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result of the destruction of benthos (deep sea plant or animal orga- 
nisms) will also reduce oxygen in the water. On the other hand, nutri- 
ent stimulated photosynthesis will increase the oxygen concentration. 
Perhaps a more serious effect is that discharged particulate material 
will produce turbidity in the euphotic zone cutting down light inten- 
sity and reducing photosynthetic activity. 
POLLUTION FROM SHIPBOARD PROCESSING 
Another environmental consideration would be the potential impact 
of the discharge of wastes or residues from possible shipboard pre- 
liminary processing of nodules. If any such methods are developed 
that are not self contained, wastes or residues could produce a severe 
strain on the ecosystem in the mining area. However, most major con- 
cerns involved in the development of manganese nodules have deter- 
mined that at least for first generation plants, economical processing 
can be accomplished only ashore. The principal reasons for this are 
that the reagent transportation costs will be equal to, or greater than 
the nodule costs, and problems of waste disposal and environmental 
protection will be much greater at sea than on land. 
Common EFFEcts 
Although several different mining systems are proposed, some com- 
mon effects can be expected and some impacts are unique to each 
system. Among the common impacts are: 
(1) the destruction of the benthic (bottom dwelling) organisms 
and their habitats in the path of the mining operation ; 
(2) stirring up sedimentary material as the mining implement 
sweeps the ocean floor; and 
(3) introduction of sedimentary material, associated bottom 
organisms, and bottom water into various layers of the water 
column, including, in some cases, the surface water. 
The extent of each of these impacts depends on the mining technique 
used. Both the air-lift pumping (ALP) and hydro-lift systems trans- 
port nodules, sediment, benthos and deep water to the surface. In these 
processes abrasion produces quantities of fine nodule material and 
macerated organic material. Except for the nodules, all these materials 
are discharged into the ocean surface water where they may remain 
in suspension or sink depending on their physical conditions. The con- 
tinuous-line bucket system is designed to bring only nodules to the sur- 
face; however, in practice some benthos and sediment may be en- 
trapped and distributed throughout the water column. This system 
will introduce more sediment into the lower water column but less 
material into the surface water than the ALP or hydro-lft systems. 
In addition to environmental concerns, stirred sediment is also a min- 
ing problem. It may obscure the bottom or cover the nodules making 
recovery difficult. 
FINDINGS AND FurRTHER INVESTIGATIONS 
In reporting on preliminary investigations, including monitoring 
an ALP mining system on the Blake Plateau in the Atlantic and a 
CLB system in the silicious ooze province in the North Pacific, the 
NOAA report concluded, “In this preliminary work, no definite effects 
