Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.

No abstract

Systema Naturae includes representatives of every major lineage of the animal phylum Cnidaria.  However, Linnaeus did not classify the members of the phylum as is now done, and the diversity of the group is not well represented.  We contrast the Linnaean perspective on cnidarian diversity with the modern, phylogenetic perspective.  For each order, we detail diversity at the family level, providing phylogenetic context where possible.

204w ww ww w. .f fr ro on nt ti ie er rs si in ne ec co ol lo og gy y. .o or rg g © © The Ecological Society of America C ompelling evidence is accumulating from terrestrial, freshwater, and marine systems to suggest that sustainable ecosystem services depend upon a diverse biota (Daily et al. 1997;Loreau et al. 2001;Tilman et al. 2001;Wall et al. 2004; MA 2005;Sala and Knowlton 2006;Worm et al. 2006;Butler et al. 2007;Hector and Bagchi 2007). In principle, such knowledge should be useful in guiding a national ocean policy that maintains the services provided by oceans into the future. But does knowing the link between diversity and services usefully inform policy? We argue that management to sustain biodiversity could provide a critical foundation for a practical, ecosystem-based management (EBM) approach to the oceans.Globally, 60% of ecosystem services are degraded (MA 2005). These ecosystems provide food, shelter, recycling, and other support mechanisms that human communities require, but fundamental services are declining as ecosystems are unraveled by human impacts (Palmer et al. 2004). Marine ecosystems (Figure 1) provide a constellation of services: they produce food, receive and assimilate wastes, protect shorelines from storms, regulate the climate and atmosphere, generate tourism income, and provide recreational opportunities MA 2005). The extraordinary diversity of the world's oceans -across the different levels of ecosystems, habitats, species, functional roles, and genetic diversity (Carpenter et al. 2006; Sala and Knowlton 2006) -and the interconnections of marine, coastal, freshwater, and terrestrial ecosystems make managing ocean ecosystems crucial for long-term prosperity. Although degradation of ecosystems might be reversed through appropriate policies (MA 2005), there are substantial information gaps in our understanding of ecosystem processes (Carpenter et al. 2006), which impede practical ideas about implementing policy.EBM involves incorporating knowledge of ecosystem processes into management, but defining EBM and specifying how it can be implemented has been difficult, particularly for marine ecosystems (Arkema et al. 2006). Grumbine (1994)