employed on 12 hauls, we learned that the actual 

 sampling depth exceeded the estimated depth by 

 about 26 percent. It was calculated that, on the 

 'average, the net was fishing between 227 and 369 

 meters' depth. 



Surface Hauls 



At the "front," on stations 98-104, 7 

 shallow hauls were made with an open net. The 

 first haul reached an estimated depth of 45 m. 

 and the rennainder 4 to 8 m. 



Midwater Trawling 



A 1 -hour haul with an Isaacs -Kidd trawl 

 of 10-foot mouth diameter was made at 53 sta- 

 tions, usually between 2000 and 2100 hours. The 

 trawl net and diving vane were patterned after 

 gear developed at the Scripps Institution of Ocea- 

 nography (Devereaux and Winsett 1953), but with 

 modifications to permit hauling at vessel speeds 

 of 6 to 7 knots . The net was of nylon, 1 1/2- 

 inch stretched mesh in the forward section, 3/4- 

 inch mesh in the middle section, and 1/2-inch in 

 the cod end. The cod end for about 6 feet of its 

 length was lined with stramin. 



Employing a 3/8-inch towing cable and an 

 Olympic trawl cable meter recording infathoms, 

 the trawl was lowered rapidly until 450 fathoms 

 of cable were paid out. The trawl was then re- 

 trieved at a slow, uniforna speed of the winch. 

 The paying -out required about 20 minutes and the 

 hauling -in about 40 minutes. The wire angle and 

 amount of wire-out were recorded at 3- to 5- 

 minute intervals. With the tota?_— QVffl'tof wire- 

 out, the wire angle at the surface was usually 

 between 72° and 76°. By plotting the wire-out 

 and wire angle measurements recorded during 

 the haul, we obtained an estimate of the curva- 

 ture of the towing wire and the maximum depth 

 reached. At a vessel speed of 6-7 knots and 

 with 450 fathoms (824 meters) of wire-out, the 

 estimated maximum depth averaged about 350 

 meters. 



Carbon Fixation Measurements 



occurring in the samples during this period will 

 utilize dissolved carbon dioxide and the carbonate 

 (CO3) a-nd bicarbonate (HCO3) ions in the sample 

 including proportionally, that bearing C . 

 Upon subsequent filtration the C fixed within 

 the phytoplankton cells is retained on a filter 

 while that still in solution is passed through. 

 Knowing the ratio of C^^jas disintegrations per 

 minute) to C^^ at the start of illumination, and 

 then nneasuring the increase in radioactivity of 

 the cells, enables us to calculate the amount of 

 both kinds of carbon fixed. The amount of car- 

 bon fixed in the light bottles after subtracting 

 the amount fixed in the dark bottles is tabulated 

 as net productivity. This Is calculated in terms 

 of milligrams of carbon fixed per unit of time 

 per unit of volume. 



Collection of Samples 



A clean, plastic bucket was used in 

 dipping sannples from the surface. Three clean, 

 276-ml. glass -stoppered, pyrex bottles were 

 filled from the bucket by simply pouring the sea 

 water through a rinsed, plastic funnel. One 

 bottle was covered with an opaque coating; the 

 other two sample bottles were clear glass. 



A 1 -liter, weighted, plastic bottle was 

 used to obtain the 20 -m. sample. After the 

 bottle was lowered to the desired depth, the 

 rubber stopper was jerked free by means of an 

 auxiliary line, allowed to fill, and then re- 

 trieved. Three sample bottles were filled 

 directly from the sampler. Collections were 

 made, as much as possible, away from parts of 

 the vessel where there was any discharge (e.g. 

 from bilge, heat exchangers , etc.). 



Extensive laboratory and field tests 

 conducted prior to the cruise by the University 

 of Hawaii had shown that metal objects should 

 not contact the sample water since such contact 

 was found to reduce greatly the rate of carbon 

 fixation. Also, the sample should not be sub- 

 jected to rougher treatment (e.g. shaking) than 

 necessary, since this also tended to reduce 

 fixation. 



On EASTROPIC, water samples were 

 collected at 76 stations from the surface and 

 20 meters for productivity measurements by the 

 radioactive carbon (C^*) method. The method 

 was introduced by Steemann Nielsen (1952) and 

 involves the addition of the isotope as sodium 

 carbonate to samples of sea water and then hold- 

 ing these samples in a water bath, some in the 

 dark (dark bottles) and some under uniform con- 

 ditions of light (light bottles) for a known period 

 of time. Photosynthesis and other processes 



Addition of Radioactive Sodium 

 Carbonate Solution 



The top of an ampoule containing an 

 aliquot portion of the radioactive carbonate 

 solution was broken off. A clean glass pipette, 

 attached to an automatic delivery pipette and 

 calibrated to deliver between 1 and 2 ml. , was 

 used to withdraw the contents. The solution 

 was then released at the bottom of the filled 

 sample bottle and the pipette rinsed with water 



