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Are Pollutants Disrupting Marine Ecosystems?A WHOI researcher stands up for the spineless—invertebrates in coastal waters |
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| Enlarge ImageChemicals, especially pesticides, may be causing unexpected and unintentional harm to many invertebrate species that play essential roles in marine ecosystems and food webs, says WHOI biologist Tim Verslycke. (Courtesy of Tim Verslycke, Woods Hole Oceanographic Institution) |
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| Enlarge ImageSmall crustaceans called mysids, shown here swarming in the ocean, could act as canaries in a coal mine to indicate when marine environments are being exposed to chemicals that could affect other invertebrates as well, says Tim Verslycke. Adult mysids are between 10 to 30 millimeters long.
(Photo courtesy of Tim Verslycke, Woods Hole Oceanographic Institution) |
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| Enlarge ImageVerslycke began his research on hormonal disruption in invertebrates on Neomysis integer, a species of mysid common in European estuaries, which could also be used to test the susceptibility of invertebrates to potentially harmful chemicals. (Photo courtesy of Tim Verslycke, Woods Hole Oceanographic Institution) |
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Related Links |
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» Endocrine Disruptors
from the National Institute of Environmental Health Sciences-National Institutes of Health
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» Our Stolen Future
A Web site that tracks the most recent developments in endocrine disruption and contaminants
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Ask people to name some animals—any animals—and they will give you a
long list. But chances are, all the animals will have one thing in
common: a spine.
The animals that people think of—mammals, reptiles, amphibians, fish,
and birds—constitute only about 5 percent of the animal diversity on
Earth. The other 95 percent are invertebrate species; hundreds of
thousands, or perhaps millions of species that we largely ignore—to
their peril and our own, said Tim Verslycke, a biologist at Woods Hole
Oceanographic Institution.
Researchers are now finding that some chemicals, especially pesticides,
cause unexpected and unintentional harm to many invertebrate
species that play essential roles in marine ecosystems and food webs,
Verslycke said. These chemicals also may pose threats to crustaceans
that
humans love to eat: lobsters, crabs, and shrimp.
Invertebrates include both insects and crustaceans, which diverged long
ago into separate branches on the evolutionary tree. But the two retain
many fundamental biological mechanisms that have stood the tests of
time and evolution and proved effective and beneficial.
Insects and crustaceans are both arthropods, which in addition to
jointed limbs, share another common trait: They use the same hormones
to carry out a wide range of crucial biological functions, ranging from
molting, egg production, embryonic development, and sexual maturation,
to energy metabolism, and even limb regeneration. So an insecticide
targeted to disrupt hormones that help mosquitoes develop could easily
disrupt other essential biological functions in crustaceans, Verslycke
said.
Take methoprene, for example, a pesticide widely used to kill mosquito
larvae and prevent mosquito-borne illnesses such as West Nile virus. It
works by mimicking and disrupting insect hormones, Verslycke said.
“These pesticides are hardly toxic or effective in vertebrates, because
vertebrates don’t have these hormones,” he said. “What we’ve been able
to show, however, is that they are very effective against other
non-targeted animals that do have these hormones, such as crustaceans
and other coastal invertebrate populations. The fact that most
invertebrates use the same hormones to regulate very different
processes makes it a bigger problem.”
Overlooked environmental threats
In the lab, Verslycke and colleagues have found that very low levels of
exposure to hormone-disrupting chemicals, in just the parts-per-billion
range, have resulted in impaired embryonic development, molting, and
growth in marine crustaceans, and they have found such low levels of
these chemicals in coastal waters, sediments, and crustaceans. In
ongoing field studies, Verslycke is also investigating the levels and
effects of hormone-disruptors in local coastal invertebrate populations.
Recently, for example, New England fishermen have observed female
lobsters molting their shells before they have carried their eggs to
term. “This obviously means something is going wrong with their hormone
regulation,” Verslycke said. He believes that increased chemical
exposure in coastal waters may be a factor fueling the recent outbreak
of lobster shell disease, which has run rampant in southern New England
waters and led to large declines in lobster catches (see "A Mysterious Disease Afflicts Lobster Shells").
More than half the nation’s population lives near coastal waters, which
provide valuable commercial and recreational resources, as well as an
essential source of food. About 1 billion pounds of conventional
pesticides are used each year in the United States to control insects,
weeds, and other pests. These pesticides, from both agricultural and
urban sources, run off into nearby estuaries and coastal waters that
are critical in the life cycles of important marine fish and crustacean
species.
“Industry is looking to regulatory agencies to come up with the tests
they need to do to prove whether these chemicals pose environmental
threats,” Verslycke said.
Screening for harmful chemicals
“Tim has certainly been a voice for this issue,” said Jesse Meiller, a
scientist at the U.S. Environmental Protection Agency. He has been
skilled at bringing together colleagues from academia, industry, and
governmental agencies to work on the problem, she said.
In 1996, Congress passed the Food Quality Protection Act, which
directed the EPA to develop a program to identify substances with the
potential to disrupt human hormonal systems, Meiller said. In June, the
EPA’s Endocrine Disruptor Screening Program published a draft initial
list of pesticides, commercial chemicals, and environmental
contaminants. The program is also developing and validating tests to
determine the effects and effective dose levels of endocrine-disrupting
chemicals.
Verslycke argues that any comprehensive program that seeks to protect
our environment from the potential harmful effects of chemicals that
disrupt hormones should include invertebrates, and not just
vertebrates, as is now mostly the case.
“As a society, people are generally a little more worried about things
that directly affect humans,” he said. “So it’s a little harder to get
funding to look at effects in some obscure marine copepod species
rather than studying similar effects in humans. However, from an
ecological perspective that doesn’t make sense.”
Copepods, for instance, are tiny, abundant marine crustaceans that
constitute perhaps the largest animal biomass on Earth. They are the
major food source for small fish, whales, seabirds, and other
crustaceans in the word’s oceans.
Crustaceous canaries?
Verslycke is doing his part by developing new invertebrate-based assays
to detect low, but still potentially harmful, levels of certain
chemicals in water and sediment samples. His research has contributed
to our basic knowledge of hormonal systems and processes in
long-overlooked marine invertebrate species such as copepods and a
group of small crustaceans called mysids.
“To say something is disrupted, you must first know what’s normal,” he said.
The EPA is presently considering using mysids in its Endocrine
Disruptor Screening Program as a model invertebrate species to test for
the toxic effects of chemicals, Meiller said. Mysids are an important
link in the food chain, especially in estuaries, she said, and they are
generally more sensitive to toxic substances than other species.
Verslycke says mysids could act as canaries in a coal mine to indicate
when marine environments are being exposed to endocrine disruptors that
could affect other invertebrates as well.
Verslycke first discovered this area of research while studying for an
undergraduate and then a master’s degree in bioscience engineering and
environmental technology at Ghent University in Belgium, where he
investigated the way certain chemicals can disrupt the hormones of
freshwater snails.
After receiving his master’s in 1999, he followed his interest in
marine species downstream to the Scheldt estuary in The Netherlands,
where he conducted his doctoral research, also at Ghent University, on
chemically induced hormone disruption in mysids.
—Sara E. Pratt
Verslycke’s research has been funded
by the Ocean Life Institute at WHOI, the Belgian-American Educational
Foundation, MIT Sea Grant, and the New England Lobster Research
Initiative administered by Rhode Island Sea Grant.
Posted: October 18, 2007 [top] |
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