Chapter 3
THE EPIFAUNAL ASSOCIATES OF FUCUS SERRATUS.

Abstract:
The sessile epifaunal associates of Fucus serratus were examined from sites around Anglesey, Wales and from Robin Hood's Bay, Yorkshire.  A total of 20 sessile species were recorded which included 8 bryozoan, 4 hydroid and 3 barnacle species. The polychaete Spirorbis spirorbis was the most ubiquitous species, being recorded at all but one site.  Of the bryozoans the two most prevalent species were Flustrellidrahispida and Electra pilosa both of which possess spines.  The abundance of the commonest species at each site was determined for (a) concave and convex sides; and (b) basal, middle and distal segments of F. serratus fronds.

Seasonal changes in ubiquity and abundance of the common epifaunal species Alcyonidium hirsutum, F. hispida, E. pilosa and S. spirorbis were monitored at Church Island (CI) and Porth Cwyfan b (PCb), Anglesey over 4 seasons.  Seasonal and site differences were evident for all 4 species but were most marked in S. spirorbis.  As with the initial epifaunal surveys the abundance of species on different regions of F. serratus fronds was examined.

Characteristics of spine morphology and number were compared for colonies of F. hispida from Anglesey sites contrasting in their exposure to wave action.  West Anglesey colonies possessed significantly more spines per peripheral zooid than colonies from the sheltered Menai Strait but the lengths of spines did not differ significantly.  Reciprocal transplanting of young colonies between the two sites CI and PCb resulted in a significant change in the number of spines per peripheral zooid: the PCb to CI transplant exhibiting a decrease in spines; the CI to PCb transplant exhibiting an increase in spines.