A hierarchical framework for classifying seabed biodiversity with application to planning and managing Australia’s marine biological resources

A conceptual hierarchical framework for classifying marine biodiversity on the sea floor, used successfully for continental-scale bioregionalisation and adopted to guide marine resource planning and management in Australia, has wider application at a global scale. It differs from existing schemes for classifying marine biota by explicitly recognizing the overarching influence of large-scale biodiversity patterns at realm (ocean basin and tectonic), provincial (palaeohistorical) and bathomic (depth-related) levels. The classification consists of 10 nested levels within realms, of which the first seven are primarily spatially nested and ecosystem based, and the lowest levels represent units of taxonomic inheritance: 1 - provinces, 2 - bathomes, 3 - geomorphological units, 4 - primary biotopes, 5 - secondary biotopes, 6 - biological facies, 7 - micro-communities, 8 - species, 9 - populations, and 10 - genes. According to this scheme, marine biodiversity is characterised in a systematic way that captures the scale-dependence and hierarchical organization of the biota. Levels are defined with respect to their functional roles and spatial scales, in a manner that directly supports the incorporation of biodiversity information in regional-scale planning by highlighting centres of endemism, biodiversity richness and priority information needs. Whereas species are the fundamental units of biodiversity, biological facies are the smallest practical unit for conservation management at regional scales. In applying the framework we make extensive use of biological and physical surrogates because marine data sets, particularly those of the deep sea, are usually sparse and discontinuous. At each level of the hierarchy, attributes and surrogates are defined to reflect the scale and range of biogeographic and ecological processes that determine the spatial and temporal distribution of marine biodiversity. The Australian experience in applying this framework suggests that it provides a workable systematic basis for defining, managing and conserving biodiversity in the sea.