Benthic grab samples were taken in August, 1972, and January-February, 1973, from bottoms ranging from very fine sand to sandy gravel. Gammarid amphipods collected were identified to species, feeding type, and life style. Cluster analysis and principal coordinates analysis were used to examine sample and species distribution similarities. Two methods were used to analyse correlation between measured sedimentary factors and faunal distributions. Summer species distribution was interpreted as being primarily a response to feeding considerations; gravel content being the most important sedimentary factor. Between-habitat faunal changes in summer were primarily clinal, following a gradual change in sediment texture. A strong correlation between the Shannon-Weaver diversity and sediment texture existed in summer, with diversity increasing due to decreasing species dominance and, most importantly, increasing species richness as sediments became coarser. The diversity of life styles was similarly higher in the coarser sediments. Winter species distribution primarily reflected the distribution of life styles, with gravel again being the most important sedimentary factor. This is interpreted as indicating a correlation between faunal distribution and increased sediment instability caused by winter storms. This decreased sediment stability resulted in a marked diversity decrease in several medium and coarse textured samples, relative faunal homogeneity of the medium and coarse textured samples and observable changes in faunal distribution. © 1979.
