Re: Marine creatures and the sea levels

Hi Kim,

How much the sea level would drop if all the animals suddenly disappeared is an interesting question. The short answer is not much.

I wasn’t able to find a figure for the total volume of animals in the ocean, but I did find an estimate for the total biomass in the ocean: 3.9 x 10^12 kg (Whittaker, R.H. Communities and Ecosystems. Second Edition. Macmillan, London, 1975). Biomass includes plants and dead organisms so I hope you don’t mind if I answer the slightly different question of how much would the sea level change if all life were removed from the ocean. Biomass does not include the watery portion of the organisms’ mass. Assuming that removing all the life means that we’d take it out whole (not drying stuff out and returning the water to the ocean), we have to divide the biomass by around 0.3 (a typical ratio of "other stuff" to water – this is just a guess since the biomass is made up of all sorts of different organisms). Thus, the mass of life in the ocean is around 1.3 x 10^13 kg. Now, to figure out the volume being removed from the ocean, we need to divide this mass by the density (mass per unit volume) of the organisms. Again, the density will vary from organism to organism, but we know they’re mostly made up of water, so let’s just use water’s density (1000 kg per cubic m) . The volume of the life in the ocean is 1.3 x 10^10 cubic meters. And, finally, dividing the volume of life in the ocean by the surface area of the ocean will give an estimate of how much the sea level will change if all life were removed. The surface area of ocean is 361 million square kilometres or 3.61 x 10^14 meters squared. The sea level change would be 0.03 mm.

Cheers,
Tetjana