Ch. 6— Environmental Considerations • 223 



changes in seasonal and spatial patterns of organ- 

 isms.' Eggs and larvae in the mining area will be 

 unable to escape. Most adult fish — the prime com- 

 mercial species in the water column — are active 

 swimmers and would be able to avoid the area of 

 high particulate concentrations. Nonetheless, a 

 large-scale, long-term mining operation will pro- 

 duce a "curtain" of turbidity (cloudiness due to 

 particulates) in the water column which might in- 

 terfere with normal spawning habits, alter migra- 

 tion patterns, or cause fish to avoid the mining area 

 altogether. 



Heavy metals, e.g., copper, zinc, manganese, 

 cadmium, and iron, may be released into the water 

 column in biologically significant forms from some 

 mining operations. The quantities of dissolved me- 

 tals generally will be quite low, but current hypoth- 

 eses suggest that small spatial and temporal differ- 

 ences in metal concentrations regulate the kinds of 

 plankton found^ '". Metals could, therefore, cause 

 changes in species composition; such changes have 

 been verified for copper both in the laboratory'' 

 and at sea.'^ Trace metals may be as important as 

 macronutrients (nitrogen, phosphorus, and silicon) 

 in controlling species composition and productivity 

 in the marine environment, If so, then any large- 

 scale disruptions in the naturtd metal balance due 

 to mining activities could alter marine food webs. 

 However, our understanding of the role of metals 

 in unpolluted marine environments is currently 

 constrained by the difficulty of measuring such min- 

 ute quantities. 



Benthic Impacts 



Little is known about the dynamics of animal 

 communities on the seafloor. There are, however, 

 several possible effects of concern. Animals within 

 the mined area will be destroyed. Large-scale 

 removal of bottom sediments will alter the topog- 

 raphy and therefore could affect currents and sub- 

 strate characteristics, which in turn affect species 

 composition.'^ Benthic plumes from mining devices 

 will cause sedimentation on the bottom-dwelling 

 organisms and eggs in the vicinity. Surface plumes 

 from rejection of some of the mined material will 

 eventually settle over a much wider area and cover 

 animals with a thin layer of sediment. Silt depos- 

 its can smother benthic organisms and inhibit 

 growth and development of ju'/enile stages.'*'^ 

 WhUe the first new colonizing organisms in a mined 

 area probably will be those with the highest disper- 

 sal, the direction of succession and final composi- 

 tion of the community is difficult to predict and is 

 likely to be affected by grain size and suitability of 

 the deposited sediment for colonization by benthic 

 invertebrates. 



The areas affected by mining will tend to be 

 smaller than those affected by commercial fishing 

 (especially bottom-trawling operations), which also 

 removes large numbers of organisms and may dis- 

 turb large sections of the seafloor. However, ma- 

 rine mining impacts may be more intense than 

 those of fisheries. 



'A. Shar and H.F. Mulligan, "Simulated Seasonal Mining Impacts 

 on Plankton," Internationale Revue Gesamte Hydrobiologie, 62(4) 

 1977, pp. 505-510. 



'S.A. Huntsman and W.G. Sunda, "The Role of Trace Metals 

 in Regulating Phytoplankton Growth with Emphasis on Fe, Mn, and 

 Cu," The Physiological Ecology of Phytoplankton , 1. Morris (ed.) 

 (Boston: Blackwell Scientific Publications, 1981), pp. 285-328. 



'°F.A. Cross and W.G. Sunda, "The Relationship Between Chem- 

 ical Speciation and Bioavailability of Trace Metals to Marine 

 Organisms — A Review," Proceedings of the Internationa] Sympo- 

 sium on Utilization of Coastal Ecosystems: Planning, Pollution, and 

 Productivity, Nov. 21-27, 1982 (Rio Grande, Brazil: 1985). 



"W.H. Thomas and D.L.R. Siebert, "Effect of Copper on the 

 Dominance and the Diversity of Algae: Controlled Ecosystem Pollu- 

 tion Experiment," Bulletin of Marine Science, No. 27 (1977), pp. 

 23-33. 



"W. G. Sunda, R.T. Barber, and S.A. Huntsman, "Phytoplank- 

 ton Growth in Nutrient-Rich Seawater: Importance of Copper- 

 Manganese Cellular Interactions," Journai of Marine Research, No. 

 39 (1981), pp. 567-586. 



"J.S. Gray, "Animal-Sediment Relationships," in Oceanography 

 and Marine Biology-An Annual Review, H. Barnes (ed.). No. 12 

 (1974), pp. 223-262. 



'■•WB. Wilson, "The Effects of Sedimentation Due to Dredging 

 Operations on Oysters in Copano Bay, Texas" (M.S. thesis, Texas 

 A&M University, 1956). 



"R.S. Scheltema. "Metamorphosis of the Veliger Larvae of Nas- 

 sarius Obsoletus (Gastropoda) in Response to Bottom Sediment," Bio- 

 logical Bulletin, No. 120 (1961), pp. 92-109. 



'*G. Thorson, "Some Factors Influencing the Recruitment and 

 Establishment of Marine Benthic Communities," Netherlands Jour- 

 nal of Sea Research, No. 3 (1966), pp. 267-293. 



"Grigg and Kiwala, "Some Ecological Effects of Discharged Wastes 

 on Marine Life." 



"S.B. Saila, S.D. Pratt, and T.T. Polgar, Dredge Spoil Disposal 

 in Rhode Island Sound, University of Rhode Island Marine Techni- 

 cal Report No. 2, 1972. 



"P.S. Meadows and J.I. Campbell, "Habitat Selection by Aquatic 

 Invertebrates," Advances in Marine Biology, No. 10 (1972), pp. 

 271-382. 



