Final answer:
All components listed are necessary for a designer ecosystem. An energy source, consumers, and a nutrient source work together to support life and function within such systems.
Step-by-step explanation:
The component that is not a necessary part of a designer ecosystem is d) All of the above are necessary components. In a designer or artificial ecosystem, an energy source is crucial as it fuels the activities of organisms within the ecosystem. Consumers are an integral part of the food web, as they eat the producers and provide energy for other trophic levels. A nutrient source is essential for providing the building blocks for both producers and consumers to grow and function properly.
In an aquatic system with excess producers relative to consumers, option a. Oxygen depletion would result in dieoff may occur due to oversupply of organic matter and subsequent microbial activity consuming dissolved oxygen. Light energy supports consumers indirectly; it is utilized by producers through photosynthesis to create organic compounds that consumers eat.