. ii-vf ft. *»M,V» »-4f'ni* *«.«,» ' .».. 



It la Intevegtlnc to point out that no slnllar canyon cwi b« found in front of 

 the Bay of Snn Illruel tlu-owJi which emptlon the entire dralnace of the nrovinco of Darlon. 

 Teri7,r (n'll) oucroots that In Plelotocene tlnon the Dorien draina,-:e moy have tui-ned north- 

 v;oot round the Ponrl Islondo. The hjrootheaia 1b, howeveri difficult to reconcile v;ith the 

 OTifltonco in front of the "bay of a well-marked chnnnol vhich oxtenda south to the l-il'-fathon 

 eui"vo. TlilH orlrin of the oubmorine valley in the Gulf of Panomn presenta, tliercforo, an 

 intereetinf: iDroblon to fioolorlctn. Trom an ecolorloal point of viou, t}ie ijreeence of such 

 a valloy nJonr the western aide of the Peai-1 Inlnnda la sli-Tilf leant, for It affects the 

 vmtor Movement of the Oulf which In turn influences the distribution of water ten-nerattu-o 

 and of current-borne larvae of marine invertebrates. 



WATER MOVEHKMTS IN THE OUU 01 PMAMA 



The movement of water in any tiart of the aea is one of the principal phyoical 

 factoro of marine environment which affecto the propagation, distribution, and the rate of 

 fTOwth of vario^is forms, whether living freely or attached to the bottom. In the Gulf of 

 Panama the movement of v/ator la definitely related to bottom topocraphy. It has been shoxra 

 by Floralnfi (193G) that, because of the ahoallne of bottom toward the head of the Gulf, 

 tliore la a corroB-oondinf; increase in the ron^te of tide from the entrance to the head of the 

 bay. Over the entire area, the maximun difforoncea in the ronce of tide are f^eat, varying 

 In T)laceB from 5 feet at neap tides to over 22 feet at sprine tides. The ^Teatest tidal 

 ranco is found in the innermost part of the Oulf. Thus, nonr Balboa the values for the 

 average neap and average spring tidal raiv;08 are 12,6 and Ib.U feet respectively. At the 

 entrance to the Oulf on the west aide at Ca-oe Mala the average ranges are 10.3 o^d 13'0, 

 and on the east side at PlHas Bay, 10.8 and I3.S feet. 



ABEociated with the large tidal range and its periodical fl\:ictuatlon8 are, of 

 course, the tidal movements of water, v/hich ore also related to bottom topography. Thus, 

 In Til&ceB, one encoimters very strong tidal currents, especially rapid in many narrow 

 channels between the numerous Islands of the Archiplelaf;o de Ian Porlas. rioiilni'; lias com- 

 ■nutod that an average velocity rluring the half-tidal period la about O.I7 n/sec. (about 2 

 nautical miles during: the hnlf-tidal period) at neap tides. At spring tides, tlie movement 

 Is of the mai'Tiltudo of U nautical milos in each direction during the same period. 



The tides along the coast of Panwna are of semidiurnal tyne. Because of the great 

 range of tide In the Oulf of Panama, large volumes of water enter and leave the Oulf, reach- 

 ing maximum velocities twice during each tidal interval of about 12.5 hovu-s, and following 

 down to almost zero twice during the same period of tide. Since the direction of the tidal 

 current reverses itself with each flood and obb, no actual transport of water is involved 

 in tidal clionges, but the tidal currents are of great importnjxco in mixing the water of the 

 G\ilf, and, presumably, in replenishing and dlGpersing the nutrient salts. The mixing must 

 be important also in distributing the froe-Bwiramlng larvae of many sedentary animals, 

 including the peoi'l and edible oysters. One must expect also tlmt near the edge of the 

 continental shelf there Is considerable vortical movement of water. Fleming (i.e.) has 

 deduced tliot, benidcs tidal movementa, there is in tlie Oulf of Panama a countorcloclcwise 

 rotating motion of water which haa a velocity of about O.5 !cnot. The tidal currents are 

 superimposed on this nontldal movement wliicli la probably of greater oceanographlc Importance 

 in bringing new nutrient materlalB to the Oulf. 



TEI^IPERATURK, SALINITY, AND pH OF WATE31 



During Februaary-March 19^8, the distribution of temperature in the upper layer of 

 sea water (O to 8 fathoms) along the Pacific coast of Panama followed a definite pattern 

 \/liich may luive biological significance. Aa can be seen from examination of the chart 

 (Fig. 7) • there was a noticeable difference between the temperature of water east and v;est 

 of the Pearl Islands. All the readings made west of the Islondo fall within 25-27° C. , 

 while -luch cooler water of 21-22° C. prevailed on the west coast of the islands. I had no 

 opportunity to malco a studj' of temperatui-o distribution in the vrestern portion of the Gulf, 

 between San Joei Island and Parita Ba^v. Unfortunately', the dac' when the CHUCUIJA made a rxui 

 fron Cape Mala to Taboga, the sea was too rough to raalce any obseirvatlons. Temperatures of 



16 



