The jellyfish debate

The following two articles, from fictional newspapers, offer different viewpoints on whether increased jellyfish numbers are a symptom or a cause of damage to the oceans.

Not So Jolly Jelly

THE colourful and captivating jellyfish community of the North Sea has gained some unwelcome notoriety after it was revealed that their swelling numbers are a potential threat to fish stocks.

Jellyfish have existed in our oceans for many millions of years, predating even the dinosaurs. Lately however, these old timers have been enjoying the more favourable climate conditions a little too much, and their numbers are increasing, fast. Despite their body mass being up to 97% water, the booming population is putting a strain on local fish stocks by consuming the fish larvae and supplies of plankton.

Professor Martin Atrill, Director of the Marine Institute at Plymouth University, has been quoted as saying “Looking ahead over the next 50 to 100 years, all climate projections expect the North Sea to become warmer, so jellyfish will become more common in our waters.”

Their expanding presence is also contributing to a build up of carbon dioxide in the oceans. The carbon given off when animals die is usually recycled by bacteria and other animals, but jellyfish are not as appetising due to their high concentration of carbon, which is being processed into carbon dioxide. This in turn is leading to eutrophication of the oceans, the likes of which hasn't been seen for 600 million years.

Due to their invertebrate nature and the tendency of most species to drift wherever the tide takes them, no jellyfish volunteered for comment.

Jellyfish not to blame for ocean's woes

The vilification of jellyfish is easy because they are spineless and unable to stand up for themselves. But their growing numbers are a symptom and not a cause of the dwindling fish stocks, the dying coral and the general decline in the state of the sea. To find the real cause we need to look much closer to home. To ourselves.

The warming of the ocean is upsetting the balance by breaking local food chains and artificially changing the survival rate of creatures that have evolved over millennia. Dan Laffoley, from the International Union for the Conservation of Nature, has described the need to protect 'the blue heart' of our planet as urgent. Extreme weather patterns linked to climate change are reflected in the record temperatures that killed 16% of the world's tropical reefs in 1998, and more extreme weather is predicted. The result will be vast areas of barren ocean where thriving life could once be found.

Run-off from fertilisers and industrial chemicals used by humans are also contributing to the problems of anoxia and hypoxia and the destruction of phytoplankton, a micro-organism vital to the oxygenation of water. It is believed that conditions similar to these resulted in up to half of all deep sea species being wiped out 55 million years ago.

The depleted fishing stocks can also be traced back to us – over-fishing has reduced some species to less than 10% of their earlier recorded number, resulting in endangered status. Millions of other sea creatures, including birds, choke to death after eating plastic waste discarded into the oceans and onto the beaches.

Although the 'bloom' in jellyfish numbers has undoubtedly caused some issues to worsen, the root cause is human society and our collective lack of responsible decision making.

We created the flow of change, the jellyfish are just going along with it.

Definitions

Anoxia

The absence of oxygen in water.

Hypoxia

Low levels of oxygen in water.

Eutrophication

Process by which sea water becomes gradually more acidic and unable to support life.

Phytoplankton

Micro-organisms found in water, responsible for the Oxygen Cycle in which carbon-dioxide is processed into oxygen.

Jellyfish

Not actually a fish (or jelly), these invertebrates are found in both fresh and salt water habitats. Some are poisonous. The feared Portugese Man o' War jellyfish is not actually a jellyfish but a collection of four different life forms working together.

Watch The Oceanic Food Chain  to find out more about life under the sea.