Eco-systems are of course very complex things – the success of one species is linked to the success of another, which is linked to another, and all of which are linked to outside factors such as climate etc etc. Now there is direct evidence of another degree of complexity in the ocean eco-system, namely that fish (and other swimmy things) have a significant role to play in mixing the ocean.
The hypothesis is not new – it was postulated by Charles Darwin (grandson of his more famous namesake) in the 1950s – but now experimental evidence has been found. Katija and Dabiri (Nature 460, 624-626) have measured the effect of jellyfish migrating upwards from deeper, cold water, to closer to the surface where the water is warmer. As they move, they drag with them the cold water. This is denser than the warm water nearer the surface, and so, once it leaves the vicinity of the jellyfish, it will fall, creating a circulation that mixes the water.
The researchers argue that this mixing is as significant as some other forms of ocean mixing, and shows that we must add jellyfish (and, the researchers point out, other fish that migrate in depth) to the list of creatures that influence the environment in a big way.
That’s it! The solution to climate change – genetically engineer a species of fish to do more or less upward / downward migration (whichever is appropriate for influencing the ocean in the right way), and we control the surface temperature of the oceans! No more silly than putting a giant sunshade in orbit.