CHAPTER XII 



ECOLOGY OF SALT MARSHES 



In comparison with the rocky coast fewer studies have been 

 carried out on the algal ecology of salt marshes, but those that have 

 been published can be regarded as having made considerable 

 advances in our knowledge of these extremely interesting areas. 

 Their neglect in the past has probably been due to the fact that the 

 algae are often microscopic and hence not so pleasing aesthetically 

 even when present in abundance, and also they are more difficult to 

 determine taxonomically. In practice, however, a detailed study of 

 any one area often produces the rather unexpected result of a very 

 extensive flora. For example, the number of species recorded from 

 the English salt marshes of Norfolk is about two hundred, which 

 does not compare unfavourably with the number on a rocky coast. 



An investigation of any salt-marsh area shows that the algal 

 communities offer a somewhat different aspect to the algal 

 communities of a rocky coast. In the latter case it has been seen 

 that zonation is a characteristic feature together with some super- 

 imposed seasonal changes and migrations. On the salt marshes it is 

 not really possible to distinguish any zonation but there may be 

 well-marked seasonal changes in any one area. Thus on a fairly low 

 marsh the "Autumn Cyanophyceae " appear in autumn and early 

 winter, they disappear and are replaced in spring by the Ulothrix 

 community, which in its turn is replaced during the summer 

 months by Enterofnorpha and so the cycle proceeds. Furthermore, 

 as each year the ground level increases in height in relation to the 

 tide through the continual deposition of silt, the submergences 

 become fewer and the communities are replaced by others on 

 account of the modified conditions. As a result there is a definite 

 dynamic succession of the different communities over a long period 

 of years. This cannot be seen on a rocky coast where there is no 

 succession in time and where the succession in space is static. 



The phenomenon of dynamic succession in this type of habitat 

 necessitates a somewhat different approach to the problem of the 

 status of the community. The continual replacement of one 



CS A 21 



