Annual changes in selected aspects of soft-shore biology

Abstract

SynopsisAnnual variations in a number of parameters over the period 1977–84 are described: they were generally site-specific in character. Linear shell dimensions of Cerastoderma edule populations (seven sites) remained stable but trends in both shell and soft-tissue dry weights changed over this period. Population structure and growth rates of C. edule are described using growth-ring analysis: they provide evidence of sporadic recruitment and persistent dominance by one or more yearclasses, although several populations are particularly individual in character. Populations of Macoma balthica (two sites) had a stable structure. Populations of both species at one site (inner Houb of Scatsta) declined markedly following the Esso Bernicia oil spill in 1982 and had not recovered before the study was terminated. Studies of transects at two sites are described: sedimentary changes were small while infaunal community characteristics showed both persistent environmental trends for some species and random fluctuations in others. The communities at each site showed high diversity, with generally stable structures upon which are superimposed annual and site-specific fluctuations in abundance of component species.