Yes, sea turtles breathe air. Unlike fish, these marine reptiles possess lungs and do not have gills, meaning they cannot extract oxygen directly from the water. They must regularly come to the ocean’s surface to inhale and exhale. This requirement to surface is a fundamental aspect of their biology, despite spending most of their lives underwater.
Breathing Basics
Sea turtles breathe air using lungs. These spongy, multichambered organs are located directly beneath their carapace (upper shell) and along the vertebral column. When at the surface, a sea turtle will extend its head out of the water and use its nostrils to draw in air.
Air then travels through the glottis, a valve at the back of the tongue, and down the trachea into the lungs. Ventilation of the lungs is achieved through movements of muscles attached to their pelvic and shoulder girdles, and to the plastron (lower shell). This muscular action changes the pressure inside the lungs, allowing them to efficiently exchange gases, taking in oxygen and expelling carbon dioxide.
Mastering Underwater Time
Sea turtles exhibit remarkable adaptations that allow them to remain submerged for extended periods. Their ability to hold their breath is largely due to a slow metabolic rate, which significantly reduces their oxygen consumption when resting or sleeping. They can further conserve oxygen by dramatically slowing their heart rate, sometimes beating only once every few minutes.
These reptiles also possess high concentrations of hemoglobin in their blood and myoglobin in their muscles, enabling them to store a substantial amount of oxygen. When diving, sea turtles can shunt blood away from less critical organs and tissues, directing oxygenated blood primarily to their brains and hearts. They also have a notable tolerance for higher levels of carbon dioxide and lower oxygen levels in their blood than many other animals, allowing them to endure prolonged dives.
Why They Return to the Surface
Despite their impressive breath-holding capabilities, sea turtles must eventually return to the surface to breathe. The primary reason for surfacing is to replenish their oxygen supply and release accumulated carbon dioxide from their bodies. This exchange is essential for their physiological functions and overall survival.
The frequency with which a sea turtle surfaces depends on several factors, including its activity level and water temperature. An active turtle, such as one foraging for food, will need to surface more often, perhaps every few minutes, than a resting or sleeping turtle. When resting, a sea turtle can remain submerged for several hours, especially in colder water as their metabolism slows down.