Jelly and Plastic

By Tom Green, Written for Big Blue Scuba School, Cheshire

In this blog we asked Tom Green, a University of Liverpool Masters student, to write about his research regarding Jellyfish. Plastics are increasingly present in marine ecosystems and have caused problems for many marine organisms. But, as with any change to an environment, there are winners and losers. Jellyfish appear to be one of the winners. Hopefully Tom’s research can help us further understand the issue and positive changes can be made accordingly.

A little bit about Jellyfish

Jellyfish populations seem to be increasing at an alarming rate; Bloom events in which a large number of medusa (adult Jellyfish) occupy a small space are becoming more frequent and severe. These events often cause large amounts of economic damage, through both direct (Competing with fish) and indirect (Closing tourist destinations) means. The causes of these events currently remains unknown. However, their complex 5 stage life-cycle can be seen as the mediator allowing populations to explode in favourable conditions.

The process of strobilation in which a polyp produces a number of juvenile medusa can be thought as the proximate cause of these bloom events. The greater the number of polyps available to strobilate directly correlates with the numbers of observed medusa. Environmental conditions such as ocean temperature can also increase the rate at which polyps form strobila; also acting to increase abundance of medusa.

The Research

In my research I wanted to look to two factors the first of which was if Iodine would act to increase the rate at which polyps morph to strobila and if the presence of plastic waste in the ocean creates a suitable habitat for colony formation, thus increasing the abundance of polyps.

It was hypothesised that iodine could act to increase the rate at which polyps morph to strobila and that the presence of plastic waste in the ocean creates a suitable habitat for colony formation, thus increasing the abundance of polyps. This research identified iodine when coupled with a cooling of around 10°C, produces reliable bouts of strobilation in the Moon Jellyfish (Aurelia aurita), while also providing a lower mortality rate than tested alternatives. Plastic waste was found to be a preferred substrate for polyp re-attachment, with higher rates of attachment on polystyrene and polyethylene compared to natural substrates. To conclude the results presented in my paper will provide future researchers with a reliable method to produce medusa on demand, while also suggesting plastic waste is allowing for a two-fold jellyfish population increase. This is as polyps can both settle and re-attach to anthropogenic materials better than natural alternatives, providing two avenues to successful colony formation. If we are to better prepare for bloom events, jellyfish life-history needs to be a research priority, without a greater knowledge base jellyfish will continue to pose an expensive problem for coastal industry.

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