Question

In which ecosystem is the biomass of primary consumers greater than producers?

• A. Forests
• B. Grassland
• C. Desert
• D. Sea

Answer 1

The Correct Option is D

In an ecosystem, the biomass of primary consumers being greater than that of producers is a characteristic of certain environments. This situation primarily occurs in aquatic systems, such as the sea. Let's explore why this occurs: 

• Productivity: In the sea, microscopic producers like phytoplankton reproduce and grow rapidly, but individual biomass remains small. Despite their rapid turnover, their standing biomass at any moment is relatively lower.
• Consumer Efficiency: Zooplankton, the primary consumers in marine ecosystems, have a high efficiency in consuming these producers. Because they have longer lifespans compared to phytoplankton, their cumulative biomass can exceed that of the producers they consume.
• Turnover Rate: The high turnover rate of phytoplankton ensures continuous availability of food for zooplankton, maintaining a higher biomass of consumers over producers.

Therefore, the ecosystem where the biomass of primary consumers is greater than that of producers is the sea.

Answer 2

Zooplankton vs. Phytoplankton Biomass in Marine Ecosystems

Rapid Reproduction of Zooplankton

Zooplankton, which are primary consumers, reproduce very quickly. This rapid reproduction rate allows them to maintain a high population density even when they are being consumed by higher trophic levels.

• Zooplankton can complete their life cycle in just a few days, leading to a rapid turnover and high biomass.

Efficient Consumption of Phytoplankton

Zooplankton feed extensively on phytoplankton, which are primary producers. The high consumption rate by zooplankton can lead to a situation where the biomass of zooplankton exceeds that of phytoplankton.

• This is particularly evident in nutrient-rich environments where phytoplankton blooms occur, providing an abundant food source for zooplankton.

Role of Trophic Interactions

In marine food webs, the biomass distribution across trophic levels is influenced by the efficiency of energy transfer. While it is common for biomass to decrease with each trophic level due to energy loss, certain conditions can lead to exceptions.

• In some marine ecosystems, the biomass of zooplankton can exceed that of phytoplankton due to the high efficiency of energy transfer and rapid reproduction rates.

Conclusion

The biomass of zooplankton can exceed that of phytoplankton in marine ecosystems due to their rapid reproduction and efficient consumption of phytoplankton. This dynamic is influenced by trophic interactions and environmental conditions, such as nutrient availability.