The RV
Yuzhmorgeologiya at the dock in Punta Arenas, Chile before the start of
the 2006 cruise. |
RV
Yuzhmorgeologiya
The
"Yuzhmo" (as we affectionately refer to the ship) is our main research
platform for this project, as well as our home for the duration of the
6 week cruise. It is an ice-strengthened ship, ~ 300 ft. long, that was
originally used for geophysical oceanography research in the USSR.
This year (2006) is the ship's 20th anniversary. The ship and crew are
Russian which means a lot of signs in Cyrillic around the boat and that
we regularly have borscht for lunch. In addition to being one of the
most stable platforms to work on, this ship contains one of the (if not
THE) friendliest crew in the oceans. The AMLR program has chartered the
Yuzhmo for many years so many of the crew have become a part of the
AMLR family.
|
Multiple
Frequency Acoustics
The Yuzhmo has four hull-mounted acoustic echosounders operating at 38,
70, 120,
and 200 kHz. Tony Cossio and Dr. Christian Reiss are in charge of
monitoring and processing the acoustic data, as well as calibrating the
echosounders before each cruise (a process that involves metal spheres,
4 small motors, and a LOT of fishing line). With the echosounders we
can see scattering layers or patches in the water column down to 500 m.
By comparing how much acoustic energy a patch scatters at the different
frequencies, the acoustic system can be used to distinguish copepods
from small fish from krill. The acoustic system provides a high
resolution 2-D picture of the ocean interior as we proceed on our
survey track. However, when using any acoustic system to obtain
information about biological creatures it is necessary to ground-truth
(or sea-truth in our case) the data with other means of sampling the
biology. |
Cassandra and Darci work up a net tow by counting and identifying the
different zooplankton caught by the net. (Photo by Darci). |
Zooplankton
Net Sampling and Identification
The "Zoo van" on board the Yuzhmo contains several dissecting
microscopes, lots of petri dishes and tupperware containers, numerous
zooplankton identification books and manuals, and (most importantly)
Dr. Valerie Loeb and a team of 7 zooplanktoneers. At each station
during the survey, an Isaacs-Kidd Midwater Trawl (IKMT) is lowered to
170 m (or the bottom whichever is shallower) and brought back up to the
surface. What is truly remarkable about the Zoo van
team
is
that the samples are processed (identified and enumerated) on board the
ship, so that when we walk off the boat in Punta Arenas, we have all
the zooplankton data in hand. This is a great advantage
over preserving the samples and then processing them back in the lab.
|
Physical Oceanographic
Measurements
Derek Needham and Marcel van den Berg are in
charge of
the hydrographic measurements on board the Yuzhmo. They have been with
the AMLR program for many years and provide a Southern Hemisphere view
(they're both from South Africa) for the rest of us from the other side
of
the world. At each station during the survey, they conduct a CTD cast
which collects measurements of conductivity, temperature, depth
(pressure), fluorescence, dissolved oxygen, several other parameters,
and water samples from different depths. These data allow us to
identify water masses (bodies of water that have similar physical
properties) and determine some water movement (upwelling, downwelling,
mixing).
|
The CTD
rosette being launched off the ship.
|
The Bird Hut for observations of predators on the flying bridge of the
ship.
|
Bird and
Mammal Observations
Jarrod Santora and Mike Force are
responsible for
monitoring and recording the distribution and behavior of sea birds and
marine mammals during the survey. They work their shifts from the new
Bird Hut on the flying bridge of the Yuzhmo where they have a great
vantage point for monitoring the animals that depend on the krill for
their food needs. As we are studying an ecosystem (and not just the
krill population), their data are essential to understanding the
interactions between prey and predators in the marine environment.
|
|
Phytoplankton
Measurements
One of the factors that affects the
distribution
and
abundance of krill is the availability of their food source,
phytoplankton. Chris Hewes is responsible for analyzing the water
samples that are brought up in the CTD casts and assessing the amount
of phytoplankton that are found in the water column. When one combines
this information with the hydrographic data, we get a better idea of
what the ecosystem is doing on a "bottom-up" basis. Additional data
sets such as ocean color images from satellites passing over the area
can complement the shipboard observations.
|
|
