36 



1960). The tremendous plankton blooms (Byrne and Emery, 1960), 

 which have been observed since the Spanish originated the name "Ver- 

 milion Sea" for the red tides in the Gulf, account for the extremely high 

 production of all forms of surface life in the Gulf from whales down to 

 small invertebrates (Steinbeck and Ricketts, 1941). These same con- 

 ditions are also found in the Gulf of Tehuantepec, investigated by the 

 present author as part of this study. Because of the almost hurricane 

 strength winds which sweep across the Isthmus of Tehuantepec, throughout 

 most of the year, a semi-permanent upwelling dome occurs in the Gulf, 

 much of it overlying the continental slope. Dredges taken in depths of 

 from 200 to 1,000 meters in this region produced no typical benthic life, 

 but large amounts of semi-fossilized wood, completely unaltered leaves, 

 pine cones and fish bones were obtained. Goldberg and Parker (1960) 

 investigated the chemical composition of the bottom waters and the age 

 and composition of the phosphatized wood. It was quite evident that at 

 these slope depths where no life and well-preserved floral and faunal 

 remains were found, oxygen was almost non-existent, but phosphate was 

 very high. Those portions of wood buried in the sediment and still in a 

 fresh condition, proved to be older than 28,000 years B.P., as determined 

 by C-14 age-dating by Hans Suess of Scripps Institution. The antiquity of 

 the wood would lead one to believe that the bottom oxygen-minimum 

 conditions along the coast where upwelling is now present have existed 

 for a long time. Wood in similar state of preservation was also found in 

 roughly the same depths along the east side of the Gulf of California from 

 Mazatlan to Guaymas. 



A complete reversal of the depleted oxygen situation exists in the San 

 Lorenzo and Ballenas Channel region between Angel de la Guarda Island 

 and the islands to the south and the coast of Baja California (fig. 9). The 

 depths of this channel range from 1,000 to over 1,500 meters (500 to 

 800 fathoms). Throughout most of the rest of the Gulf these depths are 

 characterized by very little to almost no oxygen at the bottom. However, 

 because of the tremendous tidal transport through this narrow strait, 

 turbulence is effective throughout the whole water column and oxygen 

 values are between 1 and 3 ml/L., which is sufficient to sustain almost any 

 form of marine life. This phenomenon has been discussed by Roden and 

 Groves (1959, pp. 17-19). It might be mentioned here that the high oxygen 

 concentrations in this channel support a fairly rich fauna including a 

 number of species of solitary corals. 



The faunas at the southern, deep part of the Gulf also reflect the high 

 oxygen conditions, which appear to be related to the underlying deep 



