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Ongoing global
climate change causes changes in the species
composition of marine ecosystems, especially in shallow coastal oceans.
This
applies also to fish populations. Previous studies demonstrating a link
between
global warming and declining fish stocks were based entirely on
statistical
data. However, in order to estimate future changes, it is essential to
develop
a deeper understanding of the effect of water temperature on the
biology of
organisms under question. A new investigation, just published in the
scientific
journal Science, reveals that a warming induced deficiency in oxygen
uptake and
supply to tissues is the key factor limiting the stock size of a fish
species
under heat stress. Scientists of the
Alfred Wegener Institute for Polar and
Marine Research in During evolution,
animals have specialized on environmental
conditions and are often very limited in their tolerance to
environmental
change. In this context, fish species from the North Sea which
experience large
seasonal temperature fluctuations, are more tolerant to higher
temperatures and
display wider thermal windows than, for instance, fishes from polar
regions
living at constant low temperatures. The latter are able to grow and
reproduce
only within a very limited thermal tolerance window. Investigations at
the Alfred Wegener Institute show the key
importance of oxygen uptake and distribution – through
respiration and blood
circulation – in setting the animals' thermal tolerance
range, in that these
processes are optimized to only a limited temperature window. With
increasing
temperature, the organism's oxygen supply is the first to deteriorate,
followed
by other biochemical stress responses. Finally, oxygen supply fails
entirely,
leaving the organism to perish. These results represent a significant
step
forward towards understanding the mechanisms involved in
climate-induced
alterations in marine ecosystems. The paper 'Climate
change affects marine fishes through the
oxygen limitation of thermal tolerance' is published on
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