EFFECTS OF REMOVAL OF SEAGRASS CANOPY ON ASSEMBLAGES OF SMALL, MOTILEINVERTEBRATES

To test the importance of seagrass canopy to epifaunal invertebrates i n a southern Australian estuary, patches of the short, fine-leaved sea grass Zostera muelleri Irmisch ex Aschers, were cleared of canopy. All other factors were known to be consistent with seagrass presence, and a procedural control was used to measure any effects of the method us ed to remove seagrass. Effects on epifauna were measured as changes in abundance and biomass of key taxa and in total production, and as dif ferences amongst assemblages, tested using an analysis of similarity ( ANOSIM) randomisation routine. Removal of seagrass canopy had a weak b ut detectable effect on epifauna over and above the slight effect caus ed by the disturbance concomitant with seagrass removal. Epifauna asso ciated with habitat from which seagrass had been removed did not, howe ver, match that from areas unvegetated prior to the experiment. The ep ifauna from these previously unvegetated areas were characterised by l ow abundance and biomass of several key taxa, apart from 1 group, cuma ceans, which were far more common in this habitat. The results suggest that the overriding importance of Z, muelleri to epifauna is not simp ly the presence of seagrass canopy, and explanations of the higher abu ndance of epifaunal invertebrates in vegetated compared to unvegetated habitats based merely on the presence of seagrass canopy are not supp orted.