7.4.3 Transfer of Biomass

In this lesson, we will explore how biomass is transferred between trophic levels, as well as the factors and losses involved.

Biomass Transfer

In an ecosystem, energy flows through different trophic levels as organisms consume and are consumed by others. Along with the energy transfer, there is also a transfer of biomass, which refers to the organic matter present in living organisms. 

Pyramids of Biomass

Pyramids of biomass provide a visual representation of the relative amount of biomass at each trophic levelThe position an organism occupies in a food chain, influencing nitrogen isotope ratios. in a food chain or ecosystem. Biomass pyramids typically show a decrease in biomass as you move up the trophic levels, reflecting the energy losses and inefficiencies of energy transfer between organisms.

Energy and Biomass Transfer

Energy is captured by the producersBusinesses or organisations that combine resources to produce goods and services for consumers. (plants and algae) through photosynthesisThe process by which plants use light energy to produce glucose.. However, only a small fraction of the incident energy is converted into biomass. Producers transfer approximately 1% of the incident energy from light for photosynthesis. The remaining energy is lost as heat or used for metabolic processes.

Energy Losses between Trophic Levels

Energy Loss through Respiration:

• Organisms, including plants and animals, release energy through respiration, which is the process of breaking down organic molecules to release usable energy.
• As organisms respire, they use a significant portion of the energy they obtain from food or photosynthesis for their own metabolic needs, resulting in energy losses.

Energy Loss through Inefficiency:

• Energy transfer between trophic levels is inefficient. When organisms consume other organisms as food, only a portion of the biomass is assimilated and converted into new biomass.
• This inefficiency occurs due to factors such as indigestible parts, incomplete digestion, and energy used for movement and other activities.

Energy Loss through Heat:

• Energy is continuously lost as heat at each trophic level. Organisms release heat energy as a byproduct of their metabolic processes, and this heat is not available for further use by other organisms.

Biomass Transfer Efficiency

In ecosystems, biomass is transferred between trophic levels as organisms consume and are consumed by others. However, not all biomass is efficiently transferred from one level to the next.

• Only a fraction of the biomass from each trophic level is transferred to the level above it. On average, approximately 10% of the biomass is transferred between trophic levels.
• This means that for every 10 units of biomass at a lower trophic level, only 1 unit is passed on to the next trophic level.

Losses of Biomass

• Ingestion and Egestion: When organisms consume food, not all of the ingested material is absorbed and assimilated into their bodies. Some portion of the ingested material is egested as waste in the form of faeces. This undigested material contains biomass that is not transferred to the next trophic level.
• Metabolic Waste: As organisms carry out metabolic processes, they produce waste products that contain biomass. For example: Carbon dioxide and water are released during respiration; urea and water are excreted in urine. These metabolic wastes contain biomass that is lost from the organisms and is not transferred to the next trophic level.
• Energy Used in Respiration: Organisms utilise a significant amount of glucose, a primary energy source, in the process of respiration. During respiration, glucose is broken down to release energy for the organism's metabolic activities. The energy released is vital for sustaining life processes but does not contribute to the transfer of biomass between trophic levels.

Conclusion

In ecosystems, biomass is transferred between trophic levels as organisms consume and are consumed by others. Pyramids of biomass illustrate the decrease in biomass as you move up the trophic levels, highlighting the energy losses and inefficiencies of energy transfer. Producers transfer a small fraction of the incident energy from light for photosynthesis, and energy is further lost through respiration, inefficiency in energy transfer, and heat release. In the transfer of biomass, approximately 10% of the biomass is typically passed on to the next level. The losses of biomass occur due to factors such as incomplete absorption and egestion of ingested material, metabolic waste production, and the energy used in respiration.