Scientific Name: Chelonia mydas

Status: Endangered or Threatened

There is a well understood pattern for terrestrial herbivory grazing, however, the grazing patterns in seagrass meadows are far less understood. Understanding herbivory patterns in seagrass meadows can help to understand the top-down influence affecting the structure of meadows and how they function. In ecology, top-down refers to how a top predator can influence the structure and population dynamics of an ecosystem. In seagrass meadows, the green sea turtle consumes a large amount of seagrass biomass that respectively alters the meadow’s structure.
Recent studies have shown that green sea turtles establish a grazing plot for 13 months to 2 years. This grazing pattern allows green turtles to crop blades at the base and then graze the regrowth. The benefit to grazing on the regrowth is that it is nutrient-rich and easily digestible. Recent studies have also found that green turtles will occasionally consume the entire blade, root, and rhizome because it contains more carbohydrates.
Grazing can modify seagrass bed ecosystems and their services based on top-down control. For example, if there are few green sea turtle predators like sharks, seagrass meadows can become overgrazed. Thus, there will be less habitat and resources for smaller invertebrates and the developing species. This is just one example of how difficult it can be to maintain the balance of seagrass ecosystems.

Description

Green sea turtles are unique because as juveniles they are omnivorous but once they reach adulthood, they are strictly herbivores. The green turtle is the largest of the Cheloniidae family, weighing about 240-420 pounds and their carapace measuring about 3-4 feet in length.

Fun Fact: Green turtles have a greenish hue to their cartilage and fat because of their grassy diet. However, their shells can be in a range of different colors.

Green turtles, like other sea turtles, will migrate from foraging habitats to nesting beaches. They may travel hundreds or thousands of kilometers to mate and lay their eggs. Males will reproduce each year, but females can only reproduce every three to four years. This creates fluctuations in the number of nesting females available from year to year.

Conservation

The greatest threats to green turtles are bycatch in fishing gear, boat strikes, harvesting of eggs or intentional killing, loss of nesting habitats, ocean pollution, and disease. Over the past fifty years, green turtle populations have declined 90% due to these threats. Green sea turtles are protected under national and state law and international treaties. Many restoration projects have begun to improve and protect nesting habitats. NOAA has many research projects and population monitoring projects to aid in better management and conservation policies to protect and conserve.

How Can You Help?

Reduce Ocean Trash

Responsibly dispose of fishing waste, participate in beach clean-ups, reduce your single use plastic by using reusable bags and water bottles.  

Keep Your Distance

Be respectful and only observe from a distance. Never disturb a nesting site and while boating, steer around and slow down while near any turtles. Keep nesting beaches safe by removing any recreational beach equipment at night, not driving through them, and keeping the beaches dark so not to confuse the nesting females.

Report Marine Life Distress

Please contact your local professional responders and trained scientists if you ever encounter a stranded, injured, or entangled sea turtle.

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References

Photo Credit: Nicole Kieda, Florida Keys

Abigail L. Scott, Paul H. York, Michael A. Rasheed, Green turtle (Chelonia mydas) grazing plot formation creates structural changes in a multi-species Great Barrier Reef seagrass meadow, Marine Environmental Research, Volume 162, 2020, 105183, ISSN 0141-1136, https://doi.org/10.1016/j.marenvres.2020.105183.

Fisheries, N. (n.d.). Green Turtle. Retrieved January 31, 2021, from https://www.fisheries.noaa.gov/species/green-turtle#overview

Green Sea Turtle. (n.d.). Retrieved January 31, 2021, from https://www.nwf.org/Educational-Resources/Wildlife-Guide/Reptiles/Sea-Turtles/Green-Sea-Turtle