800 1000 



o 



:: 



500 



Si. uM 



Figure 4. [NO3" + NO2 - ] versus Si relationships for water 



samples collected at Pele's Vent. The upper figure presents 

 the data collected during the Alvin dive expedition. The 

 middle figure presents the data collected during the Pisces 

 V dive expedition. The bottom figure is the combined data 

 base. The linear regression analyses were: [N03~ + NO2 - ] = 

 47.66 - 0.045Si ( Alvin ); [N0 3 " + N0 2 "] = 46.23 - 0.028Si 

 ( Pisces V); [N0 3 " + N0 2 ~] = 45.94 - 0.037Si ( Alvin + Pisces 

 V). 



203 



