In an ecosystem containing only producers (autotrophs) and no consumers or decomposers, which statement best describes what would happen over time?

• A. Primary productivity would stop immediately because producers require consumers to regulate population size and enable photosynthesis.
• B. Energy flow would increase over time because producers create energy from sunlight and store it permanently in the ecosystem.
• C. The ecosystem would remain stable indefinitely because producers can recycle all nutrients internally without any other organisms.
• D. The ecosystem would not be sustainable long-term because nutrients would become locked in dead biomass without decomposers to recycle them.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the roles of producers, consumers, and decomposers in an ecosystem. Producers (autotrophs) create organic material using sunlight, consumers feed on producers or other consumers, and decomposers break down dead organic matter to recycle nutrients back into the soil or environment.
2. Step 2: Recognize that in an ecosystem with only producers and no consumers or decomposers, producers will continue to perform photosynthesis and produce biomass initially, but dead plant material will accumulate over time.
3. Step 3: Consider nutrient cycling: decomposers are essential for breaking down dead biomass and releasing nutrients back into the soil, which producers need to grow. Without decomposers, nutrients become trapped in dead organic matter and are not available for reuse.
4. Step 4: Analyze the consequence of nutrient lock-up: as nutrients become unavailable, producers will eventually face nutrient limitations, reducing their growth and primary productivity over time.
5. Step 5: Conclude that the ecosystem would not be sustainable long-term because the lack of decomposers prevents nutrient recycling, leading to nutrient depletion in the soil and accumulation of dead biomass.