ANTARCTICA
Antarctic and antarctic biology and research have fascinated marine biologists for many years. While much of the Antarctic biota contains representatives that are familiar to us, the realm is very much isolated from the rest of the ocean, and several groups are confined to this southern end of the planet. It may surprise you that the Antarctic benthos is very diverse and extraordinarily beautiful, despite the extreme cold. A very productive water column provides in many areas a rich source of sedimenting organic matter for soft bottom benthos and a source of food for suspension-feeding animals. Thus we find a diverse community of benthic particle consumers and their predators. Of course the great ice cap, with its extremes of climate and local biota, has the greatest of fascinations. Every spring the edge of the ice cap begins to break and ships can approach the few research stations, such as the one at McMurdo Sound. In recent years the breakup of the ice has drawn special attention, owing to concerns about global warming. The Palmer Station is located on the Antarctic Peninsula, which has experienced steady warming and reduction of sea and land ice in recent years. This has caused drops in certain species there, such as Adelie penguins.
What follows is a taste of the Antarctic biota.
Breakup of Ice, 1995. Photograph by Diane Stoecker
Minke Whale at Ice Edge. Photograph by Diane Stoecker
Adelie Penguins. Photograph by Diane Stoecker
Rookery of Adelie Penguins at McMurdo Sound. Photograph by Diane Stoecker
Sampling the water column at the ice edge. Photograph by Diane Stoecker
Dog skeleton – the dry cold climate results in many mummified carcasses that are found throughout Antarctica. Some areas are so dry that their climate has been likened to what might be expected on the Martian surface. Photograph by Richard B. Aronson
Emporer Penguin. Photograph by Peter Ritchie
Antarctic Seal. Photograph by Peter Ritchie
Diver preparing to enter through a hole in the ice. Photograph by Diane Stoecker
Diving under an ice crack in Granite Harbor. Photograph by Richard Aronson
Seascape with the vase sponge Scolymastra joubini at 70 feet depth, Granite Harbor. Photograph by Richard Aronson
Ice and Brine Microorganisms. Photograph by Diane Stoecker
Ice and Brine Microorganisms. Photograph by Diane Stoecker
A flagellate- and ciliate-dominated microbial community has recently been described from brine channels and pockets in the upper land-fast ice in McMurdo Sound. This community has similarities to the assemblages reported from Antarctic pack ice. An important feature of this community is the dominance of athecate, photosynthetic dinoflagellates. Above is a vegetable cell and below is a cyst. Bar is 10 micrometers long in both photos.
A group of the seastar Odontaster validus with the nermertean (purple) Parborlasia corrugatus. Photograph by Richard Aronson
The Cactus Sponge Dendrilla membranosa. Photograph by Richard Aronson
The Vase Sponge Scolymastra joubini. Photograph by Richard Aronson
The anemone Urcticinopsis antarctica. Photograph by Richard Aronson
The polychaete Flabelligera sp. Photograph by Richard Aronson
The isopod Glyptonotus antarcticus. Photograph by Richard Aronson
Seascape, dominated by the Octocoral Alcyonium paessleri (light yellow). Photograph by Richard Aronson
The pycnogonid Thavmastopygnon striata
Photograph by Richard Aronson
Unidentified Octopod. Photograph by Richard Aronson
The sea urchin Sterechinus neumayeri. Photograph by Richard Aronson
Group of the seastar Odontaster validus. Photograph by Richard Aronson
Special Physiological Features of Antarctic Fishes
Shallow-water members of the Antarctic suborder Notothenioidei include a number of species that have special physiological properties that apparently evolved for survival in cold water. Recall that the Antarctic Ocean surface waters are quite cold, and close to the freezing point of seawater. Bony fish have the special problem of having cellular fluids whose freezing point is higher than that of seawater. Because salt lowers the freezing point of seawater, the seawater surrounding the fish may actually be in a liquid state at a temperature at which water would normally freeze within the fish. This is a special problem for shallow-water fishes that must ingest seawater for osmotic balance and inevitably ingest ice crystals, which would nucleate further freezing within the body.
Trematomus bernachii. Photograph by Richard Aronson
This and other members of this genus synthesize special glycoproteins, which behave like an automobile antifreeze.
Trematomus hansoni. Photograph by Ian McDonald
Pagothenia borchgrevinski. Photograph by Ian McDonald
This species also contains glycoproteins, which prevent freezing of cellular fluids. Photograph by Peter Ritchie
This shows a sample of blood of a species of Channichthyid fish, compared with a vial of blood from a more typical fish. Why do you think this fish and others, who live in icy surface waters, lack hemoglobin?
A pool of P. borchgrevinski. Photography by Peter Ritchie