GARRISON: NET PLANKTON AND NANNOPLANKTON IN MONTEREY BAY 



'Value appears low, corresponding growth rate [fJi) may be too high. 



seasonal effect during upwelling seems to be a 

 reduction of the average concentration of nan- 

 noplankton and an increase in the average con- 

 centration of net plankton. 



ro 

 I 



E 

 oi 



o 

 o> 2 



E 



9.26 



mg Chi a M'' 



4 



6.88 



1^ . 



4 



+ 



+ 



Jan. Feb Mar. Apr. May June July Aug. 



Figure 5. — Seasonal changes in the concentration of net 

 plankton chlorophyll (heavy line) and nannoplankton chloro- 

 phyll (thin line). (Davidson Current period — January; upwell- 

 ing period — February through June; oceanic period — July, 

 August.) Average and range of concentrations in the euphotic 

 zone are shown. The number of samples for each month is 

 given in Table 1. 



Standing Stock Growth Rate 



The growth rate, /x (doublings day"^), and as- 

 similation ratio (mg C mg Chi a'^ h"^), of the nan- 

 noplankton fraction was greater than the corre- 

 sponding value for the net plankton during all 

 three seasons, and both fractions showed their 

 highest growth rate during the upwelling period; 

 however, assimilation ratios of the surface sam- 

 ples for both fractions were higher in the oceanic 

 period than during upwelling (Table 2). There is 

 no correlation {P > 0.10) between the growth 

 rates of either phytoplankton fraction and aver- 

 age nutrients (NO3, Si02) in the upper 10 m on 

 individual sampling days for the three hydro- 

 graphic periods. 



Net plankton growth rates exceeded nanno- 

 plankton growth rates in only two of the samples; 



Table 2. — Growth rates of the standing stocks in the euphotic 

 zone and assimilation ratios of surface samples.' 



'Growth rates were calculated from daily productivity and standing stock 

 estimates integrated to the depth of 1% light penetration, while assimilation 

 ratios are for surface samples incubated at 0.06 langley min*'. 7 ± SD(W); 

 questionable data indicated in Table 1 have been excluded. 



187 



