Final answer:
The disruption of the nitrogen cycle related to eutrophication is known as an algal bloom, which leads to dead zones due to oxygen depletion caused by microorganism growth.
Step-by-step explanation:
The disruption of the nitrogen cycle in the context of eutrophication is known as an algal bloom. This occurs when excess nitrogen and phosphorus nutrients enter an ecosystem, often through agricultural runoff. This sudden influx of nutrients causes the rapid growth of algae on the surface of the water bodies. As the algae die and decompose, microorganisms that break down the dead algae consume large amounts of dissolved oxygen, which can lead to oxygen depletion or hypoxia. Dead zones are areas where the oxygen level is so low that it can no longer support aquatic life.
The specific processes involved in nitrogen cycling relevant to this condition include nitrogen fixation, whereby nitrogen gas is converted into a form usable by plants, and nitrification and denitrification where nitrogen compounds are converted into different forms throughout the cycle. In the context of agricultural influence and the excess use of fertilizers, these processes can become unbalanced, leading to ecological issues such as eutrophication.