iiNrr.ASSTFTF.n 



SECURITY CLASSIFICATION OF THIS PAGEfWTiBn Data Entered) 



Major associations of macrobiota (organisms >1 millimeter in size) were 

 distinguished on the basis of cooccurrences of conspicuously dominant organ- 

 isms. Thirteen major associations, covering various parts of the island 

 between the upper intertidal zone and shell debris or natural bottom at the 

 foot of the rock revetments, were defined. The boundaries of each of the 

 major associations and certain questionable or transition zones were mapped 

 over the entire island. These associations were further characterized by 

 extensive measurements of biomass and abundance of macrobiota occurring in 

 quadrats placed according to a stratified random sampling scheme. Using 

 these data, statistically based comparisons of biotic character were made 

 between certain transition areas and definite associations. In some cases, 

 questionable associations were lumped together. 



A major part of the study was devoted to analysis of seasonal dynamics 

 in biotic composition. Permanent transects extending from the high inter- 

 tidal to natural bottom were established normal to each of the four cardinal 

 sides of the island. All macrobiota were censused in duplicate 1-square 

 meter quadrats along each transect during each of the four seasons. Data 

 analysis indicated that many species exhibit significant variability in 

 abundance from one season to the next. 



Other studies included a gill net survey of fish fauna, mapping of 

 mussel "talus" beds at the base of the island, and a survey of biota along 

 a natural bottom transect between the island and shore. 



In general, the findings indicate a rich and varied fauna and flora 

 associated with the high-relief solid substrate of Rincon Island which 

 differs substantially from the more depauperate natural bottom habitats 

 in the area. 



2 UNCLASSIFIED 



SECURITY CLASSIFICATION OF THIS PAGEfMTien Data Ent 



