Calculating efficiency of biomass transfers

The efficiency of transfer is a measure of the proportion of biomass transferred from a lower to a higher one. Usually around ten per cent of biomass is transferred between trophic levels in a healthy and the remaining ninety per cent is used by the organisms during .

This is an example of a food chain:

phytoplankton → zooplankton → herring → sea lion

To complete this calculation, we divide the amount from the higher trophic level by the amount from the lower trophic level and multiply by one hundred. That is, we divide the smaller number by the bigger one (and multiply by one hundred).

\(\text{percentage energy transfer} = \frac{\text{biomass in higher trophic level}}{\text{biomass in lower trophic level}} \times 100\)

\(\text{percentage energy transfer} = \frac{1.3~\text{kg}}{14.6~\text{kg}} \times 100 = 8.9%\)

The amount of biomass contained within each trophic level is shown in the table below.

Trophic level	Organism	Total biomass (kg)
1	Phytoplankton	14.6
2	Zooplankton	1.3
3	Herring fish	0.15
4	Sea lions	0.017

Trophic level	1
Organism	Phytoplankton
Total biomass (kg)	14.6

Trophic level	2
Organism	Zooplankton
Total biomass (kg)	1.3

Trophic level	3
Organism	Herring fish
Total biomass (kg)	0.15

Trophic level	4
Organism	Sea lions
Total biomass (kg)	0.017

Question

Calculate the efficiency of the transfer of energy between each trophic level.

Trophic level	Organism	Total biomass (kg)	Biomass transferred (%)
1	Phytoplankton	14.6	No transfer
2	Zooplankton	1.3	8.9
3	Herring fish	0.15	11.5
4	Sea lions	0.017	11.3

Trophic level	1
Organism	Phytoplankton
Total biomass (kg)	14.6
Biomass transferred (%)	No transfer

Trophic level	2
Organism	Zooplankton
Total biomass (kg)	1.3
Biomass transferred (%)	8.9

Trophic level	3
Organism	Herring fish
Total biomass (kg)	0.15
Biomass transferred (%)	11.5

Trophic level	4
Organism	Sea lions
Total biomass (kg)	0.017
Biomass transferred (%)	11.3

Calculating efficiency

Question

A bullock has eaten 10 kg of biomass in the form of grass, and excreted 6.3 kg in the form of faeces, urine and gas. The increase in its body tissues is 0.4 kg. So how much biomass has been used up in respiration?

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How are organisms in an ecosystem interdependent? - OCR 21st CenturyCalculating efficiency of biomass transfers