Sea turtles and the environment
By Andrea Jackson
The Sea Turtle Preservation Society’s motto is “Helping sea turtles survive.” The question is, why? Besides the obvious bottom of the food chain contribution, what makes sea turtles so worth saving.
As it turns out, sea turtles impact both the beach/dune ecosystem as well as the marine ecosystem. Here are just a few contributions made by our sea turtles.
Green Sea Turtle
Green sea turtles feast mostly on seagrasses and algae. They get their name not for the color of their carapace, but for the greenish hue of the turtle’s fatty tissue. When green sea turtles graze, they help to maintain healthy seagrass beds. Without constant grazing, seagrass beds become overgrown and obstruct currents. Overgrown beds will shade the ocean bottom and begin to decompose, which in turn provides a suitable habitat for the growth of slime molds. Like normal lawn grass, seagrasses need to be “trimmed” to stay healthy and grow across the sea floor rather than just getting longer grass blades.
Seagrasses are known as the “lungs of the sea.” One square meter of seagrass can generate approximately 10 liters of oxygen every day through photosynthesis. Seagrass beds also provide breeding and developmental grounds for many species of fish, shellfish and crustaceans. They stabilize the sea bottom and help maintain water quality.
Hawksbill Sea Turtle
Hawksbill sea turtles like to dine on marine sponges and soft reef invertebrates. They use their beak-like mouths to extract their food from coral reefs and cervices. Sponges are an unusual food choice due to their toxic chemical make-up and are not eaten by most predators. As the hawksbill rip sponges apart, they expose food to marine species that cannot otherwise penetrate the sponge’s exterior. By removing sponges from reefs, Hawksbills allow other species, such as the coral itself, to colonize and grow. It’s estimated that one hawksbill sea turtle can consume over 1,000 pounds of sponges per year. This is very an important to the overall health of the reef community. Without the hawksbill, sponges would be able to overgrow corals and suffocate reefs.
Healthy coral reefs provide habitat and protection for many species of fish and sea life. They protect the coastline from strong currents and waves by slowing down the flow of water. Coral reefs impact carbon dioxide levels in the ocean as well. Without coral, the amount of carbon dioxide in the ocean rises, which in turn, affects all living things on Earth.
Leatherback Sea Turtles
Leatherback sea turtles specialize in eating jellyfish which keeps the jellyfish populations in check, which in turn helps other species in the ocean thrive. Smaller jellyfish will eat plankton, a term which refers to very tiny, floating sea animals, like brine shrimp. Other jellyfish, which are larger, will eat fish eggs, while even larger jellyfish will devour crustaceans like sea snails and crabs. The very largest jellyfish will eat small fish. A rise in jellyfish would have a negative effect on many of our fish populations. Leatherbacks, thankfully, can consume twice their own body weight in prey per day, feeding exclusively on soft-bodied invertebrates like jellyfish.
On the beach…
Nesting sea turtles provide important nutrition to the beach ecosystem. The unhatched eggs and trapped hatchlings are excellent sources of nutrients for the vegetation in the sandy ecosystem. Since sand does not hold nutrients very well, all the unhatched nests, eggs and trapped hatchlings play a vital role in dune vegetation.
Dunes are very important to the coastal ecosystem for many reasons. For one, coastal areas are protected from erosion because sand dunes absorb the effects of storms. As the dune vegetation grows stronger and healthier, the health of the entire beach/dune ecosystem improves. Healthy vegetation and root systems helps to hold the sand in the dunes and helps protect the beach from erosion.
- Why Healthy Oceans Need Sea Turtles: the importance of sea turtles to marine ecosystems” by Wilson, E.G., Miller, K.L., Allison, D. and Magliocca, M.; oceana.org/seaturtles