A Warming Environment for Antarctic Marine Species

31 Oct 2005 - Interviews, Logistics, Flora & Fauna

Professor Lloyd Peck

After his recent interview by BBC NEWS for an article entitled 'Antarctic species feel the warmth', SciencePoles has put further questions to Professor Lloyd Peck of the British Antarctic Survey to try and shed more light on his research and the effect of warming sea temperatures on Antarctic marine species.

Professor Peck, how did you come to study the temperature sensitivity of Antarctic clams?

Hans Portner of the Alfred Wegener Institute and I were studying bio flexibility and physiology changes in response to temperature changes, or how animals can survive in extreme conditions and how they can adapt to changes in their habitat. With sea temperatures increasing around the Antarctic Peninsula, it is important to understand how life is responding and Antarctic species such as clams are possibly the least capable of coping with temperature change of any group of animals on the planet. Hence their relevance and why we are studying them.

Can you explain why rising temperature can become a problem to the clams, scallops and other marine bottom species?

All animals have problems under stress and have increasing difficulty to adapt the further you take them away from their natural habitat. Whilst animals in temperate latitudes are more adaptable because of the greater temperature fluctuations in these environments, polar sea bottom species live in some of the most temperature stable environments on Earth and have therefore evolved into highly temperature restricted organisms with very little physical ability to cope with change or a rise in temperature. They have evolved to live at 0°C over 10-15 million years. They die when temperatures are raised to 5°C, and lose the ability to perform normally at about 2-3°C.

The cold also means that these organisms produce larger, but fewer eggs for reproduction and have very slow rates of growth, developments and metabolism, thereby restricting the speed at which they can evolve and adapt, as well as their ability to make proteins. What's more, because the Antarctic landmass encircles the South Pole, marine animals are unable to migrate further south to colder waters when sea temperatures rise in and around their local habitat.

What is your gut feeling about the adaptability of bottom species? What do you think will be their reaction to warming temperatures?

Because of their reduced physiological flexibility and capacity to adapt, numbers will certainly decrease, which, in turn, will probably translate into other problems higher up in the water column (i.e. other species dependent on bottom species). I think these problems will become increasingly apparent over the next ten years.

What consequences would a reduction in sea ice as a result of warming temperatures have for Antarctic marine species?

Krill, which is a focal point in the Antarctic food chain, is dependent on sea ice, both for feeding and for surviving the winter. In winter, its preferred habitat is close underneath the sea ice. It also feeds on algae that grows in between the ice crystals and on phytoplankton on the ice edge. If sea ice decreases around the Antarctic continent, so will the circumference of the sea ice edge, thus reducing the growing area for phytoplankton and de facto the amount of phytoplankton or biomass for krill to feed on.

Over the last few decades numbers are already estimated to have decreased by up to 80% in some areas. And whilst data on to the broader impact of this decrease across the water column is very thin, it is thought that it has impacted on the middle (size) consumers of krill such as fish and jellyfish and is probably linked to the fluctuations in seal and penguin numbers. Only whales' numbers are on the increase, but that is because they were brought close to extinction by 19th and 20th century whaling activities and have only begun to recover, their numbers still well below even what a heavily reduced krill biomass is able to support.

Why is it that the Antarctic circumpolar current is not keeping Antarctic waters cool as was predicted in past computer models?

This simply goes back to the computer models themselves, and the data they are based on. Because of its remoteness and the harshness of its environment, the Antarctic region is notoriously difficult to monitor. The result is that the data are quite scarce and do not go far enough back in time. Therefore we still have an incomplete understanding of regional systems in the Antarctic and there is still a wide margin for error for computer models.

As for the circumpolar current, it is important to understand that it is responsible for driving the Earth's oceanic thermohaline circulation by pushing cold water North and thus replacing it by drawing in warm water into its system. And because the ocean is divided into several layers, we can have a situation where the top layer remains cold, with mid-water and deep-water layers warming up. As with everything, however, data remains scarce and the picture incomplete.

Is biological data taken into account in modern computer models such as the British Antarctic Survey's COMPLEXITY programme?

The simple answer to that question is no. At the moment, it is still regarded as a box on the side and much more effort is put into physical modeling than biological modeling. However, it is clear to me that the effect to the biosphere will become increasingly apparent within the context of climate change, at first with the spreading of deserts and the decrease of rainforests, but also through its effect phytoplankton both inside and outside of the polar regions. Over time the responses of the biosphere will be some of the largest factors in dictating the final outcome of climate change.

By: Jean de Pomereu