Successional Dynamics in Seagrass Communities

Abstract

The sequence of ecological changes in which one species is replaced by another is known as succession. Den Hartog (1971) was the first to propose successional schemes for seagrass communities based on competition-colonization hierarchies, which have rarely been challenged. Wave-disturbed subtidal systems are characterized by the presence of gaps, the distinct topographic depressions devoid of vegetation defined. We present a study of a Caribbean seagrass bed exemplifying macroalgal-seagrass succession dynamics in relation to gap disturbance. We report a shift in species composition at the study site consisting of the replacement of seagrass by an extensive macroalgal cover. Succession patterns were tested in each zone by sampling macrophyte cover along transects running across gaps. Our results show that seagrass is always the first colonizer, independent of dominant cover in control plots. The reversal of competitive hierarchy described has important consequences for the understanding and management of seagrass ecosystems.