Saving Sharks
And Why You Should Care

,Here's a (very) rough guide to how sharks keep our oceans in balance, and what could happen when they don't.

During the process of photosynthesis, phytoplankton (tiny ocean plants) use carbon dioxide and the light from the sun to create the nutrients they need to survive. As they use the carbon dioxide from the water it allows the ocean to absorb more from the air, thus preventing a build up in the atmosphere.

A by-product of photosynthesis is oxygen which is released back into the water and then out into the atmosphere. So, the plants in the ocean provide us with over half of the oxygen our planet needs to survive. (The rest comes from land-based plants which we are also destroying by hacking down the rain forests for the wood and clearing land for building/grazing etc.)

So, as well as putting oxygen into the air which, since we need it to survive, is (obviously) a good thing, the phytoplankton also removes the carbon dioxide. This is (not so obviously) a good thing too.

Why?

Because carbon dioxide is a greenhouse gas and can contribute to the warming of the earth’s atmosphere. But that’s not the scariest thing it does. As it is absorbed into the ocean’s water it dissolves and becomes carbonic acid which decreases the pH (increases the acidity) of the water.

This increase in acidity affects the ability of marine life to build skeletons, so the coral reefs, bony fish, zooplankton (and anything that feeds off them) will be harmed.

So, how does phytoplankton prevent ocean acidification and what does it have to do with sharks?

We're getting to the saving sharks bit, really, we are, but here’s the bit about the phytoplankton. As well as absorbing CO2 during photosynthesis, it also acts as a carbon sink. When it dies phytoplankton falls to the ocean bed and is soon buried under other marine detritus thus trapping it, and the carbon, safely in the earth.

Terrestrial plants act as a sink too. When they die they are buried and eventually fossilise. The only trouble with terrestrial sinks is that we keep digging them up and burning them, thus putting the CO2 back into the atmosphere.