BIOLOGICAL RESULTS OF LAST CRUISE OF CARNEGIE 



below the stated level. Another uncertainty, caused by 

 the wire angle, amounts to ± per cent. This error does 

 not apply to the physical and chemical data. 



No examination of the samples could be made on 

 board ship because of the limited personnel and crowd- 

 ed program of other work. In the laboratory the sam- 

 ples were washed into 250-ml graduated cylinders and 

 allowed to settle over night. Then the water was si- 

 phoned off, usually to about 20 ml, depending on the 

 richness of the sample. This concentrate was vigorous- 

 ly stirred by blowing through it with a pipette after which 

 1 ml was taken up in the pipette. This milliliter of the 

 sample was run into a Sedgwick -Rafter counting cell and 

 ten random counts made of the diatom and dinoflagellate 

 cells with the aid of a Whipple micrometer. The mean 

 of the ten counts was taken and from this the number of 

 cells per liter of sea water at the place of sampling was 

 computed as described by Whipple (1927). By making 

 duplicate samplings of the concentrated sample, the er- 

 ror of the method was computed to be within 10 per cent. 

 No accuracy is claimed for values below 10 cells per 

 liter. 



The number of all diatom and dinoflagellate cells 

 has been reported. The Coccolithophoridae escape 

 through the net as do some of the smaller diatoms. 

 Some of the dinoflagellates cannot be preserved. Other 

 algal groups such as the Cyanophyceae and Chlorophy- 

 ceae were extremely rare in the samples and have not 



been reported here. This report, therefore, is restrict- 

 ed to the diatoms and dinoflagellates that are to be found 

 in net samples preserved in formaldehyde. Specific 

 identifications have not been reported. They are of no 

 particular significance in the present paper and com- 

 plete lists of diatoms and dinoflagellates with the dis- 

 cussion of their distribution are reserved for other re- 

 ports. 



The water samples for chemical analysis and the 

 temperatures were obtained by means of Nansen bottles, 

 and Richter and Wiese reversing thermometers. Salin- 

 ities were determined electrometrically with a Wenner 

 salinity bridge (Wenner, Smith, and Soule, 1930). Dis- 

 solved oxygen was determined by the Winkler method 

 Qacobson, 1921), the percentage saturation being com- 

 puted from the tables of Jacobsen (1925). Phosphates 

 were determined by the Deniges method as described by 

 Atkins (1925). For the estimation of silicates the meth- 

 od of Dienert and Wandenbulcke as modified by Atkins 

 (1923) was employed. Standards as recommended by 

 King and Lucas (1928) were used. Hydrogen-ion con- 

 centration was measured by means of a double-wedge 

 comparator as described by Moberg (1926). For a more 

 detailed description of the chemical analysis see the 

 report of the physical and chemical results obtained on 

 cruise VII of the Carnegie (in press). With a few excep- 

 tions the observations and collections were made in the 

 morning between eight o'clock and noon ship s time. 



RESULTS 



To simplify the discussion of the data the area in- 

 vestigated has been divided into three regions: (1) the 

 southern region, lying south of latitude 20° south; (2) 

 the tropical region, lying between latitudes 20° south 

 and 20° north; (3) the northern region, lying north of 

 latitude 20° north. Figure 1 shows the distribution of 

 the stations in the regions and the relative abundance of 

 diatoms and dinoflagellates at all stations. 



Southern Region 



The southern region included nineteen stations (Car- 

 negie stations 49 to 68 inclusive), all of which were in 

 the southeastern Pacific between South America and 

 longitude 120° west. The most southern station was 

 number 60 at latitude 40° 24' south. There were forty- 

 eight samples collected in this region; eighteen at the 

 surface, sixteen at 50 m, and 14 at 100 m. 



This was apparently a barren region. Of the forty- 

 eight samples eight contained no diatoms or dinoflagel- 

 lates and thirty-nine had less than 50 cells. Only two 

 samples had more than 50. One of these, the richest 

 collected in the southern region, was taken at station 61 

 and contained 9 diatom and 111 dinoflagellate cells per 

 liter. 



The collections in this region were made in Novem- 

 ber and December 1928 and January 1929, the southern 

 summer--a season during which a low plankton produc- 

 tion would be expected. 



The stations in the southern region were distributed 

 in an area bounded by the edges of the Antarctic Drift, 

 the Peruvian Currents, and the westward extension of 

 the Peruvian Current. The only sample with more than 

 100 cells per liter occurred north of the Antarctic 

 Drift. 



Tropical Region 



The tropical region included fifty -five stations (Car- 

 negie stations 35 to 48, 69 to 108, and 150 to 153) ex- 

 tending from Panama and Peru as far west as Guam. 

 Fifteen stations were north of the equator and forty were 

 in the southern hemisphere. In this region one hundred 

 and forty-three samples were collected, including fifty- 

 four at the surface, forty-eight at 50 m, and forty -one at 

 100 m. 



This was another region of very scant plant life. Of 

 the one hundred and forty-three samples collected, 

 thirty-eight contained no diatoms or dinoflagellates and 

 eighty-six of those containing cells had less than 50 per 

 liter. Six samples contained between 50 and 100 cells. 

 Only fourteen samples showed more than 100 cells per 

 liter. Three of these were in the western part of the re- 

 gion, one in the north central, and the rest in the eastern 

 part. The richest sample occurred at station 73 on the 

 surface and contained 2065 diatom cells and 51 dinoflag- 

 ellate cells per liter of water. 



The collections in this region were made at widely 

 separated dates--from Panama to station 48 during Oc- 

 tober and November 1928, from station 69 to Peru dur- 

 ing January 1929, from Peru to Samoa during February 

 and March 1929, from Samoa to station 108 duringApril 

 and May 1929, and stations 150 to 153 during October 

 1929. 



The stations in this region lay in the North Equato- 

 rial, South Equatorial, Counter Equatorial, and Peruvian 

 currents, and in adjoining waters. Four of the thirty- 

 eight samples with over 100 cells per liter were widely 

 separated in the equatorial currents; the remainder 

 were in the Peruvian Current and its continuation into 

 the South Equatorial Stream. 



