antarctic plant geography 347 



Algae 



Fresh-water algae^ are comparatively abundant in the Antarctic. 

 In the South Orkneys alone about seventy species have been recorded.^ 

 The most interesting are those that color snow. Red snow is the com- 

 monest and, as in the Arctic and elsewhere, is generally caused 'by 

 Sphaerella but occasionally, as in the Alps, by red rotifers. Yellow 

 snow is rare and may be due to a remarkable association of many 

 algae and fungi or, when it occurs on sea ice, to diatoms. Some scanty 

 deposits of a peatlike material that have been found in fresh-water 

 lakes are composed of algae which have been compressed but have not 

 undergone the partial decomposition characteristic of peat. In fact, 

 putrefactive organisms, where they have been searched for, are no 

 more abundant in Antarctic than in Arctic soils, while examination 

 of the air has proved it to be sterile, except where contaminated by 

 contact with soil or animal life. 



Marine algae, ^ both unicellular and multicellular, are very abundant 

 in the Antarctic seas. The scouring action of drifting ice prevents 

 much growth except of encrusted calcareous algae, between tide marks 

 and for some feet below; and where glaciers reach the sea, of course, 

 no littoral vegetation can exist. Strange to say, algae grow at times 

 in pools that are frozen solid every winter. Luxuriant species, like 

 Laminaria and Macrocystis, flourish only on sub- Antarctic coasts 

 which remain open throughout the year and are little exposed to drift- 

 ing pack. Below the influence of ice, within range of the penetration 

 of light, the larger algae flourish in the Antarctic seas and seldom have 

 to contend with the low salinity of the water which is a deterrent in- 

 fluence to alga growth on certain Arctic coasts. 



Most remarkable, however, is the wealth of diatom life in the Ant- 

 arctic seas,^ a phenomenon that has long been noted in the Arctic seas. 

 A few minutes' haul is enough to fill a silk townet with a gelatinous 

 mass of these unicellular plants. Various reasons have been given in 

 explanation of this abundance of phytoplankton in cold seas by con- 

 trast with its scarcity in warm seas. The most important features are 

 probably the scarcity and decreased activity of denitrifying bacteria 

 in cold seas; the tendency for surface layers of water to sink and be 



8 W. West and G. S. West: Freshwater Algae (British Antarctic Expedition 1907-9, Reports on 

 the Scientific Investigations, Botany, Vol. i. Part VII), London, 1911. 



G. W. F. Carlson: Siisswasseralgen aus der Antarktis, SUdgeorgien und den Falkland Inseln 

 (Wiss. Ergebn. Schwed. Sudpolar-Exped., Vol. 4: Botany, Part II, No. 14), Stockholm, 1921. 



F. E. Fritsch: Freshwater Algae (British Antarctic ("Terra Nova") Expedition, 1910, 

 Nat., Hist. Repts.: Botany, Part I, pp. 1-16), London, 1917. 



''idem: Freshwater Algae of the South Orkneys (Scottish Natl. Antarctic Exped. Sci. Res., 

 Vol. 3: Botany, pp. 95-134), Edinburgh, 1912. 



3 Carl Skottsberg, H. Kylin, D. E. Hylmo: Zur Kenntnis der subantarktischen und antarktischen 

 Meeresalgen (Wiss. Ergebn. Schwed. Siidpolar-Exped., Vol. 4: Botany, Parts I and II, Nos. 6, 15, 16), 

 Stockholm, 1908 and 1921. 



' L. Mangin: Phytoplancton antarctique, Memoires Acad, des Sci. de I'Inst. de France, Vol. 57, 

 1922. 



