Climate Matters. J is for Jellyfish

This if for J in the A-Z Blogging Challenge 2012. Link in the sidebar.

Jellyfish don’t strike me as being the most appetising creature in the sea. In fact, I think they look decidely unpallatable. But I’ve been told that with overfishing and the changing pH levels in our oceans that they will become more abundant and we might need to start finding some tasty recipes as fish stocks plummet and species become extinct.

One indication that ocean pH levels are changing and becoming unbalanced is when Jelly fish “blooms” occur. Pollution and overfishing affect jellyfish – they adapt quickly to take advantage of the changes and breed very quickly creating a bloom or infestation.

Overfishing in oceans worldwide has resulted in less predators. Because there’s less competition for food, jellyfish thrive and can reach plague proportions. The overfished species struggle to recover as the jellyfish feed on fish eggs and small fish.

Image from Wikimedia Commons

As the temperature rises, as is happening with climate change, the ocean chemistry changes. What happens with warming waters and the dilution from arctic and antarctic ice, is a bit similar to when you put cold milk in a cup of coffee, creating currents within and between the different temperature liquids. They mix at different rates. When you add winds, heated land, ocean currents, storms and tides, it enables warm water jellyfish to migrate along with the warming waters and reach new environments. 

At times jellyfish which have adapted and survived in plague proportions become a pest to shipping when they clog ship filters. Beachside holiday locations become undesirable and local economies suffer.

Man-o-war

Algal blooms occur when algae die in vast quantities, stripping oxygen from the water. Jellyfish can survive in these low oxygen dead zones which can also be created by urban pollution and agricultural run-off. The rising levels of carbondioxide in the oceans affects the brains and central nervous systems of fish which increasingly interferes with their ability to survive and evade predators but which doesn't affect jellyfish.

Urban runoff occurs when we put fertilisers and pesticides onto crops, and in our gardens. When it rains, the residues run into waterways, rivers, lakes and eventually into the oceans as a polluted soup - along with garbage, cigarette butts, and litter, affecting the breeding cycles, breeding ability and health of whole fish populations.

Heavy metals get into the oceans, from smog which is absorbed by the water, and from other sources of pollution (think oil spills, run off from mines etc.) This is absorbed by little fish, which is then eaten by bigger fish, which is then eaten by bigger fish again which are then eaten by us. These bigger fish are the Tuna, Salmon, Flake etc. of the oceans. This is a form of bioaccumulation where we essentially eat the fish with the highest density of heavy metals.

The Australian Marine Conservation Foundation has noted that overfishing and destructive fishing practises have led to “An incredible 80% of the world’s fish stocks are now over-exploited or fished right up to their limit. Once considered inexhaustible, our oceans are now in a state of global crisis, and they need our help.”

The Australian Marine Conservation Society has prepared this excellent guide for the many Australians who love seafood but also love their oceans. "it’s not enough to simply buy what is fresh. If we want to keep eating fish we’ll have to learn to buy what is sustainable.” Tim Winton, Australian Author, AMCS Patron.

Last year I wrote about the importance of keeping a Journal for J in my theme of workplace bullying. Here.

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