similar to BACI, the BACIR design includes repeated sampling before and after a disturbance.the rationale behind the design is that multiple sampling over time gives an indication of the temporal variability in the population (underwood 1991), avoiding identification of natural temporal perturbations as impact. long and colleagues examined the effect of maintenance dredging of shipping channels in australia on seagrass beds in 1996. grids overlaying the dredged and control areas produced 78 impact and 39 control sampling locations, and a random selection of these locations were sampled once prior to and twicr following dredging. they demonstrated that distribution of zostera capricorni and halophila