ORTNER ET AL.: SARGASSO SEA ZOOPLANKTON BIOMASS DISTRIBUTION 



average 0-200 m zooplankton biomass (milligrams 

 of carbon per square meter calculated using equa- 

 tion 4, table 2 in Wiebe et al. 1975) by 0-200 m 

 phytoplankton carbon (milligrams of carbon per 

 square meter from Table 5), excluding salp-rich 

 MOC 18 and 19, we obtain the following ratios: 



Aug. 1975 

 Nov. 1975 



Sargasso Slope 



Sea Ring water 



253 138 84 



332 131 28 



Ratios in the ring are low, as are those in the slope 

 water. Lower ratios suggest to us lower overall 

 trophic efficiency within the upper 200 m. Al- 

 though biased in that many cells are quite small, 

 particularly in the Sargasso Sea, phytoplankton 

 carbon of cells >5 ixm is probably a reasonable 

 estimate of the food available at the time of sam- 

 pling to many of the herbivorous animals caught 

 by our 0.333-mm mesh nets. The direction of dif- 

 ference noted above conforms with ideas expressed 

 by Menzel and Ryther ( 1961 ), Heinrich ( 1962), and 

 others who argued that especially close 

 phytoplankton-zooplankton coupling may charac- 

 terize oceanic tropical-subtropical waters. 



The biomass data presented here illustrate the 

 fact that geographic demarcation of oceanic faunal 

 provinces is not sufficient. Hydrographic as well as 

 faunal mapping is essential in explaining that 

 portion of station-to-staion variability associated 

 with mesoscale hydrographic variability resulting 

 from phenomena like Gulf Stream cold core rings. 



ACKNOWLEDGMENTS 



We express our grateful appreciation to Alfred 

 Morton for his assistance at sea; to Michael Stro- 

 man who measured many of the displacement vol- 

 umes; and to our typist Jane Peterson, for her 

 remarkable tolerance and good humor. James Cox 

 and Margo Haygood critically read the manu- 

 script. This study was supported by ONR 

 NOOO14-66-C-0240, NOOO14-24-C-0262 NR 

 083-004, NSF DES 74-02783A1, the Woods Hole 

 Oceanographic Institution Graduate Education 

 Program, and the Tai Ping Foundation. 



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