E. Transparency and Plankton 



Transpai-ency of the s\irface waters was determined at all oceano- 

 graphic stations where light intensity permitted, and at other locations 

 whenever possible. A white Secchi disc, 30 centimeters in diameter, was 

 used in making these determinations, all the observations being made by 

 the oceanographer to ininimize personal error in observations. In general, 

 the transparency of surface water closely followed the abundance of 

 plankton oi- detritus in the water. Although plankton tows were not a 

 part of the regular oceanographic program, vertical or oblique hauls 

 with a haLf -meter net at depths of 2^ to ^0 meters were made whenever 

 possible as a matter of interest. 



In the Little America area, transparency of the surface waters 

 ranged from 5 'to 7 meters, and was correlated with a moderately heavy 

 plankton concentration, also much detritus. Off Cape Colbeck, trans- 

 parency reached 19 meters in the icepack where it was impracticable 

 to make a plankton tow. In the Amundsen Sea off Mt. Siple, where no 

 plant plankton or detritus were visible in the collection, a trans- 

 parency of 23 meters was obtained. Farther to the eastward, off 

 Peter I Island, transparency was reduced to a low of ^ meters^ a 

 plankton tow revesJ-ed an extremely heavy concentration of greenish 

 colored plankt,on composed of diatoms and many copepods. In this 

 area, and in the Ross Sea area, considerable concern was felt by 

 the ship's engineer over faulty operation of the evaporators which 

 became plugged with a heavy coating inside, making frequent cleaning 

 necessary and greatly impairing tho ship's capacity for making fresh 

 water, Th3.s trouble quickly cl'-nred up upon entering clearer waters 

 having less p].ajnkton. In Bransfield Strait transparency ranged from 

 11 to 12 meters, and plankton tows collected only moderately concen- 

 trated plankton' except at the station off E'Urville Island where 

 diatoKd were very abundant. In Atka and Admiral Byrd Bays trans- 

 parency was 13 meters. Moderate amounts of plankton were present in 

 Atlffli Bay, A plankton sample was not obtained in Admiral Byrd Bay 

 because both nets were lost. 



The greatest transparency reading obtained during the cruise was 

 at 72°38' S. 17°39' W. along the Princess Martha Coast, Queen Maud Land. 

 Here, at the head of a little bay (Penguin Bay) in the shelf ice of 

 the Weddell Sea, a transparency of 27 meters was observed along a 

 narrow fringe of fast ice. A plankton tov7 was not obtained. 



Dr. Thomas E. Bowman of the Smithsonian Institution, U, S, National 

 Museum, identKied many of the dominant forrnr: of plankton obtained. 

 Dr. Harold A. Rehder identified the pteropod:;i. The composition of the 

 tows shovjed no new forms, all forms having been previously reported 

 from the Antarctic regions. Off Little America there was much detritus, 

 but no plpjtikton, A tow taken west of Little America conl.ained the 



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