Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 115-133. 



The hydrography of the Gulf of Venezuela 



By Alfred C. Redfield 



Woods Hole Oceanographic Institution 



and 



Department of Biology 



Harvard University 



One of the very distinguished contributions of Henry B. Bigelow to the 

 subject of oceanography is his study of the hydrography, plankton, and 

 and fishes of the Gulf of Maine. It is the most complete description and 

 analysis which exists of any circumscribed body of coastal water. Because 

 of its breadth of outlook and high technical standard, this work is a 

 model for studies in marine ecology. It is appropriate to contribute to 

 this volume in Professor Bigelow's honour a sketch of the hydrographic 

 conditions which are found in another gulf of somewhat similar pro- 

 portions, but under far different influences than those which dominate 

 the Gulf of Maine. 



Summary — The distribution of salinity, temperature, oxygen, and total phosphorus in the Gulf of 

 Venezuela is described. 



The physical circulation appears to consist of two estuarine cells. The first is generated by the 

 outflow from Lake Maracaibo, which terminates in a mixing zone over the sill off Calabozo Bay. 

 where the water which occupies the deeper basin of the Bay is formed. The second is fed by water 

 formed in this mixing zone which escapes seaward after mingling with more saline water drawn in 

 from subsurface layers of the Caribbean. 



The semi-diurnal components of the tide are augmented by resonance in the Gulf of Venezuela, 

 and with the wind account for the vertical mixing which occurs over the sill of Calabozo Bay. 



The trade winds, which predominate in winter, produce large seasonal differences in mean sea level 

 across the Gulf, and control the distribution of the brackish water as it moves seaward from the outlet 

 of Lake Maracaibo. Upwelling, which occurs in the lee of the Peninsula of Paraguana. is accompanied 

 by an accumulation of phosphorus and a depletion of oxygen in the deep water near the coast. 

 Similar conditions are found in the basin of Calabozo Bay. 



The influence of countercurrents on the biochemical circulation is discussed. 



The Gulf of Venezuela lies in the seaward extension of the syncline which fornix the 

 Maracaibo Basin. It opens directly on the deep water of the Caribbean Sea, and 

 carries into it the entire outflow from Lake Maracaibo. This is the most substantial 

 accession of fresh water along the Venezuelan coast of the Caribbean, and is estimated 

 at 21 billion cubic metres per year. The northeast trades blow steadily along the axis 

 of the Gulf from December through April. The annual range in temperature is small, 

 being about 2° C at Maracaibo. Being situated in 12^ N latitude the Corioli parameter 

 is weak. Differences in salinity and the winds thus dominate the hydrography ol' the 

 Gulf. 



* Contribution No. 776 of the Woods Hole Oceanographic Institution 



115 



