The subtidal macrozoobenthos of the river-dominated Great Berg Estuary

Abstract

The subtidal macrozoobenthos of the Great Berg Estuary was sampled between February 2003 and February 2006 at 15 sites on each of seven occasions. The estuary is river dominated and salinity distribution shifted significantly between wet and dry seasons. A typical euryhaline assemblage characterised the macrozoobenthos along most of the estuary, with 44 species present in total. No seasonal pattern was evident between the number of species or in the dominance pattern at higher taxonomic levels. Amphipods were numerically the most important group (54% average for the seven series), followed by polychaetes (32%) and isopods (9%). Among amphipods and polychaetes, the same species tended to numerically dominate spatial and temporal patterns, with maximum abundance associated with the dry season. These data highlight the adaptability of the macrozoobenthic assemblage to the temporal and spatial variability in salinity. The euryhalinity of the species assemblage is also reflected in the lack of distinct faunal changes or spatial population shifts up- or downstream between wet and dry seasons.