Aquatics Dissolved Oxygen Management – NAVLE Study Guide

Overview and Clinical Importance

Dissolved oxygen (DO) is the single most critical water quality parameter in aquaculture and aquatic veterinary medicine. Unlike terrestrial animals that breathe atmospheric oxygen (approximately 21% O2), aquatic organisms must extract oxygen from water where it exists in far lower concentrations (typically 5-14 mg/L at saturation). This fundamental difference makes DO management essential for the health, welfare, and survival of fish, crustaceans, and other aquatic species.

Oxygen depletion (hypoxia) is the most common cause of fish mortality in aquaculture systems and ornamental ponds. Conversely, excessive oxygen (hyperoxia or supersaturation) can cause gas bubble disease, analogous to decompression sickness in human divers. Understanding the physiology, monitoring techniques, and management strategies for DO is essential for any veterinarian working with aquatic species.

Physiology of Oxygen in Aquatic Systems

Oxygen Solubility and Physical Factors

The amount of oxygen that can dissolve in water is governed by Henry's Law, which states that the concentration of a dissolved gas is proportional to its partial pressure. Several physical factors affect DO solubility.