Spatial heterogeneity in an intertidal sedimentary environment and its macrobenthic community

Abstract

Abstract The intertidal sedimentary environment is an extremely varied one in which marked differences in habitats and animal communities occur over very short distances. This study reports small scale heterogeneity of an intertidal macrobenthic community and its sedimentary environment in large sand waves in a bay in the Clyde Estuary, Scotland. Three 50 m transects ran across sand waves along a peak (P), along a trough (T) and across a peak and trough (P/T). Five sediment parameters [redox potential (Eh), organic carbon, particle size, shear strength and water table] and abundance of 14 macrobenthic species were measured in contiguous 1 m 2 quadrats along each transect. There were more positive and negative significant correlations along the P/T transect than the P and T transects. Thirteen correlations were common between pairs of transects. Multivariate cluster and principal component analyses were conducted on the data. The results of the two techniques were broadly in agreement. Distinct clusters of macrobenthic species and sediment parameters were identified. Some species clustered with sediment parameters. Others clustered only with species. These analyses may imply important causal relationships some of which are physically controlled and some of which are biologically controlled. Some clusters contained solely species that were deposit feeders. Clusters of quadrats along the P/T transect grouped quadrats on the peaks, in the troughs and on the slopes of the sand waves. These show that the peaks, troughs and slopes are significantly different sedimentary microenvironments. Clusters of quadrats along the P and along the T transect grouped quadrats that were spatially adjacent. These clusters indicate significant small scale spatial variability along the peaks and along the troughs of the sand waves.