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round Agerø, in Louns Bredning, Skivefjord, in the waters between Løgstør and 
Nibe. In Thisted and Livø Brednings, where the shores slope down fairly steeply, 
it only occurs as a narrow belt along the coast. 
In our other fjords also, in the East Jutland fjords, in Odense Fjord, in 
Roskilde and Holbæk Fjords, the Zostera vegetation occurs extensively and 
luxuriantly. 
In the Kattegat there is a belt of (narrow-leaved) Zostera along the east 
coast of Jutland. In patches it occurs over great parts of the Kattegat, especially 
south of Læsø and in Samsø Belt, but, as a glance at the Charts quickly shows, 
the Kattegat vegetation in comparison to the extent of the water, is many times 
less than that of the Limfjord; it is also, as above-mentioned, less luxurious than 
the fjord Zostera. 
In addition, some other flowering plants belong to the grass-wrack formation 
as well as Zostera, the most important of which are Zostera nana, Ruppia maritima 
and Potamogeton pectinatus (see Warming, 1906, p. 185 and Ostenfeld 1908 p. 
38). In comparison with the Zostera they play quite a subordinate role, occurring 
more seldom and forming only small growths. Most important are Ruppia and 
Potamogeton. 
More important than these in quantitative regards is probably the epi- 
phytic algal vegetation, which grows on the Zostera leaves (Ostenfeld, 1908, 
p. 32). The leaves of the fjord Zostera are often quite laden with short brown 
and red algae (Ostenfeld calls them Ceramium and Eectocarpus species). Further 
thick mattings of diatoms occur. The whole of this epipbytie flora constitutes the 
food for a rich fauna, which likewise lives on the Zostera leaves, various gastro- 
pods (Rissoa, Hydrobia), Bryozoa etc. (see figure in Ostenfeld 1. ce. p. 33). This 
fauna will be discussed in more detail later. 
The marine algae formation is also represented in the Danish waters. 
Round about the Zostera belt, both within and outside, numerous stones are of 
frequent occurrence and thus offer possibilities for the growth of marine algae. 
Ostenfeld (1. c., p. 32), distinguishes between pure and mixed Zostera vegetations. 
The pure Zostera vegetation occurs on soft muddy soil; at such places it is the 
only plant occurring except for the above-mentioned ephiphytie algal vegetation. 
Marine algae are not able to grow at such places, partly because there are no 
stones and partly because the Zostera is able to smother them by excluding the 
light. In shallower water, on the other hand, and on solid bottom on the whole 
where stones occur and where the Zostera as mentioned grows less luxuriantly, a 
rich algal vegetation develops at certain places. Regarding the production of the 
marine algae in our waters Dr. Kolderup Rosenvinge has most kindly written 
a brief account, which may be given here. 
»If we wish to determine the total, annual production of matter by the 
algal vegetation in the Danish waters, we may for the few most important species 
endeavour to find out, how much new material is formed each year and on the 
other hand, how much dies or is thrown off. 
To be able to make such an investigation some of the species must first 
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