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Alien Invaders

Seaweed and ShellsWe all saw the pictures of the aftermath of the Sendai earthquake and resulting tsunami in Japan last year – it was a terrible event that caused huge devastation and rocked entire communities.  As the people of Japan still try to put their lives back together, what impact has the event had on the environment?  A week ago, a dock (no really, an entire dock) from Japan was washed up on a beach in Oregon, USA. If the tsunami had the power to dislodge something this large, what affect has it had on smaller organisms, such as fish, crabs and shellfish that occupy our seas?

The ecosystem in the sea is a lot more complex than you might imagine.  Firstly, the amount of nutrients, sunlight, salt and heat can vary hugely within the space of a few metres. Light, for example only really goes down to a depth of 100m below sea level. As well as that, the oceans also have something called the thermocline, again at a depth of about 100m. Go deeper than this level and suddenly the effects of waves, temperature and light are not felt.  Imagine you are a small animal used to living in the top few metres of the sea, if you were washed out deeper than the thermocline, you would be in serious trouble, and that’s before we’ve even thought about the water pressure.

So what effect do large tsunamis have on aquatic ecosystems?  Well luckily large scale tsunamis are very rare, but this means that scientists have very little chance to study them. One of the major worries scientists have is that certain species may be carried on debris by the wave from one area, where they are a part of the ecosystem, to a new area, with similar conditions, where they can survive, but which contains an ecosystem that cannot cope with them. Imagine a pride of lions being let loose in the New Forest in the south of England. The lions would adapt quickly and would learn to survive and hunt new animals, but the ecosystem would not be ready for such a vicious predator and all the animals which are currently found in the New Forest would not be able to adapt to this change in their environment quickly enough to survive. This is what happens in areas of the sea after a tsunami. It is a particularly big worry where the new species lives in a similar way to species that already live in the area – eats the same food, likes the same type of house – as there may not be enough resources to go around.

We don’t know how much this is a problem. After all, we understand very little of the deep seas, and life on earth has managed to survive for over 3 billion years, despite tsunamis – in part this is just the way that nature works. We also know that any new invasive species to the west coast of the States will take a while to take hold (we are talking about a relatively small number of animals here). But certain marine ecosystems are very fragile, and need looking after.  So with monitoring, hopefully environmentalists in the US can stop invader species from taking over and destroying the rich ecosystem that already exists.


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Blog post by Linda Seward of Seward Technical Writing, providers of original science content.


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