2U.0°-2U.6° C. were foimd along the southern coast of the peninsula which separates the 

 Gulf of Panama from Chiriqui Gulf (between Cape Mala and Punta Harlato) . The temperature 

 of v;ater in the eastern part of Chiriq.ui Gulf was consistently higher than that in the 

 Gulf of Panama, varying from 28.0° to 30.0° C. The difference of a'bout 5° C. hetween the 

 tv;o gulfs nnist have considerable biological significance. 



The presence of relatively cold water in the western part of the Gulf of Panama 

 may suggest an upwelling along the submarine valley west of the Pearl Islands. It would 

 be, hov;ever, premature to make fax-resiching deductions from the admittedly inadeo.uate 

 data. Ihorther hydrographical studies are needed to explain the observed distribution of 

 temperature along the coast of Panana. The suggestion that the difference in water 

 temperature in the Gulf of Panama and Chiriqui Gulf is due to the influx of cold water from 

 the Humboldt Current or from its branch known as the Galapagos Current does not appear to 

 be sound, for the latter current extends north only as far as 5° N. latitude and veers west. 



Therroal conditions in the upper layer of water in the Gulf of Panama are rather 

 unstable. This is disclosed by a series of temperature measurements made during World 

 War II by the Woods Hole Oceanographic Institutionit/* They show that, during a few days 

 betv/een January 2^-25 and January 28-29, IS'+S" ^'^^ surface temperature of water taken at 

 hourly intervals between 3iOO a.m. and 7»00 p.m. at two stations located west and northwest 

 of the Pearl Islands varied as nnich as 2.1° C. and 2.9° C. depending on direction ftw<^ 

 velocity of wind and v;ater currents. 



In viev/ of these observations, it is reasonable to expect that the temperature 

 differences east and west of the Pearl Islands are caused by meteorological conditions and 

 may not be alv;ays as pronounced as they were during my observation in February-March 19^8. 

 On the other hand, it seems that the temperature differences between the Gulf of Panama 

 and the western part of the Chiriq.ui Gulf are of more permanent nature and are determined 

 by the hydrography of the tv;o bodies of v;ater. 



The salinity of the vxater at different stations varied from 32.0 to 35*9 parts 

 per thousand; the highest values were observed at the stations located offshore, or near 

 the coast, biit far away from the discharge of fresh-water streams. The decrease in the 

 concentration of salts to about 32 parts per thousand was due to the influx of fresh water 

 (Tables 3 and U) . 



The same is true for the pH of the water, which, with the exception of one read- 

 ing of 7-6 (station 29) and two readings of S.U (Station 9 and 2U) , fluctuated between 

 7.9 SQii. 8.3« Changes in the pH primarily caused by the intensity of photosynthesis can be 

 attributed to local concentrations of phytoplankton and variations in the intensity of 

 illumination. 



There was no evidence of the influx of less alkaline waters from the greater 

 depths of the Gulf which could have adversely affected the pearl oyster. 



Thinking of a popular belief that pearl oysters may have been poisoned 'by dvniping 

 of explosives and ammunition at the entrance of the Gulf, I made a limited number of 

 determinations of copper in the samples of water collected at Taboga Islands (Sta. 11), Sem 

 Jos^ Island (Sta. lU) , Morro Puercos (Sta. 16) , and Coiba Island (Sta. IS). Ho copper was 

 detected in 100 ml. samples of water, using dl-ethyl-di-tio carbonate reagent. Since 

 copper can be detected by this reagent in the concentration of 0.01 mg. per cubic meter or 

 more, I conclude that there was no excess of Cu ions which may have been indicative of the 

 pollution of the water by heavy metals. I had no opportunity to make analyses for other 

 metals. In the water contaminated by dumping of chemicals and explosives, one may have 

 expected to find significant deviation from the normal values of the pH. As can be seen 

 from Table k, the pH values were all within the range of fluct\jations that one may- expect 

 to find under normal conditions in the sea. 



_/ I an grateful to the Woods Hole Oceanographic Institution for permission to coasnlt 

 these still unpublished data. 



18 



