116 College of Forestry 
for a period of about eight months, but when transported to 
the central part of this body of water they increased to four 
or five times their original weight. This observation led to 
the conclusion that there was a serious deficiency in the food 
supply of the first named locality. To obtain this informa- 
tion it Was necessary to examine certain areas in different 
parts of the body of water and to estimate the amount of the 
available food supply. ‘To carry on this investigation Peter- 
sen experimented with various types of dredges until an 
apparatus was devised, known as the ‘ o.1m* bottom sampler ” 
which brought up for examination an area of one-tenth of a 
square meter with its top layers in their natural position, con- 
taining the living organisms in their natural relations. This 
bottom sampler showed that some of the Danish waters were 
rich in food supply while others were very poor, some of 
these differences being correlated with the character of the 
deposit covering the bottom. This will be discussed on a 
later page. 
With this apparatus Petersen collected from the bottom of 
the Thisted Bredning more than a hundred samples of the 
bottom, each one-tenth of a meter square, and carefully 
counted the number of different animals present. These were 
tabulated and averaged. In addition to the numerical studies, 
the animal matter was extracted, dried and weighed so that 
the amount of dry matter per o.1m* could be found and the 
amount of actual available food supply in the whole area esti- 
mated. The relative density of the bottom fauna was illus- 
trated by means of diagrams showing the population of one- 
fourth of a square meter of sea bottom. By means of these 
studies, Petersen was able to calculate that the fish consumed 
about 3 grams per square meter, and the whelks and star- 
fishes, predaceous animals, about 6 grams dry weight per 
square meter. The total amount of dry matter on the bottom 
was estimated to be about 30 grams per square meter. He 
also estimated that the bottom fauna consumes several times 
its own weight in the course of a year. 
