Abyssal Giants in the Southern Ocean

The Mountains of Antarctica as seen from the Southern Ocean

The great Southern Ocean which swirls in a clockwise circle around Antarctica is home to many of the Earth’s largest animals.  Blue whales come here to gorge on vast schools of krill. Among the icebergs and the towering waves, southern elephant seals (the largest member of the order Carnivora) fight duels to build their harems, and highly intelligent killer whales hunt together in pods.  There are populations of sperm whales living in the Southern ocean as well and these leviathans dive to the cold floor of the world hunting for the world’s largest mollusk, a huge cephalopod which can only be found in the Southern Ocean.  In fact this bizarre creature, the colossal squid (Mesonychoteuthis hamiltoni) is also the world’s largest invertebrate.  Also known as the Antarctic squid or the giant cranch squid, the colossal squid lives in the abyssal depths.  Unlike other squid, the colossal squid does not have tentacles–its powerful arms are studded with sharp hooks (much like the long-extinct belemnites).  Some of these hooks swivel while others have three barbs in the manner of a fish spear.

The Colossal Squid (Mesonychoteuthis hamiltoni)

The measurements of the colossal squid are staggering.  Its eye alone (the largest of any known creature) measures 27 centimetres (11 in).  A fully grown adult squid is estimated to be 12–15 metres (39–49ft) long.  Although giant squid have longer tentacles, the colossal squid a long stout mantles and are thus much more massive. Their upper weight limits are unknown but are well over 500 kg (+1000 lbs).

The colossal squid is believed to be an ambush predator, which lurks in the depths waiting for chaetognatha, other squid, and benthic fish (such as the Patagonian toothfish) to pounce upon.  It is hypothesized that they have a slow metabolism and do no need great reserves of food (unlike the energetic endothermic sperm whales which prey on them).  The colossal squid are believed to be sexually dimorphic—the females become much larger than the males.

A rare specimen of colossal squid

There is a reason that so much of this article is couched in ambivalent language such as “estimated”, “believed” and “probably”:  colossal squid live in an environment where humankind can barely venture.  The colossal squid are fast enough and clever enough to usually evade our nets, lines, and traps (although fishermen trying to catch Patagonian toothfish hooked a 450 kg (990 lb) specimen which was about 39 feet (13 m) long).  Additionally our submarines and submersible robots are too slow and noticeable too stalk the squid in the abyssal depths.  Other ocean creatures do not suffer from the same problem.  Juvenile colossal squid are eaten by beaked whales, elephant seals, sharks, toothfish, and even albatrosses, however the adult squid are so large that only massive sleeper sharks and giant sperm whales can threaten them.  Sperm whales are often covered with scars from their battles with the giants but the whales easily have the upper hand.  Sperm whale stomachs have been found filled with hooks and beaks (which coincidentally were much larger than those found on the largest squid specimens recovered by humans to date).

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Lake Baikal

A satellite above Lake Baikal (image courtesy of Earth Sciences and Image Analysis Laboratory, NASA)

Lake Baikal in Siberia has a surface area of 12,248 sq miles (approximately equal to Belgium).  For a better comparison, Lake Superior has a surface area of 31,700 square miles. However that comparison is in no way apt.  Lake Baikal is prodigiously deep.  It lies on one of the world’s great rift valleys. To its west lies the Eurasian plate and to its east is the Amur plate.  The two plates are springing away from each other at 4 millimeters per year.  In the void between lies Lake Baikal, which is an astonishing 5,380 feet deep.  The 5,700 cubic miles of water contained by the lake compromises twenty percent of the world’s fresh water (not counting ice or water vapor).  It could easily hold all of the water from all of the Great Lakes.  Not only is the lake deep, it is ancient.  Lake Baikal is more than twenty-five million years old, and may be one of the world’s oldest lakes.

Lake Baikal

Lake Baikal contains thousands of species of plants and animals, most of which live no where else on earth.  There is a freshwater seal, the nerpa, which lives on golomyanka, a translucent abyssal fish famous for decomposing almost instantly to fat and bones when exposed to the sun.  There are omuls, lovely small salmonids, caught and smoked by humans around the lake, and there are huge Baikal sturgeons.  The lake is ringed by forested mountains which host brown bear, lynx, wolves, foxes, and wolverines (and maybe the occasional Siberian tiger). These predators live on mountain goats, reindeer, white tailed deer, elk, moose, musk deer, Siberian roe, and wild boar.  The small mammals and birds are too numerous to name.

Golomyanka--An abyssal fresh water fish

The lake’s true oddities are invertebrates which live in the depths. Far beneath the surface, forests of Lubomirskia sponges attain towering heights as they branch into strange shapes.  Benthic and pelagic infusoria are endemic, as are huge predatory swimming flatworms which are covered with suckers.  Shrimp and crustaceans abound.  It has been estimated that the biomass of crustaceans in the lake exceeds 1,800,000 tons. Turbellarian worms, snails and amphipods are also diverse.

An amphipod regards a diver from a sponge forest in Lake Baikal

The Lake is the alleged site of one of the world’s greatest haunted treasures.  Admiral Aleksandr Kolchak, was a tsarist hero who won the golden saber for valor at the battle of Port Arthur.  After the Tsar and his family were executed by Bolsheviks, Kolchak assumed command of the imperial armies during the disastrous civil war.  A substantial detachment of his troops rescued the Empire’s gold reserves (an estimated 1600 tons of gold) and were carrying them across Siberia during the brutal winter of 1919/1920 when temperatures dropped below -60 °F.  Legend has it that both the gold and the troops found their way into Lake Baikal and have never emerged.