Threats to sea turtles are numerous and have caused many sea turtle species to be endangered. Of the seven extant species of sea turtles, six in the family Cheloniidae and one in the family Dermochelyidae, all are listed on the IUCN Red List of Endangered Species. The list classifies six species of sea turtle as "threatened", two of them as "critically endangered", one as "endangered" and three as "vulnerable". The flatback sea turtle is classified as "data deficient" which means that there is insufficient information available for a proper assessment of conservation status.IUCN 2018. IUCN Red List of Threatened Species. Version 3.1. <http://www.iucnredlist.org>. 11 August 2018 Although sea turtles usually lay around one hundred eggs at a time, on average only one of the eggs from the nest will survive to adulthood.Wright, Sara. "Hilton Head Island sees record sea turtle nesting season." Bluffton Today (2010): n. pag. Web. 8 Dec 2010. <http://www.blufftontoday.com/news/2010-08-06/hilton-head-island-sees-record-sea-turtle-nesting-season>. While many of the things that endanger these hatchlings are natural, such as predators including sharks, raccoons, foxes, and seagulls, many new threats to the sea turtle species are anthropogenic.Heithaus, Michael, Aaron Wirsing, Jordan Thomson, and Derek Burkholder. "A review of lethal and non-lethal effects of predators on adult marine turtles." Journal of Experimental Marine Biology and Ecology 356.1-2 (2008): 43-51. Web. 15 Dec 2010.
Artificial lighting
Artificial lighting is a threat to adult and hatchling sea turtles. Sea turtles use the brightest horizon as a guide to the ocean. This was created by celestial lights reflecting off the ocean's surface. With human development along the coast, artificial light sources are growing in abundance. Unfortunately, these human-made lights are brighter than celestial lights, causing sea turtles to move toward them. A sea turtle not going in the direction of the ocean is referred to as a disorientation event. Disorientations lead to an increased risk of predation, exhaustion, dehydration, and/or injury. These events are often fatal. Disorientations can be caused by any light source that is directly or indirectly seen from the beach. Also, heavily lit beaches may cause an adult to have a false crawl when the female decides the beach is not suitable for her nest and goes back to the water. False crawls cause exhaustion for the adult and may lead to her releasing her eggs in the ocean, which is fatal to all the eggs.
As awareness of the negative impact artificial lighting has on sea turtles has grown, there have been several large-scale conservation efforts by Marine Life programs and conservation groups to educate the public on turtle conservation. Communities situated on or near a beach have been warned of the effects excessive lighting has on sea turtles and there have been substantial attempts to darken beaches and replace harmful artificial lighting with turtle-safe lights. Coastal communities have also been creating and updating their lighting ordinances with the common goal to help save sea turtles. Lighting ordinances allow local governments to enforce safer lighting for sea turtles.
Magnetic interference
Ferrous metal wire mesh screens are commonly used to protect sea turtle nests from predators' excavating and devouring the eggs and hatchlings. A new concern is that nestlings' delicate magnetic sense may not develop normally in the presence of the magnetic field interference from these steel mesh cages. The effects of the use of steel mesh as a cage material may not be known for many years until assessments can be made of the success rate of the first adult populations that developed within such cages begin attempting landfall for nest-making. Gravid turtles or their hatchlings may also be affected by the presence of magnetic fields arising from power cables, iron debris, steel seawalls or other human activities that locally modify Earth's magnetic field.Lohmann, Catherine, and Kenneth Lohmann. "Sea turtles ." Current Biology 16.18 (2006): R784-R786. Web. 15 Dec 2010.
Oil spills and marine pollution
Marine pollution is both directly harmful to sea turtles as well as indirectly, through the deterioration of their natural habitats. Some of the most dangerous ocean pollutants include toxic metals, PCBs, fertilizers, untreated waste, chemicals, and a variety of petroleum products. Oil spills are particularly dangerous to sea turtles."Sea Turtle Threats: Oil Spills." Sea Turtle Conservancy (2010): n. pag. Web. 8 Dec 2010. <http://www.conserveturtles.org/seaturtleinformation.php?page=oilspills >. Although oil does not tend to stick to them as it does to other marine life, sea turtles are still at risk when they surface for air, where oil can get in their eyes, skin, and lungs, which can lead to significant health problems. Even if they are not directly in contact with marine pollution, sea turtles can still ingest harmful chemicals through the food they eat. Oil is also a cause for the death of seagrass, which is a staple in the diet of the green turtle. The diets of the hawksbill sea turtle, loggerhead sea turtle, and Kemp's ridley sea turtle species have also been affected by the oil's role in the reduction of certain sponges and invertebrates. Extended exposure has been found to deteriorate the health of a sea turtle in general, making it more weak and vulnerable to a variety of other threats.Milton, Sarah, and Peter Lutz. United States. Oil and Sea Turtles Biology, Planning, and Response. 2010. Web. 8 Dec 2010.
According to the Sea Turtle Conservancy, formerly known as the Caribbean Conservation Program, the migration habits of sea turtles increase their exposure to marine pollution at each of the stages of their lives including eggs, hatchlings, juveniles, sub adults, or nesting adults. In a 1994 study off of Florida's Atlantic coast, 63% of hatchlings surveyed were found to have ingested tar. Loggerheads in particular have been shown to have the most problems with tarball ingestion, leading to esophageal swelling that can dislocate the intestines and liver leading to serious buoyancy issues as well as excessive swelling. Many regions heavily associated with oil, either exploration, transportation, or processing, are also significant sea turtle environments, including the Gulf of Mexico and the Caribbean, and particularly the coasts of Texas and Florida. Sea turtles existing in the exact areas where oil spills occur are not the only ones at risk due to the strong and far reaching ocean currents which can move pollution to great distances from its derivation.Witherington, B.E. "Ecology of neonate loggerhead turtles inhabiting lines of downwelling near a Gulf Stream front." Sea Turtle Conservancy (2002): n. pag. Web. 8 Dec 2010.
Breeding season is in particular a dangerous time for sea turtles due to the pollution of beach nesting sites.Antworth, Rebecca, David Pike, and John Stiner. "Nesting ecology, current status, and conservation of sea turtles on an uninhabited beach in Florida, USA." Biological Conservation 130.1 (2006): 10-15. Web. 15 Dec 2010. Contamination of their diet can lead to disruption of digestion as well as physical injury to the sea turtles' digestive tracts. The nesting of female sea turtles is often deterred due to the potential of oily effluence. If the female does lay eggs, the development of the eggs is at risk due to either oil in the sand or contamination from the mother turtle that was oiled while nesting. If the eggs in the nest have contact with oil while in the last half of their incubation phase, the rate of hatchling survival sharply decreases and those that do survive have a greater chance of physical deformities.United States. Impacts of Oil on Marine Mammals and Sea Turtles, 2010. Web. 8 Dec 2010.
Ocean plastic Eight million tons of plastic make their way to the ocean every year. For many marine species, including sea turtles, plastics in our oceans can lead to threats of entanglement, habitat degradation, and ingestion. Discarded plastic bags floating in the ocean resemble jellyfish, a common food of sea turtles. If a turtle eats a plastic bag, it tends to clog the turtle's digestive system and result in the animal dying. There have been many cases of dissection showing plastic and other debris inside turtles' stomachs and intestines.Pictures of plastic items eaten by turtles Marine debris has caused mortality in all species of sea turtles. There have also been cases where sea turtles have been found with plastic straws in their noses, plastic bags or toothbrushes in their stomachs, or fish hooks stuck on their flippers. Plastic straws can be dangerous to sea turtles, too, because they are often mistaken for food. This can cause the sea turtle to choke or die of starvation because they feel full and do not eat, when they are actually full of plastic. Despite being small, plastic straws are among the top items that pollute the ocean. As previously mentioned, ingestion is also more likely to occur if the plastic resembles their typical food. Studies have found that turtles had a 50% chance of dying if they ingested more than fourteen pieces of plastic
Tourism Owing to the popularity of numerous sea turtle species, people often travel to areas where the turtles nest, live to observe and photograph them. This has resulted in numerous deaths of the turtles through boat collisions, tourists attempting to catch or steal individuals, and other incidents. In Costa Rica, tourists have recently been criticised for interfering with the nesting habits of the resident olive ridley sea turtles, disrupting and confusing the animals by attempting to take selfies with them. Many baby turtle release events occur during the day in various locations, which increases the risk of predation.
Boats
There are numerous threats to sea turtles associated with boats, including oil spills, habitat degradation, and vessel collisions. Boat strike injuries result in two types of injuries: blunt force trauma and propeller slices in the carapace. Blunt force trauma is from the hull of the boat hitting the turtle and results in a cracking, less obvious, injury on the turtle's carapace. Propeller strikes form clear cut, parallel lines on the carapace of the turtle. The propeller wounds can cut into the spinal cord or lungs if deep enough, as these are located dorsally on the animal attached to the underside of the carapace. Sea turtle stranding data is the primary method of quantifying boat strike injuries, which has increased by 20% in Florida between 1985 and 2005. In general, sea turtles are not able to avoid boat collisions when boats are travelling too quickly. Also, the faster a boat is travelling the more damage is done to the turtle, making incidents more lethal. When sea turtles surface to breathe they continue swimming in the water column just below the surface; this allows them to get a few breaths in at a time, and then dive into deeper water to hunt or forage. This depth is the ideal depth for the propeller of the boat to hit the turtle, it also makes it even more difficult for boaters to try to avoid the turtles, since they cannot be seen.