PARENT SESSION
Contributed Oral Session 69: Marine Ecology: Habitat; Communities
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 522 A, Level 5, Palais des congrès de Montréal
Biotic and abiotic factors controlling recolonization processes in boulder-fields located in highly urbanized estuaries.
Cruz-Motta, Juan *,1,2, Underwood, A1, Chapman, M1, Tolhurst, T1, 1 University of Sydney, NSW, Australia2 Depto. Estudios Ambientales, Caracas, Miranda, Venezuela
ABSTRACT- Boulder-fields represent important habitats in estuarine and coastal areas.They allow the co-existence of organisms living on rocky substrata and in sediments, but they also house a variety of organisms that are unique to these systems. Both attributes increase local diversity. In highly developed estuaries, it is not uncommon that boulder-fields are artificially created when man-made structures (e.g. sea walls, breakwaters) are built or destroyed. These become colonized and form areas of particular interest in terms of local biodiversity. It is therefore important to describe and understand the many factors that affect the colonization by benthic organisms to the different microhabitats associated with newly available boulders. Of these factors, the shape of the boulder (height/area relationship) and disturbance regimes (movement of boulders) were investigated in this study. We sampled, through time, the structure of the benthic assemblages living in: 1) sediments where biota-free boulders of two different shapes (rounded and flat) were introduced and 2) sediments below boulders that were prevented from moving or allowed to move. There were no effects of the shape of the boulder or disturbance regime on the development of soft-bottom benthic assemblages associated with boulder-fields. Throughout the study, assemblages in sediments below the introduced boulders (idenpendently of their shape) were different from the assemblages living in sediments not overlain by boulders. The organisms in sediments below introduced boulders were, however, not similar to assemblages in the same micro-environment below boulders that were found naturally at the study locations (established boulders). Likewise, assemblages that colonised the tops of introduced boulders were always different from assemblages found on top of established boulders. It is proposed, consequently, that biological factors (e.g. type of organisms/larvae available at the beginning of the experiment) are important in determining the recolonization of assemblages in sediments associated with boulder-fields.
Key words: Recolonization, Boulder-fields, Urbanized estuaries, Benthos