Going to a more gelatinous future

July 17, 2016

 

 

 

Climate Change is not a new topic nowadays. Nevertheless we are in a period where rapid changes are noticed not only by scientists, all you have to do now is look out the window.

The ocean ecosystem is getting the worse part of this, added to the overfishing, translocation of marine animals, pollution and habitat modification. Not helpful at all.

 

What happens to the ocean with such a combination of problems? Between other effects, these issues are leading to a process called “Eutrophication”. Nutrients like nitrates, phosphates and sometimes silica are added to the ocean through fertilizer runoff, salmon farming and sand storms. They are essential elements for algae growth, in small amounts they are beneficial to many ecosystems, however in excessive amounts they cause a chain process were explosive growth of algae and their later degradation by bacteria, once dead, consume the nutrients and the oxygen. This processes turn big water masses to hypoxic, or worse, anoxic causing animals physiological stress.

 

Under such conditions, the silica deficiency (important mineral for the growth of diatoms) generates a reduction of primary and secondary producers, affecting the entire food chain. ¡It would be like Africa without grass! In this case, less food for planktotrophic fish (microscopic algae eaters) which then feed turtles, tuna fish, seabirds and marine mammals.

 

On top of this, the warming of the sea surface enhances water column stratification, leading to a nutrient-poor layer that gives the advantage to flagellate protists (which can migrate into nutrient-rich deeper water), outcompeting diatoms.

 

This is an ideal scenario for Jellyfish for several reasons; because of their ability to feed on a wide range of prey including flagellates, warmer temperatures accelerate medusae growth and the great tolerance of polyps and medusae to low oxygen conditions compared to fish, ensures higher probabilities of survival. They are even able to reproduce during hypoxic events.

 

In cold southern oceans, this situation is a common issue nowadays. In the coasts of Chile, “El niño” Southern Oscillation (ENSO) warm events are more intense and longer, shifting off Equatorial species, like this Jellyfish (Chrysaora plocamia) from the picture above, which creates an obstacle to fisheries.

 

What can we do? Protect Jellyfish eater animals, such as the Leatherback turtle, the sunfish called Mola mola, as other 158 species reported to feed on them.

 

References

 

1.-The jellyfish joyride: causes, consequences and management responses to a more gelatinous future.

2.-Jellyfish blooms.

 

 

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Thomas Heran Arce

Underwater photography,  Chile

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