(Continued from "Why Science
on Ice?" page #1)
Dive hut on sea ice |
Not surprisingly, it was not difficult to find evidence that human waste
had reached beyond the city limits. Earlier studies by one of us (McFeters; see Resources) of water currents and bacteria
near the sewage outfall and the nearby desalination-plant intake pipe had
raised concern about fecal contamination years before. This time, using
special selective agar media and rapid identification kits, we looked for
C. perfringens as a retrievable indicator organism. With many samples,
we also assayed for fecal coliform bacteria (E. coli is one such
bacterium) and enterococci bacteria, both indicators of fecal contamination
but less likely than the spore-forming clostridia to survive the harsh
environment. Although we are still studying our results (and awaiting results
from other team members), it is clear that C. perfringens persists
in the nearshore environment, both in the bottom sediment and in the invertebrates. |
| For example, 72 to 100 percent of the local tunicates examined and 45 to
50 percent of the urchins tested positive for the bacterium, while those
at the far away sites were negative. The Emperor and Adelie penguins tested
negative, as expected, but our principal concern was the seals, which,
unlike the penguins still grouping near the open sea miles away from town,
at this time in the austral summer could be found just offshore from McMurdo.
In addition, other than humans, the seals were the only resident mammals
in the study area. Curiously, assays of seal scat collected from November
10 to December 1 were negative for clostridia, but began showing an increasing
rate of positives thereafter. Little study has been done on the intestinal
flora of seals and we cannot offer a definitive explanation for this phenomenon
(grist for further study, no doubt). At present, a California biochemist
also is assaying our freeze-dried sediment samples for presence of coprostanol,
a breakdown compound of cholesterol found in human feces. |
Emperor penguins |
Diane Edwards on volcanic
ash island at Hut Point |
As with any scientific research, it seems we've raised as many questions
as we've supplied answers! This study and others by McFeters have alerted
officials to potential pollution problems at McMurdo. It also illustrates
the importance of a historical and interdisciplinary approach to research.
For example, clostridial spores can remain viable for years, even under
the extreme conditions found in Winter Quarters Bay at McMurdo. Many years
ago, before flush toilets, outhouses were set over holes in the sea ice,
thereby creating a historic (microbiologically) site that may yield positive
test results long after the fact. The use of invertebrates in this study
also reminded us how useful it can be to search for microorganisms in more
than one sample system, here in sediment, sea bottom creatures, and seals. |
| Logistically, research such as this, a relatively simple process in most
settings, is, in Antarctica, particularly rewarding and frustrating. Laboratory
supplies must be anticipated and ordered long in advance, close living
quarters mean that each newly arrived plane brings another series of communicable
disease among the town's population, restricted travel outside McMurdo
necessitates careful planning, and unpredictable weather conditions mandate
constant monitoring of the horizon during field trips. Yet as a scientist
you find yourself among some of the most independent and inventive souls
you will meet, from the principal investigators of such projects as the
meteorite collection teams and the volcanologists studying still-active
Mt. Erebus nearby, to the heavy equipment operators and mechanics who make
it all work. With 24 hours of sunlight, those fortunate to work at McMurdo
during the summer season have plenty of time to produce scientific results,
wrapped 'round by spectacular scenery and a social experience none forgets. |
Tanning on ice? |
Science Seminars Archive
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