The hydrography of the Gulf of Venezuela 1 29 



Seasonal Influences on the Hydrography 



The available data on the waters of the Gulf were collected in December. While 

 there is no information on the conditions at other seasons, the annual variation in the 

 two factors which control the circulation is known, and may be used to indicate the 

 direction, if not the degree, in which the pattern will change with the season. 



The rainy season in the Maracaibo Basin extends from April to December. The 

 observations were consequently made at a time when the quantity of fresh water in the 

 Gulf is maximal. During the following four months the outflow from the Lake is 

 reduced and may come to an end (Fig. 12, C). The salinity of Calabozo Bay may 

 consequently be expected to increase, and the hydraulic forces which drive its estuarine 

 circulation to weaken. These tendencies should be reversed beginning in April. A 

 rough estimate indicates that the quantity of fresh water present in Calabozo Bay in 

 December is equivalent to about two years' outflow from the Lake. It is probable 

 consequently that in the four months of the dry season the change in the mean salinity 

 will be limited. 



The effect of the north-east trade winds in maintaining the anticyclonic circulation 

 in Calabozo Bay should continue through the winter. With the reduction in outflow 

 from the Lake, the continued wind-induced motion will mix the water, and reduce 

 the vertical and horizontal differences in salinity. 



After April the winds become more variable and slacken in intensity. As the summer 

 progresses, increasing outflow from the Lake should restore the salinity stratification. 

 With the weakened effect of wind, the brackish water should spread more diffusely 

 across the Bay. Possibly the Corioli force overcomes the wind influence and causes 

 the escaping water to follow the southern shore to the eastward in the latter part of 

 summer. 



THE BIOCHEMICAL CIRCULATION 

 The distribution of the major elements in sea water, which determine the salinity, 

 is the result of purely physical processes of advection and mixing. It may be used, 

 consequently, to trace the general circulation of the water. In contrast, the distribution 

 of those elements which are present in limited quantity, and which enter into the 

 composition of organisms, may be profoundly influenced by biological activity. In 

 particular, elements such as phosphorus and nitrogen, which become incorporated 

 into the substance of the phytoplankton growing in the surface layers of the sea, tend 

 to be carried downvvards by the sinking of organisms, and are liberated at depth by 

 the ultimate oxidation of the organic matter. There is thus a circulation of elements 

 of biochemical importance which is different from that of the water itself, and of its 

 biologically inert components. 



In the case of the Gulf of Venezuela, data on the total phosphorus and oxygen 

 content are available for an examination of the biochemical circulation. 



Total Phosphorus 



The total phosphorus content of water includes the phosphorus present as inorganic 

 phosphate ions, as organic compounds present in solution, and as components of 

 suspended organisms. 



The total phosphorus content of the Gulf is higher than that of the source waters 

 from the Caribbean. This is due primarily to the high phosphorus content of the 



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