thawing and freezing cycle also produces major shifts in salinity and other variables which dramatically affect the microbial flora.
Stephen, who first took samples in the area in 2009, says the ponds provide a unique research opportunity because there are very few places which house such extreme geochemical variability within such a small area. “Within three days of sampling for my Masters I sampled nine very diverse ponds which you’d normally have to travel kilometres for. Because of the extreme environment they’re unique, and because the communities are so simple you can describe them a lot more accurately, and they can then be used as a model for more complex environments.”
As well as bacteria the ponds contain archaea, a superficially similar group of microbes which have radically different biochemistry and which often live in extreme environments. Stephen analyses the DNA of his microorganisms using a technique called 454 sequencing, which he says is much faster and provides far more information than previously available methods, and by targeting genes which are unique to one group or the other he can readily distinguish bacteria from archaea. While the ponds’ surface layers appear to be dominated by bacteria, and particularly at some stages of the season by the photosynthetic cyanobacteria, the cold and often highly saline bottom layers contain a high diversity of archaea.
Now working on his PhD, Stephen is returning to the ice in January. The visit is scheduled to take just over two weeks – short for an Antarctic research trip. “Which my wife is very pleased about, because I’m going to be leaving her with a little two-year-old and our second child is due a couple of weeks after I get back.”
In that time he has three separate projects to work on. The first is an extension of his Masters work, sampling in more detail, and using RNA – a chemical relative of DNA involved in protein synthesis – to identify which microbes are active and metabolising.
He will also be evaluating human impacts on the area, by taking soil samples from the surrounding landscape, looking for indicators of human presence such as faecal bacteria or human DNA, and seeing how far from the campsite these are found. “The camp on the island has been there since the 80s, and by Antarctic standards it’s visited a lot. We’ll be developing some techniques for evaluating how far-reaching human impact is; hopefully it won’t be very far, because one of the central themes of Antarctic science is trying to keep the environment as pristine as possible,” he says.
Deep in the Pond: Taking samples from one of the ponds on Bratina Island.
Another question he will investigate is just how sensitive the ponds are to contamination. It has been assumed that they’re highly vulnerable to disturbance, and for this reason he will take pond water back to the university to set up artificial versions, rather than experimenting on the ponds directly.
“If you can dump a teaspoon of soil from your back yard into one of these ponds and nothing happens then we will know that they’re not quite as sensitive as we feel, and that will be interesting to know. That being said we suspect that if you’re not meticulous in cleaning your sampling gear you will probably destroy a system that is extremely unique.”
Stephen will also use the artificial systems to assess the potential impact of rising temperatures on the ponds, to see whether the most highly specialised microbes and their unique biochemistry are likely to be displaced by organisms which prefer less severe conditions if temperatures continue to increase.
“If they are going to be destroyed we need to increase our efforts to describe them before they’re gone because there could be something useful in there that may well disappear. Also, because it’s Antarctica, it’s our duty as researchers and as signing members to the Antarctic Treaty, to try to preserve the Antarctic environment as best we can, and the best way to preserve is to understand.”
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