Final answer:
A fungus covering the aquarium walls would disrupt energy flow by blocking light necessary for photosynthesis, reducing oxygen production, and affecting the food chain base. This change can impact both photosynthetic and non-photosynthetic organisms, leading to broader ecosystem imbalances.
Step-by-step explanation:
If a fungus grew in an aquarium and covered the walls/sides, it would disrupt the energy flow by blocking light, which is necessary for the growth of photosynthetic organisms like algae. Without sufficient light, photosynthesis is impaired, which affects the base of the food chain and can lead to a decrease in oxygen production. This situation leads to a negative impact on aquatic life, especially for those species that rely directly on photosynthetic organisms for food or oxygen. Additionally, a fungus might also compete with other organisms for nutrients and space, further disrupting the ecosystem balance.
The growth of fungus and its effects can be likened to algal blooms, where excessive growth of algae due to nutrient overload can block light and deplete oxygen, causing harm to aquatic ecosystems. Fungal mycelia absorbing nutrients from the environment can also cause an imbalance by siphoning off resources that other aquatic life forms might need. The decay of the excess fungus would also contribute to changes in water chemistry, such as a shift in pH, which affects metabolic processes for many organisms in the aquarium. This demonstrates the complexity and fragility of energy flow within aquatic ecosystems.