Recovery of soft sediment communities and habitats following physical disturbance

Physical disturbance in soft sediment habitats disrupts the sediment structure and can lead to the death or emigration of resident biota. Current methods used to quantify the response of benthic assemblages to physical disturbance are time consuming and expensive, requiring the analysis of a time series of samples to ascertain the time taken for a disturbed area to converge on a condition similar to that found in adjacent control areas (the recovery time). We designed an experiment that studied the effects of two intensities of physical disturbance on both the habitat and fauna of a sheltered sand flat to ascertain whether the recovery of the biota could be predicted from physical attributes of the habitat. Benthic community recovery from the lower intensity disturbance occurred within 64 days of the disturbance, whereas recovery after higher intensity disturbance did not occur until 208 days post-disturbance at this site. Sediment granulometry and percentage organic content did not alter as a result of the disturbance in either treatment. However, the depth of water that remained in the disturbed pits decreased with time, and correlated with the temporal changes in community structure. Thus although this was the most crude physical parameter measured it best described the recovery process of the fauna and may encapsulate the entire suite of other more subtle habitat changes that occur at the same time. By quantifying the persistence of physical features in different soft sediment habitats it might be possible to develop a more amenable and rapid framework for assessing the longevity of the effects of physical disturbance.