Required sampling intensity for community analyses of intertidal infauna to detect a mechanical disturbance

In coastal ecosystems, infaunal (animals living within the sediment) invertebrates are used to study and monitor disturbances. However, it is an open question as to the minimal required sampling intensity to detect that a disturbance has influenced such communities. As such, we implemented a manipulative experiment using an infaunal community with a known response (community composition and population abundances) to a mechanical disturbance (sediment scour), to determine the minimum sampling intensity required to detect differences in the infaunal community. Statistically significant differences (α = 0.05) between the infaunal community of the disturbed and reference replicates were observed in case studies consisting of 99 (4 samples per m 2 ) to 5 (0.2 samples per m 2 ) samples per treatment. Below 5 samples, the known statistical and biological difference was undetectable. However, at least 10 samples per treatment (0.4 samples per m 2 ) were required for the observed infaunal community to be within 93% similarity of our most accurate assessments of the infaunal community. These findings suggest that studies attempting to identify disturbances may require a minimal sampling intensity equivalent to 0.2 samples per m 2 , while studies attempting to determine how the infaunal community varies with disturbances may require 0.4 samples per m 2 . These potential minimal required sampling intensities will be of use in the theoretical exploration of disturbances, as well as in applied conservation, restoration, and monitoring projects.