MARINE ECOLOGY 309 



associations of the sheltered coast. Although the term "associa- 

 tion" was applied to these communities, it is probable that many of 

 them are really mere "societies" in strict ecological nomenclature 

 because they are only transient. At Lough Ine Rees (1935) 

 classified the formations on a different basis and he recognized 

 only two, the open and sheltered coast formations. Cotton's 

 formations were based on substrate or salinity whilst Rees's were 

 based on shelter. Rees further used the term "association" for 

 those communities where species that are associated with the 

 dominants are controlled by the same factors. The difficulty of this 

 criterion is the time involved in proving experimentally that certain 

 factors do control the distribution of the species concerned. 

 Seasonal communities, or those which were locally dominant, were 

 regarded as societies, whilst the term "zone" was used for those 

 algal belts which possess horizontal continuity with well-marked 

 upper and lower limits. 



In a study of some New Zealand littoral vegetation Cranwell and 

 Moore (1938) termed the associations of the successive belts which 

 follow one another in a regularly recurring sequence as an "associa- 

 tion-complex". The horizontal belts were commonly continuous 

 but they could be interrupted occasionally by another community, 

 e.g. one could have an association fragment of Durvillea in the 

 Xiphophora belt. It is apparent therefore that there is some 

 divergence of opinion about nomenclature, and at present, until 

 a thorough resurvey of the whole problem has been carried out, 

 it would perhaps be more satisfactory to use a non-committal term 

 such as "community" which implies no particular status. 



THE BASIC ZONATION 



Out of the wealth of material available it is apparent that there is 

 on British coasts what one may term a basic zonation, principally 

 composed of fucoids, and on this other communities are super- 

 imposed, the actual number being dependent upon the two factors 

 already mentioned. This basic zonation is briefly as follows : 



(i) An upper Enteroinorpha belt. Such a belt has been recorded 

 from all the localities except those around Dorset and at Castletown 

 in the Isle of Man. At Dover there are other species associated 

 with the Enter omorphay e.g. Urospora and Codiolum. On any coast 

 there will be a development of an Enteroinorpha community 



