|Fishing for an Explanation
just finished reading the May 6
article entitled, "Jellyfish 'Blooms' Could Be Sign of
Ailing Seas," and, boy, we're confused. Jellyfish,
affectionately known as "rats of the sea," seem to be
undergoing a population explosion.
Well, there are several possible explanations. Overfishing, for
decades the whipping boy of saltwater environmentalist vegans,
is offered as one reason. With fewer nongelatinous fish
occupying that sector of the food web, jellyfish seem to be
taking over their role, since they feed on the same prey as
juvenile and adult fishes. For example, in the Gulf of Mexico,
jellyfish feed on commercially important shrimp larvae. And
according to a Gulf fisherman, "you can almost walk across
the water on them."
second possibility is higher nutrient levels from agricultural
runoff. Jellyfish and their prey can survive quite nicely in
eutrophied, oxygen-depleted waters where many true fish cannot.
third explanation, of course, is the ubiquitous "global
warming." Notice that none of the reasons for these
jellyfish explosions is natural variability. Surely man has some
role; we're simply left with the trivial problem of
determining exactly what it is. Still, based on what we've
learned so far, the increasing jellyfish population is a
article ends with the following story about Jellyfish Lake on
the island of Palau. Allegedly, the 1998 El Niño warmed the
lake, wiping out the resident rare golden jellyfish. According
to Portland State University scientist Dick Dewey, "The
situation was seemingly hopeless." Said Dewey:
"Palau's reputation as one of the 'seven biological wonders
of the world' has been based on this magnificent lake and its
jellyfish" (Add Palau to our summer vacation wish-list!
how's this for a shocker—when the El Niño ended and water
temperatures returned to normal, thousands of tiny golden
jellyfish emerged from the lake bottom. What a sight that must
have been! They now number more than one million! Is that too
many jellyfish or too few? We don't know, but we're guessing
Dewey is pleased indeed.
us for stating the obvious, but El Niños have been going on for
a long time, and those golden jellyfish have been living there
for the thousands of years since that lake became isolated from
the ocean. If they hadn't somehow figured out how to survive
slight variations in water temperature, that body of water
probably wouldn't be named Jellyfish Lake, now would it? And
we're betting the jellyfish boom in other waters is part of a
natural cycle as well. Not a sexy explanation, but an
ecologically sound one.
course, we could simply rename the Gulf of Mexico
"Jellyfish Gulf—the 8th Biological Wonder of the
World," and then complain in a few years when the jellyfish
counts take their inevitable plunge into the abyss.
Dybas, C.L., 2002. Jellyfish
"blooms" could be sign of ailing seas. Washington
Post, p. A-9, May 6.
Is a Deformed Frog Better Than no Frog?
the past five years or more, stories of amphibians struggling
mightily to survive the ongoing climate changes have been
standard science-page fodder. Global population declines of
frogs, toads, salamanders, and the like, as well as frog
deformities (usually extra legs), have been reported in many
recent study by the University of Wisconsin's Pieter Johnson and
colleagues has identified the real culprit—parasitic worms
called trematodes. Trematode eggs hatch and infest larva infest
snails, where the worms then grow. Once mature, the trematodes
burrow into tadpoles, and extra legs can sprout at the burrowing
point when the tadpole becomes an adult frog. The deformed frog
is then eaten by a bird, and trematode eggs can be found in the
bird droppings. According to deformed frog expert Stan Sessions
of Hartwick College, "We think the trematode...is
increasing its chances of survival by attacking tadpoles and
destroying their hind limbs, so they are easier [prey for
birds]." These worms are clever, especially considering
their rudimentary central nervous system.
the critical question is, why has there been a boom in the
trematode population. It's indirectly caused by fertilizer and
cow manure in ponds. High fertilizer levels increase pond algae,
and the snail population booms because they love algae. So, more
snails equals more snail parasites and more deformed frogs.
looks like global warming is off the hook yet again. But there
are two ironies in this story.
based on Johnson's analysis, 80 percent of the ponds with
deformed frogs were actually built to water cattle. You guessed
it: There would be no frogs there at all, three-legged or
otherwise, if we meat-eating, cow's-milk-drinking Americans
hadn't built the ponds in the first place! So there are a lot
more frogs happily hopping, on two or more legs, than if they
were left to their own devices, which are minimal.
No. 2 is that habitat improvements
in some regions are attracting more birds such as great blue
herons, birds that serve as trematode hosts.
course, EPA officials continue to claim that the matter isn't
settled and that higher ultraviolet light levels could still be
responsible for the increase in frogs. But then the EPA has a
long history of ignoring sound science in the promulgation of
its own self-interest, so that stance is hardly surprising. That
the EPA can't explain why there aren't far more three-legged
frogs as you move toward the equator (and UV levels increase)
simply means that they haven't yet honed their excuses. (These
EPA officials are clever, especially considering their
rudimentary central nervous system.)
this story is a win-win-win situation for environmentalists, EPA
officials, and normal people. Environmentalists can campaign
against the consumption of meat and cow's milk, the EPA can fret
about fertilizer runoff into private farm ponds, and the rest of
us can sit back and be amused.
P.T.J., et al., 2002. Parasite (Ribeiroia
ondatrae) infection linked to amphibian malformations in the
western United States, Ecological