Note4Students

From UPSC perspective, the following things are important :

Prelims level : Gill-Oxygen Limitation Theory (GOLT)

Mains level : Impacts of oceanic warming

• Warming waters have less oxygen. Therefore, fish have difficulties breathing in such environments says a new study.

 Gill-Oxygen Limitation Theory

• Among various ways in which climate change is impacting life on Earth, one has been to change the distribution of fish species in the oceans.
• Scientists have predicted that the shift will be towards the poles. They have explained the biological reasons why fish species will follow that direction.
• It stems from the way fish breathe which is described as the Gill-Oxygen Limitation Theory, or GOLT.

How does it work?

• Warming waters have less oxygen. Therefore, fish have difficulties breathing in such environments.
• Additionally, such warming, low-oxygen waters also increase fish’s oxygen demands because their metabolism speeds up.
• This is because, as fish grow, their demand for oxygen increases.
• However, the surface area of the gills (two-dimensional) does not grow at the same pace as the rest of the body (three-dimensional).
• The larger the fish, the smaller it’s surface area relative to the volume of its body.
• So, the fish move to waters whose temperatures resemble those of their original habitats and that satisfy their oxygen needs.

Impact

• As the global sea surface temperature has increased by approximately 0.13°C per decade over the past 100 years, “suitable” waters are more and more found towards the poles and at greater depths.
• This will cause some fish species to shift their distribution by more than 50 km per decade.