Sea turtles are reptiles in the superfamily Chelonioidea. They are also sometimes referred to as “marine turtles,” referencing the fact that they have adapted to live primarily in the marine environment. All seven living species of sea turtle are endangered, and conservation efforts all over the world are attempting to prevent the extinction of sea turtles. The loss of sea turtles would not just be a blow to biodiversity: sea turtles are also important for the health of the world's oceans.
Like other turtles, sea turtles have a hard shell into which they can retreat. Their front legs have adapted into a flipper-like form which allows them to swim rapidly and efficiently, and their bodies are slightly flattened to reduce resistance in the water. Some sea turtles can also use their flippers for climbing.
The sea turtle has developed a respiratory system which allows it to dive and stay underwater for as long as five minutes. Depending on the turtle's level of activity and stress, it may need to surface sooner for air. Sea turtles breathe in explosively, filling their lungs with enough air to supply them during dives. They have also adapted to reduce the risk of developing decompression sickness, also known as “the bends,” a common problem for human divers who dive or ascend too quickly.
Sea turtles feed on other marine life and seagrass, a flowering plant which is widespread in the world's oceans. They can be found in every ocean except the Arctic, coming to land to lay their eggs once they reach the age of 30. Sea turtles are especially vulnerable during egg laying, since many are slow and ungainly on land, and the eggs may be broken by unwitting walkers or viewed as a tasty snack by numerous predators. Once the eggs hatch, the young make their way to the ocean and begin their aquatic lives.
The seven species of sea turtle are: loggerheads, green sea turtles, flatbacks, hawksbills, leatherbacks, olive ridleys, and Kemp's Ridleys. The smallest sea turtles reach a length of around 30 inches (76 centimeters), while the largest can exceed six feet (two meters). Sea turtles live for up to 80 years, and once they reach their maturity, they are difficult for predators to kill, thanks to their hard shells. They are vulnerable, however, to trawling and a variety of other human activities, along with changes in the marine environment such as coral bleaching and nutrient pollution.
Sea turtles help to maintain the marine environment by feeding on seagrass, ensuring that this aquatic plant stays cropped and does not overwhelm the ocean floor. They also contribute to beach health by aerating the sand and providing nutrients for beach plants with their unhatched eggs.