Ch. 6— Environmental Considerations • 243 



Box 6-G. — Cobalt Crust Case Study- 

 As part of the present program to assess the environmental impacts of crust mining in the EEZs of Ha- 

 waii and Johnston Island, a representative area, Cross Seamount, located about 100 miles south of Oahu, 

 Hawaii (at 18° 40 'N, 158° 17 'W), was selected for a comprehensive, biogeological reconnaissance. The study 

 was conducted by the Hawaii Undersea Research Laboratory. 



At depths where manganese-cobalt (Mn-Co) crusts were thickest (1,000 to 2,000 ra), the biota is un- 

 usually sparse, suggesting that larvae may be selectively avoiding crust substrates. More research will be re- 

 quired to substantiate this hypothesis. The depauperate nature of the benthic fauna of Cross Seamount, if 

 representative of other Hawaiian seamounts, suggests that environmental impacts of possible future mining 

 of Mn-Co crusts in such environments would be negligible, at least in terms of benthic species populations.' 



In general, the fauna of Cross Sejimount is patchy, low in diversity and only a few species of commercial 

 importance were seen. At depths of 1,300 feet to about 3,300 feet the fauna were about an order of magnitude 

 more abundant than the fauna from 3,300 to 13,500 feet. The density of organisms in the upper depth interval 

 (less than 1,000 feet) was about 8 organisms/ft^, approximately 3 times that in the second interval (1,300 to 

 1,650 feet). From 1,650 to 2,000 feet density declined markedly to about 1 organism/ft^. Again, from 2,000 

 to 2,300 feet density decreased to about one organism per 312 ft^. 



Most of the organisms encrusting manganese crusts are relatively small (less than two-thousandths of 

 an inch long) and cannot be identified in bottom photographs. The observed fauna is overwhelmingly com- 

 posed of various types of sessile, suspension feeders. Estimates of infaunal organisms are not included, and 

 highly mobile orgjinisms may be under-represented in the data due to avoidance of the camera. 



Detrimental Effects of Mining 



1. Direct destruction of precious coral and deep-sea shrimp populations, squid eggs, or their respective 

 habitats by the miner or subsequent sedimentation of discharged materials. 



2. A reduction in bottom habitat of 11 mi^/year at mining sites. 



3. Destruction of between 10,000 (at 7,900 feet) and 100,000 (at 2,600 feet) epibenthic macro-organisms 

 at mine sites. 



4. Effects on groundfish or pelagic fish adults or larvae from turbidity plumes generated above the bot- 

 tom by mining or at the surface from shipboard dewatering operations. 



5. A reduction in phytoplankton productivity due to shading by solid particulate matter in the surface 

 discharge plume. 



6. Death of plankton and/or pelagic fish larvae due to thermal shock. 



7. An elevation in substrate available for bacterial growth in the water column due to particulates in the 

 discharge plume. 



8. Possible aggregation of pelagic fishes by the surface mining ship. 



9. Minor behavioral disruptions to the endangered humpback whale, the green sea turtle, and resident 

 marine mammals. 



*U.S. Department of the Interior, Minerals Management Service, Tyrah Environmental Impact Statement: Proposed Mineral Lease Sale in the Hawai- 

 ian Archipelago and Johnston Island Exclusive Economic Zones, Honolulu, HI, 1987. 



Threatened and Endangered Species 



The Endangered Species Act of 1973 (ESA)'^ 

 prohibits "attempts" to harass, pursue, hunt, etc., 

 listed species. The ESA also prohibits significant 

 environmental modification or degradation to the 

 habitat used by threatened cind endangered species, 

 as well as any act that significantly disrupts natu- 

 ral behavior patterns. 



"16 U.S.C. 1531 



Living within the general proposed lease area of 

 the cobalt crusts are the endangered Hawaiian 

 monk seal (Monachus schauinslandi), the endan- 

 gered humpback whale Megaptera novaea gliae), 

 the threatened green sea turde (Chelonia mydas), 

 an occasional endangered hawksbill (Eretmocbelys 

 imbricata), the threatened loggerhead (Caretta 

 caretta), the endangered leatherback (Dermochelys 

 coriacea) and the threatened Pacific ridley 

 {Lepidochelys olivacea) sea turtles. However, in 



