ST 8T SI ST -B N 



Figure 7.--Vertical distributions of properties on cruise TO-58-1 along section B-B(see fig. 3); depth scale in m. 



Figure lOB shows the same meridional 

 arrangement of most of the isotherms as 

 observed on the previous surveys (figs. 4B 

 and 9B), but the minimum temperature is 

 lower and more widely distributed. Figure lOB 

 also differs from fig. 9B in that the cold 

 center is in mid-Gulf, as in figure 4B, not 

 adjacent to the coast. In the Gulf as a whole, 

 surface temperatures were higher than average 

 for the month, indicating continuation of the 

 anomalous temperature regime mentioned pre- 

 viously. 



These maxima occurred at station 15 (about 

 15P N., 96° W.) which was one of two stations 

 where the water was very green and nets were 

 clogged with phytoplankton; no quantitative 

 phytoplankton observations were made at the 

 other station (station 11, about 15° N.,950 W., 

 in the center of the colder more saline water). 

 Zooplankton was only moderately abundant at 

 these two stations of rich phytoplankton. The 

 high surface oxygen concentration at station 

 15 is consistent with the high productivity 

 there. 



Surface salinities (fig. IOC) were lower 

 than in May and June (cruise TO-58-1), as 

 would be expected at the end of the rainy 

 season. The highest salinities occurred broadly 

 with the lowest temperatures. Surface oxygen 

 concentrations in the same area were in the 

 range 4-5 ml. /I. (fig. lOD). Phosphate values 

 at 30 m. were highest between 95° and 94^ W. 

 (fig. lOE). 



Zooplankton standing crops (fig. lOF) were 

 highest in much the same area as in May and 

 June (cruise TO-58-1, fig. 4F), but at a much 

 higher level (200-600 ml./l,000 m.3). chloro- 

 phyll a and productivity values, the latter 

 especially, were also higher in the main with 

 maxima respectively 1.30 mg./m.3 and 161 

 mg.C/m.3/day (fig. 5). 



Vertical distributions of properties 



Figure 11 shows the following profiles along 

 the east-west section A-A: (A) and (B), tem- 

 perature on parts 2 and 3 of the cruise, re- 

 spectively; (C-F), salinity, thermosteric 

 anomaly, oxygen, and phosphate, all on part 3. 



The comparison between the two tempera- 

 ture profiles indicates the effect of a Tehuan- 

 tepecer and resulting current on the thermal 

 structure of the Gulf. Before the gale the 

 depth of the thermocline top ranged from 

 about 25 m. at 93° W. up to 20 m. at 94° W. 

 (the crest of the ridge) and thence down to 

 40 m. at 970 W.; the corresponding depths 

 after the gale were about 40, 12, and 75 m. 

 In each case the isotherms from the 



11 



