PHYSICAL OCEANOGRAPHIC , BIOLOGICAL, AND CHEMICAL DATA 



SOUTH ATLANTIC COAST OF THE UNITED STATES 



MA THEODORE N. GILL CRUISE 7 



This is the seventh in a series of 

 reports presenting basic data from cruises 

 of the Theodore N. Gill in waters off the 

 South Atlantic coast of the United States. 



Background of the investigations; 

 objectives; procedures on station; and 

 chemical, biological, and oceanographic 

 methods and procedures were presented in 

 the report for Cruise 1 (Anderson, Gehrin- 

 ger, and Cohen, 1956). Biological methods 

 and procedures were the same as those modi- 

 fied on Cruise 3 (Anderson and Gehringer, 

 1957). The basic station plan is shown in 

 figure 1. 



NARRATIVE ACCOUNT OF CRUISE 7 



The Gill sailed from Brunswick, Geor- 

 gia on June 9, 1954 and headed for special 

 station 5 to begin the southern leg of the 

 cruise. Special station 5 was reached and 

 occupied on June 10, and special stations 

 6 and 7 were made on June 11. On June 12 

 the vessel occupied special station 8 and 

 proceeded to the standard station off Elbow 

 Cay, B.W.I. From June 12 to 14 the stand- 

 ard station was occupied for 42 continuous 

 hours, during which time 15 hydrographic 

 CEists were made, including one to 2500 

 meters. Fathometer traces were taken on 

 this station for 10 minutes every hour, and 

 special plankton tows made in a study of 

 the deep scattering layer. Routine meteor- 

 ological and bathythermograph observations 

 were also taken. 



The vessel docked at Nassau, B.W.I. , 

 on June 14 for installation of special 

 equipment by Columbia University personnel. 

 On June 16 and 17 special ambient work was 

 conducted at the standard station. The 

 ship then proceeded into the Tongue of the 

 Ocean, where additional ambient observa- 

 tions were carried out. Continuous sonic 

 soundings were taken during this run for 

 correlation with the ambient work. The 

 vessel returned to Nassau, and the special 

 equipment was unloaded on June 21. Occupa- 

 tion of the regulair stations began on 

 June 23. Excellent weather prevailed during 



the remainder of the southern leg, result- 

 ing in 100 percent completion of the 

 projected stations. The vessel returned 

 to Brunswick on June 28 for supplies and 

 to unload material collected. 



The Gill departed from Brunswick to 

 begin the northern leg of the cruise on 

 July 1. Favorable weather prevailed until 

 the vicinity of Cape Lookout, North Caro- 

 lina was reached, where rain squalls and 

 winds up to about 50 knots forced the 

 vessel into port at Morehead City, North 

 Carolina. After the vessel resumed work, 

 all but one of the remaining regulcir sta- 

 tions were accomplished before bad weather 

 caused termination of the cruise. The 

 vessel returned to Brunswick on July 13. 

 The cruise track is shown in figure 2. 



The vessel traveled over 3,000 miles 

 in making this cruise, occupying 100 hydro- 

 graphic stations (including regular, spe- 

 cial, standard, and Tongue of the Ocean) 

 with Nansen casts (fig. 3) and bathythermo- 

 graph lowerings on each station. Oxygen 

 determinations were made aboard vessel for 

 all stations and all levels. Water samples 

 were secured from all stations and levels 

 for shore analysis of salinity, total 

 phosphorus, inorgjmic phosphate, carbohy- 

 drates, proteins, and nitrate-nitrite. 

 Secchi disk readings were taken during day- 

 light hours when conditions permitted. 

 Bottom samples were secured on selected 

 stations where several samples had not been 

 collected on previous cruises. Oblique 

 plankton tows were made with the Gulf III 

 all-metal plankton sampler on all but one 

 of the regular and special stations--a silk 

 net was used on this one station due to 

 heavy seas. Seventy-five runs between 

 stations were obtained with the Gulf lA 

 high-speed plankton sampler, and 31 runs 

 were made with the continuous plankton sam- 

 pler. Dip-net collections (fig. 4) were 

 good on the southern leg of the cruise but 

 poor on the northern leg. Trolling with 

 nylon and bone jigs between stations was 

 more successful than on most previous 

 cruises. Several trolling lines were also 

 carried away by large fish. 



