Life in the Southern Ocean
April 4, 2009
The Antarctic has been isolated from the other continents for millions
of years. Fossil evidence indicates that subtropical animals once
survived on the Antarctic continent, but today, 450 million years after
it began its shift from the equator to the South Pole, few species are
native to Antarctica. A handful of seal species and nineteen bird
species, which consists of penguins and seabirds, make up the large
fauna. Mosses and lichens make up most of the flora, along with two
grass species that live near the coast. Most of the animal diversity is
found offshore in the Southern Ocean. Currents in the Southern Ocean
create a barrier between it and the rest of the world for all but
seabirds and marine mammals; this isolation facilitates a unique
assemblage of life. Today we moved into an area that is rich with
icebergs and rich with life.
Fur seals sunned themselves on the water’s surface today, and a few even
hauled out on drifting ice. Minke, humpback, and southern right whales
have been seen throughout the cruise. Chinstrap penguins waddle up
iceberg slopes or float and dive at the water’s surface.
Adele penguins catch a ride on a chunk of ice floating nearby. Photo by Debbie Nail Meyer
Seabirds include Cape Petrels, Southern Giant Petrels, Antarctic
Fulmars, Sooty Shearwaters, and Prions. Seabirds are attracted to
disturbances on the sea surface, which in nature often indicates food.
When equipment such as the ROV or LSTs disturbs the surface, it attracts
the seabirds as well.
An Antarctic Fulmar is captured in action as it flies past the
ship. Photo by Kim Reisenbichler
In addition to large fauna, the ocean teems with smaller life. Shiny
fish cling to subsurface ice as salp chains drift past. Swarms of krill
cloud the water just below the surface. The MOCNESS trawls reveal the
less common plankton, including jellies, siphonophores such as Diphyes
antarctica, and a diverse set of swimming arthropods including krill,
amphipods, and decapods.
Smaller still, diatoms and other phytoplankton populate the view under
the microscope. These microscopic drifters are the base of the food
chain in the Southern Ocean; a few species of algae grow underwater on
icebergs, but the water in our study area is too deep (>3000m) for large
algae to take hold on the seafloor.
— Amanda Kahn