These types of discoveries help to foster an appreciation of the true extent of marine biodiversity, and add a considerable new dimension to estimates of how many species exist in the ocean. It is clear, however, that molecular techniques provide one of the most powerful means for revealing a new understanding of the ocean's complexity (see Box 3).
Advanced instrumentation and sampling have revealed new species assemblages in novel habitats in the oceans, such as hydrothermal vents (J.F. Grassle, 1986; Tunnicliffe, 1991), whale carcasses (C.R. Smith et al., 1989), wood debris (Turner, 1973, 1981), and sites of hydrothermal, brine, and hydrocarbon seepage (Williams, 1988; Kennicutt et al., 1989; Southward, 1989; MacDonald et al., 1990). As with the discovery of new genomes and new species, it is doubtful that hydrothermal vents or whale skeleton biotas have closed the final chapter on the discovery of novel habitats or ecosystems in the sea. Are there, for example, unique biotas in the abyssal depths of the mid-Atlantic Ocean singularly tied to sinking masses of the pelagic seaweed Sargassum? Moreover, new discoveries are unlikely to be limited to just the vast deep-sea depths. Discovery of novel chemoautotrophic associations, shallow and deep (reviewed in Bennett et al., 1994), is a striking reminder that the biodiversity of the majority of the Earth's surface may be dependent on yet undiscovered and unanticipated habitat diversity. Continually improving capabilities for exploring large regions of the ocean floor and water column (e.g., see Box 12) now set the stage for searching the sea in ways impossible to imagine only a few years ago.