Community recovery following catastrophic iceberg impacts in a soft-sediment shallow-water site at Signy Island, Antarctica

Ice disturbance is possibly the major structuring element of polar nearshor e biological communities. Effects range from encapsulation by ice forming o n rock substrata to gouging and trampling by bergs. Some 15 to 20% of the w orld's oceans are affected by this phenomenon, yet measurements of the exte nt of biological destruction from iceberg impacts and subsequent community recovery are very rare. Communities can be held at early successional stage s, or even completely destroyed by scouring, and these effects occur from t he intertidal to depths around 500 m in Antarctica. The wide scales of dist urbance intensity are thought to add to the overall high levels of Antarcti c benthic biological diversity, which has recently been shown to be similar to tropical areas. Data here indicate >99.5 % removal of all macrofauna an d >90 % removal of most meiofauna by iceberg impact on a soft-sediment habi tat at Signy Island, Antarctica. Species return was via locomotion, advecti on or larval recolonisation, and all 3 mechanisms worked on different times cales. Locomotion caused groups to return within 10 d of an impact. Storms with wind speeds around 100 km h(-1) induced water movements intense enough to advect meiofauna to the 9 m depth site. However, it was only during the strongest storm which occurred during the study (maximum wind speed 148 km h(-1)) that water movements were powerful enough to redistribute small mac rofauna such as the bivalve Mysella charcoti.