What are the implications this has for humans using the ocean for food?. Ecology

• If we assume a trophic efficiency of 10% , we can calculate how much primary production is required to support a particular fishery.
• For example tuna: tuna have a trophic level of 4, meaning they are secondary carnivores. For example a 175g can of tuna 175, 000g Carbon of phytoplankton is needed.
• Since humans often harvest secondary carnivores, such as fish, a lot more primary production is needed.
• The amount humans can take out of the ocean is largely dependent on the nitrogen and iron levels

2 ways in which productivity of the world's oceans for human food supply could be increased

1. Increase the amount of nitrogen in the ocean - causing algal blooms
2. Increase the amount of iron in the ocean - causing algal blooms
3. Dedicate coastal areas to eutrophication and phytoplankton production
4. Genetically engineer phytoplankton which need less nutrients/light