A study of long-term changes in some rocky shore communities in Orkney

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Abstract
The distribution and relative abundance of various types of coastline are reviewed briefly. The results of a 9 year investigation of selected rocky shore communities are presented. Climatic parameters showed a marked variation during the study but were not correlated with the observed variations in flora and fauna. The main study was based on annual sampling of 8 bedrock shore transects using percentage cover or density for sessile and mobile species respectively. Seasonal fluctuations were studied in fixed areas at 2 sites over a 5 year period. Patterns of seasonal variation in various algal and faunal categories are described and discussed, canopy algae showed summer maxima while understorey species showed winter maxima. Annual studies showed species stability to be site specific: in species which showed marked, apparently cyclic, patterns of change, the changes were often asynchronous both between sites and, to a lesser degree, between stations at a site. The value of obtaining a measure of ‘patchiness’ is discussed.