Sponge biodiversity patterns and their application to the management of a tropical marine reserve

Marine reserves are an important management strategy for marine resources, but we have little baseline information for most marine environments. In this study, we focus on the Oceanic Shoals Commonwealth Marine Reserve (CMR)... [ view full abstract ]

Marine reserves are an important management strategy for marine resources, but we have little baseline information for most marine environments. In this study, we focus on the Oceanic Shoals Commonwealth Marine Reserve (CMR) in northern Australia, particularly the carbonate banks and terraces of the Sahul Shelf and Van Diemen Rise which have been designated a Key Ecological Feature (KEF). We use a species-level inventory compiled from three marine surveys to the CMR to address several questions relevant to marine management: 1) Are carbonate banks and other raised geomorphic features associated with biodiversity hotspots? 2) Are there environmental or biogeographic variables that can help explain local and regional differences in community structure? 3) How do sponge communities differ between individual banks? Approximately 750 sponge specimens were collected and assigned to 348 species, of which only 18% included taxonomically described species. A species accumulation curve estimated almost 900 species, almost double the number of sponge species estimated for the Ningaloo region, thereby supporting the listing of the carbonate bank system as a KEF. Between the eastern and western CMR, there was no difference between sponge species richness or assemblages on raised geomorphic features. Within individual raised geomorphic features, sponge assemblages were significantly different, but species richness was not. There were no environmental factors related to sponge species richness, although sponge assemblages were weakly but significantly related to several environmental variables (mean depth, mean backscatter, mean slope). These patterns of sponge diversity are considered in the context of marine reserve management in order to explore how such information may help support the future management of this region at multiple spatial scales.