The deep-sea environment is probably the most striking example of an undersampled marine habitat. The previous notion of a global deep-sea bottom that is uniformly featureless has been shattered by countless discoveries of unique, sometimes bizarre, and highly diverse deep-sea communities, such as those associated with hydrothermal vents [ Grassle, 1986; Tunnicliffe, 1991] and other hydrocarbon seeps [ Kennicutt et al., 1989; MacDonald et al., 1989], wood [ Turner, 1981], seamounts [ Grigg, et al., 1987; Chave and Jones, 1991] and, most recently, whale skeletons [ Smith et al., 1989]. Even flat muddy bottoms are now known to have sources of local physical heterogeneity, such as biogenic structures [ Smith et al., 1986; Thistle and Eckman, 1990], manganese nodules [ Mullineaux, 1987], and patches of organic matter [ Billet et al., 1983; Suchanek et al., 1985]. Such heterogeneity permits niche diversification and high species richness, as discussed earlier. In fact, recent estimates suggest that deep-sea diversity is much higher than in any other marine habitat, perhaps even rivaling tropical rain forests in total species numbers [ Grassle, 1989; Grassle and Maciolek, 1992; but see also May, 1992; Poore and Wilson, 1993].
To say that the deep-sea is undersampled is, in fact, an understatement. Given that the oceans occupy about 71% of the Earth's surface, with continental shelves accounting for only about 7.5% [ Emery, 1969], the deep sea then makes up about 63.5% of the Earth's surface. And, because only a small fraction of the deep-sea bottom has been sampled, this leaves over 60% of the Earth waiting to be explored!