Newspaper article The Christian Science Monitor

More Heat = Less Oxygen ; Long before It Gets Unbearably Hot, Researchers Find, a Mild Temperature Rise Can Shrink the Population of an Animal Species

Newspaper article The Christian Science Monitor

More Heat = Less Oxygen ; Long before It Gets Unbearably Hot, Researchers Find, a Mild Temperature Rise Can Shrink the Population of an Animal Species

Article excerpt

For many species, the threat of global warming is more than too much heat. You can get temperature-related effects that may not be what you expect. Subtle environmental change can interact with physiological needs to weaken the ability of a species to maintain a viable population even when the temperature rise is too mild to kill individual organisms.

Biologists usually don't know enough about a species to assess this risk. Their knowledge comes largely from laboratory research on bits and pieces of a species' physiology. This method doesn't give much insight into how an animal as a living whole responds to climate change in its natural habitat.

Now, 10 years of research that combined laboratory study with field work has given that kind of insight into the decline of eelpout populations in the southern part of the North Sea.

To state it in a nutshell, Hans O. Poertner and Rainer Knust at Germany's Alfred Wegner Institute for Polar and Marine Research in Bremerhaven have shown that a relatively mild rise in water temperature can reduce the water's ability to hold dissolved oxygen, and, at the same time, it increases the fish's need for more oxygen to maintain its vigor.

The researchers discovered that, over the past five decades, eelpout populations declined when summer temperatures rose and vice versa. They also found that warmer summers reduced eelpout population the following year.

The results were published in the journal Science two weeks ago. In an accompanying commentary, Danish scientists Tobias Wang at Aarhus University and Johannes Overgaard at the National Environmental Research Institute in Silkeborg noted that "it remains difficult to establish increased temperature as the mechanistic cause for the [eelpout] population decline." Yet they acknowledged the correlation of the lock-step relation between temperature and population size as documented in the field with the effect of temperature on the fish's oxygen needs as documented in the laboratory. …

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