Chapter XIII 



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 

 pubUshed 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 somewhat unexpected result of a quite ex- 

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

 EngHsh 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 diff'erent aspect to the algal com- 

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

 zonation is a characteristic feature together with some superim- 

 posed 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 Enter omorpha 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 be- 

 come 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 diff'erent 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 diff'erent approach to the problem of the 

 status of the community. The continual replacement of one com- 



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