Shell Game At Sea
By Mary Jane Schramm
It was low tide and the bay was calm, sheltered from brisk northwest winds. The bright green meadow of eelgrass swayed gently, sunlight suffusing the water with an otherworldly glow. A wet-suited researcher crouched down, intent on recording the density of this marine plant within a fixed area marked by a PVC pipe frame. Unknown to her, this seagrass was also today’s Chefs’ Special for an exotic visitor. Straightening up to stretch, she snapped to attention when a large sea turtle popped to the surface just a few feet away, in slightly deeper water. It regarded her calmly for a moment, then dove to continue grazing. The visitor was an East Pacific green turtle, (Chelonia mydas).
Big Green: Green sea turtles are marine reptiles found in temperate and tropical waters worldwide, varying in size, shape and coloration among geographic regions. They are the largest hard-shelled sea turtle. Of the two species most often found in northern California waters, the East Pacific green is second in size only to the Pacific leatherback. Adults average from 250 to 450 pounds, but one Indian Ocean green weighed in at a whopping 871 pounds! A Pacific green’s shell ranges in color from dark gray to black, and is smooth and arched. Its common name derives not from its skin or shell color, but from its fat, which is green-tinted due to its herbivore diet. They can live 70 to 80 years.
Surf & Turf: East Pacific greens range from Chile to Southernmost Alaska, with northern hemisphere nesting sites in Central America and Mexico. Most California greens migrate from Mexican breeding beaches to California’s’ productive marine ecosystem to feed. They are coastal, rarely seen far offshore, preferring protected bays and estuaries rich with eelgrass such as Humboldt Bay and other inlets, even harbors.
Salad Days: As adults, greens are unique among sea turtles in their vegetarian diets, munching on seagrasses and marine algae scraped from rocky surfaces. As hatchlings and juveniles, though, they feed on sponges, crabs, fish eggs, mollusks, and jellies.
Beach Babes: Green turtles mate at sea, which concludes the male’s role. As Crush the sea turtle from “Finding Nemo” remarked: “It's awesome, Jellyman. Little dudes are just eggs, we leave 'em on the beach to hatch, and then — koo-koo ka-choo! — they find their way back to the Big Ol' Blue.” Females nest at two- to five-year intervals in late spring, laying around 100 ping pong ball size eggs per nest, from two to eight times each season. After covering her clutch, she returns to sea, leaving her hatchlings to dig out and head for the surf after a roughly 60-day incubation. Nest temperatures determine each egg’s gender: males develop in cooler nests, females in warmer ones.
Greenlighting Survival: East Pacific green turtles were federally downlisted from endangered to threatened under the Endangered Species Act in 2016, a cautiously optimistic conservation success story. As recently as the 1990s, harvesting for eggs and meat on nesting beaches was legal. But starting with protection of their beaches, then their foraging habitats, they are now making a comeback. At Playa Colola, Mexico, the largest east Pacific green rookery, nesting females went from just 250 per year in the mid-1980s to over 1,000 females in just one night in 2015!
Threats include fisheries bycatch, direct harvest, disease, habitat degradation and loss, pollution, marine debris, and vessel strikes. The National Oceanic and Atmospheric Administration (NOAA) warns that global warming is skewing the gender ratio: the number of female hatchlings is outstripping males, with possible long-term impacts on endangered and recovering populations.
Go Green: Play a role in their recovery: minimize your carbon footprint to slow global warming. Dispose of trash and fishing gear responsibly to keep it out of our ocean. Report any sea turtle sightings immediately to NOAA.
Images: (left) Maui Ocean Ctr./Creative Commons Zero - CC0. above: Kirt Edblom/ShareAlike 2.0 Generic (Green Sea Turtles-CC0-Kirk Edblom)
