624 



the flocculation rates of sediments in estuaries and coastal waters. 

 Pertinent variables appear to be in the degree of dilution of fresh 

 water suspensions entering sea water, the levels of organic matter, 

 the pH of the mixture, the oxidation potential, the relative percent- 

 ages of different clay minerals and other solid phases, the mixing 

 characteristics of the flow, and the temperature. 



(2) The rates of aggregation and sedimentation of organic particles 

 in the marine environment should be studied. Such factors as pH, 

 temperature, organic-metal ion complexing at organic particle sur- 

 faces, and the concentration of inorganic particles should be evalu- 

 ated. Organic debris appears to play a role in transporting trace 

 metals to the sediments. The organic debris may associate with inor- 

 ganic particles, thus affecting the sedimentation of inorganic phases 

 (oxides, clays, silica). 



(3) The biological and chemical transformations occurring in pol- 

 luted and unpolluted sediments should be determined with particular 

 reference to nutrients and trace elements. These studies should include 

 considerations of concentration gradients, movement of water at the 

 sediment interface, eddy diffusion, and the release of gas on the rates 

 of transport from sediments to the water column. Also included should 

 be the effects of changes from oxidizing to reducing conditions and vice 

 versa. 



(4) Adequate procedures must be developed for distinguishing 

 among inorganic particles, living organisms, and dead organic matter, 

 both in the water column and in the sediments. 



Nutrient chemistry and biochemical changes 



( 1 ) The fluxes of nitrogen and phosphorus in all phases of the cycles 

 affecting the marine environment should be explored. The study should 

 not overlook the fluxes due to rooted benthic plants, birds, and humans. 



(2) An understanding should be developed of the amount and char- 

 acter of dissolved and particulate organic matter in the ocean, its origin, 

 including the contributions from rivers and waste discharges, its 

 spatial distribution, and the biological significance. 



(3) A study of the factors that control the qualitative and quanti- 

 tative aspects of phytoplankton blooms in estuarial and coastal waters 

 should be carried out. 



(4) The effects of additions of nutrients (phosphate, nitrate, sili- 

 cate) and oxidizable carbon on the primary productivity and on the 

 resulting organic load in restricted coastal environments should be 

 determined. The relative effects of the individual nutrients are impor- 

 tant considerations. The rates of oxygen exchange between the atmos- 

 phere and other sources (e.g., ferric oxide in sediments) and the 

 coastal waters should also be studied. These studies will help predict 

 to what extent re-aeration can compensate for the oxygen demand 

 caused by the introduction of oxidizable carbon and nutrients from 

 waste outfalls. Factors such as wind stress, depth, pressure head, den- 

 sity gradient and stability, and surface films such as petroleum should 

 be considered. 



(5) The biochemical mechanisms for concentration of trace com- 

 ponents by the biota, the subsequent effect of this concentration on the 

 organisms involved, and the transport and further concentration of 

 these trace components as they move up the food chain should be 

 determined. 



