25 



IV. Distribution of the Zostera in Danish waters. 



The factors discussed iu the l'oregoiug for a successful growth of the 

 Zostera aflord in themselves some basis for judging as to the extent of tlie 

 distribution of this ]ilant iu our waters. Thej' may be summarized in the following 

 statements: The Zostera requires au at all events somewhat protected habitat, 

 and thus thrives best in our small waters; its depeudence on light has the 

 result, that it can only grow in depths which do not exceed 6 fathoms (ca. 11 

 meters) aud eonsequently one caii only expect to find it as a fringe along the 

 coast, and out ou the quite shallow parts of the Kattegat and the Smaaland 

 Waters. As it attaius its best growtli on pure and sand-mixed muddy bottom, we 

 find the riehest Zostera vegetation in our fjords. 



The following more detailed remariis about its distribution iu our waters 

 may further serve to show tlie correetness of the statements. 



Knowledge of the distribution of the Zostera iu our waters is almost 

 entirely due to the Director of the Biological Station Dr. C. G. Joh. Petersen. 

 Already in the first report of the Biologicai Station (1891) there is a chart aud a 

 thorough discussiou of the distributed of the Zostera in Holbæk Fjord (Zealand) 

 and its importance to the auimal life there. A similar detailed investigatiou Hke- 

 wise accompanied by a chart of the parts investigated is found in the third report 

 of the Biological Station, dealiug with the Little Belt together with Fænø Sound, 

 Gamborg Fjord and Kolding Fjord. At almost the same time (1893) as this report 

 appeared »Det videnskabelige Udbytte af Kanonbaaden Hauch's Togter«, in the 

 text of which (p. 437) some information is given regarding the vegetation of the 

 sea bottom, and the atlas contaius a chart (III) of the Kattegat with data on the 

 occurrence of the Zostera. In the Report IX (1900) of the Biological Station some 

 notes are given on the distribution of the Zostera iu the Northern Kattegat, and 

 finally Report X (1901) is accompanied by a chart of our waters, in which the 

 occurrence of the Zostera is compared with the position of tlie eel traps. 



The investigatiou I undertook in 1901 was to supplement these data and 

 consisted in a rapid cruise through most of our waters. 



Starting from the consideration that the vegetation, at piaces which offered 

 the Zostera practically the same conditions, would also be very similar, I tried 

 in the three weeks, iu which the expeditiou lasted, to fiud an opportunity by 



