P. piscicida – Jekyll and Hyde and More

P. piscicida – Jekyll and Hyde and More

Today”s Marco Daily News reports that the red tide along the

southwest coast of Florida appears to be diminishing in intensity.

Actually, if the conches and vultures (see earlier column) were

due to the red tide, I personally found it quite intriguing. So, I

felt relatively unconcerned until I picked up last August”s issue

of Scientific American and read JoAnn Burkholder”s article “The

Lurking Perils of Pfiesteria.” Now, I”m truly frightened! Ms.

Burkholder is professor of botany at North Carolina State

University and the world”s foremost authority on Pfiesteria,

particularly Pfiesteria piscicida. Pfiesteria is a member of a

group of characters known collectively as “harmful algae.”

Certain of these harmful algae are responsible for the

aforementioned red tide and for the “algae blooms” which result

in large-scale fish kills. The kills can be the result of toxins

released into the water by some harmful algae or of the algae

blooms simply using up the oxygen needed to sustain the marine

life.

The term “harmful algae” is actually not strictly accurate. Some

of its members are true algae, primitive plants which make

chlorophyll and their own food through photosynthesis.

Pfiesteria, on the other hand, are not plants but single cell

organisms known as dinoflagellates. These dinoflagellates are

creatures that at some stage in their existence have these tails

(flagella) that whip around driving the organism through the

water. Pfiesteria piscicida, let”s call it pfisty from now on, looks

like a sperm except that Pfisty”s head looks more like a round

ball with a ring around it, sort of like the planet Saturn. Another

form has not one but two tails. In fact Pfisty is truly an amazing

and frightening creature, a Dr. Jekyll and Mr. Hyde of the marine

environment. For example, depending on conditions, it can

change into 24 distinct forms. It can change its size, becoming

over a hundred times larger in under 10 minutes. It can change

from a benign bacteria-eating diner to a toxin-spewing

hunter/killer/devourer of fish.

Pfisty”s different forms are so varied that you would never

recognize them as being the same single-celled creature. They

range from the planetary things with tails to round balls with

spikes like a sea urchin to amoebas of various sizes, some

resembling starfish. Pfisty can also turn into round cysts that are

pretty tough objects. Pfisty likes to turn into a cyst and hibernate

when the water gets rough and swimming gets difficult.

Burkholder described some experiments in which 20% of the

cysts survived various tortures such as drying for 35 days,

dousing them in concentrated acid or alkali or even putting them

in bleach for an hour.

To witness Pfisty in action, let”s take a typical scenario. Pfisty

usually hangs around in three basic forms: #1, hibernating cysts;

#2, amoebas browsing on algae or other delights in the mud

bottom; #3, nontoxic swimmers called zoospores (our sperm-like

critters). All is rather peaceful until the fish enter the area.

Pfisty #3 quickly transforms into a toxic zoospore, starts spewing

out toxins and swims towards the fish. The commotion alerts

Pfistys #1 and #2, who gradually transform first into nontoxic

zoospores and then into toxic zoospores and the attack on the fish

intensifies. The toxins destroy the skin of the fish, allowing

various bacteria and fungi to join the fray. To make matters

worse for the fish the toxic zoospores reproduce to form smaller

versions of themselves called pametes, which promptly group

together to form large swimmers called plano-zygates. These

guys love to suck in bits of skin and other stuff leaking from the

sores on the fish – a ghastly picture! Finally, when the fish die,

many Pfistys turn into amoebae that lock onto the fish for a

leisurely repast.

In 1991, the year Pfisty was first linked to a major fish kill, a

billion fish died in the estuary where the Neuse River in North

Carolina mixes with the salt water of the Atlantic Ocean. It turns

out that North Carolina is not a great place for a Pfisty presence.

Apparently, about half the fish along the whole East Coast of the

U.S. are at some stage of their life cycle involved with North

Carolina”s estuaries. Pfisty”s effects not only include fish kills

but at various levels may lead to non-hatching of eggs and

sublethal damage to fish which result in depletion of the whole

fish population. Pfisty has now been found in coastal areas from

Chesapeake Bay down around Florida to the Gulf coast of

Alabama.

We”ve seen that Pfisty really has it in for the fish but what about

us? Consider the personal experiences of Prof. Burkholder”s

colleague Howard Glasgow, a cheerful, very sharp scientist who

made the mistake of trying to clean up the walk of a lab

contaminated with Pfisty”s toxin. It wasn”t realized for some that

the toxin can take the form of an aerosol which can be inhaled.

Well, after starting to wipe down the walls, Glasgow began to

gasp for breath, lost his coordination, vomited and just managed

to crawl out of the lab. That lab was abandoned in favor of a

new, “carefully ventilated” facility. Ironically, the contractor,

believe it or not, vented the air from the toxic culture lab directly

into Glasgow”s office! Over the next several months, he became

a moody, disoriented fellow – who suffered both long – and

short-term memory losses. Glasgow finally had to take a couple

months off work when he could no longer remember his phone

number or find his way home. He recovered but, even a couple

years later, suffered various aches and pains as well as periods of

disorientation. Burkholder herself has suffered from chronic

bronchial infections and many bouts of pneumonia.

In 1997, there were small outbreaks of Pfisty in the Chesapeake

Bay region. Fishermen who spent their lives fishing the Bay

found themselves getting lost and disoriented in familiar areas.

Of course, the question arises as to the hazards of eating fish

exposed to sublethal doses of “harmful algae” toxins.

Burkholder bemoans the fact that scientists don”t have a

thorough knowledge of either the life cycles of the “algae” or the

chemical compositions of the toxins. Furthermore, outbreaks of

harmful algae seem to be increasing in frequency and over wider

areas of the globe. Of course, global warming is postulated as a

possible factor in the increasing range of algae bloom. The

blooms are also related to increasing pollution of our waterways

by nutrient-rich runoffs from waste disposal, farming and

livestock operations, etc.

Having just enjoyed, the second grouper sandwich of our stay

here, I wasn”t too thrilled by Burkholder”s statement that some

dinoflagellates produce so-called ciguatera toxins that

accumulate in reef fish without killing them. According to

Burkholder, ciguatera-containing barracuda, red snapper, grouper

and other tropical fish cause more human illness than any other

seafood poisoning. Other dinoflagellates produce saxitoxins,

which sometimes lead to fatalities from consumption of

contaminated shellfish.

Fortunately, I never have taken to raw clams or oysters – guess

I”ll take my chances with the grouper sandwich!

Allen F. Bortrum