A Lime-incrusting Algal Community 
of a Danish Well 
By E. «FJERDINGSTAD 
(Instiliite of Hygiene, l'nivcrsity of Copenhagen.) 
Incrustations formed by blue-green algae by jirccipitatic;!! of cal¬ 
cium carbonate are of frequent occurrence in stalic waters, et. e. g. 
Ka.nn (1941). They are described from watercourscs fr{)in the Uni¬ 
ted States of America by Rhoddy (1915), from Germany by Bi ude 
(1930 and 1932), from Switzerland by Jaao (1938), from alpine 
brooks in Austria by Kann (1941), and from England by Fretsch 
& Pantin (1946) and Fritsch (1949). The literature, however, 
seems to contain no data on the occurrence of such formations in 
Wells, perhaps with the exception of the lake Kellersce, whence 
Kann (1941, p. 522) reports the spécial condition that well water 
with a higher lime content than the water of the lake trickles 
down across stones. 
From Stubberub Vad in northern Jutland (Denmark) sonie parti- 
culars will be given here regarding an incrustation community from 
a well (*). The composition of species in this well difïers to sonie 
extent from the incrustation communities previously described. If 
we consider the conimunity-forming siiecies nientioned in the above- 
quoted literature, we shall fmd that Phormidium incruslaiiim Goiii. 
seems to be one of the most important components of the comniu- 
nities in rivers - - Fritsch wriles that it is always présent and 
often dominant — as well as in iakes, especially in the eutrophic 
northern Iakes (incliiding the Danish Iakes), cf. Kann (1941, p. 512). 
As a sigiiificant additional componeiiL of these commimities, Fritsch 
(1949) mentions Schizothrix fnsciculafa (Naeg.) Goin., while Kann 
records Schizothrix laleritia (Kütz.) Gom. from Iakes. This species 
is reported by K.ann (1941, p. 497), likewise as the main forni, 
from incrustations in ponds near Abisko (Swedish Lapland), where 
it occurs in comiiany with Dicholhrix gypsophila (Kütz.) Born. et 
Flah. Phonnidinm sp. and Riinilaria Biasolettiana. In Stubberiij) 
(*) The malerial, which was collected by Dr. Anker Nielsen, Ph. D., on July 
12th, 1947, was handcd over to the author for examination, for which I hcre 
express my indebtedness. 
