Conservation news

Saving Jamaica Bay’s diamondback terrapins

  • The Diamondback terrapin (Malaclemys terrapin) is a turtle species native to coastal tidal marshes in the eastern and southern United States.
  • Its population in New York City’s Jamaica Bay has declined by more than half in the last decade – to an estimated 10,000 turtles today.
  • The underlying causes for this decline are a mystery, but researchers are now engaged in a multi-year study to identify them. As the terrapin plays a crucial role in the ecosystem’s health and resiliency, their findings have important implications for Jamaica Bay.

As the white motorboat juddered to a stop in the middle of a marsh in New York City’s Jamaica Bay, Russell Burke peered over the edge into the shallow, clear water. In the distance, a flock of Brent geese took to the crisp October air. Using a long hook, he dragged a floating orange buoy towards him. It was attached to a large crab trap, which Burke lugged out of the water.

Black mud and periwinkle shells clattered onto the boat’s pristine deck. Inside the trap sat a single palm-sized turtle, a male diamondback terrapin, gently waving flippers that were so green they were almost black. The signature diamond-shaped patterns on its shell gleamed in the afternoon sun.

“I think we’ve caught the last guy of the season,” said Burke, a professor of ecology at Hofstra University. Turtles start preparing for colder weather by moving out of marshes and staying in deeper water. Burke peered at the creature. “What were you doing out and about, buddy?”

Burke and his team spent the previous summer trapping and studying the bay’s terrapin population, a turtle species native to coastal tidal marshes in the eastern and southern United States. Its population in Jamaica Bay has declined by more than half in the last decade – to an estimated 10,000 turtles today, according to Burke. This “freefall,” he says, is due to a falling egg-laying capacity in female terrapins.

The underlying causes for this decline are a mystery, but Burke and his colleagues are now engaged in a multi-year study to identify them. As the terrapin plays a crucial role in the ecosystem’s health and resiliency, Burke’s findings have important implications for Jamaica Bay. The research will also shed light on a little-appreciated, long-lived marine species that lives in the shadow of a teeming metropolis.

Terrapins and the bay

Named for the four-edged patterns on their shells, this semi-aquatic turtle species is native to the area. In fact, the word “terrapin” itself is of Algonquin origin. Hunted almost to extinction during colonial times to feed the city’s mania for turtle soup, diamondback terrapins have bounced back, albeit precariously. Indiscriminate commercial crab traps, habitat loss, and polluted waters in the Bay continue to threaten their existence.

Still, Jamaica Bay, a 40-square-mile swath of marshy islands straddling the southern tip of Queens and Brooklyn, is home to the largest known population of terrapins in New York and, in fact, all of the northeastern United States. Today, the approximately 10,000 terrapins swim, live, and feed in the bay, primarily on periwinkle snails. Periwinkles feed widely on salt marsh cordgrass, which comprise the bay’s marsh vegetation. In short: without terrapins, the periwinkle population would grow unchecked and decimate the grasses that make up the bulk of the marsh.

Ecologists consider the terrapin a keystone species in the bay. Much as the wolves in Yellowstone manage the mountain ecosystem’s structure and population dynamics by preying on hoofed animals, the terrapins do the same in their marshes and coastal ecosystem.

Without them, the marshes — which are already eroding — could decline further. This, in turn, would chip away at the bay’s resilience and ability to buffer against extreme weather events, such as Hurricane Sandy in 2012.

And yet, despite the terrapins’ importance to the wetland ecosystem, not nearly enough is known about them. “System-level aspects of terrapin ecology are poorly studied,” said Burke.

For the past 15 years, Burke and his team have monitored terrapins as they come on land to Rulers Bar, an island in the Jamaica Bay Refuge, during their nesting months of July and August. But this summer is the first time he’s managed to trap terrapins in their natural yearlong habitat — the marshes — for a closer look.

“To help the declining population, we have to understand the problem before suggesting any solutions,” said Burke.

To that end, he is looking for traces of pollutants that accumulate in the terrapins’ shells and blood. Despite a governmental push in recent years to clean up the bay, organic pollutants – such as lead and DDT from nearby capped landfills and sewage treatment plants – still make their way into the water. Burke aims to determine the pollutants’ effects on terrapin health.

After the boat docked at the jetty, Burke and his small team helped unload the nine crab traps – all of which came up empty that day, save for the single male terrapin.

Marion Vargas, a graduate student of ecology at Hofstra University, took hold of the flailing creature. “He’s about 40 years old,” she told me. “You can tell by the dark color of his shell, and the number of rings.”

She started scraping a corner of the turtle’s shell with a small metal razor – much like filing a fingernail. Dark green shavings drifted into a test tube, marked with the date and time.

Then she passed the creature to Burke, who dipped a needle into its cloaca, the base of its tail. Blood rushed into the syringe.

“This is for your own good,” said Burke to the struggling terrapin, which he released back into the bay the following day. Both the blood and shell shavings would be sent to a lab to test for trace pollutants. This was the start of what Burke hopes will be a yearly trapping season.

The state of the bay

The interplay of ecosystem health, terrapin numbers, and Jamaica Bay’s marshes is complex. Even as scientists are racing to reverse the decline of the terrapin population, their dwindling number is hammering another nail in the coffin of the bay’s receding marshlands.

“At one point, we were losing about 40 acres of marsh a year,” said Don Riepe, who works for the American Littoral Society, a coastal conservation non-profit, as its Jamaica Bay guardian. Originally 10,000 acres, the bay’s salt marshes have shrunk by more than 60 percent since 1951. They make up less than 1,000 acres today, according to Riepe.

A juvenile diamondback terrapin (Malaclemys terrapin). Photo by Chesapeake Bay Program.

“Marsh dieback,” as it’s called, is ostensibly caused by a combination of factors. Though there hasn’t been common consensus around any one reason, researchers have proposed several: Rising ocean levels effectively drown the grass; increasingly urbanized shorelines block the flow of sediments from inland rivers, preventing a vital source of nutrients from reaching the bay; and nitrogen pollution in runoff from nearby sewage treatment plants further weaken the marsh system.

In 2011, the city awarded the Jamaica Bay Littoral Society $500,000 for marsh restoration. For the past five years, Riepe and a group of volunteers have been replanting grass out in the bay.

“Right now we have rebuilt more than 100 acres of vegetation,” he said. “While we’re trying to stabilize the rate of marsh loss, we’re rebuilding marshes to restore what we’ve lost.”

This is only one of numerous initiatives recently undertaken to protect and restore Jamaica Bay, considered the crown jewel of NYC’s natural resources. In 2012, the city and the National Park Service set up the Science and Resilience Institute at Jamaica Bay. The organization aims to protect the bay’s social and ecological systems and explore issues of coastal resilience, drawing together scientists, policymakers, and community activists.

One program at the institute is working on relocating important plant species — such as salt marsh grasses — further inland, where they’ll be safer in the event of sea level rise.

“Though the bay’s water quality has improved, it’s still pretty bad,” said Steven Handel, professor of ecology at Rutgers University, who heads the marsh restoration program. “I wouldn’t recommend swimming or fishing in the bay. The salt marsh islands are getting smaller. Lots of changes are happening.”

Wetlands, a coastal buffer

The considerable expense of money and time required to restore marshland and protect its keystone species has significant returns. Healthy and resilient coastal wetlands, say scientists, are an important buffer for coastal areas during extreme weather conditions.

For example, during a storm, “a big marsh would attenuate waves coming towards shore,” explained Riepe. “Marshes protect the mainland from the worst impacts of the wave.” However, weak and fragmented marsh would simply allow water to flow through or slough off in the wave.

A recent report from researchers at the University of California, Santa Cruz determined that coastal wetlands prevented as much as $625 million in property damage during Hurricane Sandy. The project found that neighborhoods with wetlands experienced an average of 10 percent less property losses.

“We know that wetlands do more to reduce flooding when they are taller, wider, and denser,” said Michael Beck, The Nature Conservancy’s lead marine scientist and adjunct professor of ocean sciences at UC Santa Cruz. “Improving the health of marshes will improve their natural coastal defense value.”

While terrapins are but one cog in the complicated machine of marsh health, a robust population will prevent excessive loss of marsh grasses. Without a thriving population of terrapins, marsh grass “will respond slowly to damage, and decline over time,” says Burke.

As it turns out, terrapins also play another important role — on land. Nesting females hide their eggs in the sand each summer. The eggs are a huge source of nutrients for a range of land-dwelling animals, such as raccoons, herons, gulls, and crabs. Unhatched eggs also provide nutrients for coastal plants.

According to Burke, healthy populations of such plants could also potentially contribute to coastal buffers against extreme weather. But at this point in time, there is insufficient research on the issue.

“There is so much to learn about these terrapins,” said Burke. “I’m going to study them for as long as I can.”

A female diamondback terrapin laying eggs. Photo by Bob Baruzzi.

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