Causes and consequences of gas bubble trauma on fish gill function.

Total dissolved gas supersaturation (TDGS) occurs when air mixes with water under pressure, which can be caused by features such as hydroelectric dams and waterfalls. Total dissolved gas supersaturation can cause harmful bubbles to grow in the tissues of aquatic animals, a condition known as gas bubble trauma (GBT). As gills are the primary gas exchange surface for most fish, it is through the gills that elevated total dissolved gases enter the blood and tissues of a fish. We describe the role of the gills in admitting TDGS into the body and discuss potential effects of bubbles in the gills on blood oxygen and carbon dioxide diffusion, blood ion and pH homeostasis, and nitrogenous waste excretion, as well as downstream effects on aerobic swimming performance.