INTRODUCTION 



BACKGROUND 



The success of Navy operations utilizing underwater 

 observations by divers, television, or light-emitting devices 

 is limited by the transparency of the water. Optical prop- 

 erties are characteristic of various geographic and oceanic 

 regions, and in some ocean areas reliable predictions can 

 be made concerning the limits of visibility in a given situ- 

 ation. However, inshore temperate regions adjacent to 

 large land masses are subject to great physical and biological 

 changes which affect the color and transparency of seawater 

 and the following factors must be considered: runoff from 

 shore and discharge from rivers bearing pigments, pollutants, 

 and suspended materials; inorganic materials eroded from 

 seacliffs by wave action; effluent from sewer outfalls; tidal 

 and wave scour which roils particulate material into suspen- 

 sion; and the products of organic growth. 



In the ocean off semiarid regions such as southern 

 California, many of these factors are reduced in intensity, 

 or exist, if at all, to a negligible degree. It appears, there- 

 fore, that organic production -- the life cycles of bacteria, 

 plants, and animals, and the interaction of their metabolic 

 products -- may be the primary source of material reducing 

 transparency in neritic waters within which the Navy must 

 operate. 



The development of instruments utilizing photocells 

 stimulated considerable work on the pattern of light trans- 

 mission in the oceans. (Refer to Holmes, 1957, and Tyler 

 and Preisendorfer, 1962, ^ for review articles.) Further, 

 many studies have been conducted on the suspended organic 

 matter in the seas by using the data as an index of produc- 

 tivity, and in some cases relating them to light-extinction 

 coefficients. (Parsons, 1963,^ reviews this literature. ) 

 Hart, 1962, "^ citing data from 1938 to 1939 taken on the 

 DISCOVERY II cruise, demonstrates a correlation between 

 Secchi disc readings and phytoplankton concentrations. Other 

 qualitative observations indicate that turbidity is frequently 

 associated with phjrtoplankton populations (Young, 1939;^ 



