LARISSA - LARsen Ice Shelf System, Antarctica, a NSF-funded project.

LARISSA - LARsen Ice Shelf System, Antarctica, a NSF-funded project.
We are conducting an integrated, multi-disciplinary field program to address the rapid and fundamental changes occurring in the Antarctic Peninsula region as a consequence of the abrupt collapse of the Larsen B Ice Shelf in the fall of 2002. A profound transformation in ecosystem structure and function is occurring in coastal waters of the western Weddell Sea. This transformation appears to be yielding a redistribution of energy flow between chemoautotrophic and photosynthetic production, and to be causing the rapid demise of the extraordinary seep ecosystem discovered beneath the ice shelf, providing an ideal opportunity to test fundamental paradigms in ecosystem evolution.

Monday, March 1, 2010

Lockyer Station

3 – 9 Feb The last few days of have been a flurry of oceanographic
sampling activity, during which we have collected two kasten cores, 6
megacores, one Blake trawl, numerous CTD’s, and conducted 6 yoyo camera
transects. This sampling is to characterize our first oceanography station
near Lockyer Island (dubbed “Lockyer Station”) to provide insights into
seafloor and water-column ecological processes and community structure on
the inner continental shelf site not recently influenced by an Antarctic
ice sheet. The seafloor at Lockyer Station lies 505 m below the sea
surface and is a plain covered with mud intermixed with gravel from iceberg
rafted material. Our yoyo camera transects and trawl sample reveal a
relatively rich community of megafauna (animals large enough to be
identified in photographs), including large “sea pigs” (sea cucumbers
in the genus Protelpidia, picture 38), very large brittles stars
(Ophiostarte gigas, picture 39), and an occasional giant basket glass
sponge with crinoids (sea lilies, picture 40). Many of the megafauna are
unusually large, including the 20 cm long sea pigs and meter high basket
sponges, suggesting that this is a stable sedimentary environment (low
flow, little disturbance ice bergs, and slow sediment accumulation). The
station looks very much like our continental shelf stations at similar
depths on the other side of the Antarctic Peninsula, west of Anvers Island.
 Our trawl sample also recovered a diversity of large benthic (seafloor
species) including a large icefish (picture 41) . These fish are unique to
Antarctica and have no hemoglobin in their blood; oxygen concentrations are
high enough in the cold Antarctic waters that these sluggish fish do not
need hemoglobin in their blood to carry oxygen. Their gills and blood are
translucent white.

Large sea pig 20 cm (8 inches) long. This animal is a
 “deposit feeder" and uses that tentactles at left to ingest mud particles.
It then digests off the organic matter for food. This is the most common 
feeding mode on Earth!

The large, mucus cover brittle star Ophiostarte gigas. This is
a predator that feeds on other brittle stars, polychaete worms, and

A giant filter feeding basket sponge about 1 meter tall and
 half a meter wide (this is a downward view from the Yoyo Camera). Clinging
to the sides of the sponge are yellow crinoids, or sea lilies. Both the
sponge and crinoids are suspension feeders that removed food particles as
they drift by in the water column.

An ice fish caught in the trawl. These are called ice fish
because their blood is transparent due to an absence of hemoglobin. Their
gills are translucent.

After three grueling 18-hr work days, our intrepid benthic team of Laura,
David and Craig (me) are now nearly finished with sampling of the seafloor
biota at Station Lockyer. Our samples have been excellent in quality and
we are confident we will be able to characterize biodiversity and ecosystem
function at this station (including foodweb structure and rates of sediment
mixing by mud-eating animals like sea cucumbers). It will provide an
excellent baseline to compare to the Larsen B stations recently exposed
from beneath ice shelves. Unfortunately, the sea ice is thickening around
us and further south in the Larsen B area, so it now seems unlikely that
we will be able to get to Larsen B for the rest of the cruise. Time to
develop plan B!

No comments:

Post a Comment