32 



pipe, is regarded as a Limited-Pollution-Fauna. Most 

 characteristic were two onuphids, Nothria elep;ans and 

 Djopatra ornata, also Nephtys caecoides and Glycera 

 americana . These are also intertidal forms and can 

 withstand considerable exposure or dilution. Other samples 

 in this zone (I SW-1), where sediments were coarse, had 

 considerably more Diopatra and some other kinds. Their 

 kinds and numbers increase gradually with greater distance 

 from the pipe (Zone IW-3 to 6), and they come to attain 

 excessive numbers and sizes farther away (Zone I W-6 to 

 12) where the greatest numbers and largest sizes are 

 found. Thus we may speak of peaks of productivity or 

 maximum biomass in this zone, 



Biomass is an expression of the quantity of organic 

 matters expressed in terms of unit areas. It varies with 

 kinds of bottoms, and with depth so that the greatest 

 volumes are usually in shallow depths. In Santa Monica 

 Bay such peaks are related to amounts of nutrients supplied 

 by the effluent. They have been observed in a variety 

 of species (Figure 4), some of which are listed, and 

 others are named in the Analyses, Such peaks of pro- 

 ductivity have been observed persisting through different 

 months of the year. Thus they are probably not seasonal 

 or fluctuating or the results of large numbers of larval 

 or juvenile individuals, but perhaps are directly pro- 

 portional to increased nutrients and indirectly to variations 

 in salinity from normal sea water. The estimated biomass 



