Basing conservation policies for the deep-sea floor on current-diversity concepts: a consideration of rarity

Exploitation of deep-sea resources is now underway and there is economic pressure to renew and expand currently restricted waste disposal in that environment. Since the deep sea is noted for very high species diversity, it is appropriate that diversity conservation be initiated. Review of current concepts of diversity maintenance finds that the ideas have evolved more through increasing information about sources of heterogeneity than through rigorous testing. This history weakens the immediate value of these concepts for the development of conservation strategies and demonstrates the need for additional investigation. Such inquiry might focus upon the rare component of overall species richness. A comparison of box core samples at 2100 m in the western Atlantic and the Gulf of Mexico continental shelf reveals that deep soft bottoms are not unique in having many rare species. The rare component at depth is largely comprised of species more common at other locations near and far. The rare component on the shelf is comprised mostly of species which are consistently rare and restricted in distribution. These observations suggest a shallow-deep difference that is more one of degree than fundamental in nature; the deep having larger regions and regional species pools.