By DANA
RUBINSTEIN 10/30/14 Politico
Something strange is happening to
the diamondback terrapin turtles of Jamaica Bay, though there’s some question
as to precisely what that strange thing means.
“Nobody has ever seen anything
like this before,” said Russell Burke, a Hofstra University ecology professor
and one of the foremost experts on Jamaica Bay’s population of diamondback
terrapin turtles, the largest concentration in the state. “It’s a puzzle.”
Every summer, female
representatives of North America’s only species of brackish- water turtle
lumber nervously onto the shores of the Jamaica Bay Wildlife Refuge.
Using their hind legs, they dig a
hole in the sand, deposit their “clutches” of eggs, cover them up again, and
return to the bay’s polluted waters.
While the population of female
turtles nesting in Jamaica Bay has remained constant over the past decade or
so, that population’s egg-laying capacity appears to have fallen off
dramatically.
“The number of nests that they’re
laying has dropped by 50 percent in the last 10 years,” Burke said.
Female terrapins store sperm for
as many as seven years and can lay three clutches during their two-month summer
nesting season.
But among the more than 1,200
female turtles that Burke has been following for years, those that used to lay
three nests are now laying two, and those who use to lay two are now laying
one, and those who laid one are now skipping summers entirely.
“It’s like if you had a big
population of a thousand humans and normally they would reproduce with some
frequency and the frequency has dropped by half,” he said.
At the same time, two other
phenomena are complicating the picture: the size of the clutches and the size
of the eggs inside those clutches, has each gone up by about 10 percent.
“The drop in total number of
clutches by 50 percent just swamps all that,” Burke said. “They’re clearly
putting way less energy into reproduction than they used to.”
This means that absent any
countervailing change, the population of terrapin turtles in Jamaica Bay, a
population that has rebounded dramatically since the days when turtle soup was
all the rage, stands to drop over time as the long-lived reptiles die and fewer
young ones rise up to replace them.
It also means that the
31-square-mile bay may not be as healthy as thought, despite the government’s
substantial efforts to clean and stabilize it.
“It’s certainly an indicator that
something is dramatically wrong with the health of the bay,” said Burke.
Diamondback terrapins eat clams,
snails and other invertebrates that live in marshes.
Jamaica Bay is now surrounded by
a largely concrete watershed (the Rockaways, J.F.K. Airport, Shore Parkway),
but it used to be a natural wonder.
Before European settlement, it
had more than 10,000 acres of wetlands. In 1971, it had 4,000.
“At one point we were losing up
to 40 acres a year,” said Daniel Mundy, vice president of the Jamaica Bay
Ecowatchers.
Mundy said recent, concerted
efforts by the federal, city and state governments to restore the bay have
begun to “stem the tide.”
Nevertheless, the city says there
are just 1,000 acres of marshland remaining.
There are several working
hypotheses as to why: the water quality remains poor and nitrogen rich. The
nitrogen promotes algae growth and algae smothers marsh plants. Sea level rise
destabilizes marshes.
And the streams that used to
carry sediment into the bay have all been paved over.
“All the fresh water coming into
the bay is really from sewage treatment plant outfalls,” said Robert Pirani,
NY-NJ Harbor and Estuary Program director at the Hudson River Foundation.
“There’s not a lot of sediment there.”
So instead of clams and molluscs,
the turtles are eating algae.
Burke knows because after he
watches the turtles lay eggs, he and his students collect them, soak them in
warm water, analyze their excretions and then return them to the bay.
“Sometimes their guts are just
filled with algae, that’s what they’re eating,” he said. “At the same time the
marshes are degrading really badly and have been for some time. So, my best
guess is that our terrapins are eating what they can, because they can’t find
what they normally eat. And it’s a really low-protein diet, a really
low-quality diet, they probably can’t digest it very well, and that’s
translating into reproductive problems.”
And that, in turn, might
translate into a disaster for the Jamaica Bay terrapin.
“If you don’t produce eggs to
bring young into the population, then there’s only one way for your population
to go,” said Burke. “Unless something turns around pretty dramatically, they’re
definitely on their way out.”
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