Re: the effects of a pressure wave from a tsunami on the sea life

Hi Tiago,

First let’s set up the basic picture of a tsunami passing through the deep ocean. Tsunamis are unique waves because they affect all depths, even in really deep water. This means that if you are a fish or a whale hanging out at mid depths, you’ll just get moved up and down with the rest if the water. The pressure that an animal feels is related to how much water is above him, so since these mid-depth animals aren’t moved any closer or further from the ocean surface, they won’t feel any change in pressure from the tsunami passing by. Animals that are stuck to the bottom, on the other hand, will feel a change in pressure. Since tsunamis are generally less than 1 meter high in deep water, they add only 1 meter worth of extra pressure to the animals on the bottom. Compare this to the typical 4000 meters of water these animals normally shoulder and you can see that the tsunami will be hardly noticeable.

The pressure wave of the tsunami itself will be very much the same at the epicentre as in the rest of the deep ocean (i.e. no effect on sea life). It’s possible the earthquake itself could damage sea life (imagine suddenly finding yourself hundred of meters deeper because a rift has opened beneath you or the nice rocky floor beneath you has turned to quicksand), but I don’t know of any studies of this and this would only affect a very small area right at the epicentre.

It’s closer to the shore that the tsunami has its largest potential to cause damage. Due to energy flux conservation, the waves that are less than a meter in deep water amplify to as much as 30 meters in shallow water. Again the pressure changes associated with this wouldn’t be expected to drastically affect sea life (many of whom routinely visit depths in a much larger range than 30 meters). Most damage would come from things (trees, houses, sand) being picked up onshore and smashed into or dumped onto immobile marine life (like corals). Mobile plants and animals may find themselves marooned on land. Even if they don’t, they’ll likely find their habitat destroyed or buried.

I hope this answers your question. You can learn more about tsunamis at this page.
Cheers,
Tetjana