Iceberg Disturbance and Successional Spatial Patterns: The Case of the Shelf Antarctic Benthic Communities

Abstract

High-latitude, shelf Antarctic benthic communities are highly diversified and structured, dominated by benthic suspension feeders, and are subject to major natural disturbances. This study focuses on spatial patterns of the Antarctic benthos emphasizing the succession process after iceberg disturbance. For this purpose, underwater photographs (1 m2 each) from the southeastern Weddell Sea shelf (<300 m depth) were analyzed using techniques from the field of landscape ecology. Here, we examine measurements of spatial patterns (landscape indices) to describe changes in structural patterns along successional stages on these Antarctic benthic communities. We show a gradual separation from the early to older stages of succession based on sessile benthic cover area, size, shape, diversity, and interspersion and juxtaposition indices. Conceptually, the results describe a gradient from samples belonging to first stages of recovery with low cover area, low complexity of patch shape, small patch size, low diversity and patches poorly interspersed to samples from later stages with higher values of these indices. Cover area was the best predictor of recovery. We conclude that a variety of factors affect the observed successional sequences of Antarctic shelf benthic communities after iceberg disturbance, including the existence and dispersal abilities of propagules, growth rates, and competition between species. Overall, changes in the magnitude, frequency, and duration of disturbance regimes and alterations of ecosystem resilience pose major challenges for conservation of Antarctic benthos.