12 



CHEMICAL RESULTS OF LAST CRUISE OF CARNEGIE 



129. In general, however, the phosphate content in the 

 surface layer increases from southeast to northwest, 

 reaching 125 mg per cubic meter at station 125. 



The lines of equal phosphate content bend downward 

 from the two ends of the section, reaching their greatest 

 depth at station 128. The line of maximum phosphate 

 follows the same course, running from 350 meters at 

 station 125, to 1350 meters at station 128, and to 750 

 meters at station 130. The maximum phosphate content 

 ranges from 250 to 300 mg PO4 per cubic meter and in 

 the deeper water it is 250 mg per cubic meter or slight- 

 ly less. 



Section VIII, stations 94 to 104: in the tropical west- 

 ern Pacific, extending from the Samoan Islands (latitude 

 13° south, longitude 172° west) north and west to station 

 104 (latitude 20° north, longitude 161° east). --From 

 stations 94 to 99 the phosphate values at the surface are 

 about 10 mg per cubic meter, but at the other stations 

 (toward the northwest) they are below this value, the 10 

 mg PO4 per cubic meter line running from near the sur- 

 face at station 100 to about 200 meters at station 104. 



The transition zone in this section shows conditions 

 similar to those found in Section V. In the North Equa- 

 torial Drift, between 100 and 200 meters, conditions are 

 found at station 100 in this section which are similar to 

 those at station 152 in Section V. The maximum values 

 range from 225 and 275 mg PO4 per cubic meter and oc- 

 cur at depths of from 700 to 1400 meters except at sta- 

 tion 100, where it is at about 2000 meters. In the deep- 

 er water the variation in the phosphate content is great- 

 er than in most other regions, values between 175 and 

 275 mg PO4 per cubic meter occurring. 



Section XIII. stations 107 to 101: in the tropical 

 western Pacific, extending eastward from Guam (lati- 

 tude 14° north, longitude 146° east) to station 101 (lati- 

 13° 23' north, longitude 177° 27' east). --At all the sta- 

 tions the phosphate content of the surface water is very 

 low, the line representing 10 mg per cubic meter run- 

 ning at about 200 meters except at station 107, where it 

 is found at 100 meters. 



Relatively far from the surface and from each end of 

 of the section the lines of equal phosphate content curve 

 downward, reaching the lowest depth at station 104. The 

 layer of maximum phosphate is at about 1000 meters ex- 

 cept at station 101 where it is at 650 meters. The max- 

 imum values range between 225 and 275 mg PO4 per cu- 

 bic meter. No observations extend to 3000 meters but 



at 2500 meters the phosphate is about 225 mg per cubic 

 meter. 



Section IX. stations 107 to 120 : from Guam (latitude 

 14° north, longitude 146° east) north to station 113 near 

 Yokohama (latitude 35° north), thence northeast to sta- 

 tion 120 (latitude 47° 02' north, longitude 166° 20' east). 

 --In this section the hydrographic conditions are com- 

 plex and the phosphate content at most depths is varia- 

 ble. From the southernmost station, 107, to station 113 

 the phosphate content in the upper 100 meters or more 

 is less than 10 mg per cubic meter but north of this sec- 

 tion the 10 mg per cubic meter line rises to about 100 

 meters and finally reaches the surface between stations 

 117 and 118. North of station 117 the phosphate content 

 at the surface rapidly increases to more than 150 mg 

 PO4 per cubic meter at stations 119 and 120. 



In the southern half of the section the most rapid in- 

 crease in phosphate with depth begins at about 300 me- 

 ters, but in the northern half it begins immediately at the 

 surface. Between stations 114 and 116 the concentration 

 of phosphate with depth is variable, probably owing to 

 the meeting of water masses of different temperatures. 



The axis of the maximum phosphate layer lies be- 

 tween 1000 and 1500 meters in the southern half of the 

 section, but at station 113 it rises, reaching 250 meters 

 at station 120. In most of the section the maximum val- 

 ues vary between 200 and 275 mg PO4 per cubic meter 

 but are above 275 mg at stations 109, 119, and 120. At 

 greater depths they are between 200 and 250 mg PO4 

 per cubic meter. 



Section XVI. stations 118 to 125: extends in an east- 

 northeasterly direction across the northern part of the 

 North Pacific from station 118 east of northern Japan 

 (latitude 42° 29^ north, longitude 155° 24' east) to station 

 125 south of the Gulf of Alaska (latitude 51° 58' north, 

 longitude 150° 39' west), along the Aleutian Islands from 

 stations 122 to 124. --Throughout this section there is no 

 definite surface layer and the phosphate content at the 

 surface is more than 125 mg per cubic meter except at 

 station 118, where it is only 90 mg PO4 per cubic me- 

 ter. The center of the maximum phosphate layer is 

 about 500 meters except at station 118, where it is at 

 1000 meters. 



The maximum concentration varies between 250 and 

 300 mg PO4 per cubic meter, which is somewhat higher 

 than in other regions. In the deeper water the quantity 

 is about 250 mg PO4 per cubic meter. 



REGIONAL DISTRIBUTION OF PHOSPHATE AT VARIOUS LEVELS 



The regional distribution of phosphate is controlled 

 by the same physical and biological factors that control 

 the vertical distribution. It is probable that in the pho- 

 tosynthetic zone plants which consume phosphate are 

 always present except in high latitudes during the win- 

 ter months. Likewise it is probable that below this zone 

 the proper conditions for the decomposition of organic 

 matter prevail throughout the year and in all localities, 

 resulting in the release of phosphate and other inorgan- 

 ic nutrient substances. Consequently any differences 

 that may exist in the horizontal distribution of these 

 substances must be caused principally by the circula- 

 tion of the water. Other factors, such as runoff from 

 land and certain biological conditions, should not be 

 lost sight of, but these can be regarded as local or tem- 

 porary features. Consequently, the circulation of the 



water, vertical and horizontal, is the principal cause of 

 the general differences in the phosphate content of the 

 water in different regions of the oceans. 



In the subsequent discussion the regional variation 

 in phosphate will be taken up for the following levels: 

 (1) at the surface, (2) in the surface layer and transi- 

 tion zone, and (3) at 2000 meters. 



Surface 



The distribution of phosphate at the surface at all 

 Carnegie stations is shown by the chart, figure C9. The 

 relative concentrations of phosphate are indicated by 

 the shading. For regions where the surface water con- 

 tained less than 10 mg PO4 per cubic meter this chart 

 also shows the depth to which these low values extended. 



