Understanding Trophic Levels and Energy Transfer
* Phytoplankton: These are primary producers, meaning they make their own food through photosynthesis. They are the base of the food chain.
* Pacific Herring: These are small fish that feed on zooplankton, which in turn feed on phytoplankton. This makes them a secondary consumer.
The 10% Rule
A general rule of thumb is that only about 10% of the energy from one trophic level is transferred to the next. This means that for every 100 calories of phytoplankton eaten by zooplankton, only about 10 calories will be available to the herring.
Calculating the Required Phytoplankton Calories
1. Reverse the energy transfer: Since herring are at the second trophic level, we need to work backward.
2. Account for the 10% efficiency: To get the energy required at the previous trophic level, divide the herring's energy requirement by 0.1 (10%):
* 100,000 calories (herring) / 0.1 = 1,000,000 calories (zooplankton)
3. Repeat for phytoplankton: To find the phytoplankton calories, divide the zooplankton calories by 0.1:
* 1,000,000 calories (zooplankton) / 0.1 = 10,000,000 calories (phytoplankton)
Therefore, approximately 10,000,000 calories of phytoplankton are required to support 100,000 calories of Pacific herring.
Important Notes:
* The 10% rule is a simplification: Actual energy transfer efficiency can vary between ecosystems and species.
* Other factors: The actual amount of phytoplankton required could be influenced by factors like the specific species of zooplankton and the efficiency of their feeding.
* Ecosystem complexity: Real-world ecosystems are much more complex than this simplified example. There are numerous other organisms involved, and energy flows through multiple pathways.