ENGLISH SUiMMARY 



IN "Report XX from the Danish Biol. Stat.: The valuation of the Sea I 1911" it 

 has been shown how great is the importance of the sessile vegetation along the 

 coasts of the Danish waters for the nourishment of the animals living on the sea- 

 bottom. The most important species of this vegetation is undoubtedly Zostera 

 marina both on account of its rich occurrence and large annual production. It is 

 the object of the present article to give an approximate estimate in numbers of 

 this production. 



By studying the nodes of the root-stock, the number of which corresponds 

 exactly to that of the leaves, Petersen proves that each Zostera-shoot generally 

 produces ca. 10 leaves and root-stock nodes during the summer and ca. 5 during 

 the winter, The nodes are generally short in winter and long in the good time of 

 the year; on long, carefully separated root-stocks taken with the bottom-sampler 

 the number of nodes may be counted from one year to another on the same root- 

 stock; this shows alternate series of long nodes and short nodes according to whether 

 the nodes have been formed in summer or winter (see fig. 1, p. 4). As a rule each 

 shoot has only ca. 5 leaves at one time, the older ones having fallen of. Therefore 

 the Zostera-mass with its 5 leaves growing in summer on 1 ra* of bottom only re- 

 presents about one half of the leaf production during the summer. 



By mcans of the bottom-sampler Petersen has been able to determine the 

 maximum quantity of Zostera leaves per 1 m' during the summer at different piaces 

 and found this at favourable, moderately good and bad piaces to be 6000, 3500 

 and 1700 gms. per 1 m' respectively; by doubling these numbers we get 12000, 7000 

 and 3400 gms. as the total yearly production, thus paying no attention to the pro- 

 duction in winter nor to the occurrence of roots. 



The dry-stuff percentage of Zostera is ca. 16, its yearly production of dry-stulT 

 per 1 m« therefore 1920, 1120 and 544 gms. The Zostera areas in the Danish waters 

 inside the Skaw represent altogether ca. 2000 square sca-miles each == 3,430000 m*. 



Taking theaverage yearly production as 1200 gms. dry-stulT, the total production 

 will be about 8232 million kg or almost 4 times as large as Denmark 's total pro- 

 duclion of meadow and field hay in the air-dried state, that is to say, quite a con- 

 siderable production. 



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