Exploring sea-floor resources.

Outside of the caveat in his last sentence, P. A. Rona's Perspective “Resources of the sea floor” (31 Jan., p. [673][1]) reads very much like the commercial promotions implying the imminent development of sea-floor minerals that were common two and three decades ago. There's no current evidence that sea-floor mineral resources, such as manganese nodules, marine polymetallic sulfides, or cobalt crusts, are of “increasing economic value,” particularly upon a close inspection of the markets for the metals that might be recovered. Prices have been flat or declining in recent years for all of the likely prospects. Except for a few nearshore deposits in shallow waters, such as the Namibian diamonds, most of these minerals cannot be described as “ore bodies,” which by definition are commercially recoverable deposits; they must be understood instead as potential resources. The issuance of deep sea-floor exploration contracts notwithstanding, the economic activities of onshore exploration, substitution, recycling, and conservation all continue to work against the commercialization of sea-floor mining. Unfortunately, the main lesson that J. M. Broadus taught about “seabed materials” ([1][2]) is not being heard. Investments in exploration and R&D of sea-floor minerals are accelerated by the strategic behavior of firms and governments, but posturing is a component of those investments. Consequently, the advent of commercial production may be more distant than that suggested by “preproduction” activities. What science has brought to light is that the biological diversity and ecology of the sea floor are likely to be of greater significance than the economic geology. 1. 1.[↵][3] 1. J. M. Broadus , Science 235, 853 (1987). [OpenUrl][4][Abstract/FREE Full Text][5] # Response {#article-title-2} Hoagland's comments serve to reinforce points in my Perspective. Our vision of sea-floor resources has expanded in recent years to include living biota, as well as the traditional nonliving marine mineral resources. In the case of polymetallic sulfides, the same hot, metal-rich solutions that concentrate the mineral deposits energize heat-loving chemosynthetic microbes, which are hosted in these deposits at hydrothermal vents on the deep sea floor. As noted in my Perspective, certain of these microbes already have commercial applications, and others are being tested for a variety of industrial and pharmaceutical uses. The economic value of sea-floor resources is most certainly expanding. As correctly pointed out by J. M. Broadus in his article cited by Hoagland ([1][6]), “The eventual realization of the resource potential of seabed materials will be determined by their relative economic accessibility compared to rival onshore resources.” An example is diamond mining offshore of southwestern Africa, which has become commerically viable since the Broadus article was published. The point is that marine minerals are being developed selectively, so that blanket statements about the commercial prospects of sea-floor mining—either pro or con—are misleading. I avoided the term “ore deposit” in my Perspective for the very reason that it implies that deposits are commercially recoverable. Hoagland contends that my Perspective inappropriately promotes marine minerals. If it can be said to promote anything, then it is exploration of the ocean, because we are at the dawn of discovery of sea-floor resources. 1. 1.[↵][7] 1. J. M. Broadus , Science 235, 853 (1987). [OpenUrl][4][Abstract/FREE Full Text][5] [1]: /lookup/doi/10.1126/science.1080679 [2]: #ref-1 [3]: #xref-ref-1-1 "View reference 1. in text" [4]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.issn%253D0036-8075%26rft.aulast%253DBROADUS%26rft.auinit1%253DJ.%2BM.%26rft.volume%253D235%26rft.issue%253D4791%26rft.spage%253D853%26rft.epage%253D860%26rft.atitle%253DSeabed%2BMaterials%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.235.4791.853%26rft_id%253Dinfo%253Apmid%252F17778861%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [5]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEyOiIyMzUvNDc5MS84NTMiO3M6NDoiYXRvbSI7czoyMzoiL3NjaS8zMDAvNTYyMi8xMDkzLmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ== [6]: #ref-2 [7]: #xref-ref-2-1 "View reference 1. in text"