Why are Jellyfish spreading?

Why are Jellyfish Spreading

Unusually, Jellyfish are found all over the globe. Although their numbers vary in different seas and oceans, the fact is that gelatinous creatures have survived in every environment all over the world for as many as 600 million years. The graph shown below displays the spread of jellyfish life in the global oceans and continents. So why are there more jellyfish in China than there are in Indonesia?

Epipelagic

The real problem lies actually off the coast of Japan, the graph has the area down as China as it is the largest commonly known country in the region. In Japan, the jellyfish have swarmed and produced hundreds of thousands of young in what seems to be either a long dormant cycle or a freak swarm which has taken over the ocean. So what causes these blooms?

Well, jellyfish, although able to self-propel using their bell shaped top, they are almost always reliant on ocean winds and currents to move. 'Blooms' can occur when ocean winds collide driving large numbers of jellyfish on to one single coastline, making it appear that there are many more being born than usual.

A true bloom however is when jellyfish mate and produce an abnormally large number of young in one season, temperature plays a bug part in the mating and breeding of jellyfish. For instance jellyfish tend do live longer in warmer waters and the hotter the day, the more water is evaporated leaving salt behind, this in turn increases the salt content in water and so the extra iodine present helps polyps (young jellyfish) develop into adults. This temperature is rising with continuous relation to climate change and so jellyfish will continue to produce at the current rate.

So why China?

Well it is purely geographic. To begin with, the oceanic area around Chins is prone to jellyfish blooms even before all of this climate change acceleration. This is due to the relative warmth of the Southern China and Japanese ocean area. These warm waters result in high jellyfish population.

https://opentextbc.ca/geology/wp-content/uploads/sites/110/2015/08/global-distribution-of-average-annual-sea-surface-temperatures.png

The image shown is an example of a relatively small sized jellyfish paired with thousands more in a large bloom
In this post I have briefly described the growth of jellyfish and the reasons for large numbers of blooms in recent years, in the next post I will outline the reproduction of jellyfish.