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Sea Turtles: Why We Care

Would you have guessed that a sea turtle would symbolize the recent landmark climate change agreement between the U.S. and China? On November 24, 2014, Randall Robinson, American Consul General in Guangzhou, China, Frederick Yeh, IUCN marine turtle specialist and founder of Sea Turtle 911, a not-for profit organization that fosters sea turtle conservation in China, and student volunteers from Hainan Normal University released a satellite-tagged Green Turtle into the South China Sea.  Three months earlier, a China/USA workshop on sea turtles convened by the U.S. National Marine Fisheries Service (NMFS) and Chinese Academy of Fishery Science in Beijing reported that "Cross-cultural goodwill and cooperation were advanced between China and the USA, using sea turtle science and ecology as the means of person-to-person diplomacy." Goget’s release celebrated the historic U.S.-China agreement, signed two weeks earlier, to reduce emissions of climate warming emissions

Randall Robinson, U.S. Consul General (in suit), Frederick Yeh, founder of Sea Turtles 911 (in blue), and student volunteers (in green) encourage Goget, a Green Turtle as she crawls toward the South China Sea. Goget is the latest of many turtles released by Sea Turtles 911, which works to conserve sea turtles by rescuing, rehabilitating, raising and releasing sea turtles in China, along with public education and research. 

Meanwhile, half a world away, hundreds of volunteers from the Massachusetts Audubon Society’s Wellfleet Bay Animal Sanctuary patrolled Cape Cod’s beaches rescuing sea turtles that were incapacitated or dying from a sudden cold-snap. The volunteers warmed them, drove them to the New England Aquarium’s animal hospital in Quincy, Massachusetts for medical care, then private airplanes or the U.S. Coast Guard flew survivors to Florida for release into the Gulf of Mexico or to aquariums for holding until waters are warm enough for their release elsewhere.

Volunteers and animal care staff from the Virginia Aquarium, National Aquarium in Baltimore, New Hampshire Science Center, IFAW and others joined New England Aquarium (NEAq) Rescue Department staff at NEAq’s Animal Care Center in Quincy, Massachusetts, to rehabilitate sea turtles stranded on Cape Cod during November and December, 2014..

Why do people care so much about sea turtles?  

Some care for emotional reasons. Stranded turtles seem ancient, wise, puzzled and hurt. People want to help them. Anyone who has seen a female sea turtle shed tears as she lumbers up the beach, digs a nest and carefully fills it with ping-pong ball sized eggs is probably deeply moved. The tears are actually secretions of excess salt from the nasal salt glad, but they look sad anyway. Emotional factors probably contributed to veneration of turtles in some cultures as symbols of peace, prosperity, good fortune and long life.

Others have more practical interests, food and money:

Some people emphasize the turtles’ ecological importance to marine ecosystems: 
  • Sea turtle grazing keeps sea grass beds healthy and productive.  The turtles clip the tops off fronds, encouraging plants to spread laterally, allowing sunlight to penetrate better and leaving room for fish, shellfish and crustaceans, including many commercially important species, to shelter and reproduce. Without grazing, the grasses grow tall with broad fronds, reducing the flow of water currents and oxygen, shading the beds and providing conditions for bacterial decomposition and development of grass-killing diseases.  The declining condition of sea grass meadows worldwide has been attributed to the loss of grazing by sea turtles, manatees and dugongs, whose formerly abundant populations have been extirpated by human activities.     
  • Sea turtle nests nourish beach and dune ecosystems. Each female may nest several times in one season, laying a hundred or more eggs each time, leading to total deposits of thousands of pounds of eggs on popular beaches.  Eggs that fail to hatch and nestlings that fail to emerge from the nest decompose into nutrients used by beach vegetation that stabilizes and protects dunes from erosion by wind and storm waves.

Green Turtle females coming ashore to nest on a beach in Australia.  

Some people emphasize the turtles’ ecological importance to marine ecosystems: 
  • Sea turtle grazing keeps sea grass beds healthy and productive.  The turtles clip the tops off fronds, encouraging plants to spread laterally, allowing sunlight to penetrate better and leaving room for fish, shellfish and crustaceans, including many commercially important species, to shelter and reproduce. Without grazing, the grasses grow tall with broad fronds, reducing the flow of water currents and oxygen, shading the beds and providing conditions for bacterial decomposition and development of grass-killing diseases.  The declining condition of sea grass meadows worldwide has been attributed to the loss of grazing by sea turtles, manatees and dugongs, whose formerly abundant populations have been extirpated by human activities.     
  • Sea turtle nests nourish beach and dune ecosystems. Each female may nest several times in one season, laying a hundred or more eggs each time, leading to total deposits of thousands of pounds of eggs on popular beaches.  Eggs that fail to hatch and nestlings that fail to emerge from the nest decompose into nutrients used by beach vegetation that stabilizes and protects dunes from erosion by wind and storm waves.

Sea turtle female fills her nest with ping-pong ball sized eggs.  Bagaon Island, Philippines.  

  • Hawksbill turtles support biodiversity on coral reefs by eating sponges. Sponges and the bacteria they harbor often produce distasteful chemicals (some of which have important uses in human medicine) so few animals eat them.  Without predation by hawksbills, sponges could rapidly overgrow reef surfaces, preventing new corals from settling and reducing living space available to other species.   

Hawksbill turtle soars above reef.  Komodo National Park, Indonesia. 

  • Sea turtles, especially Leatherbacks, but also Hawksbills and Loggerheads, can help control jellyfish populations that have increased in some locations, perhaps as a result of overfishing, pollution and ocean acidification.  Leatherbacks feeding on Lion’s Mane and Moon Jellyfish in eastern Canadian waters ate an average of 73% of their body mass each day, more than three times their daily metabolic needs.
  •  Loggerhead turtles accelerate nutrient regeneration on shallow seabeds. They overturn sediments in search of gastropods, clams, mussels, crabs and other prey.  Their very strong jaws can crush shells too strong for other predators. Both bottom plowing and dropping of uneaten prey parts make nutrients available to other bottom plants and animals.

  • Sea turtles become floating communities. As turtles age, algae, barnacles, sponges, algae, hydrozoans, sea anemones, worms, snails, small clams and others colonize their shells, especially in Loggerhead and Hawksbill shells.  More than 125 species occur on Loggerheads.  Those hitchhikers are a boon to coral reef fish which establish ‘cleaning stations’ where wrasse, shrimps, angel fish, sheepshead bream and others eat them, cleaning the turtles’ shells in the process. Amateur videos of turtle cleaning stations in Hawaii can be seen here or here.  In the open ocean, schools of small fishes frequently shelter gather under the turtles for shelter, as they do under any floating object, perhaps  providing food to larger fishes or seabirds on occasion. 

School of fish plus several remoras (suckerfish) accompany a large leatherback turtle off the coast of Brazil.  Photo: Gary Marcovaldi.

Whatever a person’s reasons for valuing sea turtles, everyone shares the goal of conserving healthy populations, but that is a big challenge. Six of the seven species are endangered, critically endangered or vulnerable to extinction. Hawksbill (Eretmochelys imbricata) and Kemp’s Ridley (Lepidochelis kempii) are Critically Endangered; Loggerhead (Caretta caretta) and Green Turtle (Chelonia mydas) are Endangered: Olive Ridley (L.olivacea) and Leatherback (Dermochelhys coriacea) are Vulnerable. All have worldwide distribution except for Kemp’s Ridley, which only lives in the Atlantic Ocean and Gulf of Mexico. Extinction risk status is not yet known for the seventh species, the Flatback Turtle (Natator depressus), which lives only along Australia’s continental shelf.

Complicating things further, each species includes several or more populations that nest in different places, have different migration routes and face different threats and risks.