Learn about sea turtles
The green sea turtle has inhabited Earth for over 100 million years. It is the only sea turtle that when fully grown survives on a mostly vegetarian diet. This turns its flesh and cartilage a green color, giving it its name.
The sea turtle plays an important part in keeping marine environments functioning and able to thrive.
Naturally feeding on sponges and algae, sea turtles are responsible for keeping ecosystems like coral reefs healthy, and therefore continuously provide habitat for other marine life. By grazing on seagrass beds, they increase the nutrient content and productivity of the seagrass and help avoid its overgrowth and decomposition. Predation by sea turtles on organisms such as crabs, small fish, shrimp, worms, jellyfish, and vegetation (in the case of the green turtle) helps to balance the populations of these species. Additionally, sea turtles facilitate nutrient cycling by burrowing their nests into terrestrial ecosystems. Many small marine organisms such as algae and barnacles attach themselves to the shells of sea turtles. This not only provides them with a habitat in which to live, but also helps them to disperse and forage, in turn providing food for other marine life. It is thought that sea turtles orient and navigate themselves using the earth’s magnetic field. This mechanism acts like an internal compass and enables them to find their way back to the beaches where they were born. There are 7 sea turtle species in the ocean including the green, hawksbill, loggerhead, olive ridley, Kemp’s ridley, the flatback, and the biggest of all, the leatherback. All of these species are threatened with extinction, being listed on the IUCN red list (International Union for the Conservation of Nature), with the green and the hawksbill under the greatest threat.
Sea turtle populations have been exploited through poaching and trade of their meat, skin, eggs, and shells.
In 1981 international laws began to protect sea turtles by prohibiting their trade, and trade of derived items. While most countries nowadays declare it illegal to harm, harass or kill them, there are still many countries, mainly in the Caribbean and Indo-Pacific region where sea turtles are not protected from harvest and commercial use. Additionally, they continue to be harvested illegally.
One of the biggest threats they face is ending up as bycatch in commercial fisheries.
This is not restricted to sea turtles but extends to a wide variety of marine wildlife, with 40% of all animals caught being discarded. They regularly end up as bycatch when fishing using longlines, trawls, driftnets, gillnets, and seine nets, and are fatally injured by dynamite fishing. Even after being thrown back into the ocean, their chances of survival are very low as imposed stress and injuries are often too severe. To protect Sea turtles from accidental catch, in some commercial fishery methods, gear modifications such as turtle exiting devices and hook modifications have been successfully installed. ‘Ghost gear’ – discarded fishing gear left in the ocean, is another hazard for marine life with animals getting tangled in ghost nets and line, unable to free themselves.
Plastic waste in the ocean presents an everyday challenge.
This can be seen in the plastic filled stomach contents of stranded or deceased marine life, along with living animals whose ability to breathe or move is inhibited.Single use plastics are found everywhere today, ranging from shopping bags and take-out cutlery to grocery wrapping, straws and water bottles. It does seem difficult to avoid, however often when aware of the situation it is easier to reach for alternatives when possible and minimize our consumption. We produce more than 300 million tons of plastic every single year, of which roughly 8 million end up in the ocean. Human settlement and development along coastlines present sea turtles species with another threat in that it is increasingly difficult to find nesting habitats. When sea turtle hatchlings are born, they instinctively begin moving in the direction of light in order to navigate themselves towards the ocean.
Unfortunately, they are not only attracted to the natural light reflected on the ocean’s surface, but to artificial light sources from coastal human developments. This leads them in the opposite direction, a consequence of light pollution.
This increases mortality rate before even making it into the water as some simply cannot find the ocean.Adding to this, on their journey from nest to ocean, hatchlings will be preyed upon by birds, crabs, racoons, and carnivorous fish. Nesting females also confuse artificial for natural light which affects their navigation in the same way. While an individual sea turtle lays up to 150 eggs in one clutch, statistically only 1 in 1000 hatchlings will survive up to adulthood. Furthermore, the number of nesting females has declined by 48-67% over the last three generations. Sea turtles also have to battle a virus called Fibropapillomatosis. Since the 1980’s it has been observed much more frequently, especially in green turtles. This infectious disease motivates tumor growth anywhere on the turtle’s body, internally and externally, where it may cover vital organs and can make it difficult for them to see, swim, breathe, or feed. While the definite cause of this virus has not been identified, prevalence of infected cases is associated with heavy pollution, dense human settlements, and toxic run-off from agricultural production. Taking all of the risks into consideration, it seems incredibly difficult for sea turtle populations to recover. Moreover, the green turtle grows very slowly and of all the sea turtles, is the slowest to reach maturity. This makes this species even more vulnerable to population declines due to its slow reproduction rate. A change in perspective, and action from us is required to let these sea turtles survive, and hopefully thrive again.
Species Fun Fact
A turtle’s sex is determined by the surrounding temperature of the egg during incubation. Outside temperatures of 31°C will result in female hatchlings while a cooler 28°C will develop males. Global warming therefore presents a direct threat to turtle populations, as sex ratios are becoming unbalanced.
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All information was collected and up to date in 2020.