BEERS ET AL,: PLANKTON AND UPWELLING OFF PERU 



trichs, and was correlated with the generally 

 highest chlorophyll a and or phytoplankton or- 

 ganic carbon level observed. The relatively small 

 number of samples obtained, however, did not 

 allow us to determine the variability within the 

 patch at any given time. 



Average ciliate abundance over the euphotic 

 zone at the 15 stations studied ranged from 2400 

 to 18,000 liter (average, 6200/liter) (Table 4). 

 Oligotrichous forms were at least 75 "Tr of the 

 average numbers. Small (10-20 /x) oligotrichs 

 without well-developed sheaths, e.g., Lohman- 

 niella oviformis, were generally in much greater 

 number than larger sheathed species, e.g., Strom- 

 bidium conicum. Tintinnid ciliates, of which 

 AcanfhostomeUa ohtusa, Craterella urceolata, 



Codonellopsis contracta, and Epiplocylis brandti 

 were common, composed an averaged of 1% of 

 the total numbers. Estimated total ciliate or- 

 ganic carbon levels (Table 4) ranged from 0.7 

 to 4.8 /Ag/liter (average, 1.9 /ag/liter) of which 

 n^f and 78*;^, at least, were accounted for by 

 the tintinnids and oligotrichs, respectively. 



The abundance of ciliates dropped significant- 

 ly below the euphotic zone. In the approximately 

 20-m depth interval beneath the compensation 

 point (10 stations observed. Table 4) ciliate or- 

 ganic carbon was an average 16% of that in the 

 upper waters whereas the average chlorophyll 

 level was still 43% of the average concentration 

 within the euphotic zone. Ciliate abundance 

 over the upper 100 m comparable to the water 



Table 4. — Ciliate standing stock abundance. 



^ Stations with primary productivity and phytoplankton crop taxonomic composition data. 

 2 Surface chlorophyll a level <1.5 /ig/liter. 



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