Logbook
September 15, 1998
Contents:
Today's Science News
Participant Perspective
Logbook from Teacher at Sea
Question/Answer from shore to sea
Daily Science Report - Sep 15
ship's location = 45 56.0N/129 58.9W
ROPOS dive 478 returned to the upper south rift to deploy a
time-lapse
camera at the marker 33 vent, which will document changes at the site
over the next year. The rest of the dive consisted of coordinated SUAVE
chemical and biological sampling.
Tube worms were sampled from brand
new colonies (photo right shows "baby" tubeworms) on the new lava as well as pre-existing colonies on the
surrounding older lavas. The distribution of new animal communities at
vents on the new lava flow has been an intriguing aspect of the cruise.
Each vent seems to have a distinct assemblage of animals, and the
biologists are developing ideas about why this might be. Since new
colonies get started by the large numbers of drifting larvae, why don't
all the new vents get about the same number and kinds of species? Is
the biology of each vent dependent on the specific chemistry of the vent
fluids, or does the first arrival stake out a site and keep other species away?
After the dive we recovered two of the three
transponders that that we will
no longer be using on the south rift zone.
Listing of all Science News postings
Who said a desert needs to be hot and dry? The bottom of the deep sea is a
desert just like the Sahara. It's a dark and cold place, so dark that no
organism can use photosynthesis to grow and become food to other organisms. You
might know that most life on our planet is sustained by photosynthesis - the
fixation of carbon dioxide by plants, algae and other photosynthetic organisms,
using sunlight. These so-called "primary producers" grow by using carbon
dioxide, water, inorganic nutrients and sunlight - that's all they need to live
a happy life! They are then eaten by all sorts of animals (maybe not that happy
a life, after all...), which in turn are used as breakfast by bigger animals and
so on. Therefore, one might say that all life on Earth is ultimately supported
by the energy coming from the sun.
But in the late 70's, scientists discovered an oases on the ocean-floor,
thriving with a horde of bizarre creatures! (Well, you might have guessed that
at some point, I was going to talk a bit about hydrothermal vents!) The question
that immediately came to mind was: what do these organisms eat?
In the absence of sunlight and plants, the animals living in these deep-ocean
resorts can be anything but vegetarians. Bacteria play there the same role as
plants on terra firma - the role of primary producers. Instead of using light,
these bacteria use chemical energy to fix carbon for growth. These microscopic
"bugs" are absolutely fond of nasty chemicals that are toxic to us and most
organisms - like hydrogen sulfide, which is responsible for the bad smell of
rotten eggs. (To the best of my knowledge, the only organisms known to
appreciate this stinky "fragrance" are these little bugs and some of the
microbiologists onboard the R/V Brown who culture them and thus might get
addicted to their emanations! But that's another story...)
Some of these amazing microbes live inside animals such as
vestimentiferan tube
worms and giant clams. This type of association, called symbiosis, means that
the microorganisms produce food for their host animals, which in turn provide
the little bugs with a shelter where they can live with all what they need (the
condo-type deep-ocean housing...). Other 'sulfide-loving' bacteria prefer to live
a free life in the water around vents or at the surface of rocks and organisms
in the neighborhood. These little bugs can then be grazed by animals like
snails, limpets and some polychaete worms, which in turn are eaten by carnivores
like
spider crabs and nereid worms. Food webs just like those on land, except
that here, plants are replaced by microorganisms!
The exact way these unusual types of food webs work is still a mystery. Remember
that hydrothermal vent communities have been discovered just over 20 years ago,
and that doing research to understand their tricky mechanisms is not an easy
job!
That might be exactly why Damien and I ended up doing this kind of work! But
I've said enough for now and I'll let Damien tell you more about that!
Christian
It's not an easy job, that's true. Observation and sampling take much more time
there than on land. To look at what's going on at the bottom of the sea we're
using a ROV (Remotely Operated Vehicle) that is flying over the sea floor at a
depth of 1500 meters. Hours and hours of fun... During the dives we try to find
worms growing near the vents to observe their behavior and later bring them to
the surface to analyze them. To look at their behavior we're doing in situ
observation and we need to put the submarine very close to the vent. Furthermore
we need to sample the worms and their food (bacterial mats.) without destroying
the whole surface, and sometimes the samples don't exceed 0.5 cm in size. But
the ROPOS' team manages to do some exploitation with this submarine. They even
brought us to live worm combats and these fights are very new observations. We
have to understand why they do it.
Who are we ?
We are two graduate students working with
Kim Juniper at the
University of
Quebec at Montreal. Christian is trying to find out feeding relationships within
hydrothermal vent food webs by doing isotope analysis of carbon and nitrogen.
During this cruise he is mostly interested in the biology of two hydrothermal
vent polychaete worms, Paralvinella palmiformis (the "palm worm") (red animals, top photo)
and Paralvinella sulfincola (the "sulfide worm")
(orange animals, bottom photo)
What Christian is looking at is how these species share resources
in a way that allows them to coexist. So, he is collecting specimens of these
species along with bacterial mats and suspended organic matter. But he couldn't
resist the temptation to bring up other animals like scale worms, limpets and
vestimentiferan tube worms to eventually look a little closer at their feeding
habits.
As for me, I'm studying the behavior of Paralvinella sulfincola and Paralvinella
palmiformis. The first one lives very close to the hot fluid source where life
is precarious. That's the one that fights (bad guy). The second species has both
grazing and suspension-feeding behaviors, which is unusual. Their behavior seems
to be different at each site. So I want to know if their behavior depends on
where they live and if it is related to food resources or physico-chemical
conditions. To complete my research I'm looking at their food sources in terms
of kind of bacteria and amount.
Damien
|
Paralvinella palmiformis
Paralvinella sulfincola
|
Listing of all Perspectives postings
September 15- 0900 hours
Score- Lava flow 1, Scientists 0
You can read the details in the daily science report
(see 9/14 Science News), but the short form is that
2200 pounds of pull from the ship's winch could not break the rumbleometer loose
from the lava flow in which it was trapped. With that amount of tension on the
line, the weak link in the cable snapped. Subsequent inspection with the ROPOS
showed that the rumbleometer had not budged. The camera cannot see in under the
rumbleometer, but it seems like a good bet that lava may be covering the
railroad wheel anchor, and may even have sealed the release mechanism in solid
rock. While there are some other possibilities for freeing the instrument, it
is unlikely that another attempt will be made on this voyage.
Here's something for you to think about. Send us a suggestion for how we could
free the rumbleometer from the seafloor. Remember that we want to release it
without destroying the data it has collected. Dynamite is out of the question.
It may help you to look back at the
picture of the stuck rumbleometer, but
someone out there probably has a real good idea that hasn't been thought of out
here. The scientists would like to have a few new ideas about now. Maybe
you'll be famous. . .at least with the crew of the R/V Brown.
We knew things were going too well to be true. Over the past three days we have
had a variety of small things and large things go wrong with the ROPOS or the
instruments it carries. After a successful retermination yesterday, ROPOS was
back in the water at about 1700, but back out again a few hours later when the
usually reliable SUAVE developed a problem and had to be brought back to the
ship. It was a quick turn-around and this morning ROPOS is back on the seafloor
working to complete the final goals of this expedition. Time is really getting
short. Every scientist would like to get just a few more samples or an extra
set of data points, and who can blame them. For most it will be at least
another year before they can return to the observatory. The weather has
cooperated. Our big gale turned out to be maximum winds of 16 knots, and this
morning I can hardly feel the ship moving.
2000 hours
Great day today!! Fabulous tube worm fields, some of the largest I have seen
anywhere on the expedition. We worked right along the edge or the new lava
flow. The point where new lava meets the old ocean floor is called the contact.
We have spent a considerable amount of time mapping the edges of this flow and
looking at the effects it has had on the ocean floor next to it. Today we found
a tube worm "barbecue", a spot where a colony of tube worms was partially
covered and of course killed by the hot lava. We also found and sampled what
Dr. Tunnicliffe and extremely important population of tube worms growing on top
of the new flow. Since this lava is only about seven months old, the biologists
will have a much clearer picture of the growth rates of both individuals and
communities of tube worms.
SUAVE is working fine again and the fluid sampling around vents proceeds at an
unprecedented pace. ROPOS made a scheduled return to the ship this afternoon
and is currently being fitted with the instruments that will be used on the dive
later this evening. The goals tonight are to do some sampling of high
temperature vents at Ashes and then to investigate some tantalizing hints of
perhaps more unexplored vent fields south of the previous dive areas.
I haven't lost track of the head question. I don't want to put the answer up
too quickly. Look for a photograph and an explanation tomorrow. Here's a
couple of small hints. First, other heads will meet a similar fate in the near
future. Second, it has nothing to do with the high powered microwave ovens
found aboard the Brown. Those are used to burn bags of popcorn. It's a long
story, and for Julia's sake I won't go into details here. At least we didn't
have to abandon ship! (photo left shows a Safety Drill)
Logbook of all Teacher At Sea postings
All Questions/Answers from sea
Send Your Question to NeMO
(oar.pmel.vents.webmaster@noaa.gov)
Back to Calendar
|