BIOLOGY 



The pumped water samples taken in conjunction with the 

 turbidity measurements were filtered, and the materials in 

 the water studied. Although small quantities of inorganic 

 matter were found, especially in samples taken near the 

 bottom, it was concluded that the major materials causing 

 the turbidity were organic. During the summer runs, the 

 chief organisms that reduced the transmission of light, and 

 hence visibility, were phytoplankton. Usually there is a 

 mixture of several different kinds of organisms (fig. 18). 

 However, under certain favorable conditions one organism, 

 such as Gonyaulax po lyedra , will dominate the population. 

 Concentration of these organisms gives a distinct color to 

 the water. They are often most numerous in the near- 

 surface euphotic zone. When they die, they accumulate in 

 the near-bottom layers. Zooplankton do not usually reduce 

 visibility or light transmission as much as the more numerous 

 phytoplankton. 



Figure 18. Sample of coarse red water showing Gonyaulax 

 po lyedra (A), about 50 microns in diameter. Also Iso 

 present in the sample are Peridinium (B), a nauplial 

 larva (C), and a, Noct i luca (D), 



23 



