Analysis of structural variations in a shallow estuarine deposit-feeding community

Changes in the structure of an estuarine, subtidal, benthic deposit-feeding community have been investigated. Three quantitative samples were taken within a grid 10 m on a side every four weeks from May, 1971 to July, 1973. Each sample was washed over a 250 μm sieve. Streblospio benedicti Webster, Capitella capitata (Fabricius), Heteromastus filiformis (Claparède), Potydora ligni Webster, and Paranais litoralis (Müller) were the five dominant species on the basis of their total abundance, percentage occurrence, and biological index value. Repeatable cycles in diversity were observed for Fager's scaled standard deviation and scaled information measure, as well as for Lloyd and Ghelardi's equitability, but not for the unsealed information theory measure. McNaughton's dominance index was strongly inversely correlated with all diversity measures. Graphical measures of lognormal skewness and normal kurtosis, as applied to Whittaker's dominance diversity curves, followed repeatable cycles, whereas normal skewness and lognormal kurtosis did not. A strong relationship between Fager's scaled standard deviation diversity, dominance, and the degree to which resources were being shared by the deposit-feeding segment of the community was suggested. A decrease in average niche width and average niche overlap was observed as the community developed during the period of strong larval recruitment.