Which term describes a body of water that is completely lacking in oxygen?

The term that describes a body of water that is completely lacking in oxygen is "anoxic." When water is characterized as anoxic, it indicates that the dissolved oxygen levels have dropped to a point where aerobic organisms cannot survive. This condition can arise in various environments, such as deep ocean waters, stagnant ponds, or during certain periods of stratification in lakes, where layers become isolated and do not mix.

Anoxia is critical in the context of water quality because it affects the survival of fish and other aquatic life. Organisms that rely on oxygen for respiration struggle to exist in anoxic conditions, potentially leading to dead zones in aquatic ecosystems.

The other terms presented refer to different phenomena. "Anthropogenic" pertains to environmental changes caused by human activity, "aquatic respiration" relates to the process by which aquatic organisms extract oxygen from water, and "attenuated" generally refers to a reduction in force, effect, or value, not specifically to a lack of oxygen in water. Thus, anoxic is the correct term for a completely oxygen-depleted body of water.