Procedure: 



BIOLOGICAL METHODS AND PROCEDURES 



Pipet 2.5 ml. samples into 60 ml. flasks 



PlanKton 



add 22 .5 ml. of reagent by buret 



10/ 



and mix 



well by swirling. After HC1 has bubbled off, 

 pour a thin film of mineral oil over surface of 

 sample to exclude oxygen. Cover flasks with 

 30 ml . beakers and hydrolize in water bath at 

 70° C (^"0.5") for 15 minutes. Remove and 

 place in refrigerator for 10-15 minutes. Re- 

 move from refrigerator, transfer samples to 

 23 ml . absorption cells, allow to stand for at 

 least 10 minutes, and read densities using a 

 green filter (525 m,u) . 



Proteins — 



Reagents: 



1 . . 25 N Sodium Hydroxide . 



2. Standard Stock Solution - dissolve 1 gm. 

 of dl-tyrosine in sufficient amount of 



. 25 N sodium hydroxide to give a 

 clear solution, and dilute to one liter 

 with distilled water . 



Procedure: 



Pipet equal volumes of samples and 0.25 N 

 sodium hydroxide into 60 ml. flasks, cover 

 with 30 ml beakers, and autoclave for five 

 hours at 30-40 lbs. pressure. Cool, transfer 

 to centrifuge tubes, add a small amount of 

 Celite to each tube, and spin for 10 minutes at 

 900-1000 r.p.m. Draw off supernatant liquid 

 into a spectrophotometer cell, set instrument 

 at 240 m,u, and read densities . 



10 / Buret is an automatic, screw -cap acid 

 bottle type. 



11/ This method was developed by Mr. Albert 

 W. Collier, Jr., Chief, Gulf Fishery In- 

 vestigations, Fort Crockett, Galveston, 

 Texas and his associates. It has not here- 

 tofore been published and is in the process 

 of being refined. 



12/ Ahlstrom, Elbert H., 1952. 



12/ 



Method of towing 1/2 -meter silk nets — ' 



A standard half-meter No. 1 silk net was 

 towed obliquely after departing each station, 

 with the ship on course to the subsequent 

 station. A 40 -pound streamline depressor 

 was used as a weight, and an Atlas type cur- 

 rent meter suspended in the mouth of the net 

 registered the flow of water into the net. 

 Figure 2 . 



With the ship underway the net was lowered 

 slowly to a depth of 70 meters (100 meters of 

 cable out), or less in shallow water, and then 

 retrieved at die rate necessary to bring it to 

 the surface in approximately 20 minutes. The 

 ship's speed during the tow was 1-2 knots, and 

 the engine was started and stopped as often as 

 necessary to maintain a cable angle of approx- 

 imately 45 degrees. This angle of stray, 

 measured continuously with an inclinometer 

 suspended from the towing boom and riding 

 freely on the cable, was recorded every min- 

 ute, or less frequently in shallow water. 

 Plankton samples were preserved in 5% buf- 

 fered formalin . 



The depth of a tow was calculated by multi- 

 plying the cosine of the angle of stray by the 

 amount of cable out . 



Volumes of water strained 



An estimate of the volume of water strained 

 during a tow was derived from the revolutions 

 registered by the flow meter mounted in the 

 mouth of the net. Flow meters were calibrat- 

 ed by towing them at regular towing speed over 

 a known distance. From this a meter factor of 

 "meters of distance per revolution" was ob- 

 tained. This factor was multiplied by the area 

 of the net opening, and the product applied to 

 the meter readings for each tow, thus convert- 

 ing the readings to "cubic meters of water 

 strained." Meter pointers were zeroed prior 

 to each tow to prevent double errors in readings . 



