Nestled on the northern coast of San Salvador Island in the Bahamas, Graham’s Harbour's crystal-clear waters and shallow depths are home to many patch reefs, seagrass beds, and the species that live within the reefs and beds. Because of all of these features, it also makes an excellent location to snorkel. The first time that we snorkeled in Graham's Harbour, we discovered that it was a habitat for green sea turtles. The shallow waters and abundant seagrass beds create an ideal environment for the turtles.
The historical significance of Graham’s Harbour dates back to 1492, when Christopher Columbus marveled at its vastness. Columbus stated that it “would hold all the ships of Christendom.” The collapse of a concrete dock in the harbour led to the formation of an artificial reef, and many of the green sea turtles we saw in the area swam in and out of the nooks and crannies of the collapsed dock.
Photos by Liza Jones
Green sea turtles, found worldwide in tropical and subtropical seas, play a crucial role in maintaining the health of seagrass beds and coral reefs. Green sea turtles thrive in shallow coastal areas with abundant seagrass beds, making Graham’s Harbour a perfect habitat. The artificial reef formed by the collapsed dock provides additional feeding grounds and shelter.
Photo by Liza Jones
Diet and Feeding Habits:
Adult Diet: Primarily herbivorous, feeding on seagrass, algae, and various nutrient-rich species. Some of the seagrass species they feed on include:
Turtle Grass (Thalassia testudinum): This species is characterized by its broad, flat blades that grow in dense underwater meadows, providing a substantial food source for the turtles.
Manatee Grass (Syringodium filiforme): Recognizable by its cylindrical blades, Manatee Grass is found in similar habitats as Turtle Grass and is another key component of the turtles' diet.
Shoal Grass (Halodule wrightii): Featuring thin, narrow blades, Shoal Grass often grows in shallow waters, making it accessible and nutritious for green sea turtles.
In addition to seagrass, green sea turtles ingest various species of algae, which are abundant in nutrients. These algae contribute to the green coloration of their body fat as a result of the presence of chlorophyll and other pigments.
Juvenile Diet: Juvenile green sea turtles exhibit a more diverse dietary profile compared to their adult counterparts due to their omnivorous nature during this developmental stage. Their diet encompasses a wide array of invertebrates during their early development, such as jellyfish and sponges.
Photo by Loren Quintana
Life Cycle and Challenges:
Green sea turtles have a lifespan of over 70 years. They don’t reach sexual maturity until between 20 to 50 years old.
Hatchlings, which emerge from eggs deposited in sandy beaches during nesting season, undergo an incubation period ranging from 48-70 days. The thermal conditions during incubation significantly influence the sex determination of the offspring, a phenomenon known as temperature-dependent sex determination (TSD). After hatching, hatchlings face considerable challenges, with survival rates estimated at a mere 0.1%, primarily due to predation and environmental factors. Upon entering the ocean, juveniles spend several years in the open ocean before returning to shallow coastal areas. Adults migrate between feeding and nesting grounds, and females return to their natal beaches to lay their eggs. As adults, they are threatened by habitat loss, poaching, and accidental capture in fishing gear.
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