Life in a frozen environment – What´s in it for us?

Life on the moons of Jupiter, and a source of healthy polyunsaturated fatty acids and low temperature enzymes that could even make washing powders work at low temperatures: The microbes that live in Antarctic sea ice may hold the answers to a host of everyday applications as well as revealing how life forms might be able to exist on frozen planets. One of those interested in sea ice and the life forms it supports is Dr David Thomas of the University`s School of Ocean Sciences. He is presently the only scientist in the UK working on the biology of the ice dwellers, and together with German colleagues they are at the forefront of studying the life within the sea ice. In the cover article of the current issue of `Science`, (issue date 25. 01 02) he explains the current focus of scientific interest.

Sea ice, that at its maximum extent covers over 13% of the earths surface, is one of the largest ecosystems on earth covering an area as big as the deserts or tundra. Instead of being a white lifeless desert, the pack ice is home to a host of tiny plants and animals that can thrive in such large numbers that it can actually colour the ice brown by its presence.

A new breed of astro-biologists` look to these frozen seas for clues about the life forms that could exist on frozen planets. If such creatures are able to adapt to life at -20 on earth, might the same adaptations work in the far colder, far thicker frozen surfaces of Jupiter`s moons Europa, Ganymede and even on a past Mars? Such work would also cast light on the Earth`s own snowball earth` period.

Another focus for scientists` attention is the various mechanisms for survival deployed by an array of microscopic organisms. Isolating and understanding the mechanisms which allow viruses, bacteria, algae and small crustaceans to adapt to the extreme environmental changes they experience in the antarctic and arctic seas could lead to a range of new applications for technology.

Sea ice isn`t like the ice we make in our freezers, but instead is permeated by a labyrinth of channels and pores filled with a concentrated brine. These channels are home to the microscopic organisms trapped in the sea-ice so not only do the organisms have to survive their incarceration into a semi solid matrix, they also have to survive drastic chemical changes to their surroundings. The also have to withstand damage by ice crystals which constantly form around them.

“To survive, organisms need to be able to cope with extreme chemical changes not least to be able to endure the osmotic shock caused by the changes between the external solution and their own internal fluids- both when the sea freezes when they can become dehydrated due to the high brine content of their surroundings and when, having lived in the extremely harsh solution, they are bathed in almost pure water as the sea ice thaws,” Dr Thomas explains.

Many sea ice organisms have enzymes specially adapted to working at high salt concentrations combined with low temepratures. A host of antifreeze compounds are produced, that not only stop the cell contents freezing, but that can be released to melt the ice directly surrounding the cells. In the cold, membranes, which are made of fats, become solid meaning that they don`t work any more. The ice dwellers have adapted by changing the types of fats they build into their membranes so that they still function at temperatures akin to those found in a normal domestic freezer.

“Once isolated, the enzymes which protect organisms from the effects of cold could also have applications for a host of industries ranging from cleaning agents to food processing,” said Thomas.

“The most pressing line of research though, is how climate change will affect seasonal changes in the extent of the sea ice. The organisms which thrive in the sea ice are key to the survival of the entire polar food webs. Krill, small shrimp-like creatures, which are the staple food of squid, penguins, seals and baleen whales feed on these microscopic organisms. We need to consider what effect a reduction in sea ice due to global warming will have on these organisms at the base of the food chain as well as looking at other factors which rule weather systems.”