Grassle, 1989; Schaff et al., 1992; Blake and J.F. Grassle, in press) or gradual community changes with depth (Carney et al., 1983) and sediment grain-size diversity (Etter and J.F. Grassle, 1992).

Although long considered inaccessible and difficult to sample, better quantitative sampling and improved methods of experimentation are continually improving the ability to study the deep-sea biota (see Box 12). The surprisingly high diversity of benthic invertebrates in the deep sea—hundreds of species co-occurring within a square meter of ocean floor—provides a remarkable platform from which to renew empirical, experimental, and theoretical attempts to explain the causes and patterns of global diversity (Rex et al., 1993).

Although the deep sea is vast and remote, humans are still having an effect on this environment. A small, steady increase in abyssal temperature of 0.32°C in 35 years has been attributed to global climate change (Parrilla et al., 1994). Increases in pollutants from atmospheric sources have been observed on the deep-sea floor (La Flamme and Hites, 1978; Takada et al., 1994). Ocean dumping (waste disposal) and deep-sea mining are clear causes for concern. Changes in upper-water column trophic structure—directly or indirectly, for example, through pollution, overfishing, or global climate change—potentially affect deep-sea trophic dynamics (e.g., see Box 1). Because time-series information on biological diversity is unavailable for any deep-sea area, unknown changes currently may be in progress, and thus, the deepest oceans of the world are not immune to human actions. Underscoring these actual and potential changes is the concern that anthropogenic effects on deep-sea communities may be especially severe because deep-sea organisms may be more poorly adapted to change (J.F. Grassle et al., 1990).

Increasing technological sophistication for studying the deep-sea environment (see Box 12) will permit biodiversity issues to be examined experimentally at traditional, necessarily small spatial scales (cm2 to m2). Deep-sea mining technologies and waste-disposal experiments can be designed to produce well-replicated and well-controlled experiments at scales of tens to hundreds of km2. The integration of these approaches should promote better understanding of how and which processes generate and maintain biodiversity in a global environment containing one of the richest species complements.

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