5. Conditions for Life in the Sea


Marine Ecosystem

1. Introduction
2. Phytoplankton
3. Carbon in the Sea
4. Carbon Cycle
5. Conditions for Life
6. Limiting Nutrients
7. Nutrient Distribution
8. Life in the Sea
9. Food Webs

Let's examine our biochemical reaction for life in the sea, and on this earth, in general.

6H2O + 6CO2 + nutrients + energy <=> C6H12O6 + 6O2

The rate at which this reaction takes place provides a fundamental control on the amount of life in the sea.

Are any of the conditions on the left side of the reaction in short supply in the sea such that the amount of life in the ocean may be limited in places? (organic carbon = carbon in living things)

H2O or water?  Clearly is not -- since there is plenty of water. Indeed it is commonly believed that life on our planet began in the sea more than 3.3 billion years ago.

CO2, carbon dioxide? --- there is plenty of carbon dioxide dissolved in sea water, especially in the cold waters of the subpolar and polar regions.

Energy? No problem here either, at least not in the sunlight surface waters of the mixed layer during the long days of spring and summer.

So it looks like nutrients may be the main factor that limits the amount of life in the sea.

©Copyright 1999
March 13, 1999

Send to Don Reed

Department of Geology
San Jose State University

Which nutrients place limits on the amount of life in the ocean?