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Biomass Pyramid: Types, Examples, Strengths, and Weaknesses

by Widiya

Biomass in ecology means the mass of biological organisms that live in an ecosystem at any given time. The mass can include microorganisms, plants, and animals which value is the mass of the average area.

The biomass pyramid is one of the three types of ecological pyramids. This pyramid shows the estimated amount of biomass that represents each trophic level. There is energy transfer at each trophic level in an ecosystem.

The biomass pyramid unit used is the dry weight of the organism per unit area such as gram/m² or kg/ha. Measurements were made using sampling techniques by weighing each individual and then recording the amount in the ecosystem. Biomass is measured as a mass of organically bound carbon.

Measurements require a lot of time and the shape changes because it depends on the climate and some of the energy will be lost due to respiration that enters the biosphere. Globally, the amount of biomass in the world is around 560 billion tons of carbon. Most are found on land and the remaining around 5 – 10 billion tons are found in the sea.

Mainland Biomass

A pyramid of land biomass is an upright pyramid cone upward. Biomass decreases with movement towards high tropics. Generally, building new biomass only uses 10%. The remaining 90% is used for the metabolic process released as heat.

The highest biomass is occupied by producers such as trees, grass, and shrubs. While the second tropic level consists of heterotrophic organisms such as herbivores followed by primary carnivores and secondary carnivores. The lowest biomass is occupied by the highest predators such as eagles and lions.

Here is how food chain pattern looks like from the highest biomass to the top in subtropical grasslands:

Grass (producer) → Grasshopper or bison (consumer) → Lion (predator)

Ocean Biomass

The shape of the pyramid of marine biomass is inversely proportional to the land biomass pyramid. The higher the tropic level, the greater the biomass is. The reason is that the major producers of phytoplankton are very small and can breed quickly. (Also read: Characteristics of Ocean Biome and the Explanation).

Food chain pattern from lowest to highest biomass:

Phytoplankton → Zooplankton → Filter animals → Predatory fish

Phytoplankton is a primary producer capable of photosynthesis that converts inorganic carbon into protoplasm. The protoplasm is consumed by zooplankton, which is then consumed by predatory fish. (Also read: 20 Importance of Marine Life Conservation)

Bacterial Biomass

According to research, the total bacterial biomass on Earth is equivalent to plant biomass. There is even a mention which is equivalent to a combination of plant and animal biomass. The estimated amount is 5 x 10³. Bacterial cells in 1 gram of soil are estimated to be 40 million and one million cells per 1 milliliter of fresh water.

Global Biomass Primary Production Rate

Primary production produced through photosynthesis can be observed by satellites by scanning the NDVI (Normalized Difference Vegetation Index) by scanning chlorophyll levels both on land and in the ocean. The result is that organic carbon produced by land is 56.4 billion tons per year, while that produced by the ocean is 48.5 billion tons of organic carbon per year. The total photoautotrophic carbon production on Earth reaches 104.9 billion tons.

Strengths and Weaknesses of the Biomass Pyramid

Strengths: Able to show the quantitative relationship of the mass of organisms (biomass) in ecosystems that cannot be observed with the number pyramid.

Weaknesses: Unsatisfactory because it requires a lot of time and tools, the shape changes because it depends on the climate and some of the energy will be lost to respiration that enters the biosphere, and only explains the amount of biomass without any explanation taken from the rate of biomass formation. For example, the number of bacteria is greater than the number of mammals, but the energy utilization of the two groups is basically the same size.

So, that is the explanation of the biomass pyramid in the world. Hopefully it will add useful insights for all of us.

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