Blog Post By: Elaine Walters, Sea Turtle Intern
Loggerhead sea turtles spend much of their juvenile life in an area of the Northern Atlantic known as the Sargasso sea. The hatchlings emerge from their egg chamber en masse after nightfall (generally queued by a drop in sand temperature). After this emergence, which is also known as a boil, the hatchlings swim for approximately three days to reach the Sargasso sea. Here they spend much of their time until they reach sexual maturity at about thirty years old. This period of sea turtle development is sometimes called the lost years, as little is known about their exact behaviors.
The Sargasso sea is formed by the circulation of the ocean. It is bordered not by landmasses, but rather by strong currents of water. These currents are formed by the Earth’s rotation and by the differential heating of the Earth by the sun. As the earth rotates, the water in the ocean wants to follow. If there were no landmasses, the water would spin around the globe unimpeded; however, when the water hits the land, it must turn. This creates spirals of water with four boundary currents.
There are many other areas of the ocean that experience these as well, and they are referred to as gyres. These gyres often collect things within their boundaries, including plastic as more human waste makes its way into the ocean. In the case of the Sargasso sea, it has become the home of great mats of brownish seaweed called Sargassum. In addition to sea turtles, these mats provide shelter and food to many organisms (some of which become food for young turtles). This is significant because the open ocean is often limited in structure and food resources, both of which are provided by sargassum.
Because of global climate change, the circulation that causes this gyre and subsequent open ocean ecosystem to form and thrive may be threatened. More data is still needed to determine the exact ramifications of these changes; however, it has been shown that these currents are shifting and changing due to higher temperatures (Yang et. al., 2020). The effect this may have on the life cycle of loggerhead sea turtles is still unknown, but it is possible that it could pose challenges in the early stages if they have to travel longer distances to reach relative safety and food sources.
Yang, H., Lohmann, G., Krebs-Kanzow, U., Ionita, M., Shi, X., Sidorenko, D., et al. (2020). Poleward shift of the major ocean gyres detected in a warming climate. Geophysical Research Letters, 47, e2019GL085868. https://doi.org/10.1029/2019GL085868
Sea Turtle Biologist