Sea turtles are reptiles that spend most of their lives in the ocean but cannot breathe underwater. Like all reptiles, they have lungs and must periodically surface for air. This need shapes their behavior and physiology, showcasing their unique adaptations for an aquatic existence. Their ability to hold their breath for extended periods is a remarkable adaptation to their marine habitat.
How Sea Turtles Breathe
Sea turtles breathe using lungs, adapted for their aquatic environment. When a sea turtle surfaces, it rapidly exhales and takes quick, efficient breaths to exchange gases. This allows them to quickly replenish oxygen before submerging. Their respiratory system maximizes oxygen intake during brief surface intervals.
When diving, sea turtles exhibit physiological responses that conserve oxygen. One notable adaptation is bradycardia, where their heart rate significantly slows, sometimes to as few as one beat every few minutes, reducing oxygen consumption. This metabolic slowing distributes oxygen efficiently to vital organs like the brain and heart while limiting blood flow to less critical areas.
Underwater Endurance
The duration a sea turtle can remain submerged varies depending on species, activity level, and water temperature. While actively foraging or swimming, sea turtles dive for 20 to 40 minutes before needing to surface. When resting or sleeping, they can extend their breath-holding significantly, often staying underwater for several hours. Green sea turtles, for example, can remain submerged for up to five hours when inactive, and loggerhead turtles have held their breath for seven hours during overwintering in cold waters.
These impressive dive times are possible due to several biological adaptations. Sea turtles store oxygen in their blood and muscles, which contain high concentrations of oxygen-binding proteins like hemoglobin and myoglobin. Their naturally slow metabolic rate, typical of cold-blooded animals, further reduces oxygen demand during dives. Cooler water temperatures can also slow their metabolism, allowing for even longer submerged periods.
Dangers of Being Trapped
Since sea turtles must surface to breathe, any obstruction preventing them from reaching the air can be fatal. Drowning is a significant cause of mortality for these marine reptiles. A common threat is entanglement in fishing gear, often called “ghost nets” when abandoned or lost.
When entangled, sea turtles become trapped and cannot ascend for air, leading to rapid oxygen depletion and drowning, sometimes within minutes if stressed. Fishing lines, nets, and other marine debris can also cause severe injuries, impede movement, and prevent feeding, ultimately leading to death. This highlights the importance of responsible fishing practices and marine conservation efforts to protect these animals.