Who would have thought that the summer 2006 would pass into the New Year and give rise to temperatures which only a few years ago appeared incredible even for scientists. Warmer water, fewer fish and melting poles – and now?
published Deepwave Report 07
This is the question all media are actually dealing with. Scientists predict even warmer temperatures and some of them even go further. What in the past had been blocked by politics and economy cannot be dismissed now anymore. “Earth is warming and man is to blame for the most part of it”, the Spanish newspaper El Pais summarizes. It had access to the confidential report of the UN Intrergovernmental Panel on Climate Change (IPCC), which was published in parts only recently. According to the report, the mentioned temperatures would increase even further – even if the emission of greenhouse gases would be stopped.
Since 1850 the average surface temperature has increased, the IPCC is cited: “Observations of coherent warming in the global atmosphere, in the ocean, and in snow and ice now provide stronger joint evidence of warming” So, not only the atmosphere over the terrestrial zones has heavily warmed up, but also the oceans’ temperature in great depths has increased since 1955. Although the increase would be very low, it would be of great importance, because the amount of energy involved is very large. From measurements of the ice masses it can be derived, that their decline has already caused a rise of the water level in the oceans. Most notably it’s getting clear that there is an acceleration of the melting of ice, thus leading to the rise of the water level.
Global warming could also be observed with animals and plants, which either move into colder zones or change their blooming behaviour. Thus, the shift of the global climate doesn’t merely have effects on temperature and sea water level! In fact, chain reactions are occurring now, from which particularly the inhabitants of the oceans and poles are suffering. The species composition in the flat marginal seas of the oceans is changing increasingly. Fish stocks are affected as well. Earlier purely statistical data led to insufficient statements. The more specific the research works were carried out, the more imprecise were the results.
An artist of survival: The Eelmother (Zoarces viviparus)
Photo: Alfred-Wegener-Institut
Science study sheds brings light on to the darkness
A study published in Science magazine(1) is examining the connection between global warming and its effects on fish stocks. The crucial factor “thermally limited oxygen delivery” demonstrates that’s why the population density is affected. The fishes of the North Sea, which are exposed to seasonal larger temperature fluctuation have a higher thermal tolerance and a broader tolerance-window than for example fishes from the polar regions. Thus, the eel pout (viviparous blenny FAO), from the North Sea, can still exist under most difficult conditions. Experiments at the Institute for Oceanography in Kiel, carried out by Uwe Walter and Uwe Kils, demonstrated 1988, that even at low oxygen concentrations equivalent to 5% of the normal concentration, a survival of the eel pout is possible. That’s why this fish is particularly suited for research at the Alfred-Wegener-Institut für Polar- und Meeresforschung “Institute for Polar and Marine Research”, AWI) in Bremerhaven. Aim of the studies was to determine those physiological processes that would react first to temperature changes. The AWI researchers Hans O. Pörtner and Rainer Knust for the first time were able to demonstrate a direct connection between the thermally limited oxygen delivery in the eel pout and the changes of its population density.
Temperature fluctuations beyond the individual tolerance window can lead to changes
During the course of evolution, marine animals have adapted to the difficult conditions in the ocean, even have specialized. Therefore they only tolerate small changes in their habitats. But temperatures in polar regions, compared with those around the North and Baltic Sea, are more extreme – constantly deep. The fishes’ tolerance window is therefore more limited and only within this window they will grow and proliferate. The research results at the AWI demonstrate that the consumption and distribution of oxygen by respiration and blood circulation are essentially determining the tolerance of the animals and work only within limited tolerances. With increasing temperature, firstly the oxygen supply will get worse before other stress mechanisms – of biochemical origin - will react. After a short period of time, the oxygen supply will stop and the organism is capable of surviving but for a limited period.
Life is threatened not only underwater
In a recent item of its online edition, 26 / 27. 12. 2006, the news magazine Der Spiegel has shed light on the polar bear and reported statements of US researchers. Citing the article, “the melting of ice in the Arctic Ocean could drive polar bears to cannibalism”. Three cases have been documented in which starving animals have killed and eaten other polar bears. The ice regression makes it difficult for the white giants to reach the food resources and threatens their survival. Who doesn’t know the picture showing a polar bear floating lonely and abandoned on an ice floe—hoping to reach the rescuing and icy shore. Now just the US-government, held to be one of the greatest CO2-sinners, want to list the polar bear under the Endangered Species Act.
Hunting success like this is occurring less and less frequently as a result of ice regression
Photo: U.S. Fish and Wildlife Service
Environmentalists spoke of a “turning point”. The decision can be traced back to a petition of the environmental groups Greenpeace, Center for Biological Diversity and Natural Resources Defense Council (NRDC). “The time for half-measures and delay is over”, a spokesman of the NRDC said. Stepwise reactions will follow, important decisions will be made. Probably there will be a real rethinking with a lasting effect. But one item shouldn’t be missing in the balance: The benefit of this endeavour will not be obvious for decades, but nevertheless it must be carried on in the future.
Notes
PÖRTNER, H. O. and R. KNUST (5th January 2007) “Climate change affects marine fishes through the oxygen limitation of thermal tolerance” Science 315 (5808), 95-97. dx.doi.org/10.1126/science.1135471