A mangrove ecosystem has GPP of $9000{\text{kJ,m}}^{-2}{\text{d}}^{-1}$ and ecosystem respiration of $3500{\text{kJ,m}}^{-2}{\text{d}}^{-1}$. The energy transfer efficiencies are: 15% from producers to primary consumers, 10% from primary to secondary consumers, and 5% from secondary to tertiary consumers. Calculate the total energy available to tertiary consumers per square metre per day, accounting for respiration losses before each transfer.

Step-by-step solution

1. Compute Net Primary Production: $NPP=9000-3500=5500$ kJ m⁻² d⁻¹; this is the energy left after autotroph respiration.
2. Transfer to primary consumers: $E_{PC}=0.15\times 5500=825$ kJ m⁻² d⁻¹; primary consumers receive 15% of NPP.
3. Transfer to secondary consumers: $E_{SC}=0.10\times 825=82.5$ kJ m⁻² d⁻¹; secondary consumers receive 10% of $E_{PC}$.
4. Transfer to tertiary consumers: $E_{TC}=0.05\times 82.5=4.125$ kJ m⁻² d⁻¹; tertiary consumers receive 5% of $E_{SC}$.
5. Round to two decimal places: $E_{TC}approx4.13$ kJ m⁻² d⁻¹, the final energy available to tertiary consumers.

Concept tested: Energy flow with respiration losses

Published 28 September 2026 · How this solution was prepared and checked