Effects of physical disturbance on an estuarine intertidal community: field and mesocosm results compared

Abstract

The response of an estuarine macrobenthic community to different intensities of physical disturbance was examined using comparable field and mesocosm experiments. In the field study, areas of sediment (2500 cm²) were disturbed by surface-raking at a range of disturbance intensities: no disturbance, once every 2 mo, once every month, once every 2 wk, once or three times every week. These disturbance regimes were also imposed on buckets of sediment (855 cm²) collected from the field study site and maintained within a mesocosm system. In the univariate data analysis, neither field nor mesocosm communities displayed any trends in relation to the frequency of disturbance. Diversity indices were generally reduced in the mesocosm communities compared with the field communities. Multivariate analysis indicated significant differences between the field communities subjected to the most intense disturbance and those communities disturbed every ±2 wk or less. These differences were attributed to reductions in the five numerically dominant species in the high- disturbance treatments. More statistically significant differences were observed between the different disturbance intensities in the mesocosm experiment than in the field study. The implications of differences between field and mesocosm experiments results are discussed.