The rise of jellyfish due to climate change

My children and their cousins spent alot of time on the beach this summer in England collecting jellyfish. Less fun, further south in the Mediterranean, blooms of jellyfish stung thousands of holidaymakers. The rise is jelly fish blooms across Europe is an indicator of climate change and the deteriorating quality and biodiversity of our oceans.


My daughter Maya holding a jellyfish this summer in England (pic: A Kasterine)

Stung by Lisa-ann Gerwism, a US marine scientist based in Australia is a book about the rise of the jellyfish in our seas. As oceans world’s oceans become less favourable to fish due to climate change, mechanized trawling, pollution and habitat degradation, the jellyfish is thriving.

The book is popular science at its best – scientifically credible and erudite but written in an accessible and humourous way.

Climate change is the main driver for this growth – here are the main reasons why climate change is destroying our seas.

The sea food chain is being destroyed due to:

Stratification: as the water warms, the nutrient bearing layers of colder water are insulated from the sea surface – so there is reduced phytoplankton and consequently reduced zooplankton (all the stuff at the bottom of the food chain).

This results in two feedback effects: more grazing pressure on dwindling resources and less ability to absorb atmospheric carbon dioxide, which accelerated warming, which means decreasing phytoplankton and so on.

Warmer water hold less oxygen. Fish cannot just swim out further as “familiar corals and algae dont grown there, nor do the rich communities of fish and invertebrates that associate with them”

Climate warming is causing the tropical hypoxic (ie with low oxygen) zone to expand. The most productive and liveable habitats of the upper nearshore waters are being compressed by the “oxygen minimum zone” expanding out along the coasts.

“The area of the low oxygen area where mobile macroorganisms are unable to abide has increased by 4.5 million square km since the 1960s – an area half the size of the United States”.

Bleaching of corals (when heat stressed coals evict their resident algal symbionts resulting in their own death) – likely to be an annual occurance in 30-50 years time.

Ocean acidification: absorbtion of CO2 is acidifying the water destroying crabs, lobster, etc.

As links in the food chain starve and die off, ecosystems restructure. Enter jelly fish.

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